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FXUS62 KRAH 311039 CCA
AFDRAH

AREA FORECAST DISCUSSION...CORRECTED TYPO
NATIONAL WEATHER SERVICE RALEIGH NC
300 AM EST WED JAN 31 2007


SPECIAL RELEASES...GSO UA  06Z THURSDAY. MORE THAN LIKELY WILL HAVE 
A 18Z THURSDAY ALSO.

.SHORT TERM /TODAY THROUGH THURSDAY NIGHT/...
TODAY AND TONIGHT...
COLD FRONT HAS PUSHED EAST OF CWA EARLY THIS MORNING. ON ITS HEEL IS 
A COLD AND VERY AIR MASS. THIS COLD AND VERY DRY AIR WILL FILTER 
INTO CWA AS HIGH PRESSURE BUILDS IN FROM THE WEST TODAY AND SETTLES 
OVER THE AREA TONIGHT. PLENTY OF SUNSHINE EXPECTED TODAY BUT CAA 
WILL RESULT IN TEMPERATURES ACROSS MUCH OF THE CWA STRUGGLING TO GET 
OUT OF THE 30S. EXPECT A RANGE OF UPPER 30S TO LOWER 40S. 
ADDITIONALLY AIR MASS QUITE DRY WITH DEWPOINTS IN THE SINGLE DIGITS  
WITH SOME SUB-ZERO DEWPOINTS BY AFTERNOON. WILL SEE MID AND HIGH 
LEVEL CLOUDS OVERSPREAD THE AREA TONIGHT. LOWS IN THE MID 20S. 
HOWEVER THE EXTENT AND ARRIVAL OF CLOUDS TONIGHT COULD AFFECT 
OVERNIGHT MINS.
THIS COLD DRY AIR MASS IN PLACE OVER CENTRAL NORTH CAROLINA WILL BE 
SETTING THE STAGE FOR A ROUND OF WINTRY WEATHER ON THURSDAY.

THURSDAY AND THURSDAY NIGHT...
CLASSIC IN SITU COLD AIR DAMMING EVENT WILL UNFOLD DURING THIS 
TIME... WHERE DIABATIC COOLING VIA EVAPORATION WILL BE THE IMPETUS 
FOR THE DEVELOPMENT OF THE DAMMING WEDGE. TYPICALLY IN SITU DAMMING 
CASES CANNOT SUSTAIN THEMSELVES FOR LONG DURATIONS... SINCE THEY 
LACK A CONTINUAL SUPPLY OF COLD DRY AIR ADVECTION IN THE LOW 
LEVELS... COURTESY OF A PARENT SURFACE HIGH TO OUR NORTH. THE LATENT 
HEAT OF FUSION AND RESULTING WARMING DURING FREEZING RAIN ULTIMATELY 
MAKES IT SELF LIMITING. AS HAS BEEN ADVERTISED BY PREVIOUS SHIFTS... 
THE SURFACE HIGH WILL BE WEAK... TRANSIENT... AND LOCATED TOO FAR 
SOUTH TO SUPPORT A *CLASSIC* WINTER WEATHER EVENT ACROSS CENTRAL 
NORTH CAROLINA. HOWEVER... VERY COLD... DRY AIR WILL BE IN PLACE 
ACROSS THE REGION FROM THE ARCTIC AIRMASS CURRENTLY SETTLING 
OVERHEAD. THIS AIRMASS... AT 06Z 31 JANUARY... WAS CHARACTERIZED BY 
SURFACE DEWPOINTS IN THE SINGLE DIGITS UPSTREAM OVER THE TENNESSEE 
VALLEY AND BELOW ZERO WESTWARD INTO THE UPPER MIDWEST. THIS EVENT 
MAY BE ONE OF THOSE RARE CASES THAT BECAUSE THE AIR IS SO COLD AND 
DRY TO START THE EVENT... POTENTIALLY SIGNIFICANT ICING COULD RESULT 
BEFORE A GRADUAL WARMING AND CHANGEOVER TO LIQUID. 

FRICTIONAL CONVERGENCE ALONG THE SOUTHEAST US COAST AS A RESULT OF 
THE RETURN FLOW AROUND THE DEPARTING SURFACE HIGH... WILL AID IN THE 
DEVELOPMENT OF A COASTAL FRONT BY THURSDAY MORNING. MEANWHILE A 
DEVELOPING WARM FRONT ALONG THE NORTHERN GULF OF MEXICO WILL LIFT 
NORTH AND MERGE WITH THE COASTAL FRONT DURING THE DAY THURSDAY. THE 
COMBINATION OF THESE FEATURES WILL PROVIDE THE BAROCLINIC ZONE THAT 
SEVERAL WAVES OF SURFACE LOW PRESSURE WILL ULTIMATELY TRACK 
NORTHEAST ALONG. THE IN SITU WEDGE SHOULD HOLD THIS BAROCLINIC ZONE 
AND EXPECTED LOW TRACK SOUTHEAST OF OUR CWA... THEREBY MINIMIZING 
SIGNIFICANT SURFACE WARMING THROUGHOUT THE EVENT. 

THE EXIT REGION OF A STRONG SOUTHWESTERLY 170 KNOT UPPER JET 
NOSING ACROSS THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS LATE 
WEDNESDAY NIGHT/EARLY THURSDAY WILL PROMOTE THE DEVELOPMENT OF DEEP 
ISENTROPIC LIFT/WARM AIR ADVECTION IN THE THERMALLY INDIRECT LOW 
LEVEL RETURN BRANCH OF THE UPPER JET. THIS WILL RESULT IN RAPID 
MOISTENING OF THE ATMOSPHERE JUST AFTER DAYBREAK THURSDAY. 
PRECIPITATION SHOULD BEGIN REACHING THE GROUND FROM SOUTH TO NORTH 
SHORTLY THEREAFTER. THE TRENDS NOMOGRAM AND MODEL FORECAST SOUNDINGS 
BOTH INDICATE THAT PRECIPITATION AT THE ONSET WOULD LIKELY FALL IN 
THE FORM OF SNOW... WITH SLEET MIXED IN AS THE DAY WEARS ON. THIS 
PERIOD OF FROZEN PRECIPITATION WOULD BE VERY SHORT LIVED... AN HOUR 
OR SO AT MOST... ACROSS THE SANDHILLS AND COASTAL PLAIN... BEFORE 
RAPIDLY TRANSITIONING TO A COLD RAIN BY MIDDAY. THE PIEDMONT... 
ESPECIALLY THE WESTERN HALF... COULD SEE A PERIOD OF SEVERAL HOURS 
OF SNOW/SLEET BEFORE TRANSITIONING TO FREEZING RAIN DURING THE 
AFTERNOON... AS THE STRONG LOW LEVEL JET CREATES A PRONOUNCED WARM 
NOSE ALOFT. ONCE THE SNOW/SLEET TRANSITIONS TO FREEZING RAIN... THE 
FREEZING RAIN COULD CONTINUE THROUGH SUNSET ON EITHER SIDE OF A LINE 
FROM ALBEMARLE TO SANFORD TO RALEIGH TO HENDERSON... INCLUDING THE 
TRIANGLE. THE TEMPERATURE STRUCTURE IN THE LOWER TROPE WOULD BE 
SUPPORTIVE OF FREEZING RAIN AFTER SUNSET AND THROUGHOUT THE EVENING 
HOURS ACROSS THE CLIMATOLOGICALLY FAVORED AREAS APPROXIMATELY ALONG 
AND WEST OF A LINE FROM ASHEBORO TO HILLSBOROUGH TO ROXBORO... 
INCLUDING THE TRIAD.  

ITS INTERESTING THAT THE MODELS ARE KEYING ON TWO BOUTS OF DEEP LIFT 
AND PRECIPITATION DURING THE EVENT... ONE DURING THE MIDDAY TO EARLY 
AFTERNOON HOURS THURSDAY... THEN ANOTHER DURING THE EVENING HOURS. 
THE FIRST WOULD BE ASSOCIATED WITH THE INITIAL SURGE OF WARM 
ADVECTION AND CONVERGENCE ON THE NOSE OF THE LOW LEVEL JET... AND 
THE SECOND ASSOCIATED WITH THE DIFFERENTIAL CYCLONIC VORTICITY 
ADVECTION AHEAD OF THE UPPER LOW CURRENTLY SPINNING OFF THE BAJA OF 
CALIFORNIA. THE SECOND OF THE TWO AREAS OF MAXIMUM LIFT APPEARS AT 
THIS TIME THAT IT WOULD BE FOCUSED FROM SOUTHERN GEORGIA TO 
SOUTHEASTERN NORTH CAROLINA... AFFECTING PRIMARILY THE SOUTHEAST 
HALF OF OUR CWA. IF THAT WERE THE CASE... THE SECOND ROUND WOULD BE 
PREDOMINATELY LIQUID... SINCE THE BULK OF IT WOULD LIKELY NOT EXTEND 
FAR ENOUGH NORTHWEST INTO THE SUBFREEZING SURFACE AIR. THE 
ORIENTATION AND MAGNITUDE OF THE MODEL QPF FOR THE SECOND ROUND OF 
PRECIPITATION... FROM BOTH THE NAM AND GFS FOR THE PAST SEVERAL 
RUNS...  SUGGEST THAT THE MODELS ARE GENERATING DEEP MOIST 
CONVECTION IN THE AFOREMENTIONED AREAS FROM SOUTHERN GA TO 
SOUTHEASTERN NC. ACCORDINGLY... INSTABILITY PARAMETERS FROM THE 
MODELS REVEAL THAT LIKELIHOOD.. AND SPC HAS THOSE AREA HIGHLIGHTED 
IN THE SWODY2. THUS... LATER SHIFTS WILL NEED TO MONITOR THE 
POTENTIAL FOR THIS UPSTREAM CONVECTION TO ALTER THE CURRENT THINKING 
REGARDING ROUND TWO BEING A BIT TOO FAR EAST TO CAUSE ADDITIONAL 
SIGNIFICANT ICING CONCERNS.

WITH ALL OF THIS IN MIND... A WINTER STORM WATCH WILL BE ISSUED FOR 
LOCATIONS ALONG AND WEST OF A LINE FROM APPROXIMATELY ROCKINGHAM TO 
CARTHAGE TO RALEIGH TO LOUISBURG TO WARRENTON. IT IS STILL TOO EARLY 
TO GET SPECIFIC WITH PRECIPITATION AMOUNTS... BUT IT APPEARS THAT 
AROUND AN INCH OF SNOW/SLEET WOULD BE POSSIBLE IN THE WATCH AREA 
THROUGH MIDDAY THURSDAY... WITH ICE ACCRUAL OF ONE QUARTER INCH OR 
MORE THURSDAY AFTERNOON/EVENING... ESPECIALLY ACROSS THE WESTERN 
PIEDMONT. -MWS

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
FRIDAY...
SOME LIGHT RAIN AND/OR DRIZZLE WILL LINGER DURING THE MORNING HOURS 
AS STORM SYSTEM LIFTS OFF TO THE NORTHEAST. MODEL TRENDS ARE 
INDICATING CLEARING FAIRLY QUICKLY BUT THINK CLOUDS WILL BE SLOW TO 
CLEAR. WILL TWEAK CURRENT FORECAST MAXES TO ACCOUNT FOR SLOWER 
CLEARING.
FRIDAY NIGHT THROUGH TUESDAY...
NO CHANGES TO CURRENT FORECAST TRENDS. LATEST OPS GFS KEEPS PRECIP 
IN SOUTHERN STREAM SUPPRESSED SOUTH OF AREA FOR LATE IN THE WEEKEND. 
BUT TRENDS ARE SHOWING PRECIP SHIELD NUDGING A BIT FURTHER NORTH 
EACH RUN. LOOKS LIKE ANOTHER ROUND OF BITTER COLD EARLY NEXT WEEK.


