FXUS61 KAKQ 261023
AFDAKQ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
522 AM EST THU NOV 26 2009
.SYNOPSIS...
WEAK HIGH PRESSURE REMAINS OVER THE REGION TODAY. A STRONG COLD
FRONT WILL MOVE THROUGH THURSDAY NIGHT...PROVIDING A CHANCE FOR
SHOWERS. AN UPPER LEVEL LOW PRESSURE SYSTEM MOVES ACROSS THE MID
ATLANTIC STATES ON FRIDAY...THEN HIGH PRESSURE BUILDS IN FROM THE
WEST OVER THE WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
HAVE EXPANDED THE DENSE FOG ADVISORY TO COVER ALMOST ALL OF THE
CWA...EXCEPT FOR EXTREME SE VA AND NERN NC. WITH THE CLEARING
SKY...LIGHT WINDS AND WET GROUND/BOUNDARY LAYER...SEEING AREA WIDE
FOG DOWN TO A 1/4 SM OR LOWER. THIS FOG SHOULD LINGER THROUGH
ABOUT 9 AM BEFORE IMPROVING AND CLEARING OCCURS. LOTS OF DRY AIR
IN PLACE ACROSS THE SE COAST WITH ONE AREA OF LOW PRESSURE LIFTING
NE IN THE WESTERN ATLANTIC. IT SHOULD REMAIN FAR ENOUGH OFF THE
COAST TO NOT IMPACT THANKSGIVING DAY. WITH THE DRY AIR AND LIGHT
WIND...SHOULD BE A SUNNY AND MILD DAY ACROSS THE REGION. HAVE GONE
WITH HIGHS IN THE LOW TO MID 60S...ASSUMING THAT THE FOG DOES NOT
LINGER TOO LONG AND LIMIT THE HEATING.
FOR TONIGHT...THE STRONG UPPER TROUGH WILL SLIDE EAST...PUSHING A
COLD FRONT FRONT INTO THE AREA AROUND 00Z. THE GFS AND NAM ARE
SIMILAR IN TIMING WITH THE FRONT ARRIVING IN THE WEST AROUND 00Z
AND MOVING ACROSS THE AREA...EXITING THE EASTERN SHORE AROUND 9Z.
WHILE THE MOISTURE IS NOT GREAT WITH THIS BOUNDARY...THE DYNAMICS
AND THERMAL GRADIENTS MAKE IT A STRONG BOUNDARY THAT SHOULD
PRODUCE A BAND OF SCATTERED RAIN SHOWERS. HAVE INCREASED POPS TO
40 TO 50 PERCENT WITH THE BOUNDARY. SHOULD SEE GUSTY NW WINDS
DEVELOP ALONG AND BEHIND THE FRONT WITH THE STRONG COLD ADVECTION.
WITH THAT COLD AIR...TEMPERATURES WILL FALL DOWN INTO THE UPPER
30S TO MID 40S.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY/...
ONCE THE COLD FRONT EXITS THE COAST EARLY FRIDAY MORNING...THE
COLD AIR WILL HELP TIGHTEN THE THERMAL GRADIENT WHICH WILL HELP
INVIGORATE THE AREA OF LOW PRESSURE THAT IS LIFTING NE ALONG THE
COAST. THIS LOW WILL INTENSIFY OFF THE NEW ENGLAND COAST. THIS
WILL HELP THE NW FLOW TO STRENGTHEN. THIS WILL LEAD TO A CLEARING
PATTERN WITH THE DOWNSLOPE FLOW AND ALSO ALLOW FOR GOOD MIXING IN
THE COLD ADVECTION. EXPECT TO SEE GUSTY CONDITIONS ON FRIDAY...BUT
IT SHOULD BE DRY AND COOL. 850 MB TEMPS ARE AROUND -2C TO -4C.
THIS ONLY SUPPORTS HIGHS IN THE LOW TO MID 50S UNDER FULL SUN.
THE STRONG LOW AND UPPER TROUGH SLIDE OFF THE COAST FRIDAY
NIGHT...WHICH ALLOW THE FLOW TO WEAKEN...BUT IT WILL STILL BE COLD
WITH SOME LOCATIONS GOING BELOW FREEZING OVER CENTRAL VA. AS
RIDGING BUILD EAST ALOFT...WILL SEE A WARM ADVECTION PATTERN
DEVELOP SO TEMPERATURES WILL BEGIN TO MODERATE AND WITH VERY DRY
AIR AROUND...EXPECT SUNNY CONDITIONS WITH LIGHT WINDS.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
ONCE AGAIN...HAVE INCORPORATED THE LATEST HPC GUIDANCE FOR THE
EXTENDED PERIOD...WHICH IS LARGELY BASED ON THE ECMWF. THE ECMWF
CONTINUES TO SHOW MORE FVRBL RUN-TO-RUN CONSISTENCY WITH
TIMING/LOCATION OF SYNOPTIC FEATURES EARLY-MID WEEK...MOST NOTABLY
WITH THE NEXT COLD FRONT MON NIGHT AND TUE...AND THE POTENTIAL FOR
YET ANOTHER DUAL-LOW SCENARIO TAKING SHAPE BY MID-WEEK AS A
DEEPENING LOW DROPS INTO THE NRN MS VLY...WHILE LOW PRES FORMS ALONG
THE EXITING LLVL FRONT/BAROCLINIC BOUNDARY (WRN PERIPHERY OF GULF
STREAM) JUST OFF THE SE-MID ATLC COAST.
