FXUS62 KRAH 151143
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
643 AM EST TUE DEC 15 2009
.SYNOPSIS...
AN UPPER LEVEL DISTURBANCE WILL TRACK TO OUR SOUTH AND EAST THIS
MORNING. A COLD FRONT WILL MOVE EAST THROUGH NC THIS AFTERNOON.
HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD SE INTO OUR REGION
TONIGHT INTO THURSDAY...BRINGING COLD DRY WEATHER.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 430 AM TUESDAY...
07Z SFC ANALYSIS SHOWED 1007 MB LOW PRESSURE CENTERED OVER LAKE
ONTARIO...WITH A COLD FRONT EXTENDING SSW ALONG THE SOUTHERN
APPALACHIANS INTO THE DEEP SOUTH. A REMNANT WEDGE AIRMASS WAS
LOCATED OVER THE CAROLINAS...AND A STATIONARY/WEDGE FRONT WAS
LOCATED OVER NORTHEAST GA. 1036 MB ARCTIC HIGH PRESSURE WAS CENTERED
OVER THE UPPER MIDWEST...WHERE TEMPS WERE AS LOW AS -10 TO -30F OVER
THE DAKOTAS AND MONTANA. ALOFT...00Z RAOB ANALYSIS SHOWED A LONGWAVE
TROUGH OVER THE ROCKIES AND DESERT SOUTHWEST. WEST/WSW FLOW ALOFT
WAS NOTED OVER THE SOUTHEAST STATES AND CAROLINAS. SUBTLE SHORTWAVE
DISTURBANCES WERE LIKELY EMBEDDED IN WEST/SW FLOW ALOFT OVER THE
DEEP SOUTH AND SOUTHEAST STATES.
430 AM UPDATE:
BASED ON THE LATEST OBSERVATIONAL TRENDS...HAVE ISSUED A DENSE FOG
ADVISORY FOR THE ENTIRE AREA THROUGH 15Z (10 AM) THIS MORNING.
TODAY:
THE COLD FRONT CURRENTLY JUST WEST OF THE MOUNTAINS IS PROGGED TO
SWEEP EASTWARD ACROSS CENTRAL NC BY ROUGHLY 18Z TODAY. LIFT ASSOC/W
THE FRONT SHOULD BE RATHER MARGINAL...AND CONFINED TO SHALLOW
(SFC-925 MB) LOW LEVEL CONVERGENCE...WITH DOWNSLOPE FLOW AT 850 MB.
UPPER SUPPORT SHOULD BE MARGINAL...WITH PERHAPS A GLANCING BLOW THIS
MORNING FROM A SUBTLE SHORTWAVE CURRENTLY EMBEDDED IN SOUTHWEST FLOW
ALOFT OVER THE SOUTHEAST STATES. AS A RESULT...OUTSIDE OF A VERY
SMALL CHANCE OF LIGHT RAIN IN SOUTHERN PORTIONS OF THE AREA DURING
THE MORNING HOURS...SEE LITTLE CHANCE FOR ANY MEASURABLE PRECIP
TODAY. HOWEVER...THE WESTERLY LOW LEVEL FLOW AND COOL/DRY AIRMASS
MOVING INTO THE AREA BEHIND THE FRONT SHOULD SERVE AS AN EFFECTIVE
MECHANISM FOR SCOURING OUT THE REMNANT WEDGE AIRMASS ACROSS THE
CAROLINAS...AND FCST SOUNDINGS SHOW CEILINGS FINALLY LIFTING/
IMPROVING DURING THE AFTERNOON HOURS. ALTHOUGH THE MODELS TRIED TO
SHOW THE REMNANT WEDGE SCOURING OUT YESTERDAY AS WELL...GIVEN THAT
WE WILL HAVE A GOOD PHYSICAL MECHANISM FOR SCOURING IT OUT TODAY...
FEEL THAT FCST SOUNDINGS ARE PROBABLY ON THE RIGHT TRACK. STILL...
HIGH TEMPS WILL BE QUITE TRICKY...DEPENDING ON HOW LONG IT TAKES FOR
CEILINGS TO LIFT...AND HOW QUICKLY THE COOLER/DRIER UPSTREAM AIRMASS
FILTERS INTO THE AREA. HAVE DECIDED TO GO WITH HIGHS A FEW DEGREES
COOLER THAN A MOS GUIDANCE BLEND...RANGING FROM THE UPPER 50S (NW)
TO LOWER 60S (SE).
TONIGHT:
ARCTIC HIGH PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL BUILD
EAST/SE INTO THE CENTRAL MS RIVER VALLEY BY 12Z WED. ACROSS CENTRAL
NC...WE WILL SEE COLD ADVECTION THROUGHOUT THE ENTIRE NIGHT...WITH A
~10MB PRESSURE GRADIENT ACROSS THE STATE. ALTHOUGH SKIES WILL BE
CLEAR...GIVEN A DECENT MSLP GRADIENT...A NORTHWEST BREEZE IS
EXPECTED THE ENTIRE NIGHT...AND LOW TEMPS WILL LIKELY BE DRIVEN BY
COLD ADVECTION MORE-SO THAN RADIATIONAL COOLING. WILL FCST LOWS
RANGING FROM THE LOWER 30S (NW) TO MID/UPPER 30S (SE). -VINCENT
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 200 AM TUESDAY...