&&

.AVIATION /07Z-06Z/...

VFR CONDS EXPECTED THROUGHOUT THE TAF PERIOD. CAA ASSOC/W FROPA WILL 
BRING NW WINDS AT 10-15 KTS THROUGH 10Z... THEN DECREASE TO LESS 
THAN 10 KT AROUND SUNRISE. THE WINDS PICK UP AGAIN TO 8-12 KT FROM 
THE NW AROUND 14Z AND CONTINUE THROUGH THE DAY. NW WINDS DIMINISH TO 
LIGHT WIND BY MID TO LATE AFTERNOON. EXPECT AN INCREASE IN HIGH 
CLOUDINESS IN THE AFTERNOON. 
&

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM 6AM THURSDAY MORNING THROUGH MIDNIGHT 
THURSDAY NIGHT FOR NCZ007>010-021>026-038>041-073>076-083-084.

&&

$$

SHORT TERM...RA/MWS
LONG TERM...RA
AVIATION...VINCENT







FXUS62 KRAH 311503
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1000 AM EST WED JAN 31 2007

.UPDATE...

&&

.SHORT TERM /REST OF TODAY/...

WV IMAGERY SHOWS IMPRESSIVE VORT MAX CURRENTLY MOVING OFFSHORE...THE
BRUNT OF CAA OCCURRED IMMEDIATELY WITH AND BEHIND THE SHARP SHORT 
WAVE TROUGH WITH H5 HEIGHT FALLS OF 120 METERS OFFSHORE AND HEIGHT
RISES OF 120 METERS UPSTREAM OVER THE OHIO VALLEY. EMPIRICAL PROOF 
OF THE WELL ADVERTISED ARCTIC AIRMASS THAT HAS SETTLED OVER CENTRAL 
NC OVER THE PAST 6 HOURS IS THE -14C 850 TEMPERATURE AND 30C 
DEWPOINT DEPRESSION ANALYZED AT KGSO IN THE 850 AND 700MB UPPER AIR 
CHARTS. TEMPERATURES ARE STRUGGLING TO WARM INTO THE MID TO UPPER 
20S ACROSS THE WESTERN AND CENTRAL PIEDMONT UNDER FULL SUN WITH 
LOWER 30S IN THE SOUTHERN COASTAL PLAIN. CURRENTLY...DEWPOINTS ARE 
SOLIDLY IN THE SINGLE DIGITS...WITH THE FORECAST FOR DEWPOINTS TO 
DROP TO NEAR OR BELOW ZERO THIS AFTERNOON STILL ON TRACK AS 
SHORT-TERM MODEL SOUNDINGS INDICATE A DRY ADIABTIC PROFILE TO 900MB 
WITH DRIER AIR THROUGH THE MIXING LAYER JUST ABOVE THE SURFACE. 
THE DRY ADIABATIC IN-HOUSE THICKNESS SCHEME...SUPPORTS HIGHS IN THE 
MID 30S WEST...UPPER 30S CENTRAL...TO AROUND 40 EAST AND SOUTH. THIS 
WILL REQUIRE ONLY MINOR MODIFICATIONS TO FORECAST HIGHS. OTHERWISE
NO OTHER CHANGES FOR THE CENTRAL NC FORECAST IN THE QUIET BEFORE THE 
STORM PHASE. WINTER STORM WATCH CONTINUES FOR THURSDAY MORNING  
THROUGH THURS EVENING FOR AREAS SURROUNDING AND WEST AND NORTH OF 
THE US 1 CORRIDOR. 

&&

.PREV DISCUSSION...
/ISSUED 300 AM EST WED JAN 31 2007/ 

SHORT TERM /TODAY THROUGH THURSDAY NIGHT/...
TODAY AND TONIGHT...
COLD FRONT HAS PUSHED EAST OF CWA EARLY THIS MORNING. ON ITS HEEL IS 
A COLD AND VERY AIR MASS. THIS COLD AND VERY DRY AIR WILL FILTER 
INTO CWA AS HIGH PRESSURE BUILDS IN FROM THE WEST TODAY AND SETTLES 
OVER THE AREA TONIGHT. PLENTY OF SUNSHINE EXPECTED TODAY BUT CAA 
WILL RESULT IN TEMPERATURES ACROSS MUCH OF THE CWA STRUGGLING TO GET 
OUT OF THE 30S. EXPECT A RANGE OF UPPER 30S TO LOWER 40S. 
ADDITIONALLY AIR MASS QUITE DRY WITH DEWPOINTS IN THE SINGLE DIGITS  
WITH SOME SUB-ZERO DEWPOINTS BY AFTERNOON. WILL SEE MID AND HIGH 
LEVEL CLOUDS OVERSPREAD THE AREA TONIGHT. LOWS IN THE MID 20S. 
HOWEVER THE EXTENT AND ARRIVAL OF CLOUDS TONIGHT COULD AFFECT 
OVERNIGHT MINS.
THIS COLD DRY AIR MASS IN PLACE OVER CENTRAL NORTH CAROLINA WILL BE 
SETTING THE STAGE FOR A ROUND OF WINTRY WEATHER ON THURSDAY.

THURSDAY AND THURSDAY NIGHT...
CLASSIC IN SITU COLD AIR DAMMING EVENT WILL UNFOLD DURING THIS 
TIME... WHERE DIABATIC COOLING VIA EVAPORATION WILL BE THE IMPETUS 
FOR THE DEVELOPMENT OF THE DAMMING WEDGE. TYPICALLY IN SITU DAMMING 
CASES CANNOT SUSTAIN THEMSELVES FOR LONG DURATIONS... SINCE THEY 
LACK A CONTINUAL SUPPLY OF COLD DRY AIR ADVECTION IN THE LOW 
LEVELS... COURTESY OF A PARENT SURFACE HIGH TO OUR NORTH. THE LATENT 
HEAT OF FUSION AND RESULTING WARMING DURING FREEZING RAIN ULTIMATELY 
MAKES IT SELF LIMITING. AS HAS BEEN ADVERTISED BY PREVIOUS SHIFTS... 
THE SURFACE HIGH WILL BE WEAK... TRANSIENT... AND LOCATED TOO FAR 
SOUTH TO SUPPORT A *CLASSIC* WINTER WEATHER EVENT ACROSS CENTRAL 
NORTH CAROLINA. HOWEVER... VERY COLD... DRY AIR WILL BE IN PLACE 
ACROSS THE REGION FROM THE ARCTIC AIRMASS CURRENTLY SETTLING 
OVERHEAD. THIS AIRMASS... AT 06Z 31 JANUARY... WAS CHARACTERIZED BY 
SURFACE DEWPOINTS IN THE SINGLE DIGITS UPSTREAM OVER THE TENNESSEE 
VALLEY AND BELOW ZERO WESTWARD INTO THE UPPER MIDWEST. THIS EVENT 
MAY BE ONE OF THOSE RARE CASES THAT BECAUSE THE AIR IS SO COLD AND 
DRY TO START THE EVENT... POTENTIALLY SIGNIFICANT ICING COULD RESULT 
BEFORE A GRADUAL WARMING AND CHANGEOVER TO LIQUID. 

FRICTIONAL CONVERGENCE ALONG THE SOUTHEAST US COAST AS A RESULT OF 
THE RETURN FLOW AROUND THE DEPARTING SURFACE HIGH... WILL AID IN THE 
DEVELOPMENT OF A COASTAL FRONT BY THURSDAY MORNING. MEANWHILE A 
DEVELOPING WARM FRONT ALONG THE NORTHERN GULF OF MEXICO WILL LIFT 
NORTH AND MERGE WITH THE COASTAL FRONT DURING THE DAY THURSDAY. THE 
COMBINATION OF THESE FEATURES WILL PROVIDE THE BAROCLINIC ZONE THAT 
SEVERAL WAVES OF SURFACE LOW PRESSURE WILL ULTIMATELY TRACK 
NORTHEAST ALONG. THE IN SITU WEDGE SHOULD HOLD THIS BAROCLINIC ZONE 
AND EXPECTED LOW TRACK SOUTHEAST OF OUR CWA... THEREBY MINIMIZING 
SIGNIFICANT SURFACE WARMING THROUGHOUT THE EVENT. 

THE EXIT REGION OF A STRONG SOUTHWESTERLY 170 KNOT UPPER JET 
NOSING ACROSS THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS LATE 
WEDNESDAY NIGHT/EARLY THURSDAY WILL PROMOTE THE DEVELOPMENT OF DEEP 
ISENTROPIC LIFT/WARM AIR ADVECTION IN THE THERMALLY INDIRECT LOW 
LEVEL RETURN BRANCH OF THE UPPER JET. THIS WILL RESULT IN RAPID 
MOISTENING OF THE ATMOSPHERE JUST AFTER DAYBREAK THURSDAY. 
PRECIPITATION SHOULD BEGIN REACHING THE GROUND FROM SOUTH TO NORTH 
SHORTLY THEREAFTER. THE TRENDS NOMOGRAM AND MODEL FORECAST SOUNDINGS 
BOTH INDICATE THAT PRECIPITATION AT THE ONSET WOULD LIKELY FALL IN 
THE FORM OF SNOW... WITH SLEET MIXED IN AS THE DAY WEARS ON. THIS 
PERIOD OF FROZEN PRECIPITATION WOULD BE VERY SHORT LIVED... AN HOUR 
OR SO AT MOST... ACROSS THE SANDHILLS AND COASTAL PLAIN... BEFORE 
RAPIDLY TRANSITIONING TO A COLD RAIN BY MIDDAY. THE PIEDMONT... 
ESPECIALLY THE WESTERN HALF... COULD SEE A PERIOD OF SEVERAL HOURS 
OF SNOW/SLEET BEFORE TRANSITIONING TO FREEZING RAIN DURING THE 
AFTERNOON... AS THE STRONG LOW LEVEL JET CREATES A PRONOUNCED WARM 
NOSE ALOFT. ONCE THE SNOW/SLEET TRANSITIONS TO FREEZING RAIN... THE 
FREEZING RAIN COULD CONTINUE THROUGH SUNSET ON EITHER SIDE OF A LINE 
FROM ALBEMARLE TO SANFORD TO RALEIGH TO HENDERSON... INCLUDING THE 
TRIANGLE. THE TEMPERATURE STRUCTURE IN THE LOWER TROPE WOULD BE 
SUPPORTIVE OF FREEZING RAIN AFTER SUNSET AND THROUGHOUT THE EVENING 
HOURS ACROSS THE CLIMATOLOGICALLY FAVORED AREAS APPROXIMATELY ALONG 
AND WEST OF A LINE FROM ASHEBORO TO HILLSBOROUGH TO ROXBORO... 
INCLUDING THE TRIAD.  

