Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 210826
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
326 AM EST FRI NOV 21 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD ACROSS THE AREA THIS AFTERNOON AND
TONIGHT...AND THEN SHIFT OFFSHORE SATURDAY. A DEEPENING LOW
PRESSURE SYSTEM OVER THE GREAT LAKES WILL LIFT A WARM FRONT
THROUGH THE AREA SUNDAY INTO MONDAY WITH THE ASSOCIATED COLD FRONT
MOVING THROUGH BY TUESDAY MORNING. THE FRONT STALLS JUST OFFSHORE
AS HIGH PRESSURE BUILDS IN THE WAKE AS THE AREA REMAINS POSITIONED
BETWEEN AREAS OF LOW PRESSURE.
&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SFC CDFNT RESIDES ACRS SERN VA ELY THIS MRNG...AND WL BE PULLING
FURTHER AWAY. THE STRONG PD OF CAA ONGOING...WHICH HAS RESULTED IN
PDS OF GUSTY WINDS OVNGT. WHILE THESE WINDS SHUD SUBSIDE SOMEWHAT
TWD DAWN...XPCT THEM TO BE REINVIGORATED AFTER SUNRISE. MIXING SHUD
COME CLOSE TO H8...PROVIDING GUSTS 20-25 KT DURING THE DAYTIME HRS.

CLDS EVIDENT ON SATPIX BANKED UP AGAINST THE APLCNS...BUT ALSO HV A
STREAK ACRS NWRN CWFA. THESE APPEAR TO BE CONNECTED TO THRML TROF...
AND XPCT THEM TO PLAY A ROLE TIL ABT NOON. SUBSIDENCE WL BECOME AN
INCRSG FACTOR INTO THE AFTN...NOT TO MENTION DOWNSLOPING...SO CLDS
WL STRUGGLE TO LAST THRUT THE AFTN. SIMILARLY...TIMEFRAME WHERE
UPSLP SHSN FVRBL CONTS TIL ABT MIDDAY. WLY TRAJ AND LOW DEWPTS WL
WORK AGAINST APPRECIABLE ACCUMS. AM KEEPING PRVS POPS/AMTS.

SINCE H8 TEMPS DROP TO -14C...BELIEVE PTTN SUPPORTS TEMPS COLDER
THAN MOS. HV MODERATED MAXT FCST BY A CPL DEGF...BUT IT STILL WL BE
A CHALLENGE TO GET TEMPS ABV FRZG ACRS NRN MD AND IN THE PTMC
HIGHLANDS.
&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
HIPRES CRESTS ATOP CWFA TNGT. W/ LESSENING WINDS AND LOW DEWPTS...HV
A FVRBL RADL COOLING SETUP. WENT ON LOW SIDE OF GDNC...AND IN
SOME CASES A DEGF OR TWO UNDER THAT.

RDG MVS OFFSHORE SAT...ALLOWING RETURN FLOW TO COMMENCE. WAA WL
SUPPORT AN INCREASE IN MSTR BTWN H8-7...AND HV SCT TO ALMOST BKN
CLDCVR IN GRIDS. STILL HV LOW DEWPTS...SO ANY PCPN WL LKLY GO ARND
THE SFC RDG...IN THE MIDWEST AND GRTLKS RGNS. XPCT IT TO DROP SEWD
FM THERE. WL ENTERTAIN A LOW CHC ACRS THE ALLEGANY FNT AFT MIDNGT
SAT NGT.

H8 TEMPS MAKE A 10 DEGC RECOVERY FM MIDNGT TO MIDDAY SAT. WITH THAT
IN MIND AND MOS SUPPORT...HV WARMED MAXT FM PRVS FCST. RADL COOLING
NOT AS FVRBL SAT NGT. CPLD W/ WAA AND CLDS...WL BE 10-15 DEGF
WARMER. KEPT SOME CUES FM PRVS FCST...BUT WARMED RDGTOPS AND THE
DOWNTOWNS.
&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
INITIALLY DRY CONDITIONS SUNDAY MORNING AS HIGH PRESSURE SHIFTS
FURTHER OFFSHORE AND WEAK RIDGING PERSISTS ALOFT. 00Z MODEL SUITE
CONTINUING TO SUGGEST A SLOWER START TIME TO THE PCPN...WITH
INCREASING CHANCES AFTR 18Z SUNDAY. SHORTWAVE ENERGY ROUNDING THE
TROUGH NEARS MIDDAY...THEN SWINGS THROUGH FOR THE LATTER HALF OF THE
DAY. MEANWHILE...LOW PRESSURE PUSHING INTO THE GL REGION LIFTS ITS
ASSOCIATED WARM FRONT NORTH THROUGH THE AREA...WITH IT STRADDLING
THE MID ATLANTIC BY 12Z MONDAY. MULTIPLE MODEL RUNS NOW STILL
INDICATING BEST CHC FOR PCPN...AND THE HEAVIEST PCPN...AROUND 00Z
MONDAY. PCPN TAPERS OFF CLOSE TO DAYBREAK...WITH A CHC FOR SHOWERS
THROUGHOUT THE DAY ON MONDAY AS A COLD FRONT APPROACHES AND CROSSES
THE REGION. STRONG SURGE OF WAA OVER THE WEEKEND...THEN REINFORCED
WITH THE PASSAGE OF THE WARM FRONT WILL SEND TEMPS WELL ABOVE NORMAL
FOR SUN-MON. THE HIGHER TEMPS WILL ALSO KEEP ANY PCPN DURING THIS
TIME IN THE FORM OF RAIN.

