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FXUS62 KRAH 270350 CCA
AFDRAH

AREA FORECAST DISCUSSION...CORRECTION.
NATIONAL WEATHER SERVICE RALEIGH NC
1015 PM EST SAT FEB 26 2005

.SYNOPSIS...

WEAK HIGH PRESSURE WAS CENTERED OVER NE NC AT 00Z/27. A REINFORCING 
SHOT OF DRIER AIR WAS PUSHING SOUTH THROUGH N VA DRIVEN BY A 1030 MB 
SURFACE HIGH OVER MICHIGAN. DEW POINTS IN THE TEENS OVER N VA 
COMPARED TO 30S FROM RICHMOND SOUTHWARD.
&&

SATELLITE INFORMATION... AT 00Z/27 FEB THE WATER VAPOR LOOP WAS 
INDICATING AN INCREASINGLY ACTIVE SUBTROPICAL JET EXTENDING FROM 
MEXICO NE ACROSS NW-N GULF AND OVER THE SOUTHEASTERN STATES. A 
CYCLONIC CIRCULATION WAS CENTERED OVER CENTRAL TEXAS MOVING NE. IR 
LOOP INDICATED CIRRUS THICKENING ACROSS GA-SC AND HEADING TOWARD SE 
NC.

THE FORECAST OVERNIGHT INTO SUNDAY MORNING IS FOR THE SURFACE HIGH 
OVER MI TO GRADUALLY BUILD DOWN INTO NC. MUCH OF THE DRIER AIR IS 
NOT EXPECTED TO PUSH INTO CENTRAL NC UNTIL DURING THE DAY SUNDAY. 
THUS, LIGHT WINDS AND MAINLY CLEAR SKIES (SCATTERED TO THIN BROKEN 
CIRRUS AT TIMES)... WILL LEAD TO READINGS BY DAYBREAK CLOSE TO THE 
CURRENT DEW POINTS IN THE UPPER 20S TO AROUND 30. NO CHANGES NEEDED 
TO THE SHORT TERM.

AS FOR THE IMPENDING STORM FOR SUNDAY NIGHT INTO MONDAY... THE 
12Z/18Z MODEL MAJORITY DEPICTS A "MILLER TYPE A" SURFACE LOW THAT 
MOVES FROM THE NORTHERN GULF COAST SUNDAY TO A POSITION NEAR 
CHARLESTON SC AROUND 06Z/29 MON. THE 18Z GFS WAS STRONGEST... 
DEVELOPING A COASTAL BOMB MONDAY...(992 MB CAPE LOOKOUT 12Z/28... TO 
987 OFF VA 18Z/28). THE NAM (OUTLIER ON THE LEFT SIDE OF ALL MODEL 
TRACKS (UP THE MOUNTAINS - PUTTING RDU IN THE SURFACE WARM 
SECTOR)... WAS DISCARDED... THE NAM H5 HEIGHTS WERE INITIALIZED MUCH 
TOO HIGH AT 12Z TODAY OVER TX AND NE MEXICO POSSIBLY CONTRIBUTING TO 
IT BEING AN OUTLIER SOLUTION. THUS... THE GFS CONTINUES TO TREND 
TOWARD THE MODEL MAJORITY (CANADIAN... ECMWF... UKMET) IN 
EMPHASIZING A STRONGER MILLER TYPE A COASTAL LOW... INCREASING THE 
THREAT OF SIGNIFICANT FROZEN PRECIPITATION OVER THE CLIMATOLOGICALLY 
PREFERRED PIEDMONT OF NC WITH THIS EVENT. 

WE DEFERRED UNTIL AFTER THE 00Z/27 RUNS ARE ALL IN BEFORE THE 
ISSUANCE OF A WINTER STORM WATCH NW... BUT IF THE MODEL TRENDS 
CONTINUE THIS AFOREMENTIONED SCENARIO FOCUSING DEVELOPMENT OF A 
PRIMARY COASTAL LOW TRACKING JUST OFFSHORE OF CHS TO CAPE LOOKOUT... 
THEN HEAVY WET SNOW OVER THE NW-N PIEDMONT WILL BE POSSIBLE. 

ONE MAJOR FACTOR FOR HEAVY SNOW MAY BE THE LACK OF SUPPLY OF LOW 
LEVEL COLD AIR... AS ALL MODELS INDICATE THE PARENT HIGH TO BE ON 
THE WEAK SIDE (1028 MB) AND TRANSIENT (MOVES OFFSHORE QUICKLY AS THE 
STORM APPROACHES). THUS... THE DYNAMICS OF THE SYSTEM WILL HAVE TO 
GENERATE COLD AIR... AND THE DEEPENING STORM WILL HAVE TO TAP INTO 
THE COLD AIR THAT WILL BE IN PLACE JUST TO OUR NORTH. THE 18Z GFS 
INDICATED THE H85 LOW TRACK OVER E SC AND SE NC... AND THE H7 TRACK 
FROM SE OF CLT TO NEAR OR JUST SE OF RALEIGH TO ROANOKE RAPIDS. THE 
H7 LOW BEGAN TO CLOSE OFF NEAR RDU AROUND 12Z MONDAY... INDICATING 
THE POTENTIAL FOR HEAVY SNOW BANDING NORTHWEST AND NORTH OF RDU. A 
DESTINCTIVE COLD NOSE DEVELOPS IN THE NW PIEDMONT JUST ABOVE SURFACE 
LEVEL... WITH SOME COOLING FORECAST IN THE MID LAYERS. THE MID LEVEL 
WARMING OCCURS OVER EASTERN NC. 

PARTIAL THICKNESSES FOR GSO ON THE 18Z/GFS INDICATED 1000/850 AND 
850/700 THICKNESSES (AROUND 1290 TO 1295/ 1540-1544)... BETWEEN 
06Z-15Z/28 SUPPORTING ACCUMULATING SNOW AND SLEET DURING THE HEART 
OF THE EVENT. PARTIALS INDICATED A NARROW TRANSITION ZONE FROM 
FROZEN TO LIQUID OVER THE E-S PIEDMONT... TO RAIN ELSEWHERE. QPF 
FORECASTS INDICATE 0.50 TO POTENTIALLY 1.25 INCHES (LIQUID 
EQUIVALENT) OVER CENTRAL NC. 

FOR NOW... THE MODEL MODEL MAJORITY / GFS TRACK AND STRENGTH ARE 
FAVORED. THUS, A WINTER STORM WATCH IS BEING CONSIDERED FOR THE 
PIEDMONT TRIAD REGION... AND AS FAR SOUTH AS ALBEMARLE... HIGH 
ROCK... ASHEBORO... BURLINGTON... AND ROXBORO FOR ACCUMULATING SNOW 
AND SLEET SUNDAY NIGHT INTO EARLY MONDAY. A COLD RAIN APPEARS LIKELY 
ELSEWHERE... WITH A NARROW TRANSITION ZONE SOMEWHERE OVER THE 
EASTERN PIEDMONT DURING THE EVENT. MUCH MORE TO COME....

&&

.PREVIOUS DISCUSSION...
(ISSUED 230 PM EST SAT FEB 26 2005) 

SUN NGT-MON...THE GFS/CANADIAN/UKMET/ECMWF ARE NOW CONVERGING MORE 
TOWARD A MAIN COASTAL LOW MILLER-A CYCLOGENESIS SOLUTION.  WE WILL 
BE LEANING TOWARD THE DETAILS OF THE GFS MOISTURE AND THERMAL 
STRUCTURE...NOTING THIS IS THE COLDEST RUN OF THE LAST THREE BUT IN 
LINE WITH UKMET/ECMWF BULK THICKNESS (1000-500). THIS SUGGESTS MIXED 
P-TYPES IN THE NW QUADRANT AND AT THE ONSET IN THE NORTHEAST PDMT. A 
STATEMENT WILL BE ISSUED CALLING FOR A 1-2 INCH POTENTIAL OF 
SNOW/SLEET MIX WITH RAIN IN THE NW PDMT...AN UP TO A HALF INCH 
BEFORE CHANGEOVER TO RAIN IN THE NE PDMT.  LOWS 33-35 IN THE NW 
THIRD GRADUATING UP TO 42 IN SAMPSON-WAYNE.  HEAVIEST PCPN SHOULD 
EBB AROUND 10 AM AS THE 850 LOW MOVES NORTH OF CAPE LOOKOUT AND THE 
EASTERLY LOW LEVEL JET TRANSLATES NORTH OF THE CWA.  A LOOSE 
PRESSURE TROUGH IN THE WAKE OF THE LOW SHOULD ALLOW LOW CLOUDS AND 
DRIZZLE OR SPRINKLES TO LINGER INTO LATE AFTERNOON HOLDING 
TEMPERATURES NEAR 40 NW TO NEAR 50 SE.