ITS INTERESTING THAT THE MODELS ARE KEYING ON TWO BOUTS OF DEEP LIFT 
AND PRECIPITATION DURING THE EVENT... ONE DURING THE MIDDAY TO EARLY 
AFTERNOON HOURS THURSDAY... THEN ANOTHER DURING THE EVENING HOURS. 
THE FIRST WOULD BE ASSOCIATED WITH THE INITIAL SURGE OF WARM 
ADVECTION AND CONVERGENCE ON THE NOSE OF THE LOW LEVEL JET... AND 
THE SECOND ASSOCIATED WITH THE DIFFERENTIAL CYCLONIC VORTICITY 
ADVECTION AHEAD OF THE UPPER LOW CURRENTLY SPINNING OFF THE BAJA OF 
CALIFORNIA. THE SECOND OF THE TWO AREAS OF MAXIMUM LIFT APPEARS AT 
THIS TIME THAT IT WOULD BE FOCUSED FROM SOUTHERN GEORGIA TO 
SOUTHEASTERN NORTH CAROLINA... AFFECTING PRIMARILY THE SOUTHEAST 
HALF OF OUR CWA. IF THAT WERE THE CASE... THE SECOND ROUND WOULD BE 
PREDOMINATELY LIQUID... SINCE THE BULK OF IT WOULD LIKELY NOT EXTEND 
FAR ENOUGH NORTHWEST INTO THE SUBFREEZING SURFACE AIR. THE 
ORIENTATION AND MAGNITUDE OF THE MODEL QPF FOR THE SECOND ROUND OF 
PRECIPITATION... FROM BOTH THE NAM AND GFS FOR THE PAST SEVERAL 
RUNS...  SUGGEST THAT THE MODELS ARE GENERATING DEEP MOIST 
CONVECTION IN THE AFOREMENTIONED AREAS FROM SOUTHERN GA TO 
SOUTHEASTERN NC. ACCORDINGLY... INSTABILITY PARAMETERS FROM THE 
MODELS REVEAL THAT LIKELIHOOD.. AND SPC HAS THOSE AREA HIGHLIGHTED 
IN THE SWODY2. THUS... LATER SHIFTS WILL NEED TO MONITOR THE 
POTENTIAL FOR THIS UPSTREAM CONVECTION TO ALTER THE CURRENT THINKING 
REGARDING ROUND TWO BEING A BIT TOO FAR EAST TO CAUSE ADDITIONAL 
SIGNIFICANT ICING CONCERNS.

WITH ALL OF THIS IN MIND... A WINTER STORM WATCH WILL BE ISSUED FOR 
LOCATIONS ALONG AND WEST OF A LINE FROM APPROXIMATELY ROCKINGHAM TO 
CARTHAGE TO RALEIGH TO LOUISBURG TO WARRENTON. IT IS STILL TOO EARLY 
TO GET SPECIFIC WITH PRECIPITATION AMOUNTS... BUT IT APPEARS THAT 
AROUND AN INCH OF SNOW/SLEET WOULD BE POSSIBLE IN THE WATCH AREA 
THROUGH MIDDAY THURSDAY... WITH ICE ACCRUAL OF ONE QUARTER INCH OR 
MORE THURSDAY AFTERNOON/EVENING... ESPECIALLY ACROSS THE WESTERN 
PIEDMONT. -MWS

LONG TERM /FRIDAY THROUGH TUESDAY/...
FRIDAY...
SOME LIGHT RAIN AND/OR DRIZZLE WILL LINGER DURING THE MORNING HOURS 
AS STORM SYSTEM LIFTS OFF TO THE NORTHEAST. MODEL TRENDS ARE 
INDICATING CLEARING FAIRLY QUICKLY BUT THINK CLOUDS WILL BE SLOW TO 
CLEAR. WILL TWEAK CURRENT FORECAST MAXES TO ACCOUNT FOR SLOWER 
CLEARING.
FRIDAY NIGHT THROUGH TUESDAY...
NO CHANGES TO CURRENT FORECAST TRENDS. LATEST OPS GFS KEEPS PRECIP 
IN SOUTHERN STREAM SUPPRESSED SOUTH OF AREA FOR LATE IN THE WEEKEND. 
BUT TRENDS ARE SHOWING PRECIP SHIELD NUDGING A BIT FURTHER NORTH 
EACH RUN. LOOKS LIKE ANOTHER ROUND OF BITTER COLD EARLY NEXT WEEK.

AVIATION /07Z-06Z/...

VFR CONDS EXPECTED THROUGHOUT THE TAF PERIOD. CAA ASSOC/W FROPA WILL 
BRING NW WINDS AT 10-15 KTS THROUGH 10Z... THEN DECREASE TO LESS 
THAN 10 KT AROUND SUNRISE. THE WINDS PICK UP AGAIN TO 8-12 KT FROM 
THE NW AROUND 14Z AND CONTINUE THROUGH THE DAY. NW WINDS DIMINISH TO 
LIGHT WIND BY MID TO LATE AFTERNOON. EXPECT AN INCREASE IN HIGH 
CLOUDINESS IN THE AFTERNOON. 
&

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM THURSDAY MORNING THROUGH THURSDAY 
EVENING FOR NCZ007>010-021>026-038>041-073>076-083-084.

&&

$$

SHORT TERM...CBL




FXUS62 KRAH 311524 AAA
AFDRAH

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RALEIGH NC
1024 AM EST WED JAN 31 2007

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
A BROAD LONG WAVE TROUGH WITH A TAP TO THE ARCTIC DOMINATES THE FLOW 
ACROSS THE EASTERN 2/3RDS OF THE CONUS DURING THE PERIOD,  THIS 
SHOULD RESULT IN BELOW TO MUCH BELOW NORMAL TEMPERATURES OVER 
CENTRAL NC.  MODEL AND ENSEMBLE OUTPUT SHOWS ONE ARCTIC HIGH 
EXTENDING INTO THE AREA FROM THE NORTHERN PLAINS OVER THE WEEKEND 
REPLACED BY ANOTHER ARCTIC AIRMASS ON TUE AND WED.  THESE AIRMASSES 
ARE SEPARATED BY A RELATIVELY DRY COLD FRONT TRAILING A CLIPPER LOW 
OVER THE GREAT LAKES LATE MONDAY.  GIVEN THE DOMINANT FLOW ALOFT 
FROM THE NW AND NO SIGNIFICANT PERTURBATIONS IN THE SOUTHERN 
STREAM... CONDITIONS SHOULD REMAIN DRY THROUGH THE PERIOD WITH ONLY 
PASSING HIGH CLOUDINESS WITH THE COLD FRONT LATE MONDAY.  -RFG

&&

.PREV DISCUSSION...
/ISSUED 1000 AM EST WED JAN 31 2007/ 

UPDATE...

SHORT TERM /REST OF TODAY/...

WV IMAGERY SHOWS IMPRESSIVE VORT MAX CURRENTLY MOVING OFFSHORE...THE
BRUNT OF CAA OCCURRED IMMEDIATELY WITH AND BEHIND THE SHARP SHORT 
WAVE TROUGH WITH H5 HEIGHT FALLS OF 120 METERS OFFSHORE AND HEIGHT
RISES OF 120 METERS UPSTREAM OVER THE OHIO VALLEY. EMPIRICAL PROOF 
OF THE WELL ADVERTISED ARCTIC AIRMASS THAT HAS SETTLED OVER CENTRAL 
NC OVER THE PAST 6 HOURS IS THE -14C 850 TEMPERATURE AND 30C 
DEWPOINT DEPRESSION ANALYZED AT KGSO IN THE 850 AND 700MB UPPER AIR 
CHARTS. TEMPERATURES ARE STRUGGLING TO WARM INTO THE MID TO UPPER 
20S ACROSS THE WESTERN AND CENTRAL PIEDMONT UNDER FULL SUN WITH 
LOWER 30S IN THE SOUTHERN COASTAL PLAIN. CURRENTLY...DEWPOINTS ARE 
SOLIDLY IN THE SINGLE DIGITS...WITH THE FORECAST FOR DEWPOINTS TO 
DROP TO NEAR OR BELOW ZERO THIS AFTERNOON STILL ON TRACK AS 
SHORT-TERM MODEL SOUNDINGS INDICATE A DRY ADIABTIC PROFILE TO 900MB 
WITH DRIER AIR THROUGH THE MIXING LAYER JUST ABOVE THE SURFACE. 
THE DRY ADIABATIC IN-HOUSE THICKNESS SCHEME...SUPPORTS HIGHS IN THE 
MID 30S WEST...UPPER 30S CENTRAL...TO AROUND 40 EAST AND SOUTH. THIS 
WILL REQUIRE ONLY MINOR MODIFICATIONS TO FORECAST HIGHS. OTHERWISE
NO OTHER CHANGES FOR THE CENTRAL NC FORECAST IN THE QUIET BEFORE THE 
STORM PHASE. WINTER STORM WATCH CONTINUES FOR THURSDAY MORNING  
THROUGH THURS EVENING FOR AREAS SURROUNDING AND WEST AND NORTH OF 
THE US 1 CORRIDOR. 

PREV DISCUSSION...
/ISSUED 300 AM EST WED JAN 31 2007/ 

SHORT TERM /TODAY THROUGH THURSDAY NIGHT/...
TODAY AND TONIGHT...
COLD FRONT HAS PUSHED EAST OF CWA EARLY THIS MORNING. ON ITS HEEL IS 
A COLD AND VERY AIR MASS. THIS COLD AND VERY DRY AIR WILL FILTER 
INTO CWA AS HIGH PRESSURE BUILDS IN FROM THE WEST TODAY AND SETTLES 
OVER THE AREA TONIGHT. PLENTY OF SUNSHINE EXPECTED TODAY BUT CAA 
WILL RESULT IN TEMPERATURES ACROSS MUCH OF THE CWA STRUGGLING TO GET 
OUT OF THE 30S. EXPECT A RANGE OF UPPER 30S TO LOWER 40S. 
ADDITIONALLY AIR MASS QUITE DRY WITH DEWPOINTS IN THE SINGLE DIGITS  
WITH SOME SUB-ZERO DEWPOINTS BY AFTERNOON. WILL SEE MID AND HIGH 
LEVEL CLOUDS OVERSPREAD THE AREA TONIGHT. LOWS IN THE MID 20S. 
HOWEVER THE EXTENT AND ARRIVAL OF CLOUDS TONIGHT COULD AFFECT 
OVERNIGHT MINS.
THIS COLD DRY AIR MASS IN PLACE OVER CENTRAL NORTH CAROLINA WILL BE 
SETTING THE STAGE FOR A ROUND OF WINTRY WEATHER ON THURSDAY.

THURSDAY AND THURSDAY NIGHT...
CLASSIC IN SITU COLD AIR DAMMING EVENT WILL UNFOLD DURING THIS 
TIME... WHERE DIABATIC COOLING VIA EVAPORATION WILL BE THE IMPETUS 
FOR THE DEVELOPMENT OF THE DAMMING WEDGE. TYPICALLY IN SITU DAMMING 
CASES CANNOT SUSTAIN THEMSELVES FOR LONG DURATIONS... SINCE THEY 
LACK A CONTINUAL SUPPLY OF COLD DRY AIR ADVECTION IN THE LOW 
LEVELS... COURTESY OF A PARENT SURFACE HIGH TO OUR NORTH. THE LATENT 
HEAT OF FUSION AND RESULTING WARMING DURING FREEZING RAIN ULTIMATELY 
MAKES IT SELF LIMITING. AS HAS BEEN ADVERTISED BY PREVIOUS SHIFTS... 
THE SURFACE HIGH WILL BE WEAK... TRANSIENT... AND LOCATED TOO FAR 
SOUTH TO SUPPORT A *CLASSIC* WINTER WEATHER EVENT ACROSS CENTRAL 
NORTH CAROLINA. HOWEVER... VERY COLD... DRY AIR WILL BE IN PLACE 
ACROSS THE REGION FROM THE ARCTIC AIRMASS CURRENTLY SETTLING 
OVERHEAD. THIS AIRMASS... AT 06Z 31 JANUARY... WAS CHARACTERIZED BY 
SURFACE DEWPOINTS IN THE SINGLE DIGITS UPSTREAM OVER THE TENNESSEE 
VALLEY AND BELOW ZERO WESTWARD INTO THE UPPER MIDWEST. THIS EVENT 
MAY BE ONE OF THOSE RARE CASES THAT BECAUSE THE AIR IS SO COLD AND 
DRY TO START THE EVENT... POTENTIALLY SIGNIFICANT ICING COULD RESULT 
BEFORE A GRADUAL WARMING AND CHANGEOVER TO LIQUID. 