AS THE SFC LOW LIFTS TO THE NORTHEAST...IT DRAGS THE ASSOCIATED COLD
FRONT THROUGH...WITH THE TIMING ON THE LATEST MODEL RUNS SUGGESTING
A MONDAY NIGHT PASSAGE. THE DEVELOPING/DEEPENING TROUGH ALOFT IS
SLOW TO PROGRESS TO THE EAST...AND AS SUCH...THE COLD FRONT STALLS
JUST OFFSHORE TUES-THURS. THE FRONT SHOULD PUSH FAR ENOUGH OFFSHORE
AND WITH A DRIER AIRMASS IN PLACE IN THE WAKE TO KEEP THINGS MAINLY
DRY TUES. DEPENDING ON WHERE THE FRONT ACTUALLY SETTLES COULD
DICTATE A CHANGE IN POPS FOR THE DAYTIME. ITS AT THIS TIME WE ALSO
SEE DIFFERING MODEL SOLUTIONS IN THE HANDLING OF A DEVELOPING LOW
ALONG THE STALLED FRONT AS WELL AS HOW QUICKLY THE LOW FORMING IN
THE NORTHERN PLAINS PROGRESSES TO THE EAST. THE 00Z ECMWF WOULD
SUGGEST A WET SLTN WED. GFS REMAINS THE DRIER SLTN WITH THE BETTER
FORCING FURTHER TO THE EAST. HAVE MAINTAINED DRY POPS FOR NOW UNTIL
A BETTER HANDLE OF THE FEATURES CAN BE DETERMINED. THE GENERAL
AGREEMENT BETWEEN THE MODEL SOLUTIONS THOUGH IS THE AREA BEING
POSITIONED BETWEEN TWO LOWS AS WEAK HIGH PRESSURE BUILDS IN. CAA
BEHIND THE COLD FRONT WILL RETURN TEMPS TO NEAR NORMAL...AND THEN
BELOW NORMAL FOR THE SECOND HALF OF THE WEEK.
&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
VFR THRU VALID TAF PD. CLDS THIS MRNG/MIDDAY AND AGAIN MIDDAY SAT.
CIGS WL BE 050-070. WNDS WL BE THE BIGGEST IMPACT TDA...W/ NW FLOW
GUSTING TO 25 KT THRU MIDDAY. FLOW WL SUBSIDE FM THERE...BECOME LGT
TNGT...AND ATTAIN A SLY TRAJ SAT.

MAINLY VFR CONDITIONS SUNDAY WITH SUB-VFR CONDITIONS LIKELY BY
SUNDAY EVENING AND LASTING THROUGH MONDAY MORNING. IFR PSBL WITH THE
HEAVIEST PCPN SUN NIGHT.

LLWS MAY BRIEFLY BE A CONCERN SUNDAY NIGHT AS A STRONG LLJ SETS UP
OVER THE TERMINALS. AT THE SFC...SLY FLOW INCREASES AHEAD OF THE
COLD FRONT...WITH GUSTS UP TO 20-25 KTS PSBL MONDAY.

VFR CONDITIONS RETURN BY LATE MONDAY AND LAST THROUGH MID WEEK.
WINDS WILL WEAKEN AS WELL...REMAINING LESS THAN 10 KTS TUES-THURS.
&&

.MARINE...
HV SOLID SCA CONDS ONGOING...AND GNLY XPCT IT TO CONT THRU THE
DAYLIGHT HRS. THERE MAY BE A BRIEF LESSENING TWD DAWN...BUT
GUSTINESS WL RETURN UPON SUNRISE. MEAN LYR MIXING 20-25 KT DURING
THE PK.

WINDS DROP OFF RATHER QUICKLY BY SUNSET TNGT AS HIPRES WL ARRIVE
SIMULTANEOUSLY. SLY FLOW 10-15 KT SAT-SAT NGT.

GUSTS TO 20 KTS PSBL SUNDAY MORNING...WITH HIGHER CONFIDENCE OF
OCCURRENCE BY SUNDAY AFTN. SOLID SCA CONDITIONS WITH GUSTS TO 25 KTS
SUNDAY NIGHT-MONDAY. WINDS WILL DIMINISH AND DROP BELOW SCA CRITERIA
ONCE AGAIN FOR TUES-THURS.
&&

.TIDES/COASTAL FLOODING...
BLOWOUT TIDES OF 1 FT BELOW ASTRO PREDICTIONS...MAINLY ACRS NRN
WATERS. NNWLY WNDS CONTG THRU THE DAY. DEPARTURES MAY APPROACH 2 FT
BY LOW TIDE THIS AFTN.
&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR
     ANZ530>543.

&&

$$
SYNOPSIS...HTS/SEARS
NEAR TERM...HTS
SHORT TERM...HTS
LONG TERM...SEARS
AVIATION...HTS/SEARS
MARINE...HTS/SEARS
TIDES/COASTAL FLOODING...HTS






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