MON NGT-TUE...COLD DRY NW FLOW SETS IN WITH MOSTLY CLEAR SKIES AND 
BELOW NORMAL TEMPERATURES. 850 TEMPERATURES REMAIN MINUS 5-MINUS 10 
ON TUE.  LOWS 30-35. HIGHS MID-UPPER 40S.

LONG TERM (MONDAY NIGHT THROUGH SATURDAY)...
UPPER TROF REMAINS IN PLACE THROUGH WEDNESDAY AND CAA ACCOMPANYING 
THE SHORT WAVE ROTATING THROUGH TUESDAY NIGHT INTO WEDNESDAY SHOULD 
BE ENOUGH TO INDUCE CONSIDERABLE STRATOCUMULUS...ESPECIALLY ACROSS 
THE NORTHERN TIER. HIGHS WEDNESDAY 45 TO 50. SUNNY THURSDAY AS WEAK 
RIDGING BUILDS IN BRIEFLY FROM THE WEST...A BIT OF REBOUND ON THE 
AFTERNOON HIGHS TO 50 TO 55. 

WILL NOT BITE ON POPS THIS EARLY FOR THE POTENTIAL SYSTEM WHICH IS 
DIGGING SOUTHEAST ACROSS THE MOUNTAINS LATE FRIDAY AS TIMING THE 
UPPER IMPULSES IN NORTHWEST IS NOT A HIGH OR EVEN A MEDIUM 
CONFIDENCE EVENT AT THAT RANGE. FAIR AMOUNTS OF MID/HIGH CLOUDINESS 
DO LOOK TO BE IN THE STREAM FOR BOTH DAYS.

AVIATION...
CLEAR SKIES AND LIGHT TO CALM WINDS EARLY TONIGHT MAY LEAD TO BRIEF 
MVFR VISIBILITIES IN THE 11-13Z TIME FRAME. THINK THAT PROGRESSIVELY 
THICKENING HIGH CLOUDINESS OVERNIGHT SHOULD DELAY THE RADIATION 
PROCESS...HOWEVER...SO WILL FORECAST VFR THROUGH THE TAF PERIOD. 
INCREASING/THICKENING MID CLOUDINESS WILL BE ON TAP TOMORROW 
AFTERNOON...JUST BEYOND THE TAFS 18Z ENDING TIME. 

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS...
SHORT TERM...BADGETT/HARTFIELD/TDP








FXUS62 KRAH 270729
AFDRAH

AREA FORECAST DISCUSSION...PRELIMINARY.
NATIONAL WEATHER SERVICE RALEIGH NC
220 AM EST SUN FEB 27 2005

.SHORT TERM (TODAY THROUGH MONDAY)...

.SYNOPSIS...
WEAK HIGH PRESSURE WAS CENTERED OVER NC AT 06Z/27. A REINFORCING 
SHOT OF DRIER AIR WAS PUSHING SOUTH THROUGH VA DRIVEN BY A 1030 MB 
SURFACE HIGH OVER MICHIGAN. A DEVELOPING STORM SYSTEM WAS LOCATED 
OVER THE WESTERN GULF OF MEXICO. 
&&

.TODAY THROUGH MONDAY... 
THE REAL CONCERN BEGINS AROUND SUNSET TONIGHT AS THE MODEL MAJORITY/ 
GFS TRACK AND STRENGTH ARE STILL FAVORED AFTER THIS EVENINGS MODEL 
RUN... WITH THE DEVELOPING GULF OF MEXICO STORM. A WINTER STORM 
WATCH WILL BE ISSUED FOR THE PIEDMONT TRIAD REGION... NORTHEAST TO 
ROXBORO FOR ACCUMULATING SNOW TONIGHT INTO MONDAY MORNING. A COLD 
RAIN APPEARS LIKELY ELSEWHERE... WITH A NARROW TRANSITION ZONE 
SOMEWHERE OVER THE EASTERN PIEDMONT DURING THE EVENT. IT IS STRESSED 
THAT A STORM TRACK DEVIATION OF 50 MILES OR SO FARTHER EAST COULD 
BRING ACCUMULATING SNOW TO THE RALEIGH-DURHAM AREA. THIS IS STILL 
POSSIBLE GIVEN THE RECENT COLDER TRENDS IN THE MODEL RUNS. 

THE LATEST DATA ANALYSIS AND 00Z/27 FEBRUARY MODEL RUNS CONTINUE TO 
POINT TO A "MILLER A" TYPE SFC COASTAL CYCLOGENESIS TODAY THROUGH 
MONDAY FROM THE GULF OF MEXICO... NE ACROSS THE FL PANHANDLE... AND 
UP THE COAST OF SC/NC. THE 00Z/27 NAM TRACK CONTINUED TO BE ON THE 
LEFT SIDE OF ALL GUIDANCE... BUT CONTINUED TO TREND TOWARD THE MODEL 
MAJORITY OF A SIGNIFICANT COASTAL STORM. HPC CONTINUED TO SUPPORT 
THE GFS WITH THIS SYSTEM AS IT HAS BEEN THE MOST CONSISTENT RUN TO 
RUN IN THE PAST 24 HOURS. A LITTLE QUICKER ACCELERATION OF THE STORM 
IS ALSO PREFERRED AS TRENDED BY THE LAST SEVERAL GFS RUNS.  

WITH THE GFS BEING THE PREFERRED MODEL FOR THIS DEVELOPING STORM... 
THE FORECAST STORM TRACK STRONGLY SUGGESTS ACCUMULATING SNOW OVER 
PORTIONS OF THE NORTHWEST-NORTH PIEDMONT... ESPECIALLY OVER THE 
PIEDMONT TRIAD REGION EAST TO NEAR ROXBORO. THE FORECAST H85 AND H7 
LOW PRESSURE CENTER TRACKS FROM NEAR CHARLOTTE TO RALEIGH AND 
ROANOKE RAPIDS TONIGHT AND MONDAY MORNING... IMPLYING THE P-TYPE 
TRANSITION ZONE WILL BE IN THAT GENERAL AREA... WITH ACCUMULATING 
SNOW JUST WEST-NORTH OF THE TRACK. THE 00Z/28 GFS H7 LOW FORECAST 
TRACK WAS SLIGHTLY WEST OF THE PREVIOUS TRACK... BUT STILL 
INDICATING THE MID LEVEL WARM NOSE TO MAINLY RUN UP THE COASTAL 
PLAIN OR FAR EASTERN PIEDMONT... WITH A PIVOT POINT AROUND 
RALEIGH... IMPLYING A VERY TIGHT NARROW P-TYPE TRANSITION ZONE TO BE 
IN THAT GENERAL LOCATION. TO THE NW... THE COLD AIR IS DEEPER WITH 
THE LATEST GFS RUNS INDICATING A SIGNIFICANT LOW LEVEL COLD NOSE 
AROUND 925 MB EXTENDING FROM CENTRAL VIRGINIA S-SW TOWARD GSO/INT... 
WITH CORRESPONDING LOW LEVEL THICKNESSES FALLING TO BETWEEN 1288 AND 
1295 DURING THE 03Z-12Z MON TIME FRAME (DURING THE MAXIMUM QPF). 
CORRESPONDING MID LEVEL THICKNESSES AT GSO TO ROX DROP BELOW 1535. 

