FXUS61 KAKQ 050229
AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
929 PM EST THU DEC 4 2008

.SYNOPSIS...
A COLD FRONT WILL MOVE ACROSS THE AREA THIS AFTERNOON AND
EVENING...THEN PUSH OFF THE MID ATLANTIC COAST AFTER MIDNIGHT.
HIGH PRESSURE BUILDS INTO THE REGION FROM THE WEST FRIDAY AND
FRIDAY NIGHT...WHILE A WEAK LOW PRESSURE SYSTEM FORMS OFF THE MID
ATLANTIC COAST. ANOTHER COLD FRONT APPROACHES FROM THE WEST ON
SATURDAY...THEN MOVES OFF THE COAST SATURDAY NIGHT. HIGH PRESSURE
REBUILDS OVER THE AREA FROM THE WEST SUNDAY AND MONDAY. LOW
PRESSURE WILL TRACK ACROSS THE LOWER MISSISSIPPI AND TENNESSEE
VALLEYS ON TUESDAY...AS A WARM FRONT EXTENDING EAST OF THE LOW
APPROACHES FROM THE MID ATLANTIC REGION FROM THE SOUTH.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
FEW MINOR TWEAKS TO POP FORECAST TONIGHT...BASICALLY TO BEEF UP
POPS FOR FA THRU THE OVERNIGHT HOURS. THOUGH LITTLE IN THE WAY OF
PRECIP IS FALLING ATTM(QPF-WISE)...THINK COVERAGE IS SUFFICIENT
ENUF TO WARRANT LIKELY POPS OVR THE NW FLANK OF THE FA...AND CHC
POPS ELSEWHERE OVERNIGHT. THOUGH THERE IS CONSIDERABLE COLD AIR
BEHIND THE FRONT...SFC TEMPS STILL QUITE WARM ACROSS THE AREA SO
THAT ANY PRECIP THAT DOES REACH THE GROUND SHOULD CONT TO FALL AS
RAIN. NO OTHER CHANGES TO FORECAST AT THIS TIME. PREV DISC
FOLLOWS.

RATHER MEAGER/NARROW REGION OF LOW-MID FRONTOGENESIS AND
ASSOCIATED MOISTURE (1000-500 MB RH'S ABOVE 70%) WILL QUICKLY
PUSH ACROSS THE FCST AREA THIS EVENING. NARROW...FAST MOVING FVRBL
DYNAMICAL FORCING...ALONG WITH SHORT-LIVED MOIST S/SE LOW LEVEL
TRAJECTORIES AHEAD OF THE FRONT...WILL MAKE FOR A BRIEF PERIOD OF
LIGHT SHOWERS OR SPRINKLES AT BEST.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/...
COOLER ON FRI BEHIND THE FRONT...AS LOCAL LLVL THICKNESS SCHEME
SUPPORTS A MAV/MET BLEND FCST OF HIGHS FROM THE LWR 40S N TO NEAR
50 S.

FRI NIGHT COULD GET A LITTLE INTERESTING OVER SERN AREAS OF THE
FCST AREA...INCLUDING THE TIDEWATER VA REGION AND ESPECIALLY NERN
NC. GFS/NAM/SREF AND EVEN THE ECMWF ALL SHOW A WEAK SFC-850 MB LOW
DEVELOPING IN THE LLVL BAROCLINIC ZONE...IN THE GULF STREAM ALONG
THE STALLED FRONT AHEAD OF THE DEEPENING MID/UPR LEVEL LOW ACROSS
THE MIDWEST REGION. FOR NOW...IT APPEARS FRONTOGENETIC MOISTURE
SHIELD NW OF THE LOW TRACK WILL CONTINUE TO NECESSITATE LOW POPS
(20-30%) ALONG THE SERN VA/NERN NC COASTAL AREAS SAT NIGHT...
WHILE AT THE SAME TIME LLVL (100-850 MB) THICKNESSES AND SFC WET
BULB TEMPS SUPPORT THE POSSIBILITY OF A R/S MIX. AT THIS POINT THE
DEPTH OF FORCING/MOISTURE APPEARS TO WEAK FOR ANYTHING OTHER THAN
A LIGHT EVENT...AND CONSIDERING THE LIGHT INTENSITY EXPECTED (LACK
OF EVAP COOLING AT LOW LEVELS)...IT'S CERTAINLY NOT A GUARANTEE
THAT A MIX OR EVEN A CHANGEOVER TO SNOW WILL DEVELOP. FOR
NOW...THIS IS SOMETHING TO KEEP AN EYE ON.