CONTINUED FAIR CONDITIONS WITH MODERATING TEMPS ON TAP FOR SUN TO
WRAP UP THE HOLIDAY WEEKEND. HIGHS THROUGH THE 60S (LOW-MID 60S N...
MID/UPR 60S S)...CONSISTENT WITH THE LLVL THICKNESS. ECMWF STILL
SLOWER WITH THE FROPA EARLY NEXT WEEK...THOUGH RECENT GFS RUNS HAVE
TRENDED TOWARD THE ECMWF (WHICH IS AGAIN A GOOD SIGN FOR THE ECMWF'S
CREDIBILITY WITH THIS EVOLVING PATTERN). DEPENDING ON HOW QUICKLY WE
SEE INCREASING CLOUDS/RAIN CHCS MOVING IN FROM THE W...TEMPS CAN GET
QUITE MILD ONCE AGAIN BASED ON THE PROJECTED LLVL THICKNESS
STRUCTURE. FOR NOW...HAVE FCSTD UPR 50S OVER FAR NW PTNS TO MID/UPR
60S FAR SE.
SHOWERS WITH THE FROPA MOST LIKELY MON NIGHT AND TUE...AND AS SUCH
HAVE RAISED POPS TO 40-50% (STILL TOO EARLY TO GO HIGHER BASED ON
THE HIGH PROBABILITY OF TIMING ERRORS 5-6 DAYS AWAY). ANOTHER SWATH
OF SYNOPTIC "STRATIFORM" RAIN/DRIZZLE LOOKS LIKE A GOOD POSSIBILITY
BY WED-THU...AS ANOTHER LOW FORMS OFF THE SE CST ALONG THE LLVL
BAROCLINIC ZONE AND TRACKS NE.
&&
.AVIATION /10Z THURSDAY THROUGH MONDAY/...
PATCHY FOG...LOCALLY DENSE...NOTED ACROSS PHF-RIC-SBY THIS MORNING
IN THE WAKE OF DEPARTING CIRRUS DECK. MAINLY IFR/LIFR AT THESE
SITES...WITH VFR/HIGH END MVFR ACROSS SE TERMINALS ECG/ORF...WHERE
CIRRUS PERSISTS THIS MORNING. AS THE CIRRUS PUSHES OFFSHORE THIS
MORNING AND DRIER MIDLVL AIR PUSHES EASTWARD...COULD YET SEE SOME
LOWER MVFR/IFR CONDITIONS FOR A BRIEF TIME TWDS SR AT
ECG/ORF...THOUGH HV HELD OFF ON THIS WORDING FOR NOW IN TAFS. ENOUGH
LLVL MOISTURE WL PERSIST TODAY FOR SOME LINGERING LOW CLDS
(4-6KFT)...WITH THE GREATEST SKY CVR ALONG AND NORTH OF SBY.
OTW...DRY CONDS EXPECTED ACROSS TERMINALS TODAY.
BIGGER OPERATIONAL CONCERN GOING FORWARD LOOKS TO BE WITH GUSTY WNDS
LT TONIGHT AND FRIDAY AS A COLD FNT CROSSES THE REGION THROUGH AFTER
MIDNIGHT TNGT/ERY FRI MORNING. WNDS BEHIND THE FNT BECOME W/NW WHICH
WL USHER IN DRIER AIR. TIGHTENING PRESSURE DIFFERENTIAL BETWEEN LOW
TO THE NE AND APPROACHING SFC RIDGE TO THE SOUTH WL ALLOW FOR BREEZY
TO WINDY CONDITIONS FRI AFTN...WITH GUSTS TO 20-30KT POSSIBLE DURING
THIS PERIOD. OTW...LOOK FOR MAINLY VFR CONDS FRI AND THROUGH THE
WEEKEND. NEXT CHC OF PCPN LOOKS TO BE LATE MON INTO TUE.
&&
.MARINE...
