000
FXUS62 KRAH 271940
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
240 PM EST MON DEC 27 2010
.SYNOPSIS...
A POWERFUL LOW PRESSURE SYSTEM OFF THE NEW ENGLAND COAST WILL
CONTINUE MOVING NORTHEAST AWAY FROM OUR REGION TODAY. COLD HIGH
PRESSURE WILL BUILD SLOWLY OVER THE SOUTHEAST STATES AND THE
CAROLINAS THROUGH MID WEEK.
&&
.NEAR TERM /THROUGH TUESDAY NIGHT/...
AS OF 1255 PM MONDAY...
SFC ANALYSIS THIS AFTERNOON SHOWED INTENSE ~960 MB LOW PRESSURE
CENTERED ABOUT 150 MILES ENE OF BOSTON. 1030 MB HIGH PRESSURE WAS
CENTERED ALONG THE CENTRAL/LOWER MS RIVER VALLEY. ALOFT...12Z RAOB
ANALYSIS AND WV IMAGERY SHOWED A DEEP H5 LOW OFF THE NEW ENGLAND
COAST... WITH AN H5 TROUGH EXTENDING SW TO THE CAROLINA/SE COAST.
AN H5 RIDGE WAS NOTED ALONG THE MS RIVER VALLEY.
TODAY:
THE COLUMN WILL DRY OUT TODAY IN ASSOCIATION WITH HEIGHT RISES
AND SYNOPTIC SUBSIDENCE AS THE DEEP H5 LOW OFF THE NEW ENGLAND
COAST LIFTS NORTHEAST INTO NOVA SCOTIA AND THE H5 RIDGE OVER THE
MS RIVER VALLEY SHIFTS EASTWARD INTO THE TN/OH VALLEY. EXPECT
DECREASING CLOUD COVER THIS AFTERNOON. GIVEN A TIGHT PRESSURE
GRADIENT ACROSS THE STATE...WITH FCST SOUNDINGS SHOWING 30 KNOT NW
FLOW AT THE TOP OF THE MIXED LAYER...EXPECT BREEZY NW WINDS
TODAY...WITH SUSTAINED WINDS 10-20 MPH AND GUSTS GENERALLY UP TO
30 MPH...ALTHOUGH A FEW HIGHER GUSTS WILL BE POSSIBLE. WINDS OF
THIS MAGNITUDE COMBINED WITH SNOW/ICE COVERED TREES COULD RESULT
IN A FEW DOWNED TREES/POWER LINES AND SPORADIC POWER OUTAGES THIS
AFTERNOON...PARTICULARLY WHERE THE HEAVIEST SNOW FELL JUST
EAST/NE OF THE TRIANGLE. AT THIS TIME WILL CONTINUE TO MENTION THE
THREAT FOR DOWNED TREES/POWER LINES IN THE HAZARDOUS WEATHER
OUTLOOK...AND PERHAPS IN A SPECIAL WEATHER STATEMENT IF NEEDED.
HIGH TEMPS TODAY WILL GENERALLY BE IN THE MID 30S (34-38F)...WITH
THE LOW END OF THAT RANGE PRIMARILY IN AREAS THAT RECEIVED THE
HIGHEST SNOW ACCUMULATIONS.