FRICTIONAL CONVERGENCE ALONG THE SOUTHEAST US COAST AS A RESULT OF 
THE RETURN FLOW AROUND THE DEPARTING SURFACE HIGH... WILL AID IN THE 
DEVELOPMENT OF A COASTAL FRONT BY THURSDAY MORNING. MEANWHILE A 
DEVELOPING WARM FRONT ALONG THE NORTHERN GULF OF MEXICO WILL LIFT 
NORTH AND MERGE WITH THE COASTAL FRONT DURING THE DAY THURSDAY. THE 
COMBINATION OF THESE FEATURES WILL PROVIDE THE BAROCLINIC ZONE THAT 
SEVERAL WAVES OF SURFACE LOW PRESSURE WILL ULTIMATELY TRACK 
NORTHEAST ALONG. THE IN SITU WEDGE SHOULD HOLD THIS BAROCLINIC ZONE 
AND EXPECTED LOW TRACK SOUTHEAST OF OUR CWA... THEREBY MINIMIZING 
SIGNIFICANT SURFACE WARMING THROUGHOUT THE EVENT. 

THE EXIT REGION OF A STRONG SOUTHWESTERLY 170 KNOT UPPER JET 
NOSING ACROSS THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS LATE 
WEDNESDAY NIGHT/EARLY THURSDAY WILL PROMOTE THE DEVELOPMENT OF DEEP 
ISENTROPIC LIFT/WARM AIR ADVECTION IN THE THERMALLY INDIRECT LOW 
LEVEL RETURN BRANCH OF THE UPPER JET. THIS WILL RESULT IN RAPID 
MOISTENING OF THE ATMOSPHERE JUST AFTER DAYBREAK THURSDAY. 
PRECIPITATION SHOULD BEGIN REACHING THE GROUND FROM SOUTH TO NORTH 
SHORTLY THEREAFTER. THE TRENDS NOMOGRAM AND MODEL FORECAST SOUNDINGS 
BOTH INDICATE THAT PRECIPITATION AT THE ONSET WOULD LIKELY FALL IN 
THE FORM OF SNOW... WITH SLEET MIXED IN AS THE DAY WEARS ON. THIS 
PERIOD OF FROZEN PRECIPITATION WOULD BE VERY SHORT LIVED... AN HOUR 
OR SO AT MOST... ACROSS THE SANDHILLS AND COASTAL PLAIN... BEFORE 
RAPIDLY TRANSITIONING TO A COLD RAIN BY MIDDAY. THE PIEDMONT... 
ESPECIALLY THE WESTERN HALF... COULD SEE A PERIOD OF SEVERAL HOURS 
OF SNOW/SLEET BEFORE TRANSITIONING TO FREEZING RAIN DURING THE 
AFTERNOON... AS THE STRONG LOW LEVEL JET CREATES A PRONOUNCED WARM 
NOSE ALOFT. ONCE THE SNOW/SLEET TRANSITIONS TO FREEZING RAIN... THE 
FREEZING RAIN COULD CONTINUE THROUGH SUNSET ON EITHER SIDE OF A LINE 
FROM ALBEMARLE TO SANFORD TO RALEIGH TO HENDERSON... INCLUDING THE 
TRIANGLE. THE TEMPERATURE STRUCTURE IN THE LOWER TROPE WOULD BE 
SUPPORTIVE OF FREEZING RAIN AFTER SUNSET AND THROUGHOUT THE EVENING 
HOURS ACROSS THE CLIMATOLOGICALLY FAVORED AREAS APPROXIMATELY ALONG 
AND WEST OF A LINE FROM ASHEBORO TO HILLSBOROUGH TO ROXBORO... 
INCLUDING THE TRIAD.  

ITS INTERESTING THAT THE MODELS ARE KEYING ON TWO BOUTS OF DEEP LIFT 
AND PRECIPITATION DURING THE EVENT... ONE DURING THE MIDDAY TO EARLY 
AFTERNOON HOURS THURSDAY... THEN ANOTHER DURING THE EVENING HOURS. 
THE FIRST WOULD BE ASSOCIATED WITH THE INITIAL SURGE OF WARM 
ADVECTION AND CONVERGENCE ON THE NOSE OF THE LOW LEVEL JET... AND 
THE SECOND ASSOCIATED WITH THE DIFFERENTIAL CYCLONIC VORTICITY 
ADVECTION AHEAD OF THE UPPER LOW CURRENTLY SPINNING OFF THE BAJA OF 
CALIFORNIA. THE SECOND OF THE TWO AREAS OF MAXIMUM LIFT APPEARS AT 
THIS TIME THAT IT WOULD BE FOCUSED FROM SOUTHERN GEORGIA TO 
SOUTHEASTERN NORTH CAROLINA... AFFECTING PRIMARILY THE SOUTHEAST 
HALF OF OUR CWA. IF THAT WERE THE CASE... THE SECOND ROUND WOULD BE 
PREDOMINATELY LIQUID... SINCE THE BULK OF IT WOULD LIKELY NOT EXTEND 
FAR ENOUGH NORTHWEST INTO THE SUBFREEZING SURFACE AIR. THE 
ORIENTATION AND MAGNITUDE OF THE MODEL QPF FOR THE SECOND ROUND OF 
PRECIPITATION... FROM BOTH THE NAM AND GFS FOR THE PAST SEVERAL 
RUNS...  SUGGEST THAT THE MODELS ARE GENERATING DEEP MOIST 
CONVECTION IN THE AFOREMENTIONED AREAS FROM SOUTHERN GA TO 
SOUTHEASTERN NC. ACCORDINGLY... INSTABILITY PARAMETERS FROM THE 
MODELS REVEAL THAT LIKELIHOOD.. AND SPC HAS THOSE AREA HIGHLIGHTED 
IN THE SWODY2. THUS... LATER SHIFTS WILL NEED TO MONITOR THE 
POTENTIAL FOR THIS UPSTREAM CONVECTION TO ALTER THE CURRENT THINKING 
REGARDING ROUND TWO BEING A BIT TOO FAR EAST TO CAUSE ADDITIONAL 
SIGNIFICANT ICING CONCERNS.

WITH ALL OF THIS IN MIND... A WINTER STORM WATCH WILL BE ISSUED FOR 
LOCATIONS ALONG AND WEST OF A LINE FROM APPROXIMATELY ROCKINGHAM TO 
CARTHAGE TO RALEIGH TO LOUISBURG TO WARRENTON. IT IS STILL TOO EARLY 
TO GET SPECIFIC WITH PRECIPITATION AMOUNTS... BUT IT APPEARS THAT 
AROUND AN INCH OF SNOW/SLEET WOULD BE POSSIBLE IN THE WATCH AREA 
THROUGH MIDDAY THURSDAY... WITH ICE ACCRUAL OF ONE QUARTER INCH OR 
MORE THURSDAY AFTERNOON/EVENING... ESPECIALLY ACROSS THE WESTERN 
PIEDMONT. -MWS

LONG TERM /FRIDAY THROUGH TUESDAY/...
FRIDAY...
SOME LIGHT RAIN AND/OR DRIZZLE WILL LINGER DURING THE MORNING HOURS 
AS STORM SYSTEM LIFTS OFF TO THE NORTHEAST. MODEL TRENDS ARE 
INDICATING CLEARING FAIRLY QUICKLY BUT THINK CLOUDS WILL BE SLOW TO 
CLEAR. WILL TWEAK CURRENT FORECAST MAXES TO ACCOUNT FOR SLOWER 
CLEARING.
FRIDAY NIGHT THROUGH TUESDAY...
NO CHANGES TO CURRENT FORECAST TRENDS. LATEST OPS GFS KEEPS PRECIP 
IN SOUTHERN STREAM SUPPRESSED SOUTH OF AREA FOR LATE IN THE WEEKEND. 
BUT TRENDS ARE SHOWING PRECIP SHIELD NUDGING A BIT FURTHER NORTH 
EACH RUN. LOOKS LIKE ANOTHER ROUND OF BITTER COLD EARLY NEXT WEEK.

AVIATION /07Z-06Z/...

VFR CONDS EXPECTED THROUGHOUT THE TAF PERIOD. CAA ASSOC/W FROPA WILL 
BRING NW WINDS AT 10-15 KTS THROUGH 10Z... THEN DECREASE TO LESS 
THAN 10 KT AROUND SUNRISE. THE WINDS PICK UP AGAIN TO 8-12 KT FROM 
THE NW AROUND 14Z AND CONTINUE THROUGH THE DAY. NW WINDS DIMINISH TO 
LIGHT WIND BY MID TO LATE AFTERNOON. EXPECT AN INCREASE IN HIGH 
CLOUDINESS IN THE AFTERNOON. 
&

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM THURSDAY MORNING THROUGH THURSDAY 
EVENING FOR NCZ007>010-021>026-038>041-073>076-083-084.

&&

$$

LONG TERM...RFG


FXUS62 KRAH 311950
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
245 PM EST WED JAN 31 2007

.SHORT TERM /TONIGHT THROUGH FRIDAY/...

NON-CLASSICAL DAMMING WINTER EVENT TO UNFOLD ACROSS CENTRAL NC 
THURSDAY MORNING...AS TRANSITORY PARENT HIGH CURRENTLY CENTERED
OVER WV/VA/KY MOVES QUICKLY WELL OFF THE CAROLINA COAST. 

TEMPERATURES WILL QUICKLY DROP OFF THIS EVENING...THEN LEVEL OFF
OR RISE A DEGREE OR TWO AS HIGH-LEVEL CLOUD DECK SPREADS WEST TO 
EAST INTO THE AREA. THUS EXPECT MINS TO BE ACHIEVED BY MIDNIGHT
WITH A NON-DIURNAL TEMPERATURE TREND. WITH THE PARENT HIGH IN AN 
UNFAVORED/ATYPICAL LOCATION TO PROVIDE A CONTINUOUS SOURCE OF 
CAA...MIN TEMPERATURES TONIGHT/THURSDAY MORNING ARE HIGHLY CRITICAL 
IN DETERMINING THE AMOUNT OF FROZEN AND FREEZING PRECIP THAT WILL BE 
REALIZED THROUGH 00Z FRIDAY. THE DIFFERENCE OF OVERNIGHT LOWS 
IN THE MID 20S VERSES UPPER 20S WILL BE ONE FACTOR IN DETERMINING
WHETHER WARNING CRITERIA OF ICE ACCRUAL IS ACHIEVED. THE OTHER 
SIGNIFICANT PLAYER DUE TO THE ATYPICAL SET UP IS TIMING AND QPF 
AMOUNTS...WHICH IS A MUST TO LOCK IN IN-SITU DAMMING HIGH...WITH 
DIABATIC COOLING MAXIMIZED WITH SFC DEWPOINTS IN THE SINGLE TO LOWER 
TEENS AT THE START OF PRECIP. AGAIN...I CANNOT STRESS THESE TWO 
CRITICAL COMPONENTS ENOUGH...THE PRE-EXISTING COLD AIR AND THE 
TIMING AND QPF AMOUNTS ARE KEY IN REALIZING ADVISORY (LESS THAN 
0.10") OR WARNING (0.25" OR MORE)ICE CRITERIA. 


