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FXUS62 KRAH 171503 CCA
AFDRAH

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE RALEIGH NC
1002 AM EST THU JAN 17 2008

.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL TRACK NORTHEAST ALONG THE SOUTHEAST COAST 
TODAY.  WEAK HIGH PRESSURE WILL MOVE ACROSS CENTRAL NORTH CAROLINA 
ON FRIDAY.  ANOTHER LOW PRESSURE SYSTEM FROM THE GULF OF MEXICO WILL 
MOVE UP THE SOUTHEAST COAST ON SATURDAY.  HIGH PRESSURE WITH MUCH 
COLDER AIR WILL EXPAND INTO THE AREA FROM THE WEST ON SUNDAY. 

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1000 AM THURSDAY...
STRONG LOW LEVEL FLOW VEERING WITH HEIGHT FROM NE TO SE IS EVIDENT
ON THE RADAR VWP NETWORK ACROSS THE REGION. UPPER AIR ANALYSES
SHOW A SHORT WAVE NOW ENTERING GA AND AND THE SRN APPALACHIANS TO
CONTINUE WIDESPREAD RAIN OVER CENTRAL NC THE NEXT FEW HOURS.
LATEST AIRCRAFT AND RUC SOUNDINGS CONTINUED POTENTIAL FOR FREEZING
RAIN IN THE NW PIEDMONT WITH TEMPERATURES HOVERING AT ABOUT 32.
BUT AIR CONTINUES TO WARM ABOVE 950 MB...1500 FT AGL...AND RELEASE
OF LATENT HEAT IN THE FREEZING PROCESS SHOULD LIMIT ANY FURTHER
ACCRETION. THUS...THE WINTER STORM WARNING HAS BEEN CANCELLED IN
THE NW PIEDMONT AND PERSON COUNTY...AND REPLACED WITH A WINTER
WEATHER ADVISORY FOR ANY REMAINING SLICK SPOTS UNTIL NOON. THE
AREA SOUTH AND EAST PREVIOUSLY COVERED BY A WINTER WEATHER
ADVISORY HAS NOW BEEN CANCELLED WITH SURFACE AIR TEMPERATURES
HAVING WARMED TO THE MID 30S.

CONTINUED SATURATION IN THE LOWEST LAYERS AND LACK OF PUSH OF ANY
DRIER AIR INTO THE REGION IS LIKELY TO RESULT IN LINGERING
CLOUDINESS AND POSSIBLY FOG INTO THE NIGHTTIME HOURS. TEMPERATURES
WILL FALL SLOWLY AND SHOULD HOLD AT OR ABOVE FREEZING MOST OF THE
NIGHT. NEAR DAYBREAK...PARTIAL CLEARING COULD LEAD TO SURFACE
COOLING AND A BRIEF PERIOD OF BLACK ICE POTENTIAL MAINLY IN THE
WEST. -RFG

&&

.SHORT TERM /FRIDAY/...
AS OF 330 AM THURSDAY...
FRIDAY...HIGH CLOUDINESS IS EXPECTED TO REMAIN ACROSS THE AREA.
HIGH TEMPS WILL RANGE FROM NEAR 50 IN THE NW PIEDMONT TO THE MID
50S IN THE COASTAL PLAIN. -VINCENT

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
AS OF 330 AM THURSDAY...
FRIDAY NIGHT: MID AND HIGH CLOUDINESS WILL RAPIDLY SPREAD
NORTHEASTWARD FROM THE GOM AND MISSISSIPPI VALLEY FRIDAY NIGHT...
IN SOUTHWEST FLOW AHEAD OF AN APPROACHING POSITIVELY TILTED UPPER
TROUGH. LOW TEMPS SATURDAY MORNING FROM AROUND FREEZING ACROSS THE
NORTHERN PIEDMONT TO UPPER 30S IN THE SOUTH... TEMPERED SOMEWHAT
BY INCREASING CLOUD COVER.