TONIGHT:
120-150 METER H5 HEIGHT RISES WILL OCCUR TONIGHT AS THE DEEP
UPPER LOW CURRENTLY EAST OF BOSTON MOVES NORTHEAST INTO NOVA
SCOTIA. EXPECT CLEAR SKIES ASSOC/W SYNOPTIC SUBSIDENCE. THE MSLP
GRADIENT WILL ALSO WEAKEN OVERNIGHT...ALTHOUGH IT SHOULD REMAIN
STRONG ENOUGH FOR A 5-10 KT WIND TO PERSIST THROUGH AT LEAST
MIDNIGHT...WITH PERHAPS A ~5 KT WIND PERSISTING THROUGH SUNRISE IN
THE EAST. LOW TEMPS TONIGHT SOMEWHAT TRICKY...WITH A WEAKENING
MSLP GRADIENT FROM THE WEST AND VARYING SNOW COVER ACROSS THE
AREA. GIVEN CLEAR SKIES...A FRESH SNOW PACK AND A DRY AIRMASS IN
PLACE (DEWPOINTS IN THE TEENS)...EXPECT VERY COLD LOWS IN THE
UPPER TEENS ACROSS THE ENTIRE AREA. JUST HOW LOW TEMPS FALL WILL
ULTIMATELY DEPEND ON WHETHER OR NOT WINDS CAN GO CALM SEVERAL HRS
PRIOR TO SUNRISE. ANY LOCATIONS THAT GO CALM COULD SEE LOW TEMPS
SEVERAL DEGREES LOWER THAN ELSEWHERE. A WINTER WEATHER ADVISORY
FOR BLACK ICE WILL BE REISSUED THIS AFTERNOON...LIKELY STARTING
AROUND OR SHORTLY AFTER SUNSET THIS EVENING AND PERSISTING THROUGH
NOON TUESDAY.
TUESDAY AND TUESDAY NIGHT:
H5 HEIGHT RISES WILL CONTINUE THROUGH THE DAY TUE...BEFORE FLOW
ALOFT BECOMES UNIDIRECTIONAL TUESDAY EVENING/NIGHT. WITH CONTINUED
SYNOPTIC SUBSIDENCE AND SFC HIGH PRESSURE BUILDING TOWARD THE
CAROLINAS FROM THE WEST...EXPECT CLEAR SKIES BOTH TUE AND TUE
NIGHT...ALTHOUGH CANNOT RULE OUT A FEW WISPY HIGH CLOUDS BY SUNRISE
WEDNESDAY IN ADVANCE OF A SOUTHERN STREAM SHORTWAVE MOVING FROM THE
DESERT SW INTO TX BY THAT TIME. HIGH TEMPS TUE SOMEWHAT DIFFICULT
WITH UP TO A 10F SPREAD IN MOS GUIDANCE...AND THICKNESSES SHOWING
TEMPS NEAR 50F. FCST SOUNDINGS SHOW A VERY SHALLOW MIXED LAYER ON
TUE...NO MORE THAN 1500 FT DEEP...AND THIS MAY BE PART OF THE
PROBLEM WITH MOS GUIDANCE AND IN USING THE 1000-850 MB THICKNESS
SCHEME. HAVE DECIDED TO GO MORE ON PERSISTENCE...WITH TEMPS SEVERAL
DEGREES HIGHER THAN MAX TEMPS TODAY DUE TO AIRMASS MODIFICATION AND
MELTING OF THE SNOW PACK...IN THE UPPER 30S TO LOWER 40S. WITH CLEAR
SKIES...CALM WINDS AND A SNOW PACK IN PLACE (WELL...IN LOCATIONS
WHERE IT HASN'T MELTED BY SUNSET TUE)...EXPECT CHILLY LOWS IN THE
LOWER 20S...OR 21-24F. COLDEST EAST/NE OF THE TRIANGLE AND THE
TYPICAL COLD SPOTS. A WINTER WEATHER ADVISORY OR SPECIAL WEATHER
STATEMENT FOR BLACK ICE WILL LIKELY BE NEEDED AGAIN FOR PORTIONS OF
CENTRAL NC ON TUE NIGHT. -VINCENT
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 220 PM MONDAY...
SURFACE HIGH PRESSURE WILL DOMINATE THE PERIOD. LIGHT WEST WINDS
EARLY IN THE PERIOD BECOME VARIABLE AS THE HIGH NEARS NORTH
CAROLINA... THEN EAST AS THE MAIN HIGH ESTABLISHES ITSELF OVER THE
MID ATLANTIC STATES. IN THE MID LEVELS... WEAK RIDGING OVER
TENNESSEE MOVES TO THE COAST BY FRIDAY MORNING AND STRENGTHENS IN
RESPONSE TO A DIGGING TROUGH OVER THE ROCKIES. VARIABLY CLOUDY SKIES
WITH CLOUDS ABOVE 10000 FEET THROUGH THURSDAY. GOOD MOISTURE AND
WARM ADVECTION ON THE BACK SIDE OF THE SURFACE HIGH WILL LIKELY
BRING LOW STRATUS INTO CENTRAL NORTH CAROLINA THURSDAY NIGHT.