THE ONLY MISSING INGREDIENT FOR A CLASSICAL WINTER STORM IS THE LACK 
OF A STRONG PARENT SFC HIGH PRESSURE TO OUR N-NE. THERE IS A RATHER 
WEAK SURFACE HIGH (1028 MB) TODAY AND TONIGHT IN A FAVORED LOCATION 
TO DELIVER COLD DRY LOW LEVEL AIR... BUT THE HIGH IS FORECAST TO 
MOVE QUICKLY EAST TONIGHT AS THE PRECIP ROLLS IN. THUS... THIS IS 
NOT A CLASSICAL COLD AIR DAMMING SET UP. WE WILL HAVE TO RELY ON 
DYNAMICAL COOLING WITH THE STRENGTHENING MID LEVEL SYSTEM... AND THE 
TAPPING OF COLDER AIR OVER VIRGINIA INTO THE NC PIEDMONT REGION AS 
THE SFC STORM STRENGTHENS... AND MOVES UP THE SC/NC COAST TONIGHT 
... THIS SUPPORTS THE SIGNIFICANT SNOW IN THE CLIMATOLOGICALLY 
PREFERRED NW-N PIEDMONT REGIONS. 

PARTIAL THICKNESS NOMOGRAMS ALSO SUPPORT THE MEASURABLE AND 
SIGNIFICANT SNOW THEME NW-N WITH A NARROW TRANSITION ZONE TO RAIN 
MIXED WITH SNOW OVER THE EASTERN AND SOUTHERN PIEDMONT... WITH ALL 
RAIN EAST AND SOUTH OF RDU. IF THE H7 LOW CLOSES OFF BEFORE EXITING 
TO THE NE EARLY MONDAY MORNING... THERE SHOULD BE HEAVY SNOW JUST NW 
OF ITS TRACK. LOOKING BACK INTO THE DOCUMENTED CASE STUDIES OF 
PREVIOUS WINTER WEATHER EVENTS (KEETER FILES)... THE CURRENT 
FORECAST PARTIAL THICKNESSES SUPPORT MEASURABLE SNOWFALL AT GSO. RDU 
HAS HAD MOSTLY RAIN EVENTS... SOME MIXED WITH MEASURABLE SNOW... 
GIVEN SIMILAR PARTIALS. 

QPF SHOULD AVERAGE AT LEAST 0.50 TO 1.00 INCHES WITH THIS EVENT... 
GIVEN THE FORECAST STRENGTH AND TRACK. MOST SHOULD OCCUR BETWEEN 
02Z-15Z TONIGHT AND MONDAY. SNOWFALL ACCUMULATIONS SHOULD REACH 3-6 
INCHES IN THE WATCH AREA... POSSIBLY AS HIGH AS 8 INCHES IN LOCAL 
AREAS. 

THE GROUND TEMPS HAVE COOLED IN RECENT DAYS DUE TO THE RECENT 
SOAKING RAIN EVENT... AND THE COLDER NIGHTS IN THE 20S. THE SOIL 
TEMPS WERE STILL IN THE LOWER 40S OVER THE NW PIEDMONT... INDICATING 
THAT SNOW ACCUMULATIONS WOULD MELT SOME FROM BELOW. ROAD TEMPS ARE 
ALSO LIKELY TO BE ABOVE 32 UNTIL WELL AFTER THE PRECIP BEGINS... 
INDICATING WET ROADS BECOMING SLUSHY AS THE SNOW EVENT UNFOLDS.  

FOR NOW... A WINTER STORM WATCH WILL BE ISSUED FOR 3-6 INCHES OF 
SNOW ACCUMULATION TONIGHT THROUGH 15Z/MONDAY FOR FORSYTH... 
GUILFORD... DAVIDSON... RANDOLPH... ALAMANCE... ORANGE... AND PERSON 
COUNTIES... (THE CLIMATOLOGICALLY PREFERRED AREA WITH THIS STORM 
TRACK). PRECIP MAY BEGIN AS LIGHT RAIN... BUT QUICKLY CHANGE TO WET 
SNOW AS THE STRONG DYNAMICAL COOLING DEVELOPS. A ONE-TWO COUNTY 
TRANSITION BUFFER ZONE WILL COVER AREAS JUST EAST AND SOUTH OF THESE 
COUNTIES INCLUDING AREAS FROM ALBEMARLE TO SANFORD... RALEIGH... AND 
ROANOKE RAPIDS... WHERE RAIN WILL LIKELY OCCASIONALLY MIX WITH 
SNOW... SOME ACCUMULATION WILL BE POSSIBLE AND A WINTER WEATHER 
ADVISORY MAY BE NEEDED TONIGHT. RAIN IS EXPECTED EAST AND SOUTH OF 
RALEIGH. THE RAIN MAY CHANGE TO SNOW BEFORE THE STEADY PRECIP TAPERS 
OFF FROM SW TO NE MONDAY MORNING... FOLLOWED BY COLD WINDY WEATHER 
MONDAY NIGHT AND TUESDAY. 

IT SHOULD BE STRESSED THAT IF THE FORECAST STORM TRACK DEVIATES ONLY 
25 TO 50 MILES IN EITHER DIRECTION... IT WILL HAVE HUGE IMPLICATIONS 
ON THE LOCATION OF THE P-TYPE TRANSITION ZONE SET UP AND SNOW 
ACCUMULATIONS. A TRACK FARTHER EAST WILL LIKELY BRING SIGNIFICANT 
SNOW TO RALEIGH-DURHAM... AND A TRACK MORE LIKE THE NAM WILL LIMIT 
SNOW TO THE BLUE RIDGE MOUNTAINS ONLY.  

STAY TUNED ON THIS ONE AS IT HAS THE POTENTIAL TO BRING A MAJOR WET 
SNOW EVENT OVER MUCH OF THE W-N PIEDMONT... WHICH MAY EXTEND FURTHER 
SOUTH AND EAST THAN WHAT IS CURRENTLY FORECAST. 
&&

.LONG TERM (MONDAY NIGHT THROUGH SATURDAY)...

MID LEVEL LOW CLOSES OFF OVER THE MIDWEST EARLY IN THE PERIOD AS 
DEEP COLD AIR FILTERS INTO THE STATE. VORT AXIS SWINGS THROUGH BY 
TUE MORNING & WITH LOW LEVEL FLOW REMAINING STRONG FROM THE WSW... 
THIS ENERGY MAY BE ENOUGH TO SQUEEZE OUT A SPRINKLE OR SNOW 
SHOWER... IF THE LIFT CAN SATURATE THE PRIME DEDRITE GROWTH REGION 
ALOFT. THE CLOSED VORTEX MOVES TOWARD NEW ENGLAND WHEN A SECOND 
STRONG VORT MAX DROPS INTO THE TROUGH BASE... THROUGH NC... ON WED. 
AGAIN MOISTURE WILL BE LIMITED... THUS WILL KEEP CONDITIONS DRY... 
BUT IT REMAINS QUITE CHILLY WITH LOW LEVEL THICKNESSES PROGGED BY 
THE NAM & GFS TO BE IN THE 1260S-1270S ALL DAY WED. EXPECT A DRY 
NORTHWEST LOW LEVEL FLOW THEN THU-SAT AS THE LOW ALOFT MOVES INTO 
THE CANADIAN MARITIMES & THE HIGH PRESSURE AREA BUILDING INTO NC 
FROM THE WNW MODERATES SOMEWHAT. 
&&

.AVIATION...

TERMINAL FORECASTS DEPICT A THICKENING AND LOWERING OF THE HIGH AND 
MID CLOUDS TONIGHT INTO SUN MORNING. HAVE BROUGHT CIGS DOWN TO MVFR 
BY 18Z (SOUTH) TO 21Z (NORTH) AND SPED UP PRECIP ONSET TO 21Z-00Z 
SOUTH TO NORTH... AS CIGS/VSBYS GO IFR.
&&

.RAH WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FOR NCZ007-
021>024-038-039 FROM 6 PM SUNDAY TO 10AM MONDAY. 
&&

$$

SHORT TERM...BADGETT/GIH/RHJ/RLH
LONG TERM...HARTFIELD
AVIATION...HARTFIELD/RLH








FXUS62 KRAH 270818 AAA
AFDRAH

AREA FORECAST DISCUSSION...FINAL.
NATIONAL WEATHER SERVICE RALEIGH NC
319 AM EST SUN FEB 27 2005

.SHORT TERM (TODAY THROUGH MONDAY)...