THERE ARE NO MAJOR CHANGES TO CHANGEOVER TIMING OR DOMINANT PRECIP 
TYPE...WITH THE WARM NOSE QUICKLY WARMING THE MID-LEVELS
AND THEN THE LOW-LEVELS IN THE COASTAL PLAIN AOA 15Z...MORE GRADUAL 
IN THE CENTRAL PIEDMONT AND NORTHERN COASTAL PLAIN AOA 17Z...WITH 
THE WARMING MUCH DELAYED IN THE WESTERN PIEDMONT AND NORTHERN 
CENTRAL PIEDMONT UNTIL AROUND 00Z PER FORECAST SURFACE TW. ONE TO 
TWO INCHES OF SNOW IS POSSIBLE INITIALLY THROUGH 21Z WITH AN 
ADDITIONAL 0.25" OF ICE FROM 21Z TO 00Z ALONG AND WEST OF A LINE 
EXTENDING FROM ALBEMARLE...TO SILER CITY...TO DURHAM...THROUGH 
WARRENTON. WILL UPGRADE THE WINTER STORM WATCH TO A WINTER STORM 
WARNING FOR THIS AREA.

JUST EAST OF THAT AREA...INCLUDING ROCKINGHAM...SANFORD... 
RALEIGH...ROCKY MOUNT AND ROANOKE RAPIDS...A WINTER STORM ADVISORY 
WILL BE ISSUED FOR ICE ACCRUAL OF A TRACE TO 0.10" WITH SNOWFALL OF 
LESS THAN INCH AT ONSET. A SPECIAL WEATHER STATEMENT WILL BE ISSUED 
FOR THE REMAINDER OF THE FORECAST AREA HIGHLIGHTING A BRIEF PERIOD 
OF SNOW/RAIN BEFORE QUICKLY CHANGING OVER TO RAIN.

THERE ARE NOTABLE LIQUID QPF DIFFERENCES BETWEEN THE NAM AND GFS 
WITH THE GFS STILL SLIGHTLY FASTER AT ONSET. THE NAM QUICKLY CATCHES 
UP THOUGH WITH THE HEAVIEST QPF AXIS MUCH FARTHER NORTH AND WEST
OF THE GFS FROM 18Z TO 00Z. THE GFS QPF IS PREFERRED KEEPING THE 
HEAVIEST QPF ALONG THE SE CWA WITH THE BAROCLINIC ZONE ALONG THE  
COASTAL TROUGH AND STRONGEST WAA. ANOTHER IMPORTANT FEATURE IS A 
LULL IN PRECIP LATE THURSDAY AFTERNOON ACROSS THE WEST WITH A 
SECONDARY WAVE OF PRECIP DEVELOPING IN THE WEST FROM 00 TO 06Z AS 
VORTICITY ADVECTION ALOFT APPROACHES FROM THE WEST. AT THIS POINT 
EXPECT TEMPERATURES IN THE EXTREME NW PIEDMONT TO BE RIGHT AT OR 
JUST ABOVE FREEZING...RESULTING IN LITTLE TO NO ADDITIONAL ICE 
ACCRUAL. WILL END PRECIP AS DRIZZLE OR FREEZING DRIZZLE IN THE FAR 
NW FRIDAY MORNING...ENDING AS RAIN EVERYWHERE ELSE. LIQUID QPF 
TOTALS OF A HALF INCH IN THE WEST TO JUST OVER AN INCH IN THE 
SOUTHEAST.   
 
&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...

FRI NGT-SAT NGT...A SOUTHERN STREAM WAVE PASSES TO OUR 
SOUTH...KEEPING MAINLY HIGH CLOUDINESS OVER CENTRAL NC AND NARROWING 
THE DIURNAL TEMPERATURE RANGE SOMEWHAT FROM THE PREVIOUS CYCLE FOR 
FRI NIGHT THROUGH SAT NGT.  

SUN-WED...A BROAD LONG WAVE TROUGH WITH A TAP TO THE ARCTIC 
DOMINATES THE FLOW ACROSS THE EASTERN 2/3RDS OF THE CONUS DURING THE 
PERIOD.  THIS SHOULD RESULT IN BELOW TO MUCH BELOW NORMAL 
TEMPERATURES OVER CENTRAL NC.  MODEL AND ENSEMBLE OUTPUT SHOWS ONE 
ARCTIC HIGH EXTENDING INTO THE AREA FROM THE NORTHERN PLAINS OVER 
THE WEEKEND REPLACED BY ANOTHER ARCTIC AIRMASS ON TUE AND WED.  
THESE AIRMASSES ARE SEPARATED BY A RELATIVELY DRY COLD FRONT 
TRAILING A CLIPPER LOW OVER THE GREAT LAKES LATE MONDAY.  GIVEN THE 
DOMINANT FLOW ALOFT FROM THE NW AND NO SIGNIFICANT PERTURBATIONS IN 
THE SOUTHERN STREAM... CONDITIONS SHOULD REMAIN DRY THROUGH THE 
PERIOD WITH ONLY PASSING HIGH CLOUDINESS WITH THE COLD FRONT LATE 
MONDAY.  


&&

.AVIATION /18Z-18Z/...

VFR CONDITIONS PREVAIL OVER CENTRAL NC THROUGH DAYBREAK THU BUT WITH 
INCREASING HIGH CLOUDINESS LOWERING BASES TO AROUND 9 THSD FT AROUND 
06Z AND TO AROUND 5 THSD FT AROUND 12Z.  SHORTLY AFTER 12Z SNOW AND 
SLEET IS EXPECTED TO OVERSPREAD THE AREA FROM THE WEST LOWERING 
CONDITIONS TO IFR BY 15Z WITH VSBY BELOW 3 MILES AND CIGS BELOW 1 
THSD FT.  BY 18Z...PRECIPITATION IS EXPECTED TO TURN TO RAIN AT KFAY 
AND KRWI AND TO FREEZING RAIN AT KRDU...KGSO...AND KINT.



&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 6 AM THURSDAY TO MIDNIGHT EST 
THURSDAY NIGHT FOR NCZ007>010-021>025-038>040-073-074.

WINTER WEATHER ADVISORY FROM 6 AM THURSDAY TO MIDNIGHT EST 
THURSDAY NIGHT FOR NCZ011-026>028-041-043-075-076-083-084.

&&

$$

SHORT TERM...CBL
LONG TERM...RFG
AVIATION...RFG







FXUS62 KRAH 010256
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
956 PM EST WED JAN 31 2007

.SHORT TERM /REST OF TONIGHT THROUGH THURSDAY/...
PRECIPITATION MOVING QUICKLY EAST ACROSS THE DEEP SOUTH THIS
EVENING. TEMPS ACROSS THE OUR AREA HAVE LOWERED INTO THE UPPER
20S TO AROUND 30. IF TEMPS HOLD STEADY AT CURRENT
LEVELS...UPCOMING EVENT MAY NOT BE AS DIRE AS FORECAST. HOWEVER
STILL APPEARS THAT WE ARE STILL 3-4 HOURS FROM OVERCAST SKIES SO
TEMPS MAY STILL FALL A FEW MORE DEGREES BEFORE LEVELING OFF.

12Z/18Z RUN OF GFS DID A DECENT JOB WITH EASTWARD PROGRESSION OF
PRECIP OVER THE DEEP SOUTH THIS AFTERNOON. BASED ON THIS TREND
WENT AHEAD AND MENTIONED A CHANCE POP ALONG THE SOUTHERN BORDER
COUNTIES AFTER 08Z. 

STILL APPEARS THAT PRECIP WILL EXPAND ACROSS CENTRAL NC THU
MORNING. WITH SUB CLOUD LAYER BONE DRY...EVAPORATIVE COOLING WILL
CAUSE PRECIP TO START OUT AS SNOW MIXED WITH SLEET THEN TRANSITION
TO FREEZING RAIN AS WARMER AIR ALOFT OVERSPREADS CENTRAL NC IN
STRENGTHEN LOW LEVEL SLY FLOW. DID NOTE ON 00Z ANALYSIS THAT THE
850MB 0 DEGREE ISOTHERM EXTENDED FROM ATLANTA TO MOREHEAD CITY SO
THE WARMER AIR ALOFT DOES NOT HAVE FAR TO GO.

BIG UNCERTAINTY REMAINS ON EXPECTED PRECIP AMOUNTS. IF PRECIP
AMOUNTS HEAVIER THAN EXPECTED (AND A FEW SHORT RANGE MODELS ARE
DEPICTING AMOUNTS AROUND 0.75 THU IN THE TRIAD REGION), MAY BE
LOOKING AT A SIGNIFICANT ICING EVENT OVER THE NW PIEDMONT.
ALSO...BASED ON THE SURFACE WET BULB TEMPERATURES NOT WARMING TO
NEAR FREEZING UNTIL THU EVENING...FREEZING RAIN EVENT IN THE NW
PIEDMONT MAY LAST A FEW HOURS LONGER THAN EARLIER ANTICIPATED.

THUS...HAVE SEGMENTED THE WARNING TO INDICATE THE POTENTIAL FOR A
BIT MORE ICING IN THE FAR NE AND NW PIEDMONT VERSUS THE REMAINDER
OF THE WARNING AREA. MADE MENTION OF SCATTERED POWER OUTAGES AND A
FEW DOWN TREES IN THIS REGION. 

ALSO ADDED HARNETT AND JOHNSTON TO THE ADVISORY AREA AS THEY MAY
EXPERIENCE ENOUGH FREEZING RAIN TO RESULT IN A LIGHT GLAZE ON
EXPOSED OBJECTS.

THE PARAMETERS TO WATCH THE NEXT FEW HOURS WILL BE HOW LOW THE
TEMPS GET IN THE REGION BEFORE THE THICKER CLOUDS ARRIVE...AND HOW
FAST THE PRECIP EXPANDS TO OUR SW. IF PRECIP ARRIVES A COUPLE OF
HOURS EARLIER THAN ANTICIPATED...SNOW AMOUNTS MAY BE A BIT GREATER.

&&

.PREV DISCUSSION...
/ISSUED 245 PM EST WED JAN 31 2007/ 

SHORT TERM /TONIGHT THROUGH FRIDAY/...

NON-CLASSICAL DAMMING WINTER EVENT TO UNFOLD ACROSS CENTRAL NC 
THURSDAY MORNING...AS TRANSITORY PARENT HIGH CURRENTLY CENTERED
OVER WV/VA/KY MOVES QUICKLY WELL OFF THE CAROLINA COAST. 

TEMPERATURES WILL QUICKLY DROP OFF THIS EVENING...THEN LEVEL OFF
OR RISE A DEGREE OR TWO AS HIGH-LEVEL CLOUD DECK SPREADS WEST TO 
EAST INTO THE AREA. THUS EXPECT MINS TO BE ACHIEVED BY MIDNIGHT
WITH A NON-DIURNAL TEMPERATURE TREND. WITH THE PARENT HIGH IN AN 
UNFAVORED/ATYPICAL LOCATION TO PROVIDE A CONTINUOUS SOURCE OF 
CAA...MIN TEMPERATURES TONIGHT/THURSDAY MORNING ARE HIGHLY CRITICAL 
IN DETERMINING THE AMOUNT OF FROZEN AND FREEZING PRECIP THAT WILL BE 
REALIZED THROUGH 00Z FRIDAY. THE DIFFERENCE OF OVERNIGHT LOWS 
IN THE MID 20S VERSES UPPER 20S WILL BE ONE FACTOR IN DETERMINING
WHETHER WARNING CRITERIA OF ICE ACCRUAL IS ACHIEVED. THE OTHER 
SIGNIFICANT PLAYER DUE TO THE ATYPICAL SET UP IS TIMING AND QPF 
AMOUNTS...WHICH IS A MUST TO LOCK IN IN-SITU DAMMING HIGH...WITH 
DIABATIC COOLING MAXIMIZED WITH SFC DEWPOINTS IN THE SINGLE TO LOWER 
TEENS AT THE START OF PRECIP. AGAIN...I CANNOT STRESS THESE TWO 
CRITICAL COMPONENTS ENOUGH...THE PRE-EXISTING COLD AIR AND THE 
TIMING AND QPF AMOUNTS ARE KEY IN REALIZING ADVISORY (LESS THAN 
0.10") OR WARNING (0.25" OR MORE)ICE CRITERIA. 