SATURDAY: DETAILS OF THE UPPER TROUGH AND ASSOCIATED SURFACE LOW ARE 
IN QUESTION... BUT THE 00Z/17TH NAM/GFS/ECMWF/GEM ARE IN REMARKABLY 
GOOD AGREEMENT WITH A MILLER A LOW AND ASSOCIATED PRECIPITATION 
SHIELD LIFTING NORTHEASTWARD OUT OF THE GULF OF MEXICO AND UP THE 
SOUTHEAST US COAST... CLOSER TO THE COAST THAN PREVIOUS MODEL RUNS. 
THE EXACT TIMING AND POTENTIAL PHASING OF THE UPPER LOW OVER THE 
BAJA THIS MORNING WITH ADDITIONAL SHORTWAVE ENERGY NOW CRESTING THE 
EAST PACIFIC RIDGE MAY ULTIMATELY DICTATE THE FATE OF THIS LOW. A 
FASTER EJECTION OF THE BAJA LOW WOULD ALLOW A MUCH WEAKER AND MORE 
SUPPRESSED GULF LOW TO PASS RELATIVELY HARMLESSLY OUT TO SEA... 
WHEREAS A SLOWER EJECTION OF THIS TROUGH WOULD ALLOW MORE 
INTERACTION WITH THE NORTHERN STREAM WAVE AND STRONGER AND MORE 
WESTWARD LOW TRACK AS DEPICTED BY THE AFOREMENTIONED MODELS.  
FORECAST PARTIAL THICKNESSES OFF THE NAM AND GFS TRANSITION FROM 
RAIN... TO THE WINTRY MIXTURE... TO MEASURABLE SNOW WITH RAIN 
CATEGORIES BEFORE THE PRECIPITATION ENDS. THIS WOULD BE THE MOST 
LIKELY SCENARIO SINCE MOST MILLER A STORMS TYPICALLY HAVE 
NARROW P-TYPE TRANSITION ZONES (RAIN/SNOW LINE) WITH LITTLE TO NO 
ICING. SOMETHING TO WATCH... THE NWP MODELS ARE CONSISTENT IN 
DEVELOPING THE LOW ALONG THE TRAILING COLD FRONT FROM THE STORM 
CURRENTLY AFFECTING OUR REGION. HOWEVER... THERE IS A CHANCE THAT 
THE LOW COULD DEVELOP WESTWARD ALONG THE LOW LEVEL BAROCLINIC ZONE 
ASSOCIATED WITH THE APPROACHING ARCTIC FRONT. FOR NOW... WILL PLAY 
IT CONSERVATIVELY AND KEEP THE P-TYPE ALL RAIN... GIVEN THE COLD 
SURFACE HIGH WILL BE CHASING THE MOISTURE AND THE EJECTION OF THE 
BAJA TROUGH AND POTENTIAL PHASING WITH ADDITIONAL SHORTWAVE ENERGY 
ARE STILL VERY MUCH IN QUESTION. LOOK FOR HIGHS SATURDAY TO REMAIN 
IN THE 30S TO NEAR 40 WITH EXPECTED CLOUDS AND PRECIPITATION. THIS 
IS IN LINE WITH THE LATEST MAV/MEX GUIDANCE WHICH CAME IN SOME 8-10 
DEGREES COOLER THAN PREVIOUS FORECASTS.