.SYNOPSIS...
WEAK HIGH PRESSURE WAS CENTERED OVER NC AT 06Z/27. A REINFORCING 
SHOT OF DRIER AIR WAS PUSHING SOUTH THROUGH VA DRIVEN BY A 1030 MB 
SURFACE HIGH OVER MICHIGAN. A DEVELOPING SFC STORM SYSTEM WAS 
LOCATED OVER THE CENTRAL GULF OF MEXICO. 
&&

.TODAY THROUGH MONDAY... THE WATER VAPOR LOOP/UPPER AIR ANALYSIS 
INDICATE A STRONG SOUTHERN BRANCH JET OVER NRN MEXICO/S TX EXTENDING 
ACROSS NC. A MID LEVEL VORTEX WAS OVER THE RED RIVER. A POLAR VORTEX 
WAS DIGGING SOUTH INTO ND FROM CANADA. THE CURRENT INDICATIONS ARE 
THAT THE SOUTHERN BRANCH SYSTEM OVER THE RED RIVER WILL RACE EAST 
AHEAD OF THE DIGGING POLAR VORTEX... FAVORING THE LATEST 
GFS/ECMWF/UKMET FOR THE SE COASTAL STORM. TODAY... EXPECT LOWERING 
AND THICKENING CLOUDS WITH TEMPS IN THE LOWER TO MID 40S. 

THE REAL CONCERN BEGINS AROUND SUNSET TONIGHT AS THE MODEL MAJORITY/ 
GFS TRACK AND STRENGTH ARE STILL FAVORED AFTER THIS EVENINGS MODEL 
RUN... WITH THE DEVELOPING GULF OF MEXICO STORM. A WINTER STORM 
WATCH WILL BE ISSUED FOR THE PIEDMONT TRIAD REGION... NORTHEAST TO 
ROXBORO FOR ACCUMULATING SNOW TONIGHT INTO MONDAY MORNING. A COLD 
RAIN APPEARS LIKELY ELSEWHERE... WITH A NARROW TRANSITION ZONE 
SOMEWHERE OVER THE EASTERN PIEDMONT DURING THE EVENT. IT IS STRESSED 
THAT A STORM TRACK DEVIATION OF 50 MILES OR SO FARTHER EAST COULD 
BRING ACCUMULATING SNOW TO THE RALEIGH-DURHAM AREA. THIS IS STILL 
POSSIBLE GIVEN THE RECENT COLDER TRENDS IN THE MODEL RUNS. 

THE LATEST DATA ANALYSIS AND 00Z/27 FEBRUARY MODEL RUNS CONTINUE TO 
POINT TO A "MILLER A" TYPE SFC COASTAL CYCLOGENESIS TODAY THROUGH 
MONDAY FROM THE GULF OF MEXICO... NE ACROSS THE FL PANHANDLE... AND 
UP THE COAST OF SC/NC. THE 00Z/27 NAM TRACK CONTINUED TO BE ON THE 
LEFT SIDE OF ALL GUIDANCE... BUT CONTINUED TO TREND TOWARD THE MODEL 
MAJORITY OF A SIGNIFICANT COASTAL STORM. HPC CONTINUED TO SUPPORT 
THE GFS WITH THIS SYSTEM AS IT HAS BEEN THE MOST CONSISTENT RUN TO 
RUN IN THE PAST 24 HOURS. A LITTLE QUICKER ACCELERATION OF THE STORM 
IS ALSO PREFERRED AS TRENDED BY THE LAST SEVERAL GFS RUNS.  

WITH THE GFS BEING THE PREFERRED MODEL FOR THIS DEVELOPING STORM... 
THE FORECAST STORM TRACK STRONGLY SUGGESTS ACCUMULATING SNOW OVER 
PORTIONS OF THE NORTHWEST-NORTH PIEDMONT... ESPECIALLY OVER THE 
PIEDMONT TRIAD REGION EAST TO NEAR ROXBORO. THE FORECAST H85 AND H7 
LOW PRESSURE CENTER TRACKS FROM NEAR CHARLOTTE TO RALEIGH AND 
ROANOKE RAPIDS TONIGHT AND MONDAY MORNING... IMPLYING THE P-TYPE 
TRANSITION ZONE WILL BE IN THAT GENERAL AREA... WITH ACCUMULATING 
SNOW JUST WEST-NORTH OF THE TRACK. THE 00Z/28 GFS H7 LOW FORECAST 
TRACK WAS SLIGHTLY WEST OF THE PREVIOUS TRACK... BUT STILL 
INDICATING THE MID LEVEL WARM NOSE TO MAINLY RUN UP THE COASTAL 
PLAIN OR FAR EASTERN PIEDMONT... WITH A PIVOT POINT AROUND 
RALEIGH... IMPLYING A VERY TIGHT NARROW P-TYPE TRANSITION ZONE TO BE 
IN THAT GENERAL LOCATION. TO THE NW... THE COLD AIR IS DEEPER WITH 
THE LATEST GFS RUNS INDICATING A SIGNIFICANT LOW LEVEL COLD NOSE 
AROUND 925 MB EXTENDING FROM CENTRAL VIRGINIA S-SW TOWARD GSO/INT... 
WITH CORRESPONDING LOW LEVEL THICKNESSES FALLING TO BETWEEN 1288 AND 
1295 DURING THE 03Z-12Z MON TIME FRAME (DURING THE MAXIMUM QPF). 
CORRESPONDING MID LEVEL THICKNESSES AT GSO TO ROX DROP BELOW 1535. 

THE ONLY MISSING INGREDIENT FOR A CLASSICAL WINTER STORM IS THE LACK 
OF A STRONG PARENT SFC HIGH PRESSURE TO OUR N-NE. THERE IS A RATHER 
WEAK SURFACE HIGH (1028 MB) TODAY AND TONIGHT IN A FAVORED LOCATION 
TO DELIVER COLD DRY LOW LEVEL AIR... BUT THE HIGH IS FORECAST TO 
MOVE QUICKLY EAST TONIGHT AS THE PRECIP ROLLS IN. THUS... THIS IS 
NOT A CLASSICAL COLD AIR DAMMING SET UP. WE WILL HAVE TO RELY ON 
DYNAMICAL COOLING WITH THE STRENGTHENING MID LEVEL SYSTEM... AND THE 
TAPPING OF COLDER AIR OVER VIRGINIA INTO THE NC PIEDMONT REGION AS 
THE SFC STORM STRENGTHENS... AND MOVES UP THE SC/NC COAST TONIGHT 
... THIS SUPPORTS THE SIGNIFICANT SNOW IN THE CLIMATOLOGICALLY 
PREFERRED NW-N PIEDMONT REGIONS. 

PARTIAL THICKNESS NOMOGRAMS ALSO SUPPORT THE MEASURABLE AND 
SIGNIFICANT SNOW THEME NW-N WITH A NARROW TRANSITION ZONE TO RAIN 
MIXED WITH SNOW OVER THE EASTERN AND SOUTHERN PIEDMONT... WITH ALL 
RAIN EAST AND SOUTH OF RDU. IF THE H7 LOW CLOSES OFF BEFORE EXITING 
TO THE NE EARLY MONDAY MORNING... THERE SHOULD BE HEAVY SNOW JUST NW 
OF ITS TRACK. LOOKING BACK INTO THE DOCUMENTED CASE STUDIES OF 
PREVIOUS WINTER WEATHER EVENTS (KEETER FILES)... THE CURRENT 
FORECAST PARTIAL THICKNESSES SUPPORT MEASURABLE SNOWFALL AT GSO. RDU 
HAS HAD MOSTLY RAIN EVENTS... SOME MIXED WITH MEASURABLE SNOW... 
GIVEN SIMILAR PARTIALS. 