ABNORMALLY LOW MIXING HEIGHTS LIKELY IMPACTING REGRESSION EQUATIONS
IN GUIDANCE. HIGH TEMPERATURES WILL BE FORECAST CLOSER TO THE
COOL MET GUIDANCE FOR WEDNESDAY... AT MID 40S. THURSDAY HIGH
TEMPERATURES 45 TO 50. WEDNESDAY NIGHT LOW TEMPERATURES IN THE
UPPER 20S WEDNESDAY NIGHT AND NEAR FREEZING THURSDAY NIGHT.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 220 PM MONDAY...
OPERATIONAL GFS MODEL ON THE FAST SIDE OF MODELS AND ENSEMBLES
ACCORDING HPC. SINCE SLOWER IS FREQUENTLY BEST... THE 12Z ECMWF
WILL BE THE TEMPLATE FOR THE WEEKEND RAIN STORM. THIS WILL PLACE
THE BEST CHANCE FOR RAIN LATE SATURDAY NIGHT... CONTINUING INTO
SUNDAY.
THERE WILL BE A WARMING TREND INTO SATURDAY AHEAD OF THE APPROACHING
COLD FRONT. HIGH TEMPERATURES IN THE MID 50S THURSDAY AND UPPER 50S
TO MID 60S SATURDAY. FORECASTING ABOUT A FIVE DEGREE RISE IN THE
WEST SUNDAY... AND TEN IN THE EAST. AFTERNOON HIGHS MID 50S TO MID
60S. BEHIND THE FRONT MONDAY HIGH TEMPERATURES 49 TO 55. FRIDAY
NIGHT LOW TEMPERATURES UPPER 30S TO MID 40S... LOW TO MID 50S
SATURDAY NIGHT... UPPER 20S TO MID 30S SUNDAY NIGHT.
&&
.AVIATION /20Z MONDAY THROUGH SATURDAY/...
AS OF 100 PM MONDAY...
24-HR TAF PERIOD:
VFR CONDITIONS WILL RULE THROUGH THE TAF PERIOD IN ASSOCIATION
WITH INCREASING SYNOPTIC SUBSIDENCE AS A POWERFUL LOW PRESSURE
SYSTEM OFF THE NEW ENGLAND COAST CONTINUES TO MOVE FURTHER AWAY
FROM THE CAROLINAS. BREEZY NW WINDS ARE EXPECTED THIS AFTERNOON...
WITH SUSTAINED WINDS IN THE 10-20 KT RANGE AND GUSTS IN THE 23-28
KNOT RANGE. WINDS WILL DECREASE TO 8-13 KT AFTER SUNSET...FURTHER
DECREASING TO 3-8 KT IN THE 06-12Z TIME FRAME TONIGHT AS THE MSLP
GRADIENT FURTHER WEAKENS. CLEAR SKIES AND WESTERLY WINDS AT 5-10
KT ARE EXPECTED DURING THE DAY TUE.
LOOKING AHEAD:
ASIDE FROM THE POSSIBILITY OF A FEW HOURS OF FREEZING FOG DURING
THE PREDAWN HOURS WED/THU MORNINGS...VFR CONDITIONS WILL RULE
THROUGH THURSDAY IN ASSOCIATION WITH HIGH PRESSURE BUILDING OVER
THE AREA. IFR/LIFR CEILINGS WILL BE POSSIBLE THU NIGHT/FRI
MORNING AS HIGH PRESSURE MOVES OFFSHORE AND A SOUTHERLY RETURN
FLOW SETS UP OVER THE AREA. -VINCENT
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO NOON EST
TUESDAY FOR NCZ007>011-021>028-038>043-073>078-083>086-088-089.
&&
$$
SYNOPSIS...VINCENT
NEAR TERM...VINCENT
SHORT TERM...
LONG TERM...
AVIATION...VINCENT
