Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 010754
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
354 AM EDT TUE SEP 1 2015

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OFFSHORE TODAY. AN UPPER-LEVEL
DISTURBANCE ALONG WITH ITS ASSOCIATED SURFACE TROUGH WILL PASS
THROUGH THE REGION WEDNESDAY. WEAK HIGH PRESSURE WILL BUILD
OVERHEAD THURSDAY BEFORE A BACKDOOR COLD FRONT MOVES INTO THE AREA
LATE FRIDAY INTO THE WEEKEND.
&&

.NEAR TERM /THROUGH TONIGHT/...
SFC HIPRES ANALYZED ACRS THE MID ATLC/SERN CONUS. HWVR WK LOPRES
INVOF HSE IS RESULTING IN LCL ONSHORE FLOW. MARINE STRATUS RAPIDLY
BCMG THE BIGGER ISSUE ACRS SERN VA...AND ITS CREEPING NWWD. ITS
ALREADY ENGULFED EZF/GVE/OMH/CJR. SUSPECT IT/LL MAKE FURTHER INROADS
ACRS THE PIEDMONT OF VA. ACRS PA FOG HAS BEGUN TO FORM...AND IT
SEEMS AS THO THERE ARE PATCHES OF IT ACRS NRN MD AS WELL.

MESOSCALE GDNC PERFORMING BETTER THAN SYNOP MDLS IN TERMS OF
IDENTIFYING THE LLVL MSTR. HWVR...IT WASNT DELINIATING BTWN FOG/LOW
CLD VERY WELL...PROVIDING SOME UNCERTAINITES AS TO HOW EXTENSIVE THE
SHIELD WL BECOME. AM CONCERNED THAT IT CUD REACH THE NRN VA DC
BURBS. IF IT DID...IT WUD HV BIG IMPLICATIONS ON THE FCST EVOLUTION
LATER TDA. FOR NOW AM HOLDING A RIBBON LOW CLD IN VA E OF THE BLURDG
UP TO ABT HEF. WL BE MONITORING OBS AND ADJUSTING GRIDS AS NEEDED.

THE SYNOP HGT PTTN FEATURES A RDG ACRS THE APLCNS/GRTLKS/MIDWEST.
THERES A WK CUTOFF H5 LOW IN/NEAR OH...WHICH SHUD STAY W OF AREA
TDA. THEREFORE...MAIN FORCING WL COME FM TRRN CICRULATIONS...AS
INSTBY/SHEAR MINIMAL. CONFINING 20-30 POP TO THE APLCNS S OF W99.
OTRW JUST BILLOWING DIURNAL CU...WHICH WL DSPT AFTR SUNSET.

ASSUMING MARINE CLDS ERODE JUST AFTER SUNRISE...WL BE ABLE TO ACCESS
THE WARMTH IN THE COLUMN...AND BE ABLE TO REACH LWR 90S. AM STILL
HOLDING ONTO THAT SOLN...BUT THE ONLY THING THATS ERODING RIGHT NOW
IS FCSTR CONFIDENCE.

UNDERNEATH THE RDG TNGT SKIES SHUD BE MOCLR AND WNDS LGT. DEWPTS IN
THE UPR 60S. THUS... PTTN SHUD FAVOR FOG DVLPMNT SINCE THERES NO
FEATURE THAT CUD BRING A MARINE LYR INLAND. WL HV PATCHY FOG ACRS
MUCH OF THE CWFA. MIN-T CLOSE TO GDNC.
&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
THE MIDWEST H5 LOW SHUD BE OPENING UP AND HEADING EAST. THIS CUD
PROVIDE A MECHANSIM FOR A SLGTLY MORE ORGANIZED AND WIDESPREAD TSRA
DVLPMNT. FCST WL FEATURE SCT POPS ACRS MUCH OF THE AREA FOR TSRA.
METRO BALT FURTHEST AWAY FM THIS FORCING FEATURE AND HAS ONLY SCHC
POPS. EMPHASIS WL BE ON MIDDAY-AFTN HRS.

THE S/WV WL BE SHEARING OUT AND HEADING SE WED EVNG. WL BE KEEPING
SOME LINGERING POPS...BUT GRDLY TAPERING CHCS OFF OVNGT. CAPE WASNT
HIGH TO START WITH AND WL BE DIMINISHING. THEREFORE HV TRANSITIONED
TSRA TO SHRA. ANY ADDTL PCPN SHUD BE MINIMAL.