QPF SHOULD AVERAGE AT LEAST 0.50 TO 1.00 INCHES WITH THIS EVENT... 
GIVEN THE FORECAST STRENGTH AND TRACK. MOST SHOULD OCCUR BETWEEN 
02Z-15Z TONIGHT AND MONDAY. SNOWFALL ACCUMULATIONS SHOULD REACH 3-6 
INCHES IN THE WATCH AREA... POSSIBLY AS HIGH AS 8 INCHES IN LOCAL 
AREAS. 

THE GROUND TEMPS HAVE COOLED IN RECENT DAYS DUE TO THE RECENT 
SOAKING RAIN EVENT... AND THE COLDER NIGHTS IN THE 20S. THE SOIL 
TEMPS WERE STILL IN THE LOWER 40S OVER THE NW PIEDMONT... INDICATING 
THAT SNOW ACCUMULATIONS WOULD MELT SOME FROM BELOW. ROAD TEMPS ARE 
ALSO LIKELY TO BE ABOVE 32 UNTIL WELL AFTER THE PRECIP BEGINS... 
INDICATING WET ROADS BECOMING SLUSHY AS THE SNOW EVENT UNFOLDS.  

FOR NOW... A WINTER STORM WATCH WILL BE ISSUED FOR 3-6 INCHES OF 
SNOW ACCUMULATION TONIGHT THROUGH 15Z/MONDAY FOR FORSYTH... 
GUILFORD... DAVIDSON... RANDOLPH... ALAMANCE... ORANGE... AND PERSON 
COUNTIES... (THE CLIMATOLOGICALLY PREFERRED AREA WITH THIS STORM 
TRACK). PRECIP MAY BEGIN AS LIGHT RAIN... BUT QUICKLY CHANGE TO WET 
SNOW AS THE STRONG DYNAMICAL COOLING DEVELOPS. A ONE-TWO COUNTY 
TRANSITION BUFFER ZONE WILL COVER AREAS JUST EAST AND SOUTH OF THESE 
COUNTIES INCLUDING AREAS FROM ALBEMARLE TO SANFORD... RALEIGH... AND 
ROANOKE RAPIDS... WHERE RAIN WILL LIKELY OCCASIONALLY MIX WITH 
SNOW... SOME ACCUMULATION WILL BE POSSIBLE AND A WINTER WEATHER 
ADVISORY MAY BE NEEDED TONIGHT. RAIN IS EXPECTED EAST AND SOUTH OF 
RALEIGH. THE RAIN MAY CHANGE TO SNOW BEFORE THE STEADY PRECIP TAPERS 
OFF FROM SW TO NE MONDAY MORNING... FOLLOWED BY COLD WINDY WEATHER 
MONDAY NIGHT AND TUESDAY. 

IT SHOULD BE STRESSED THAT IF THE FORECAST STORM TRACK DEVIATES ONLY 
25 TO 50 MILES IN EITHER DIRECTION... IT WILL HAVE HUGE IMPLICATIONS 
ON THE LOCATION OF THE P-TYPE TRANSITION ZONE SET UP AND SNOW 
ACCUMULATIONS. A TRACK FARTHER EAST WILL LIKELY BRING SIGNIFICANT 
SNOW TO RALEIGH-DURHAM... AND A TRACK MORE LIKE THE NAM WILL LIMIT 
SNOW TO THE BLUE RIDGE MOUNTAINS ONLY.  

STAY TUNED ON THIS ONE AS IT HAS THE POTENTIAL TO BRING A MAJOR WET 
SNOW EVENT OVER MUCH OF THE W-N PIEDMONT... WHICH MAY EXTEND FURTHER 
SOUTH AND EAST THAN WHAT IS CURRENTLY FORECAST. 
&&

.LONG TERM (MONDAY NIGHT THROUGH SATURDAY)...

MID LEVEL LOW CLOSES OFF OVER THE MIDWEST EARLY IN THE PERIOD AS 
DEEP COLD AIR FILTERS INTO THE STATE. VORT AXIS SWINGS THROUGH BY 
TUE MORNING & WITH LOW LEVEL FLOW REMAINING STRONG FROM THE WSW... 
THIS ENERGY MAY BE ENOUGH TO SQUEEZE OUT A SPRINKLE OR SNOW 
SHOWER... IF THE LIFT CAN SATURATE THE PRIME DEDRITE GROWTH REGION 
ALOFT. THE CLOSED VORTEX MOVES TOWARD NEW ENGLAND WHEN A SECOND 
STRONG VORT MAX DROPS INTO THE TROUGH BASE... THROUGH NC... ON WED. 
AGAIN MOISTURE WILL BE LIMITED... THUS WILL KEEP CONDITIONS DRY... 
BUT IT REMAINS QUITE CHILLY WITH LOW LEVEL THICKNESSES PROGGED BY 
THE NAM & GFS TO BE IN THE 1260S-1270S ALL DAY WED. EXPECT A DRY 
NORTHWEST LOW LEVEL FLOW THEN THU-SAT AS THE LOW ALOFT MOVES INTO 
THE CANADIAN MARITIMES & THE HIGH PRESSURE AREA BUILDING INTO NC 
FROM THE WNW MODERATES SOMEWHAT. 
&&

.AVIATION...

TERMINAL FORECASTS DEPICT A THICKENING AND LOWERING OF THE HIGH AND 
MID CLOUDS TONIGHT INTO SUN MORNING. HAVE BROUGHT CIGS DOWN TO MVFR 
BY 18Z (SOUTH) TO 21Z (NORTH) AND SPED UP PRECIP ONSET TO 21Z-00Z 
SOUTH TO NORTH... AS CIGS/VSBYS GO IFR.
&&

.RAH WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FOR NCZ007-
021>024-038-039 FROM 6 PM SUNDAY TO 10AM MONDAY. 
&&

$$

SHORT TERM...BADGETT/GIH/RHJ/RLH
LONG TERM...HARTFIELD
AVIATION...HARTFIELD/RLH










FXUS62 KRAH 271544 AAA
AFDRAH

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE RALEIGH NC
1045 AM EST SUN FEB 27 2005

.SHORT TERM (REST OF TODAY THROUGH MONDAY)...
INCREASED SKY COVERAGE TO OVERCAST DUE TO CIRRUS CANOPY CURRENTLY 
OVERHEAD AND GRADUALLY INCREASE IN MID LAYER DECK FROM THE SOUTH 
THIS AFTERNOON. 15Z TEMPS CURRENTLY 4-6 DEGREES FROM FORECAST MAX 
TEMPS...SO LITTLE CHANGE REQUIRED IN THAT DEPARTMENT.

FOR TONIGHT AND MONDAY....WHILE STILL AWAITING THE 12Z GFS...CALLED 
AROUND REGION TO GET A FEEL FOR SOIL AND ROAD TEMPS.  IN NW 
PIEDMONT SOIL TEMPS  AROUND 40 TOT HE LOWER 40S WHILE ROAD SURFACE 
TEMPS IN THE MID 40S.  FARTHER E AND S....SOIL TEMPS WARM TO THE MID 
40S WHILE ROAD SURFACE TEMPS ARE IN THE UPPER 40S TO LOWER 50S. THUS 
APPEARS THAT THERE IS THE POTENTIAL FOR SNOW TO STICK/ACCUMULATE ON 
GROUND AND ROAD SURFACE IN THE NW PIEDMONT...ESPECIALLY IF HEAVY 
BANDS OF PRECIP OCCUR WHICH IS HIGHLY PROBABLE DUE TO CLOSED H7 
CYCLONE JUST SE OF AREA OVERNIGHT/EARLY MON. ROADS OVER THE 
REMAINDER OF THE PIEDMONT MAY INITIALLY BE WET WITH SLUSH DEVELOPING 
IN AREAS THAT EXPERIENCE HEAVY BANDS. 