SATURDAY NIGHT THROUGH SUNDAY NIGHT: THE AIRMASS BEHIND THE ARCTIC 
FRONT PROMISES SOME OF THE COLDEST AIR IN QUITE SOME TIME FOR 
CENTRAL NC... AS A 1032-1040 MB HIGH WITH ORIGINS IN THE NORTHWEST 
TERRITORIES BUILDS INTO OUR REGION. DEEP LAYER DRYING AND BRUTAL 
COLD ADVECTION WILL ENSUE SATURDAY NIGHT AS THE ARCTIC HIGH BUILDS 
EASTWARD. THE H85 THERMAL TROUGH WILL BE OVER CENTRAL NC LATE 
SATURDAY NIGHT INTO SUNDAY... WITH H85 TEMPERATURES DROPPING TO 
BETWEEN MINUS 10 AND 15 DEGREES. CORRESPONDING 1000-850 MB 
THICKNESSES ARE PROGGED TO FALL TO INTO THE 1230 TO 1240 METER RANGE 
BY 12Z SUNDAY. THIS WOULD RESULT IN LOWS DIPPING INTO THE TEENS FOR 
MOST OF THE CWA SUNDAY MORNING. THINK THAT EVEN THOUGH THE CORE OF 
THE COLD AIR WILL HAVE LIFTED NORTHEASTWARD AND A NORTHWESTERLY 
DOWNSLOPE FLOW WILL DEVELOP SUNDAY... THE ARCTIC AIR NEAR THE 
SURFACE WILL BE SLOW TO MODIFY AND ADVECT OUT OF OUR REGION DESPITE 
WARMING H85 TEMPS. FORECAST LOW LEVEL THICKNESSES WOULD SUPPORT 
HIGHS HOLDING IN THE MID 20S SUNDAY. NOT BITING ON THIS EXTREME JUST 
YET... BUT WILL INSTEAD CONTINUE THE TREND OF PREVIOUS SHIFTS AND 
TRIM YET A FEW MORE DEGREES OFF PREVIOUS HIGHS AND SHOW A RANGE OF 
27 TO 34 FROM NORTH TO SOUTH. RIDGE AXIS SHOULD BE DIRECTLY OVERHEAD 
SUNDAY NIGHT... AND RESULT IN IDEAL RADIATIONAL COOLING SOLIDLY INTO 
THE LOWER TO MIDDLE TEENS. 

MONDAY AND MONDAY NIGHT. SURFACE RIDGING AND MOSTLY CLEAR SKIES WILL 
CONTINUE THIS PERIOD. HIGHS AROUND 40 AND LOWS IN THE MID 20S. 

TUESDAY THROUGH WEDNESDAY NIGHT: THE HIGH WILL GRADUALLY SHIFT 
OFFSHORE AND RESULT IN AN INCREASE IN SHALLOW ISENTROPIC LIFT AND 
RESULTANT CLOUD COVER IN RETURN FLOW AROUND THE HIGH. WESTERLY FLOW 
AND NO SIGNIFICANT TROUGHS ALOFT SHOULD LIMIT THE DEPTH OF THE 
MOISTENING AND RAIN POTENTIAL UNTIL MID WEEK... WHEN THE MEDIUM 
RANGE MODELS AGREE ON A COLD FRONT SETTLING INTO OUR REGION. DAYTIME 
HIGHS MODERATING INTO THE 45 TO 50 DEGREE RANGE... WITH LOWS AROUND 
FREEZING. -MWS

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
AS OF 800 AM THURSDAY... LOW PRESSURE MOVING OVER NORTHERN FLORIDA 
WILL MOVE NORTHEAST ALONG THE ATLANTIC COAST TODAY... AND BE OFF THE 
DELMARVA COAST AROUND MIDNIGHT. AS MOISTURE OVERSPREADS THE AREA... 
RAIN WILL CONTINUE OVER THE AREA THROUGH THE EVENING. THE ONLY MIXED 
PRECIP WILL BE IN THE EXTREME NORTHWEST PIEDMONT WITH SOME PATCHY 
FREEZING RAIN. 

IFR TO LIFR CONDITIONS WILL PERSIST THROUGH THE DAY AS RAIN PERSISTS 
OVER THE REGION. CONDITIONS WILL IMPROVE DURING THE EVENING AS THE 
RAIN TAPERS OFF AND ENDS AROUND SUNSET. HIGH PRESSURE WILL BUILD 
OVER THE AREA FROM THE WEST EARLY FRIDAY. 

ANOTHER LOW PRESSURE CENTER WILL TRACK NORTHEAST FROM THE GULF OF 
MEXICO SATURDAY THROUGH SATURDAY NIGHT. THERE MAY BE A PERIOD OF 
MVFR CONDITIONS AS THE SYSTEM MOVES UP THE COAST... HOWEVER THEY 
SHOULD BE SHORT LIVED. ANOTHER HIGH PRESSURE SYSTEM WILL BUILD INTO 
THE REGION FROM THE WEST LATE SATURDAY AND CONTINUE THROUGH MONDAY. 
VFR CONDITIONS WILL PREVAIL SUNDAY AND MONDAY.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ007-
021>023-038-039.

&&

$$
SYNOPSIS...RFG
NEAR TERM...RFG
SHORT TERM...VINCENT
LONG TERM...MWS
AVIATION...RHJ