ANOTHER POTENTIAL WEATHER CONCERN IN THE SHORT TERM WILL COME SAT
NIGHT...AHEAD OF THE DEEPENING 700-500 MB TROUGH. COMPARED TO THE
NAM/SREF/ECMWF...THE GFS REMAINS THE MOST BULLISH IN TERMS OF
LOW-MID LVL FGEN LIFT SUPPORT AND DEEPENING MSTR. MUCH WILL DEPEND
ON HOW QUICKLY (AND HOW FAR S) THE MID LEVEL TROUGH DEEPENS...OR HOW
SOON THE TROUGH BECOMES NEGATIVELY TILTED BEFORE MOVING OFF THE
MID ATLC COAST. FOR NOW HAVE MAINTAINED THE LOW CHANCE POPS IN THE
FCSTS...BUT CERTAINLY GIVEN THE LOWERING LLVL THICKNESSES (AOB
1300M BTWN 1000-850 MB FOR ALL BUT CSTL LOCATIONS)...ALONG WITH
LOWERING SFC TEMPS/WET BULBS AND FREEZING LEVELS WHILE THIS
FORCING WOULD BE OCCURRING...HAVE LEFT THE MENTION OF SNOW OR R-S
IN THE FCST SAT NIGHT INTO EARLY SUN. THIS WILL BE ANOTHER FEATURE
THAT WILL BEAR SOME WATCHING OVER THE NEXT 24-48 HRS.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
HI PRES WILL BLD OVR THE REGION AND JUST OFF THE CST SUN NGT AND
MON. THE HI WILL MOVE OFF THE NRN MID ATLC CST MON NGT INTO TUE
MORNG...WHILE A FRNTL BNDRY PUSHES THRU THE MIDWEST INTO THE LWR MS
VLLY WITH LO PRES DEVELOPING ON THE SRN END OF THE FRNT. SOME LGT
PCPN IN THE WRM ADVECTION AREA WELL AHEAD OF THE FRNT/LO PRES AREA
MAY BREAK OUT LATE MON NGT OR ERLY TUE MORNG OVR OUR WRN CNTIES. THE
PCPN CUD BE IN THE FORM OF LGT SNOW SHRAS ACRS THE NW CNTIES OR A
MIX OF LGT SNOW AND RAIN SHRAS ACRS THE SW CNTIES. IT WILL BE BRIEF
HOWEVER...AS ESE WNDS IN ADVANCE OF THE LO TO OUR SW...WILL QUICKLY
WRM UP TEMPS IN THE MORNG FOR JUST CHC OF RAIN ALL AREAS THROUGHOUT
THE DAY. THE CHC FOR RAIN WILL CONTINUE TUE NGT THRU ERLY WED EVENG
AS LO PRES TRACKS NE FM THE GULF CST STATES UP ACRS THE REGION.
COLDER AIR FILTERS IN BEHIND THE EXITING LO PRES AREA AND COLD FRNT
LATE WED NGT INTO THU MORNG...RESULTING IN A SLGT CHC OF SNOW SHRAS
OR FLURRIES. HI PRES/DRIER AIR WILL THEN BLD IN DURING THU.

MAX TEMPS WILL BE IN THE LWR TO MID 40S MON...IN THE MID 40S TO UPR
50S TUE AND WED...AND IN THE UPR 30S TO UPR 40S THU. MIN TEMPS WILL
BE IN THE UPR TEENS TO UPR 20S MON MORNG...IN THE UPR 20S TO UPR 30S
TUE MORNG...IN THE 40S TO LWR 50S WED MORNG...AND IN THE UPR 20S TO
NR 40 THU MORNG.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
A COLD FRONT EXTENDING FROM NE TO SW OVER WRN VA NEAR CHO WILL
MOVE THROUGH THE TAF SITES OVERNIGHT. A BAND OF LGT RAIN IS FOUND
JUST BEHIND THE FRONT WHICH MAY BRING SHOWERS...MAINLY TO RIC AND
SBY WHERE 3 HOUR TEMPO GROUPS ARE INCLUDED. CEILINGS WILL LOWER TO
MVFR OVERNIGHT. THEY WILL IMPROVE BY MID MORNING AT SBY AND RIC.
AS THE FRONT STALLS OFF THE CAROLINA COAST...LOW LEVEL MOISTURE
WILL LINGER OVER THE SE TAF SITES WITH MVFR MUCH OF THE DAY FRI.
AT THIS TIME...IFR IS NOT EXPECTED BUT ECG WILL NEED TO BE
MONITORED FOR THAT POSSIBILITY.

LGT PRECIPITATION WILL BE POSSIBLE IN SE PORTIONS FRI NIGHT. THERE
WILL BE A CHANCE OF MIXED PRECIPITATION ACROSS THE ENTIRE AREA
SAT NIGHT... ASSOCIATED WITH A STRONG LOW PRESSURE SYSTEM ALONG
THE CANADIAN BORDER. SOME MARGINAL CONDITIONS WILL BE POSSIBLE
DURING PRECIPITATION.

AS HIGH PRESSURE BUILDS INTO THE AREA...VFR CAN BE EXPECTED BOTH SUN
AND MON. LOW PRESSURE APPROACHES FROM THE WEST WITH A CHANCE OF
RAIN AND LOWERING AVIATION CONDITIONS ON TUE.

&&

.MARINE...
WILL MAINTAIN SCA FOR THE CHES BAY AND CSTL WTRS FM FENWICK ISL TO
THE NC/VA BORDER UNTIL 6 PM THIS EVENG DUE TO SW WNDS 15 TO 20 KT
WITH GUSTS TO 25 KT IN ADVANCE OF COLD FRNT. HI PRES WILL BLD IN FM
THE W LATER TNGT AND FRI...THEN MOVE ACRS THE AREA FRI NGT INTO THE
FIRST PART OF SAT. WNDS WILL BECOME NW OR N OVRNGT...BUT WILL NOT GO
ANY HIER THAN 15 KT. N OR NW WNDS WILL START OUT 15 TO 20 KT ON FRI
THEN DIMINISH DURING THE AFTN (EXCEPT MAY SRN TWO CSTL ZNS) AS HI
PRES BLDS CLSR TO THE AREA. MAY HAVE TO ISSUE SCA FOR SEAS FOR NC
CST FRI AND FRI NGT. OTHRWISE...DON'T EXPECT SCA CONDS SAT EVENG/NGT
WITH NEXT FRNTL BNDRY THAT SWINGS ACRS THE REGION. SCA CONDS LIKELY
THO SUN INTO SUN NGT...AS STRNG W OR NW WNDS PREVAIL BEHIND THAT
SYSTEM.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...BKH
NEAR TERM...BKH/SMF
SHORT TERM...BKH
LONG TERM...TMG
AVIATION...LSA
MARINE...TMG



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