AT THIS TIME PLAN WILL LET WATCH RIDE AS IS FOR NOW. PRESENT 
THINKING IS TO UPGRADE WATCH TO A WARNING SOME TIME EARLY THIS 
AFTERNOON (ONCE 12Z GFS IS IN AND HOPEFULLY CONSISTENT WITH PREVIOUS 
RUNS)...HOPEFULLY BEFORE 3 PM. BASED ON STORM TRACK AND PARTIAL 
THICKNESSES...MAY NEED TO EXTEND WATCH/WARNING A LITTLE FARTHER 
SOUTH AND EAST.  WILL NEED TO COORDINATE THIS WITH WFO NEIGHBORS W 
AND N OF RAH. IF CURRENT PATTERN AND STRONG DYNAMICS AND PLENTIFUL 
MOISTURE CONTINUE...POTENTIAL FOR HEAVY SNOW (EXCESS OF 6 
INCHES)OVER NW PIEDMONT APPEARS LIKELY.

FINAL NOTE...THE MAIN CONCERN/FLY IN THE OINTMENT ITO THE ABOVE 
SCENARIO IS THE LACK OF A COLD AIR SOURCE. POTENTIAL FOR LOW/MID 
LEVEL FLOW TO PUMP ENOUGH WARM AIR INTO THE NW PIEDMONT TO KEEP 
P-TYPE A SNOW/RAIN MIX...CUTTING DOWN ON SNOW ACCUMULATION TOTALS.

&&

.PREVIOUS DISCUSSION...
(ISSUED 319 AM EST SUN FEB 27 2005) 

SHORT TERM (TODAY THROUGH MONDAY)...

SYNOPSIS...
WEAK HIGH PRESSURE WAS CENTERED OVER NC AT 06Z/27. A REINFORCING 
SHOT OF DRIER AIR WAS PUSHING SOUTH THROUGH VA DRIVEN BY A 1030 MB 
SURFACE HIGH OVER MICHIGAN. A DEVELOPING SFC STORM SYSTEM WAS 
LOCATED OVER THE CENTRAL GULF OF MEXICO. 

TODAY THROUGH MONDAY... THE WATER VAPOR LOOP/UPPER AIR ANALYSIS 
INDICATE A STRONG SOUTHERN BRANCH JET OVER NRN MEXICO/S TX EXTENDING 
ACROSS NC. A MID LEVEL VORTEX WAS OVER THE RED RIVER. A POLAR VORTEX 
WAS DIGGING SOUTH INTO ND FROM CANADA. THE CURRENT INDICATIONS ARE 
THAT THE SOUTHERN BRANCH SYSTEM OVER THE RED RIVER WILL RACE EAST 
AHEAD OF THE DIGGING POLAR VORTEX... FAVORING THE LATEST 
GFS/ECMWF/UKMET FOR THE SE COASTAL STORM. TODAY... EXPECT LOWERING 
AND THICKENING CLOUDS WITH TEMPS IN THE LOWER TO MID 40S. 

THE REAL CONCERN BEGINS AROUND SUNSET TONIGHT AS THE MODEL MAJORITY/ 
GFS TRACK AND STRENGTH ARE STILL FAVORED AFTER THIS EVENINGS MODEL 
RUN... WITH THE DEVELOPING GULF OF MEXICO STORM. A WINTER STORM 
WATCH WILL BE ISSUED FOR THE PIEDMONT TRIAD REGION... NORTHEAST TO 
ROXBORO FOR ACCUMULATING SNOW TONIGHT INTO MONDAY MORNING. A COLD 
RAIN APPEARS LIKELY ELSEWHERE... WITH A NARROW TRANSITION ZONE 
SOMEWHERE OVER THE EASTERN PIEDMONT DURING THE EVENT. IT IS STRESSED 
THAT A STORM TRACK DEVIATION OF 50 MILES OR SO FARTHER EAST COULD 
BRING ACCUMULATING SNOW TO THE RALEIGH-DURHAM AREA. THIS IS STILL 
POSSIBLE GIVEN THE RECENT COLDER TRENDS IN THE MODEL RUNS. 

THE LATEST DATA ANALYSIS AND 00Z/27 FEBRUARY MODEL RUNS CONTINUE TO 
POINT TO A "MILLER A" TYPE SFC COASTAL CYCLOGENESIS TODAY THROUGH 
MONDAY FROM THE GULF OF MEXICO... NE ACROSS THE FL PANHANDLE... AND 
UP THE COAST OF SC/NC. THE 00Z/27 NAM TRACK CONTINUED TO BE ON THE 
LEFT SIDE OF ALL GUIDANCE... BUT CONTINUED TO TREND TOWARD THE MODEL 
MAJORITY OF A SIGNIFICANT COASTAL STORM. HPC CONTINUED TO SUPPORT 
THE GFS WITH THIS SYSTEM AS IT HAS BEEN THE MOST CONSISTENT RUN TO 
RUN IN THE PAST 24 HOURS. A LITTLE QUICKER ACCELERATION OF THE STORM 
IS ALSO PREFERRED AS TRENDED BY THE LAST SEVERAL GFS RUNS.  

WITH THE GFS BEING THE PREFERRED MODEL FOR THIS DEVELOPING STORM... 
THE FORECAST STORM TRACK STRONGLY SUGGESTS ACCUMULATING SNOW OVER 
PORTIONS OF THE NORTHWEST-NORTH PIEDMONT... ESPECIALLY OVER THE 
PIEDMONT TRIAD REGION EAST TO NEAR ROXBORO. THE FORECAST H85 AND H7 
LOW PRESSURE CENTER TRACKS FROM NEAR CHARLOTTE TO RALEIGH AND 
ROANOKE RAPIDS TONIGHT AND MONDAY MORNING... IMPLYING THE P-TYPE 
TRANSITION ZONE WILL BE IN THAT GENERAL AREA... WITH ACCUMULATING 
SNOW JUST WEST-NORTH OF THE TRACK. THE 00Z/28 GFS H7 LOW FORECAST 
TRACK WAS SLIGHTLY WEST OF THE PREVIOUS TRACK... BUT STILL 
INDICATING THE MID LEVEL WARM NOSE TO MAINLY RUN UP THE COASTAL 
PLAIN OR FAR EASTERN PIEDMONT... WITH A PIVOT POINT AROUND 
RALEIGH... IMPLYING A VERY TIGHT NARROW P-TYPE TRANSITION ZONE TO BE 
IN THAT GENERAL LOCATION. TO THE NW... THE COLD AIR IS DEEPER WITH 
THE LATEST GFS RUNS INDICATING A SIGNIFICANT LOW LEVEL COLD NOSE 
AROUND 925 MB EXTENDING FROM CENTRAL VIRGINIA S-SW TOWARD GSO/INT... 
WITH CORRESPONDING LOW LEVEL THICKNESSES FALLING TO BETWEEN 1288 AND 
1295 DURING THE 03Z-12Z MON TIME FRAME (DURING THE MAXIMUM QPF). 
CORRESPONDING MID LEVEL THICKNESSES AT GSO TO ROX DROP BELOW 1535. 

THE ONLY MISSING INGREDIENT FOR A CLASSICAL WINTER STORM IS THE LACK 
OF A STRONG PARENT SFC HIGH PRESSURE TO OUR N-NE. THERE IS A RATHER 
WEAK SURFACE HIGH (1028 MB) TODAY AND TONIGHT IN A FAVORED LOCATION 
TO DELIVER COLD DRY LOW LEVEL AIR... BUT THE HIGH IS FORECAST TO 
MOVE QUICKLY EAST TONIGHT AS THE PRECIP ROLLS IN. THUS... THIS IS 
NOT A CLASSICAL COLD AIR DAMMING SET UP. WE WILL HAVE TO RELY ON 
DYNAMICAL COOLING WITH THE STRENGTHENING MID LEVEL SYSTEM... AND THE 
TAPPING OF COLDER AIR OVER VIRGINIA INTO THE NC PIEDMONT REGION AS 
THE SFC STORM STRENGTHENS... AND MOVES UP THE SC/NC COAST TONIGHT 
.. THIS SUPPORTS THE SIGNIFICANT SNOW IN THE CLIMATOLOGICALLY 
PREFERRED NW-N PIEDMONT REGIONS. 