A COLD DRY PERIOD EXPECTED...WITH TEMPERATURES 4-8 DEGREES BELOW
NORMAL.
A STRONG (1035 MB) SURFACE HIGH OF POLAR ORIGIN WILL EXTEND FROM
THE GREAT LAKES SE THROUGH THE OHIO VALLEY... AND INTO THE MID
ATLANTIC STATES WEDNESDAY THROUGH FRIDAY. COLD DRY ADVECTION WILL
PREVAIL ACROSS NC THROUGH THE PERIOD... WITH THE LOW LEVEL
THICKNESS FORECAST TO BOTTOM OUT FRIDAY. DEW POINTS SHOULD EASILY
DIP INTO THE TEENS WEDNESDAY THROUGH THURSDAY... WITH SOME 0-10
DEW POINTS LIKELY OVER THE WESTERN PIEDMONT. EXPECT CLEAR/SUNNY
SKIES. HIGHS WEDNESDAY AND THURSDAY SHOULD HOLD IN THE 45-50
RANGE NW... AND 50-55 SE. LOWS WILL BE IN THE 20S. HIGHS FRIDAY
SHOULD BE MOSTLY IN THE 40S.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 200 AM MONDAY...
THE +PNA/-NAO PATTERN WILL CONTINUE THROUGH THE WEEKEND. THIS DOES
FAVOR STORMINESS AND COLD CONDITIONS OVER THE SE UNITED STATES. THERE
IS VIRTUALLY LITTLE AGREEMENT NOR CONSISTENCY IN THE MODEL FORECASTS
LATE IN THE WEEK INTO THE WEEKEND. THE WESTERN GULF COAST WILL HAVE
TO BE MONITORED CLOSELY AS MOST MODELS DO SHOW A SURFACE LOW
DEVELOPMENT THERE BY FRIDAY. FROM THERE... THERE IS A LARGE SPREAD
AMONG THE MODELS AS TO THE TRACK AND STRENGTH OF THE LOW PRESSURE.
WITH A REX BLOCK DEVELOPMENT EXPECTED OVER EASTERN CANADA...
THERE SHOULD BE AN AMPLE COLD AIR SUPPLY DOWN THE EASTERN SEABOARD
INTO NC. ANY STORM TRACK FROM THE GULF NE ALONG THE SE ATLANTIC
SEABOARD WOULD LIKELY CAUSE SOME P-TYPE ISSUES FOR PORTIONS OF OUR
REGION. UNTIL THERE IS SOME CONSISTENCY AND FAVORED SOLUTION AMONG
THE MODELS... WE WILL CONTINUE THE COLD/DRY FORECAST. LOWS IN THE
20S AND HIGHS IN THE 40S TO LOWER 50S SE.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
AS OF 645 AM TUESDAY...
24-HR TAF PERIOD:
LIFR/IFR CONDITIONS EXPECTED ACROSS THE ENTIRE AREA THROUGH 12-16Z
THIS MORNING AS A REMNANT WEDGE AIRMASS REMAINS IN PLACE ACROSS
CENTRAL NC. A COLD FRONT CURRENTLY LOCATED IN THE MOUNTAINS SHOULD
PROGRESS EASTWARD THROUGH THE AREA BY 18-21Z...AND LOW LEVEL FLOW
SHOULD VEER TO THE NORTHWEST BY THE AFTERNOON...USHERING IN A DRIER
AIRMASS FROM THE WEST/NW. AS A RESULT...THE REMNANT WEDGE AIRMASS
SHOULD BEGIN TO SCOUR OUT BY THE EARLY AFTERNOON...WITH IMPROVEMENTS
IN VISBYS/CEILINGS. IT IS DIFFICULT TO DETERMINE EXACTLY WHEN
CONDITIONS WILL BECOME VFR...HOWEVER...BASED ON THE LATEST FCST
SOUNDINGS AND UPSTREAM OBSERVATIONAL DATA...VFR CONDITIONS ARE
ANTICIPATED TO ARRIVE BY 18Z IN THE NW PIEDMONT...AND BY 21Z AT
RDU/FAY/RWI.
ONCE THE COLD FRONT CLEARS OUT THE AREA...VFR CONDITIONS ARE
EXPECTED TO HOLD TONIGHT THROUGH THE END OF THE WORK WEEK AS COOL
HIGH PRESSURE BUILDS INTO THE AREA. THE NEXT CHANCE FOR ADVERSE
AVIATION CONDITIONS MAY NOT BE UNTIL THE WEEKEND...WHEN A STORM
SYSTEM EMANATING FROM THE GULF OF MEXICO MAY AFFECT PORTIONS OF THE
SOUTHEAST STATES. -VINCENT
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR NCZ007>011-
021>028-038>043-073>078-083>086-088-089.
&&
$$
SYNOPSIS...BADGETT
NEAR TERM...VINCENT
SHORT TERM...BADGETT
LONG TERM...BADGETT
AVIATION...VINCENT