THERE ARE NO MAJOR CHANGES TO CHANGEOVER TIMING OR DOMINANT PRECIP 
TYPE...WITH THE WARM NOSE QUICKLY WARMING THE MID-LEVELS
AND THEN THE LOW-LEVELS IN THE COASTAL PLAIN AOA 15Z...MORE GRADUAL 
IN THE CENTRAL PIEDMONT AND NORTHERN COASTAL PLAIN AOA 17Z...WITH 
THE WARMING MUCH DELAYED IN THE WESTERN PIEDMONT AND NORTHERN 
CENTRAL PIEDMONT UNTIL AROUND 00Z PER FORECAST SURFACE TW. ONE TO 
TWO INCHES OF SNOW IS POSSIBLE INITIALLY THROUGH 21Z WITH AN 
ADDITIONAL 0.25" OF ICE FROM 21Z TO 00Z ALONG AND WEST OF A LINE 
EXTENDING FROM ALBEMARLE...TO SILER CITY...TO DURHAM...THROUGH 
WARRENTON. WILL UPGRADE THE WINTER STORM WATCH TO A WINTER STORM 
WARNING FOR THIS AREA.

JUST EAST OF THAT AREA...INCLUDING ROCKINGHAM...SANFORD... 
RALEIGH...ROCKY MOUNT AND ROANOKE RAPIDS...A WINTER STORM ADVISORY 
WILL BE ISSUED FOR ICE ACCRUAL OF A TRACE TO 0.10" WITH SNOWFALL OF 
LESS THAN INCH AT ONSET. A SPECIAL WEATHER STATEMENT WILL BE ISSUED 
FOR THE REMAINDER OF THE FORECAST AREA HIGHLIGHTING A BRIEF PERIOD 
OF SNOW/RAIN BEFORE QUICKLY CHANGING OVER TO RAIN.

THERE ARE NOTABLE LIQUID QPF DIFFERENCES BETWEEN THE NAM AND GFS 
WITH THE GFS STILL SLIGHTLY FASTER AT ONSET. THE NAM QUICKLY CATCHES 
UP THOUGH WITH THE HEAVIEST QPF AXIS MUCH FARTHER NORTH AND WEST
OF THE GFS FROM 18Z TO 00Z. THE GFS QPF IS PREFERRED KEEPING THE 
HEAVIEST QPF ALONG THE SE CWA WITH THE BAROCLINIC ZONE ALONG THE  
COASTAL TROUGH AND STRONGEST WAA. ANOTHER IMPORTANT FEATURE IS A 
LULL IN PRECIP LATE THURSDAY AFTERNOON ACROSS THE WEST WITH A 
SECONDARY WAVE OF PRECIP DEVELOPING IN THE WEST FROM 00 TO 06Z AS 
VORTICITY ADVECTION ALOFT APPROACHES FROM THE WEST. AT THIS POINT 
EXPECT TEMPERATURES IN THE EXTREME NW PIEDMONT TO BE RIGHT AT OR 
JUST ABOVE FREEZING...RESULTING IN LITTLE TO NO ADDITIONAL ICE 
ACCRUAL. WILL END PRECIP AS DRIZZLE OR FREEZING DRIZZLE IN THE FAR 
NW FRIDAY MORNING...ENDING AS RAIN EVERYWHERE ELSE. LIQUID QPF 
TOTALS OF A HALF INCH IN THE WEST TO JUST OVER AN INCH IN THE 
SOUTHEAST.   
 

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...

FRI NGT-SAT NGT...A SOUTHERN STREAM WAVE PASSES TO OUR 
SOUTH...KEEPING MAINLY HIGH CLOUDINESS OVER CENTRAL NC AND NARROWING 
THE DIURNAL TEMPERATURE RANGE SOMEWHAT FROM THE PREVIOUS CYCLE FOR 
FRI NIGHT THROUGH SAT NGT.  

SUN-WED...A BROAD LONG WAVE TROUGH WITH A TAP TO THE ARCTIC 
DOMINATES THE FLOW ACROSS THE EASTERN 2/3RDS OF THE CONUS DURING THE 
PERIOD.  THIS SHOULD RESULT IN BELOW TO MUCH BELOW NORMAL 
TEMPERATURES OVER CENTRAL NC.  MODEL AND ENSEMBLE OUTPUT SHOWS ONE 
ARCTIC HIGH EXTENDING INTO THE AREA FROM THE NORTHERN PLAINS OVER 
THE WEEKEND REPLACED BY ANOTHER ARCTIC AIRMASS ON TUE AND WED.  
THESE AIRMASSES ARE SEPARATED BY A RELATIVELY DRY COLD FRONT 
TRAILING A CLIPPER LOW OVER THE GREAT LAKES LATE MONDAY.  GIVEN THE 
DOMINANT FLOW ALOFT FROM THE NW AND NO SIGNIFICANT PERTURBATIONS IN 
THE SOUTHERN STREAM... CONDITIONS SHOULD REMAIN DRY THROUGH THE 
PERIOD WITH ONLY PASSING HIGH CLOUDINESS WITH THE COLD FRONT LATE 
MONDAY.  

AVIATION /18Z-18Z/...

VFR CONDITIONS PREVAIL OVER CENTRAL NC THROUGH DAYBREAK THU BUT WITH 
INCREASING HIGH CLOUDINESS LOWERING BASES TO AROUND 9 THSD FT AROUND 
06Z AND TO AROUND 5 THSD FT AROUND 12Z.  SHORTLY AFTER 12Z SNOW AND 
SLEET IS EXPECTED TO OVERSPREAD THE AREA FROM THE WEST LOWERING 
CONDITIONS TO IFR BY 15Z WITH VSBY BELOW 3 MILES AND CIGS BELOW 1 
THSD FT.  BY 18Z...PRECIPITATION IS EXPECTED TO TURN TO RAIN AT KFAY 
AND KRWI AND TO FREEZING RAIN AT KRDU...KGSO...AND KINT.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 6 AM THURSDAY TO MIDNIGHT EST 
THURSDAY NIGHT FOR NCZ007>010-021>025-038>040-073-074.

WINTER WEATHER ADVISORY FROM 6 AM THURSDAY TO MIDNIGHT EST 
THURSDAY NIGHT FOR NCZ011-026>028-041>043-075>077-083-084.

&&

$$

SHORT TERM...RLH/WSS


FXUS62 KRAH 010814
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
312 AM EST THU FEB 1 2007

SPECIAL GSO UA IN FOR 06Z AND 18Z SCHEDULED.

.SHORT TERM /TODAY THROUGH SATURDAY NIGHT/...
TODAY THROUGH FRIDAY...
INTERESTING AND SOMEWHAT TRICKY FORECAST FOR THE NEXT 24 HOURS OVER 
A LARGE PORTION OF CENTRAL NORTH CAROLINA. MID/HIGH LEVEL CLOUDS 
SPREADING INTO AREA RESULTING IN TEMPERATURES BOUNCING AROUND 
SHOWING RISES WHICH MAKES FORECAST ALL THE MORE TRICKY. BUT 
DEWPOINTS ARE QUITE LOW...STILL SINGLE DIGITS  IN NORTHWEST BUT A 
SLIGHT RISE OVER SOUTH/SOUTHWEST SECTIONS. HOWEVER EXPECT 
TEMPERATURES TO FALL ONCE PRECIP STARTS. ONSET TIMING AND QPF 
AMOUNTS ARE THE KEY FACTORS. PRECIPITATION CURRENTLY OVER DEEP SOUTH 
HANDLED QUITE WELL BY GFS. LATEST RADAR TRENDS SHOW AREA ADVANCING 
NORTHEAST/EAST FAIRLY QUICKLY. HEAVIER MIX PRECIP CURRENTLY INTO 
NORTH AND NORTH CENTRAL GEORGIA WITH SOME LIGHTER ECHOES ALOFT NOW 
OVER CENTRAL CWA. SOME DIFFERENCES EXIST BETWEEN NAM/GFS WHILE THERE 
ARE SIMILARITIES. NAM IS THE COLDEST AND WETTEST. NAM BRINGS CORE OF 
HIGHEST PRECIP ACROSS THE CWA WHILE GFS MOVES ACROSS MAINLY SOUTHERN 
SECTIONS. ALSO NAM HAS MORE PRONOUNCED INSITU WEDGE AND PROFILES FOR 
GSO/RDU BELOW FREEZING THROUGH 18Z INDICATING A LONGER PERIOD OF 
SNOW. GFS WEAKER ON INSITU WEDGE AND PROFILES INDICATE PRECIP 
TRANSITIONING OVER SLEET/FREEZING RAIN BY THE AFTERNOON. TOUGH CALL 
AS GFS HAS BEEN FAIRLY CONSISTENT AND PERFORMANCE GOOD SO FAR THIS 
WINTER. GFS PARTIALS ARE MORE IN LINE WITH LATEST GSO RAOB (06Z). 
06Z GSO SOUNDING SHOWING QUITE A BIT OF MID LEVEL DRY AIR. PER GFS 
GOOD ISENTROPIC LIFT COMMENCES OVER CWA AT 12Z WHILE NAM FURTHER 
SOUTH AND SOUTHWEST. BOTH NAM/GFS SHOWING TWO ROUNDS OF PRECIP 
MOVING ACROSS THE AREA...ONE DURING THE DAY...THEN ANOTHER WITH 
SECOND WAVE 00Z-06Z.  OVERALL WILL LEAN TOWARD GFS WITH 
MODIFICATION. WILL HOLD ON TO ALL SNOW LONGER IN NORTHWEST PIEDMONT. 
ALSO SLOWER TREND ON TRANSITION OF PRECIP IN EASTERN PIEDMONT TO ALL 
RAIN. ADDITIONALLY WILL ADJUST TEMPERATURE TRENDS TO KEEP COLDER 
THROUGH 00Z. FOR FRIDAY WILL KEEP DRIZZLE MENTIONED THROUGH MID 
MORNING. --RA

FRIDAY NIGHT THROUGH SATURDAY NIGHT...
AT THIS POINT WILL CONTINUE CURRENT FORECAST TREND. DRY AND COLD.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
BROAD UPPER LEVEL TROUGH REMAIN ANCHORED OVER THE AREA THROUGH THE 
PERIOD TO REINFORCE COLD AIR OVER THE AREA. AT THE SURFACE HIGH 
PRESSURE BUILDS OVER THE AREA SUNDAY. SUNDAY NIGHT...A BOUNDARY 
DEVELOPS ALONG THE VIRGINIA/NORTH CAROLINA BORDER AND EXTENDS WEST 
AND SOUTHWEST TO TENNESSEE...THEN TO A LOW OVER EASTERN TEXAS. THERE 
IS SOME MOISTURE AND WEAK UPPER SUPPORT ASSOCIATED WITH THIS FEATURE 
...HOWEVER WILL LEAVE FORECAST DRY AT THE PRESENT TIME. THIS SYSTEM 
WILL BE PUSHED TO THE SOUTHEAST LATE MONDAY AND EARLY TUESDAY AS 
ARCTIC HIGH PRESSURE BUILDS OVER THE AREA...AND REMAINS OVER THE 
REGION THROUGH WEDNESDAY. THE RESULT OF THIS ARCTIC AIRMASS WILL BE 
BELOW TO MUCH BELOW NORMAL TEMPERATURES. -RHJ


&&

.AVIATION /07Z-06Z/...
ALTOCUMULUS BEGINNING TO MOVE INTO THE FOOTHILLS AT THIS TIME. 
CLOUDS WILL LOWER OVERNIGHT AND LIKELY DROP BELOW VFR A COUPLE OF 
HOURS AFTER SUNRISE AT THE TAF LOCATIONS. CEILINGS BELOW 1000 FEET 
ONCE PRECIPITATION BEGINS WITH MVFR VISIBILITIES IN GENERAL. 
CEILINGS BELOW 600 FEET MOST OF THE AFTERNOON AND INTO THE NIGHT.