SCA IN EFFECT FOR FAR NORTHERN WATERS THS MORNING WAS ABLE TO BE
EXPIRED...AS SEAS FINALLY SAFELY BELOW CRITERIA. NEXT AREA OF LOW
PRESSURE NOW NOTED OFF THE CAROLINA COAST THIS MORNING. SHOULD BE A
GENERALLY BENIGN DAY ACROSS THE WATERS TODAY WITH MAINLY LGT NNE
FLOW TODAY INTO ERY TONIGHT.
BY TONIGHT HOWEVER...CONDITIONS LOOK TO GO DOWNHILL SLOWLY BUT
STEADILY...AS AN UPPER TROUGH CURRENTLY OVER IN/MI THIS MORNING IS
FORECAST TO DEEPEN/AMPLIFY...AND TAKE ON AN NEGATIVE TILT AS IT
PIVOTS TOWARDS THE UPR GRT LAKES BY 12Z FRIDAY. THIS FEATURE WILL
QUICKLY PUSH A STRONG COLD FRONT ACROSS THE REGION LATE TONIGHT/ERY
FRIDAY MORNING. HV GONE AHEAD WITH A SCA OVER THE WATERS FROM 02Z
TONIGHT THROUGH EARLY FRIDAY MORNING.
FORECAST GETS A BIT TRICKY FOR FRIDAY. ALL MODELS CONTINUE TO DEPICT
LOW PRESSURE OFF OF HATTERAS THIS MORNING DEEPENING RAPIDLY AS IT
REACHES THE NEW ENGLAND COAST FRIDAY MORNING. GIVEN WHAT SHOULD BE
AN INCREASINGLY STRONG PRES GRADIENT AND CAA OVER STILL RELATIVELY
WARM COASTAL WATERS...THIS SHOULD EASILY YIELD STRONG SCA WNDS
FRIDAY. CONFIDENCE DEFINITELY HIGH AT THIS TIME THAT LOW-END GALES
ARE LIKELY FROM FRI AFTN THROUGH EARLY SAT MORNING. 00Z/26NOV NAM
AND GFS BOTH SHOWING ADEQUATE MOMENTUM XFER AND 925-850 MB WIND
SPEEDS (~35-45KT BETWEEN 12-15Z FRIDAY AND EARLY SATURDAY
MORNING...WITH HIGHEST VALUES CLOSER TO THE BOMBING LOW OFF THE
EASTERN NEW ENGLAND COAST. AT THIS POINT...SCA CONDITIONS ARE A
SOLID BET FOR ALL WATERS...AND OCCASIONAL TO FREQUENT GUSTS TO GALE
ALSO APPEAR LIKELY FOR FRIDAY INTO AT LEAST EARLY SATURDAY MORNING.
HOWEVER...THE EXACT TIMING OF GALES IS PROBLEMATIC AT BEST 3
FORECAST PERIODS OUT. FOR THIS REASON...PLUS IN LIGHT OF SCA
CONDITIONS THAT WL HV TO BE DEALT WITH BEFORE THE "RAMP-UP" TO
GALES...HV DECIDED TO RUN WITH SCA FOR LATE TONIGHT INTO FRIDAY
MORNING...WITH A LONG-FUSED GALE WATCH THEREAFTER FOR FRIDAY INTO
SATURDAY. THIS WILL ALLOW DAYCREW THE CHANCE TO BETTER REFINE THE
EXACT PERIOD OF GALE GUSTS...AND ALSO AFFORDS THE CHC TO EXTEND SCA
OUT IN TIME IF PROGRESSION OF FRONT IS SLOWER THAN CURRENTLY
EXPECTED.
GRADIENT RELAXES VERY SLOWLY SATURDAY...AND SCA FOR SEAS WL LIKELY
BE NEEDED OVER THE COASTAL WATERS INTO LTR SAT AT LEAST. CONDITIONS
LOOK TO BECOME A BIT MORE BENIGN FOR SUNDAY INTO MONDAY AS FLOW
LOOKS TO TURN SSW AS HIGH PRESSURE OVER THE SOUTHEAST CONUS BUILDS
SOUTH OF THE REGION. ANOTHER FRONT APPROACHES FROM THE WEST BY LTR
MONDAY/TUESDAY.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR MDZ021>025.
NC...DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR NCZ012-013-
030.
VA...DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR VAZ048-049-
060>094-099.
MARINE...GALE WATCH FROM FRIDAY MORNING THROUGH LATE FRIDAY NIGHT FOR
ANZ630>633-650-652-654-656-658.
SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 6 AM EST
FRIDAY FOR ANZ630>633-650-652-654-656-658.
&&
$$
SYNOPSIS...ESS
NEAR TERM...ESS
SHORT TERM...ESS
LONG TERM...BKH
AVIATION...MAM
MARINE...MAM
