Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 211547 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1047 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 /TODAY/...
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HIGH PRES OVR THE RGN BRINGING A COOL AND SUNNY DAY. MIXING SHUD COME CLOSE TO H8...PROVIDING GUSTS 20-25 KT WHICH WL BE SUBSIDING TOWARDS SUNSET. HIGHS IN THE 30S OUTSIDE OF THE HIGHLANDS.
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&& .SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
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HIPRES OVR FCST AREA TNGT. W/ LESSENING WINDS AND LOW DEWPTS...HV A FVRBL RADL COOLING SETUP. LOW TEMPS U20S IN THE CITIES...GNRLY L20S AND TEENS ELSEWHERE. 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.
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&& .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 /15Z FRIDAY THROUGH TUESDAY/...
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VFR THRU VALID TAF PD. 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.
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&& .MARINE...
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HV SOLID SCA CONDS 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.
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&& .TIDES/COASTAL FLOODING...
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CHES BAY IS CURRENTLY IN A LOW TIDE CYCLE...W/ TIDES OF 1 FT BELOW ASTRO PREDICTIONS. NNWLY WNDS CONTG THRU THE DAY BUT W/ WINDS DIMINISHING THIS AFTN NEXT LOW TIDE CYCLE SHOULD NOT BE AS BAD.
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&& .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. && $$ UPDATE...WOODY! PRVS...HTS/AS

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