TEMPS ON WED SHUD BE FAIRLY SIMLR TO TUE...AS NOT MUCH HAS CHGD
INTHE OVERALL PTTN BTWN THESE TWO DAYS.
&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AN UPPER LEVEL DISTURBANCE SHOULD BE SOUTH OF THE REGION THURSDAY
MORNING. LINGERING SHOWERS ARE POSSIBLE IN THE MORNING MAINLY
ACROSS THE SOUTHERN MID-ATLANTIC. A SURFACE TROUGH SHOULD BE LOCATED
TO THE SOUTH AND EAST THURSDAY AFTERNOON AND WINDS SHOULD BECOME
NRLY THURSDAY. ANOTHER UPPER LEVEL DISTURBANCE WILL APPROACH THE
REGION THURSDAY AFTERNOON AND WARM CONDITIONS WITH DEWPTS IN THE MID
60S MAY RESULT IN A FEW SHOWERS AND THUNDERSTORMS MAINLY WEST OF THE
BLUE RIDGE. COVERAGE WILL LIKELY BE GREATER TO THE NORTH AND SOME
ACTIVITY MAY MOVE INTO THE REGION THURSDAY NIGHT. THE DISTURBANCE
MOVES THROUGH THE REGION FRIDAY AND FRIDAY NIGHT. TEMPS IN THE 90S
WITH DEWPTS IN THE MID 60S WILL LEAD TO ANOTHER CHANCE FOR
SHOWERS AND THUNDERSTORMS. TEMPS ABOVE NORMAL THURSDAY-FRIDAY.

HIGH PRESSURE BUILDS INTO THE MID-ATLANTIC FROM NEW ENGLAND FRIDAY
NIGHT AND INTO SATURDAY. A BACKDOOR COLD FRONT IS EXPECTED TO MOVE
INTO THE REGION AND BRING DRIER AND COOLER CONDITIONS FROM
NORTHEAST TO SOUTHWEST. SHOWERS AND THUNDERSTORMS ARE POSSIBLE ALONG
AND AHEAD OF THE FRONT MAINLY ACROSS THE SW SATURDAY. HIGH PRESSURE
BUILDS INTO THE REGION SUNDAY BEFORE DRIFTING OFF THE COAST
MONDAY.
&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
AM WATCHING AREA OF LOW CLD ACRS SERN VA THAT CREEPING NEWD. TAFS
ATTM DO NOT FEATURE THESE SUB-IFR RESTRICTIONS. GDNC SUGGESTING THAT
THE NRN PROGRESS WL STOP SHORT OF CHO/IAD/DCA. W/O EVIDENCE TO THE
CONTRARY...FCST BASED ON THESE MODEL SOLNS. INSTEAD AM FEATURING
PREDAWN MVFR FOG. MUST ADMIT LOW CONFIDENCE.

AFTER DAYBREAK...AND LOW CLD OR FOG THAT DOES MANIFEST ITSELF SHUD
ERODE. DIURNAL CU SHUD DVLP...BUT BASES 050-060 WL HV NO OPERATIONAL
IMPACT...NOR WL LGT WNDS.

ANTHR FOG OPPORTUNITY COMES TNGT. WL KEEP ANY RESTRICTIONS AT MVFR
TIL CONFIDENCE IN ITS OCCURENCE GROWS.

S/WV CROSSING TERMINALS WED WL PROVIDE A SLGTLY BETTER CHC AT TSRA.
SCT CVRG SO DIRECT HIT/TERMINAL IMPACTS STILL UNCERTAIN. BWI/MTN
SEEMS TO BE AWAY FROM PATH OF HIEST RISK. BRIEF FLGT RESTRICTIONS
PSBL W/IN ANY TSRA.

PREVAILING VFR CONDITIONS EXPECTED THU-SAT. SHRA/VCTS POSSIBLE
THURSDAY-FRIDAY...MAINLY IN THE AFTERNOON.
&&

.MARINE...
W/SW FLOW AOB 10 KT ATTM. WNDS SHUDNT BE MUCH HIER THAN THAT TDA OR
THIS EVNG. ANTICIPATE FLOW BCMG ONSHORE DURING THE AFTN.

MAY BE A FEW TSRA CROSSING WATERS WED. LGT NWLY FLOW BHD S/WV.

A SFC TROUGH WILL LIKELY BE NEAR THE WATERS THURSDAY. AN UPPER LEVEL
DISTURBANCE MAY BRING SHOWERS AND THUNDERSTORMS FRIDAY. HIGH
PRESSURE IN CONTROL AND WILL LIKELY KEEP WINDS BELOW SCA
CONDITIONS.
&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...HTS
NEAR TERM...HTS
SHORT TERM...HTS
LONG TERM...HAS
AVIATION...HAS/HTS
MARINE...HAS/HTS


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