ALL TAF SITES EXPECTING SOME NON-LIQUID PRECIPITATION THURSDAY WITH 
FAYETTEVILLE HAVING THE LEAST IMPACT AND SHORTEST DURATION...AND 
GREENSBORO AND WINSTON-SALEM MOST IMPACTED BY WINTER WEATHER. 
ACCUMULATING SNOW THURSDAY MORNING WILL MIX WITH SLEET AND CHANGE TO 
FREEZING RAIN IN THE AFTERNOON. LESSER AMOUNTS OF SNOW AND SLEET AS 
ONE MOVES EAST BUT FREEZING RAIN WILL BE A CONCERN. -RLH/VINCENT


&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 6 AM THIS MORNING TO MIDNIGHT EST 
TONIGHT FOR NCZ007>010-021>025-038>040-073-074.

WINTER WEATHER ADVISORY FROM 6 AM THIS MORNING TO MIDNIGHT EST 
TONIGHT FOR NCZ011-026>028-041>043-075>077-083-084.

&&

$$

SHORT TERM...RA/RHJ/VINCENT
LONG TERM...RHJ
AVIATION...VINCENT




FXUS62 KRAH 011547
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1045 AM EST THU FEB 1 2007

.UPDATE...

&&

.SHORT TERM /REST OF TODAY/...

THE INITIAL HEAVY BURST OF SNOW HAS RESULTED IN HEAVIEST SNOWFALL 
TOTALS ACROSS THE SOUTHERN HALF OF CWA...SEEN CLEARLY EARLIER ON THE 
KRAX RADAR IMAGERY WITH THE BRIGHT BAND REFLECTIVITY EXTENDING
OVER THE SOUTHERN SECTOR. REPORTS INDICATE THE HIGHEST AMOUNTS 
ACROSS THE SOUTHWEST PIEDMONT...STANLY...ANSON...AND MONTGOMERY
AND MOORE COUNTIES. 1 TO 1.5 INCHES WAS REPORTED IN THE SANDHILLS
AND SOUTHERN COASTAL PLAIN...WHICH PROMPTED RAISING A WINTER WX
ADVISORY THROUGH NOON. MEANWHILE ACROSS THE NORTHERN HALF...SNOW
AMOUNTS ARE LESS THAN AN INCH WITH THE TRIAD AND COUNTIES 
ALONG THE VA BORDER REPORTING ONLY A TRACE. 

CURRENTLY...
REAL TIME REPORTS...AIRCRAFT(AMDAR)SOUNDINGS...AND THE 
MRR-VERTICALLY POINTING RADAR...ARE ALL SHOWING THE ADVERTISED 
WARMING NOSE ALOFT ADVANCING NORTH WITH THE MELTING LAYER STARTING 
TO DESCEND DOWN TO THE SURFACE. REPORTS EXTENDING FROM 
ALBEMARLE...MOORE... FAYETTEVILLE HAVE CHANGED OVER TO SLEET OR 
FREEZING RAIN. THE LATEST RUC IS MODELING THE THERMAL PROFILE FAIRLY 
WELL WHEN COMPARED TO THE LATEST AMDAR SOUNDING FROM GSO...WITH IT A 
LITTLE TOO COOL ALOFT AND SLIGHTLY TOO WARM NEAR THE SURFACE 
SURFACE.  

WITH THE MAIN WARM/MOIST AIR CONVEYOR BELT DIRECTED IN A MORE
SW TO NE FASHION AND TRANSLATING IN A MORE EASTERLY
DIRECTION...RADARS RETURNS HAVE BEEN HARD TO COME BY ACROSS THE 
TRIAD. IT APPEARS THAT THE PREDICTED SNOWFALL OF 1 TO 2 INCHES 
WILL NOT BE REALIZED. HOWEVER...PRECIP WILL SPREAD BACK NORTH
THIS AFTERNOON AS THE WELL-DEFINED WAVE OVER ALABAMA TRANSLATES
NE TOWARDS CENTRAL NC. BY THAT TIME...THE THERMAL PROFILE WILL 
BE WARMING TO SUPPORT A TRANSITION TO SLEET AND THE ANTICIPATED
FREEZING RAIN. THERE IS STILL YET ANOTHER WAVE OVER THE TEXAS AND 
OKLAHOMA THIS IS PROGGED TO APPROACH THE AREA BETWEEN 00Z TO 06Z.
SO BY NO MEANS IS THE TRIAD OUT OF THE WOODS...WITH A QUARTER OF AN 
INCH ICE STILL VERY POSSIBLE. WILL BE KEEPING ALL WARNINGS AND 
ADVISORIES UP...BUT LOWER THE SNOWFALL AMOUNTS AND POPS.  
OTHERWISE...MINOR ADJUSTMENTS TO FORECAST OF P-TYPE AND TIMING OF 
CHANGEOVER.


&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
THE FLOW ALOFT IS DOMINATED BY A BROAD LARGE SCALE TROUGH OVER THE 
EASTERN TWO-THIRDS OF THE CONUS WITH A TROUGH AXIS THAT STEEPENS 
OVER THE APPALACHIANS AROUND TUE NIGHT...THEN FLATTENS AS THE TROUGH 
LOSES AMPLITUDE BY THU. SURFACE FEATURES SHOW WEAK HIGH PRESSURE 
DRIFTING ACROSS THE AREA SUN NGT AND MON AHEAD OF A COLD FRONT MON 
NIGHT THAT USHERS ANOTHER ARCTIC AIRMASS SOUTHEASTWARD OUT OF THE 
NORTHERN PLAINS.  THE OVERNIGHT GFS SHOWS A WEAK LOW FORMATION IN 
THE LEE OF THE APPALACHIANS WITH THE COLD FRONT LATE MON... 
SUGGESTING SOME MOISTURE CONVERGENCE IN LOWER TO MID LEVELS. OTHER 
MODELS DO NOT RESOLVE THIS FEATURE.  THE SURFACE LAYER IS EXPECTED 
TO BE VERY DRY WITH DEW POINTS OF 10-15 DEGREES AND CHANCES OF 
PRECIPITATION HITTING THE GROUND REMAIN LESS THAN 15 PERCENT IN THE 
RAH CWA.  TEMPERATURES DROP TO BETWEEN 10 AND 20 DEGREES BELOW 
NORMAL FOLLOWING THE ARCTIC COLD FRONT FOR TUE AND WED MODERATING 
BUT STILL BELOW NORMAL ON THU.

&&

.PREV DISCUSSION...
/ISSUED 312 AM EST THU FEB 1 2007/ 

SHORT TERM /TODAY THROUGH SATURDAY NIGHT/...
TODAY THROUGH FRIDAY...
INTERESTING AND SOMEWHAT TRICKY FORECAST FOR THE NEXT 24 HOURS OVER 
A LARGE PORTION OF CENTRAL NORTH CAROLINA. MID/HIGH LEVEL CLOUDS 
SPREADING INTO AREA RESULTING IN TEMPERATURES BOUNCING AROUND 
SHOWING RISES WHICH MAKES FORECAST ALL THE MORE TRICKY. BUT 
DEWPOINTS ARE QUITE LOW...STILL SINGLE DIGITS  IN NORTHWEST BUT A 
SLIGHT RISE OVER SOUTH/SOUTHWEST SECTIONS. HOWEVER EXPECT 
TEMPERATURES TO FALL ONCE PRECIP STARTS. ONSET TIMING AND QPF 
AMOUNTS ARE THE KEY FACTORS. PRECIPITATION CURRENTLY OVER DEEP SOUTH 
HANDLED QUITE WELL BY GFS. LATEST RADAR TRENDS SHOW AREA ADVANCING 
NORTHEAST/EAST FAIRLY QUICKLY. HEAVIER MIX PRECIP CURRENTLY INTO 
NORTH AND NORTH CENTRAL GEORGIA WITH SOME LIGHTER ECHOES ALOFT NOW 
OVER CENTRAL CWA. SOME DIFFERENCES EXIST BETWEEN NAM/GFS WHILE THERE 
ARE SIMILARITIES. NAM IS THE COLDEST AND WETTEST. NAM BRINGS CORE OF 
HIGHEST PRECIP ACROSS THE CWA WHILE GFS MOVES ACROSS MAINLY SOUTHERN 
SECTIONS. ALSO NAM HAS MORE PRONOUNCED INSITU WEDGE AND PROFILES FOR 
GSO/RDU BELOW FREEZING THROUGH 18Z INDICATING A LONGER PERIOD OF 
SNOW. GFS WEAKER ON INSITU WEDGE AND PROFILES INDICATE PRECIP 
TRANSITIONING OVER SLEET/FREEZING RAIN BY THE AFTERNOON. TOUGH CALL 
AS GFS HAS BEEN FAIRLY CONSISTENT AND PERFORMANCE GOOD SO FAR THIS 
WINTER. GFS PARTIALS ARE MORE IN LINE WITH LATEST GSO RAOB (06Z). 
06Z GSO SOUNDING SHOWING QUITE A BIT OF MID LEVEL DRY AIR. PER GFS 
GOOD ISENTROPIC LIFT COMMENCES OVER CWA AT 12Z WHILE NAM FURTHER 
SOUTH AND SOUTHWEST. BOTH NAM/GFS SHOWING TWO ROUNDS OF PRECIP 
MOVING ACROSS THE AREA...ONE DURING THE DAY...THEN ANOTHER WITH 
SECOND WAVE 00Z-06Z.  OVERALL WILL LEAN TOWARD GFS WITH 
MODIFICATION. WILL HOLD ON TO ALL SNOW LONGER IN NORTHWEST PIEDMONT. 
ALSO SLOWER TREND ON TRANSITION OF PRECIP IN EASTERN PIEDMONT TO ALL 
RAIN. ADDITIONALLY WILL ADJUST TEMPERATURE TRENDS TO KEEP COLDER 
THROUGH 00Z. FOR FRIDAY WILL KEEP DRIZZLE MENTIONED THROUGH MID 
MORNING. --RA

FRIDAY NIGHT THROUGH SATURDAY NIGHT...
AT THIS POINT WILL CONTINUE CURRENT FORECAST TREND. DRY AND COLD.