PARTIAL THICKNESS NOMOGRAMS ALSO SUPPORT THE MEASURABLE AND 
SIGNIFICANT SNOW THEME NW-N WITH A NARROW TRANSITION ZONE TO RAIN 
MIXED WITH SNOW OVER THE EASTERN AND SOUTHERN PIEDMONT... WITH ALL 
RAIN EAST AND SOUTH OF RDU. IF THE H7 LOW CLOSES OFF BEFORE EXITING 
TO THE NE EARLY MONDAY MORNING... THERE SHOULD BE HEAVY SNOW JUST NW 
OF ITS TRACK. LOOKING BACK INTO THE DOCUMENTED CASE STUDIES OF 
PREVIOUS WINTER WEATHER EVENTS (KEETER FILES)... THE CURRENT 
FORECAST PARTIAL THICKNESSES SUPPORT MEASURABLE SNOWFALL AT GSO. RDU 
HAS HAD MOSTLY RAIN EVENTS... SOME MIXED WITH MEASURABLE SNOW... 
GIVEN SIMILAR PARTIALS. 

QPF SHOULD AVERAGE AT LEAST 0.50 TO 1.00 INCHES WITH THIS EVENT... 
GIVEN THE FORECAST STRENGTH AND TRACK. MOST SHOULD OCCUR BETWEEN 
02Z-15Z TONIGHT AND MONDAY. SNOWFALL ACCUMULATIONS SHOULD REACH 3-6 
INCHES IN THE WATCH AREA... POSSIBLY AS HIGH AS 8 INCHES IN LOCAL 
AREAS. 

THE GROUND TEMPS HAVE COOLED IN RECENT DAYS DUE TO THE RECENT 
SOAKING RAIN EVENT... AND THE COLDER NIGHTS IN THE 20S. THE SOIL 
TEMPS WERE STILL IN THE LOWER 40S OVER THE NW PIEDMONT... INDICATING 
THAT SNOW ACCUMULATIONS WOULD MELT SOME FROM BELOW. ROAD TEMPS ARE 
ALSO LIKELY TO BE ABOVE 32 UNTIL WELL AFTER THE PRECIP BEGINS... 
INDICATING WET ROADS BECOMING SLUSHY AS THE SNOW EVENT UNFOLDS.  

FOR NOW... A WINTER STORM WATCH WILL BE ISSUED FOR 3-6 INCHES OF 
SNOW ACCUMULATION TONIGHT THROUGH 15Z/MONDAY FOR FORSYTH... 
GUILFORD... DAVIDSON... RANDOLPH... ALAMANCE... ORANGE... AND PERSON 
COUNTIES... (THE CLIMATOLOGICALLY PREFERRED AREA WITH THIS STORM 
TRACK). PRECIP MAY BEGIN AS LIGHT RAIN... BUT QUICKLY CHANGE TO WET 
SNOW AS THE STRONG DYNAMICAL COOLING DEVELOPS. A ONE-TWO COUNTY 
TRANSITION BUFFER ZONE WILL COVER AREAS JUST EAST AND SOUTH OF THESE 
COUNTIES INCLUDING AREAS FROM ALBEMARLE TO SANFORD... RALEIGH... AND 
ROANOKE RAPIDS... WHERE RAIN WILL LIKELY OCCASIONALLY MIX WITH 
SNOW... SOME ACCUMULATION WILL BE POSSIBLE AND A WINTER WEATHER 
ADVISORY MAY BE NEEDED TONIGHT. RAIN IS EXPECTED EAST AND SOUTH OF 
RALEIGH. THE RAIN MAY CHANGE TO SNOW BEFORE THE STEADY PRECIP TAPERS 
OFF FROM SW TO NE MONDAY MORNING... FOLLOWED BY COLD WINDY WEATHER 
MONDAY NIGHT AND TUESDAY. 

IT SHOULD BE STRESSED THAT IF THE FORECAST STORM TRACK DEVIATES ONLY 
25 TO 50 MILES IN EITHER DIRECTION... IT WILL HAVE HUGE IMPLICATIONS 
ON THE LOCATION OF THE P-TYPE TRANSITION ZONE SET UP AND SNOW 
ACCUMULATIONS. A TRACK FARTHER EAST WILL LIKELY BRING SIGNIFICANT 
SNOW TO RALEIGH-DURHAM... AND A TRACK MORE LIKE THE NAM WILL LIMIT 
SNOW TO THE BLUE RIDGE MOUNTAINS ONLY.  

STAY TUNED ON THIS ONE AS IT HAS THE POTENTIAL TO BRING A MAJOR WET 
SNOW EVENT OVER MUCH OF THE W-N PIEDMONT... WHICH MAY EXTEND FURTHER 
SOUTH AND EAST THAN WHAT IS CURRENTLY FORECAST. 

LONG TERM (MONDAY NIGHT THROUGH SATURDAY)...

MID LEVEL LOW CLOSES OFF OVER THE MIDWEST EARLY IN THE PERIOD AS 
DEEP COLD AIR FILTERS INTO THE STATE. VORT AXIS SWINGS THROUGH BY 
TUE MORNING & WITH LOW LEVEL FLOW REMAINING STRONG FROM THE WSW... 
THIS ENERGY MAY BE ENOUGH TO SQUEEZE OUT A SPRINKLE OR SNOW 
SHOWER... IF THE LIFT CAN SATURATE THE PRIME DEDRITE GROWTH REGION 
ALOFT. THE CLOSED VORTEX MOVES TOWARD NEW ENGLAND WHEN A SECOND 
STRONG VORT MAX DROPS INTO THE TROUGH BASE... THROUGH NC... ON WED. 
AGAIN MOISTURE WILL BE LIMITED... THUS WILL KEEP CONDITIONS DRY... 
BUT IT REMAINS QUITE CHILLY WITH LOW LEVEL THICKNESSES PROGGED BY 
THE NAM & GFS TO BE IN THE 1260S-1270S ALL DAY WED. EXPECT A DRY 
NORTHWEST LOW LEVEL FLOW THEN THU-SAT AS THE LOW ALOFT MOVES INTO 
THE CANADIAN MARITIMES & THE HIGH PRESSURE AREA BUILDING INTO NC 
FROM THE WNW MODERATES SOMEWHAT. 

AVIATION...

TERMINAL FORECASTS DEPICT A THICKENING AND LOWERING OF THE HIGH AND 
MID CLOUDS TONIGHT INTO SUN MORNING. HAVE BROUGHT CIGS DOWN TO MVFR 
BY 18Z (SOUTH) TO 21Z (NORTH) AND SPED UP PRECIP ONSET TO 21Z-00Z 
SOUTH TO NORTH... AS CIGS/VSBYS GO IFR.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FOR NCZ007-021>024-038-039 FROM 6 PM SUNDAY 
TO 9 AM MONDAY.
&&

$$

SHORT TERM...WSS





FXUS62 KRAH 272212
AFDRAH

AREA FORECAST DISCUSSION... RETRANSMISSION
NATIONAL WEATHER SERVICE RALEIGH NC
308 PM EST SUN FEB 27 2005

.SHORT TERM (TONIGHT THROUGH MONDAY NIGHT)...
MAIN FORECAST CHALLENGE REMAINS ON AMOUNT OF SNOW TO EXPECT OVER THE 
SECTIONS OF NORTHERN PIEDMONT LATE TONIGHT/EARLY MON. 

FIRST THE FACTS: ANTECEDENT CONDITIONS SUCH AS GROUND AND PAVEMENT 
TEMPS MARGINAL TO QUITE WARM. REPORTS FROM PTI AIRPORT AUTHORITY HAVE 
PAVEMENT AND GROUND SURFACE TEMPS RANGING IN THE 45 TO 50 DEGREE RANGE. 
IN ADDITION...CURRENT TEMPS IN THE MID 40S WILL ONLY FALL SLOWLY 
THROUGH THIS EVENING...THUS MAY SEE TEMPS AT PRECIP ONSET LATE TONIGHT 
NEAR 40 DEGREES. ALSO SURFACE DEWPOINTS IN THE UPPER 20S TO LOWER 30S 
WITH THE MUCH LOWER DEWPOINTS CONFINED TO FAR NORTHERN VA (MID/UPPER 
TEENS).