LONG TERM /SUNDAY THROUGH WEDNESDAY/...
BROAD UPPER LEVEL TROUGH REMAIN ANCHORED OVER THE AREA THROUGH THE 
PERIOD TO REINFORCE COLD AIR OVER THE AREA. AT THE SURFACE HIGH 
PRESSURE BUILDS OVER THE AREA SUNDAY. SUNDAY NIGHT...A BOUNDARY 
DEVELOPS ALONG THE VIRGINIA/NORTH CAROLINA BORDER AND EXTENDS WEST 
AND SOUTHWEST TO TENNESSEE...THEN TO A LOW OVER EASTERN TEXAS. THERE 
IS SOME MOISTURE AND WEAK UPPER SUPPORT ASSOCIATED WITH THIS FEATURE 
..HOWEVER WILL LEAVE FORECAST DRY AT THE PRESENT TIME. THIS SYSTEM 
WILL BE PUSHED TO THE SOUTHEAST LATE MONDAY AND EARLY TUESDAY AS 
ARCTIC HIGH PRESSURE BUILDS OVER THE AREA...AND REMAINS OVER THE 
REGION THROUGH WEDNESDAY. THE RESULT OF THIS ARCTIC AIRMASS WILL BE 
BELOW TO MUCH BELOW NORMAL TEMPERATURES. -RHJ

AVIATION /07Z-06Z/...
ALTOCUMULUS BEGINNING TO MOVE INTO THE FOOTHILLS AT THIS TIME. 
CLOUDS WILL LOWER OVERNIGHT AND LIKELY DROP BELOW VFR A COUPLE OF 
HOURS AFTER SUNRISE AT THE TAF LOCATIONS. CEILINGS BELOW 1000 FEET 
ONCE PRECIPITATION BEGINS WITH MVFR VISIBILITIES IN GENERAL. 
CEILINGS BELOW 600 FEET MOST OF THE AFTERNOON AND INTO THE NIGHT.

ALL TAF SITES EXPECTING SOME NON-LIQUID PRECIPITATION THURSDAY WITH 
FAYETTEVILLE HAVING THE LEAST IMPACT AND SHORTEST DURATION...AND 
GREENSBORO AND WINSTON-SALEM MOST IMPACTED BY WINTER WEATHER. 
ACCUMULATING SNOW THURSDAY MORNING WILL MIX WITH SLEET AND CHANGE TO 
FREEZING RAIN IN THE AFTERNOON. LESSER AMOUNTS OF SNOW AND SLEET AS 
ONE MOVES EAST BUT FREEZING RAIN WILL BE A CONCERN. -RLH/VINCENT

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ078-085-
086-088-089.

WINTER STORM WARNING UNTIL MIDNIGHT EST TONIGHT FOR NCZ007>010-
021>025-038>040-073-074.

WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR NCZ011-
026>028-041>043-075>077-083-084.

&&

$$

SHORT TERM...CBL




FXUS62 KRAH 011822 AAA
AFDRAH

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RALEIGH NC
122 PM EST THU FEB 1 2007

.SHORT TERM /REST OF TODAY/...

...DROPPING ADVISORIES AND CUTTING WARNINGS BACK...

STRONG SOUTHWEST FLOW OFF THE SURFACE HAS ALLOWED THE SNOW TO END 
ACROSS ALL OF CENTRAL NC. SURFACE WET BULBS HAVE WARMED TO FREEZING
AND ABOVE FROM US1 EAST. WITH TEMPERATURES HOVERING AROUND
FREEZING AND GIVEN THE LACK OF A COLD REINFORCING SHOT OF COLD AIR
SIGNIFICANT FREEZING RAIN IS NOT EXPECTED. ONLY RAIN IS EXPECTED
OVER MOST OF CENTRAL NC FROM US1 EAST WITH SOME LIGHT FREEZING
RAIN POSSIBLE FROM DURHAM WEST AND NORTH.

A SECOND SURGE OF MOISTURE WILL MOVE IN FROM THE SE 
OVERNIGHT...HOWEVER...TEMPERATUERS OVERNIGHT WILL REMAIN JUST ABOVE 
FREEZING ALLOWING THE PRECIP TO FALL AS RAIN. GFS AND NAM 
THICKNESSES FOR BOTH GSO AND RDU SUPPORT ALL RAIN AND NO FREEZING 
RAIN BY 06Z.

WILL GO WITH AN ADVISORY FOR THE POSSIBILITY OF LIGHT FREEZING
RAIN FROM DURHAM WEST ALONG AND NORTH OF HIGHWAY 64.

&&

.AVIATION...
A COOL SATURATED AIRMASS IN THE WAKE OF LOW PRESSURE ALONG THE NC 
COAST WILL MAINTAIN IFR AND LIFR CONDITIONS ACROSS CENTRAL NC 
THROUGH TONIGHT AND FRI MORNING.  WIDESPREAD RAIN...WITH SOME 
FREEZING RAIN POSSIBLE AT KINT AND KGSO EARLY THIS AFTERNOON...WILL 
TAPER TO DRIZZLE EARLY THIS EVENING.  MORE AREAS OF RAIN WILL 
LIKELY CROSS CENTRAL NC IN THE PREDAWN HOURS FRI MORNING...ENDING 
SHORTLY AFTERNOON DAYBREAK.  CONDITIONS WILL GRADUALLY IMPROVE TO 
ABOVE IFR FRI AFTERNOON AS A SURGE OF DRIER AIR PUSHES IN FROM THE 
WEST.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR 
NCZ007-008-021>025-038>040.

&&

$$



FXUS62 KRAH 011917
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
215 PM EST THU FEB 1 2007

.SHORT TERM /TONIGHT THROUGH FRIDAY/...

TONIGHT...SATELLITE IMAGERY SHOWS A SERIES OF WAVES EMBEDDED IN THE 
LONG EXTENSION OF THE 150KT SUBTROPICAL JET...EXTENDING FROM THE 
MEXICAN PLATEAU INTO THE MID-ATLANTIC REGION. THE FIRST S/W 
DISTURBANCE IS CURRENTLY MOVING THROUGH THE FORECAST AREA...AS THE 
HEAVIEST PRECIPITATION SHIFTS TO THE EASTERN CWA. THERE WILL BE A 
LULL IN PRECIPITATION ACROSS CENTRAL NC THIS AFTERNOON AND EARLY 
EVENING...UNTIL THE SECOND MORE ROBUST UPPER WAVE(CURRENTLY ROUNDING 
BASE OF THE LONG WAVE TROUGH OVER TEXAS)APPROACHES THE AREA BETWEEN 
06Z TO 12Z. PRECIP WILL FILL BACK INTO THE AREA AS FORCING ALOFT 
FROM LF EXIT REGION AND POSITIVE VORTICITY ADVECTION SPREADS 
FROM SW TO NE OVER THE AREA. THE LATEST RUC AND MESONAM SOUNDINGS 
AND SFC TW SUPPORT ALL RAIN ACROSS THE ADVISORY AREA BY 00Z...WITH 
FURTHER SUPPORT FROM PARTIAL THICKNESS NOMOGRAM AND CONSENSUS OF THE 
VARIOUS P-TYPE ALGORITHMS(RAMER...BOURGOUIN...REVISED NCEP). AS A 
RESULT CONFIDENCE IS HIGH THAT THE THREAT OF FREEZING RAIN WILL BE 
OVER BY 6PM(IF NOT EARLIER)...AND THUS WILL NOT BE EXTENDED. 

WILL ADJUST GRIDS TO SHOW RAIN INCREASING LATE IN THE EVENING... AND 
THEN GRADUALLY TAPERING OFF INTO DRIZZLE AS MID-LEVELS BEGIN TO 
DRY OUT BY AROUND DAYBREAK. TEMPERATURES OVERNIGHT WILL BE STEADY OR 
SLIGHTLY RISING WITH ABSENCE OF CAA AND AS THE RAIN FALLS INTO THE 
3 TO 5C WARM NOSE. TEMPERATURES OVERNIGHT IN THE LOWER TO MID 30S.

FRIDAY...A CHANCE OF RAIN IN THE MORNING...THEN RAIN ENDING WEST TO 
EAST. CENTRAL NC REMAINS IN WARM SECTOR AND LOW-LEVELS REMAIN 
SATURATED UNTIL FROPA WHICH OCCURRS AROUND 00Z. HIGHS 45 TO 50. 

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...

FRIDAY NIGHT THROUGH SUNDAY..DRY SURGE COMMENCES FRIDAY NIGHT WITH 
CLEARING SKIES. NAM/GFS REMAIN A BIT AT ODDS CONCERNING THE 
DEEPENING TROF OVER THE SOUTHWESTERN CONUS...WITH THE NAM BEING 
CLOSER TO CONSENSUS WITH THE UKMET/ECMWF...HAVING A MORE AMPLIFIED 
UPPER TROF AND DELAYING THE COLD AIR PUSH INTO THE EASTERN CONUS. 
THE RESULTING MOS MAX TEMPS ARE THUS A BIT IN QUESTION...BUT WILL 
TOP OUT MAINLY IN THE MID AND UPPER 40S REGARDLESS.

THE SURFACE HIGH AND THE UPPER TROF EDGE EAST ON SUNDAY. NAM IS 
SLOWER WITH THIS PROGRESSION AS IT DRIVES ARTIC AIR DEEPER INTO THE 
MIDWEST...CONTINUING TO AMPLIFY THE UPPER TROF AND DELAY THE COLDEST 
AIR. WILL CONTINUE MOSTLY CLEAR SKIES WITH HIGHS STRUGGLING INTO THE 
40 TO 45 DEGREE RANGE.      

THE FLOW ALOFT IS DOMINATED BY A BROAD LARGE SCALE TROUGH OVER THE 
EASTERN TWO-THIRDS OF THE CONUS WITH A TROUGH AXIS THAT STEEPENS 
OVER THE APPALACHIANS AROUND TUE NIGHT...THEN FLATTENS AS THE TROUGH 
LOSES AMPLITUDE BY THU. SURFACE FEATURES SHOW WEAK HIGH PRESSURE 
DRIFTING ACROSS THE AREA SUN NGT AND MON AHEAD OF A COLD FRONT MON 
NIGHT THAT USHERS ANOTHER ARCTIC AIRMASS SOUTHEASTWARD OUT OF THE 
NORTHERN PLAINS.  THE OVERNIGHT GFS SHOWS A WEAK LOW FORMATION IN 
THE LEE OF THE APPALACHIANS WITH THE COLD FRONT LATE MON... 
SUGGESTING SOME MOISTURE CONVERGENCE IN LOWER TO MID LEVELS. OTHER 
MODELS DO NOT RESOLVE THIS FEATURE.  THE SURFACE LAYER IS EXPECTED 
TO BE VERY DRY WITH DEW POINTS OF 10-15 DEGREES AND CHANCES OF 
PRECIPITATION HITTING THE GROUND REMAIN LESS THAN 15 PERCENT IN THE 
RAH CWA.  TEMPERATURES DROP TO BETWEEN 10 AND 20 DEGREES BELOW 
NORMAL FOLLOWING THE ARCTIC COLD FRONT FOR TUE AND WED MODERATING 
BUT STILL BELOW NORMAL ON THU.  
&&

.AVIATION /18Z-18Z/...

A COOL SATURATED AIRMASS IN THE WAKE OF LOW PRESSURE ALONG THE NC 
COAST WILL MAINTAIN IFR AND LIFR CONDITIONS ACROSS CENTRAL NC 
THROUGH TONIGHT AND FRI MORNING.  WIDESPREAD RAIN...WITH SOME 
FREEZING RAIN POSSIBLE AT KINT AND KGSO EARLY THIS AFTERNOON...WILL 
TAPER TO DRIZZLE EARLY THIS EVENING.  MORE AREAS OF RAIN WILL LIKELY 
CROSS CENTRAL NC IN THE PREDAWN HOURS FRI MORNING...ENDING SHORTLY 
AFTERNOON DAYBREAK.  CONDITIONS WILL GRADUALLY IMPROVE TO ABOVE IFR 
FRI AFTERNOON AS A SURGE OF DRIER AIR PUSHES IN FROM THE WEST.  


&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR 
NCZ007-008-021>025-038>040.

&&

$$

SHORT TERM...CBL
LONG TERM...RFG/MLM
AVIATION...RFG