GFS FAIRLY CONSISTENT FROM PREVIOUS RUNS AND FAVORED WITH THIS FORECAST 
PACKAGE WITH SLIGHT MODIFICATIONS. DID NOTE THAT GFS PARTIAL THICKNESS 
WERE WARMER IN THE LOWER PARTIALS IN THE CRITICAL 06-12Z TIME FRAME 
COMPARED TO THE 06Z RUN. NAM/ETA HAS COME INTO SLIGHTLY BETTER 
AGREEMENT WITH THE GFS BUT IS STILL NOTABLY FARTHER TO THE WEST WITH 
THE 850/700MB FEATURES.

ALL SHORT TERM MODELS DEPICT STRONG MID/UPPER LEVEL FORCING LATE 
TONIGHT AS CENTRAL NC IN LEFT EXIT REGION OF 300 MB JET WHICH THE 
MODELS APPEAR 10-20 KTS TOO WEAK IN THEIR INITIALIZATION. 
ALSO...ACCORDING TO QPF DISCUSSION FROM HPC...APPEARS THAT MID LEVEL 
CIRCULATION CENTER DEVELOPING FARTHER TO THE NW THAN PROJECTED BY 
MODELS. IF THIS TREND CONTINUES (MID LEVEL CIRCULATION MOVING FARTHER 
INLAND THAN MODEL INDICATES)...THEN VAST MAJORITY OF CWA WILL SEE ALL 
LIQUID PRECIP OVERNIGHT/EARLY MON WITH PROBABILITY OF CONVECTION OVER 
THE SE COUNTIES.

DUE TO THE STRONG DYNAMICS...MODERATE HEAVY PRECIP SHOULD BE ENOUGH TO 
COOL THE COLUMN TO SUPPORT WET SNOW MIXED AT TIMES WITH RAIN OVER THE 
NW COUNTIES. AT THIS TIME...APPEARS UNLIKELY THAT CENTRAL NC WILL NOT 
BE ABLE TO TAP THE COOLER/DRIER AIR OVER NORTHERN VA (THIS WILL BE 
SOMETHING THAT THE FOLLOWING SHIFTS WILL HAVE TO MONITOR). IF ABLE TO 
TAP THIS AIRMASS...THEN GREATER POTENTIAL FOR SNOW AND HEAVIER AMOUNTS.

WHEN CONSIDERING THE ANTECEDENT CONDITIONS...THE MORE LIKELY SCENARIO 
THAT COOLER AIR TO THE NORTH WILL NOT BE TAPPED...AND THAT THE MID 
LEVEL CIRCULATION MAY TREND TO GO FURTHER INLAND...WILL MAINTAIN SNOW 
MIXED AT TIMES WITH RAIN OVER THE NW PIEDMONT. DUE TO POTENTIAL FOR 
HEAVY PRECIP BANDS...COULD SEE SNOW AMOUNTS ON GRASSY AREAS 2-4 INCHES 
OVER THE CURRENT WATCH AREA WITH ISOLATED HEAVIER AMOUNTS. DUE TO 
RELATIVELY WARM ROAD SURFACES...EXPECT MAIN ROADS TO VARY FROM WET TO 
SLUSHY. THUS WILL UPGRADE WATCH AREA TO A WARNING.  IMMEDIATELY EAST OF 
WARNING...MAINLY CHATHAM...DURHAM AND GRANVILLE...COULD SEE ENOUGH 
SLUSHY WET SNOW TO WARRANT AN ADVISORY (1-2 INCHES). FOR THE REMAINDER 
OF THE NE PIEDMONT AND THE SOUTHERN PIEDMONT COUNTIES...EXPECT RAIN 
MIXED AT TIMES WITH SNOW WITH LITTLE IF ANY ACCUMULATION.

COULD SEE SOME ISOLATED THUNDERSTORMS IN THE SE OVERNIGHT/EARLY MON BUT 
APPEARS SEVERE WEATHER THREAT MORE APPLICABLE CLOSER TO THE COAST.

EXPECT PRECIP TO RAPIDLY END SW-NE BETWEEN 12Z-16Z MON. WITH SOME 
RESIDUAL DRIZZLE/LIGHT RAIN FAR N. MAY SEE WIDELY SCATTERED SHOWERS 
WITH PASSAGE OF MID LEVEL DISTURBANCE MON EVENING BUT CONFIDENCE NOT 
HIGH ENOUGH AT THIS TIME TO WARRANT MENTIONING.

&&

.LONG TERM (TUESDAY THROUGH SUNDAY)...
TROF OVER THE EASTERN UNITED STATES CONTINUES TO DIG WITH VARIOUS 
IMPULSES REINFORCING THE COOL TREND THROUGH WEDNESDAY NIGHT. THUS 
EXPECT PREVALENT CAA STRATOCUMULUS THROUGH THE PERIOD. HIGHS TUE AND 
WED IN THE MID 40S. COOL HIGH PRESSURE BUILDING IN THURSDAY...MOSTLY 
SUNNY...AROUND 50. CONTINUED MOSTLY SUNNY WITH SOME AIRMASS MODERATION 
FRIDAY...LOW AND MID 50S.

WEEKEND IS STILL SOMEWHAT IN QUESTION WITH A PAIR OF FAIRLY STRONG 
SHORT WAVES IN THE NORTHWEST FLOW AFFECTING THE AREA. A FAST FROPA 
LOOKS LIKELY FRIDAY NIGHT/EARLY SATURDAY WHICH MIGHT DIG FAR ENOUGH 
SOUTH TO TAP SOUTHERN STREAM MOISTURE AND KICK OFF SHOWERS. WILL 
WAIT FOR LATER MODEL PERSISTENCE BEFORE INTRODUCING POPS AT THIS 
TIME. THE LATER SHORT WAVE REMAINS WELL NORTH...OVER THE GREAT 
LAKES...WHICH WOULD PRODUCE MAINLY MID CLOUDINESS. THUS...WILL 
CONTINUE DRY THROUGH THE WEEKEND WITH SLIGHTLY BELOW CLIMATOLOGICAL 
TEMPS... MOSTLY MID 50S. 


&&

.AVIATION...
VFR CEILINGS WILL BE LOWERING EARLY TONIGHT AS THE PRECIPITATION SHIELD 
GRADUALLY EDGES IN FROM THE SOUTH. IFR CEILINGS SHOULD BE IN PLACE FOR 
THE DURATION BY 06Z. EXPECT RAIN IN THE FAYETTEVILLE AREA AROUND 
SUNSET...THEN A COUPLE OF HOURS LATER...PREDOMINANT RAIN AT RWI AND RDU 
OVERNIGHT WITH SOME SNOW MIXED IN...ESPECIALLY RDU AFTER MIDNIGHT. A 
MIX INITIALLY AT GSO AND INT BY 02Z...CHANGING TO PREDOMINANTLY SNOW 
AFTER MIDNIGHT. WINDS WILL BE PICKING UP SIGNIFICANTLY AFTER SUNSET AS 
THE SURFACE LOW MOVES UP THE COAST. NORTHEAST WINDS INCREASING TO 10 TO 
15 KT WITH GUSTS TO 20 TO 25 KT AROUND 03Z WILL SWING AROUND MORE 
NORTHERLY TOWARDS SUNRISE AND GRADUALLY DIMINISH...ESPECIALLY AT GSO 
AND INT...DURING THE MORNING.   


&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FOR NCZ007-021>024-038-039 FROM TONIGHT THROUGH 
10 AM MONDAY.
WINTER WEATHER ADVISORY TONIGHT THROUGH 10 AM MONDAY FOR 
CHATHAM...DURHAM AND GRANVILLE.
&&

$$

SHORT TERM...WSS
LONG TERM...MLM
AVIATION...MLM