Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 021928
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
328 PM EDT WED SEP 2 2015

.SYNOPSIS...
SURFACE TROUGH WILL MOVE OVER THE REGION THROUGH THIS EVENING. WEAK
HIGH PRESSURE BUILDS OVERHEAD THURSDAY BEFORE A BACKDOOR COLD FRONT
MOVES INTO THE AREA FRIDAY. HIGH PRESSURE THEN RETURNS FOR THE
WEEKEND INTO EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
RADAR LIT UP BY 16Z AS S/WV ENERGY HIT THE 2000 J/KG MUCAPE AMS.
THERE/S STILL NO SHEAR TO SPEAK OF...BUT INSTBY...PVA AND STEEP
LLVL LAPSE RATES HV WORKED IN CONCERT TO PRODUCE SCT-NMRS TSRA W
OF THE BLURDG. ECHOES PRIMARILY IN THE LWX CWFA. SOME OF THESE
ECHOES HV BEEN TALL. PER PREV ANALYSIS...ALTHO SVR WX NOT
XPCTD... IF A THREAT WERE TO COME FM THESE...IT WUD BE FM A WET
MICROBURST. DO HV HVY RAIN IN THESE CELLS AS WELL. PWAT RUNNING
BTWN 1.5-1.75 INCH. WHILE FFG HIGH ENUF SO THAT SHUDNT BE AN ISSUE
EITHER /WEVE BEEN IN A DRY SPELL PAST MONTH OR TWO/...REPEATED
ECHOES MAY CAUSE LCL PONDING.

BUMPED POPS UP INTO THE LKLY RANGE FOR REST OF THE AFTN. AM
CONFINING HIEST POPS INVOF THE S/WV...WHICH WL TAKE IT S OF DC BY
SUNSET...AND OUT OF THE CWFA BY MIDNGT. AM THINKING THE CLDS WL
THIN IN THE SUBSIDENCE IN THE WAKE OF THE VORT...SO WL HV MOCLR
SKIES OVNGT. SINCE GRND WL BE WET...AMS HUMID...AND WNDS STILL
LGT...THAT MAKES FOR A GOOD FOG RECIPE. HV PATCHY FOG FOR MUCH OF
VA/PTMC HIGHLANDS BY DAWN.

HV MADE NO ADJUSTMENTS TO MIN-T...WHICH WL RANGE FM MID 60S TO LWR
70S.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
H5 RDG AXIS WL RESIDE ACRS THE MS VLY THU...WHICH PLACES CWFA IN
THE NW FLOW. HWVR...THE AMS WL BE JUST AS WARM...HUMID...AND
UNSTBL AS TDA. WUD XPCT DIURNALLY DRIVE TSRA TO DVLP ALNG THE MTNS
DURING THE AFTN. THERES CONSISTENT MDL EVIDENCE THAT THESE STORMS
WL EMERGE FM THE MTNS AND TRACK INTO THE CSTL PLAIN BY EVNG.
TIMING SPECIFIC VORTS PROBLEMATIC AT THIS POINT...BUT WUD THINK
THAT ALL OF THIS ACTIVITY WL CLEAR CWFA BEFORE DAWN.

HVNT MADE ANY BIG ADJUSTMENTS TO TEMPS...AS PERSISTENCE SHUD PROVE
TO BE A GOOD FCSTG MODEL.
&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
MAIN WEATHER FEATURE DURING THE LONG TERM WILL BE A BACKDOOR COLD
FRONT THAT MOVES THROUGH FRIDAY AFTERNOON AND EVENING...PROVIDING
RAIN CHANCES FOR THE ENTIRE AREA. ATTM...KEPT POPS AT CHANCE
EVERYWHERE...AS NOT ALL GUIDANCE SUGGESTS WIDESPREAD COVERAGE. WHILE
CAPE WILL BE LOW/MODERATE...GENERALLY AOA 1000 J/KG...EBS NEARLY
NONEXISTENT...SO EXPECT PULSE-TYPE ACTIVITY AND HEAVY RAINERS AS
INDIVIDUAL CELLS MOVE VERY SLOWLY. CLOUD COVER...ONSHORE FLOW...AND
FRONTAL PASSAGE SHOULD WORK IN CONCERT TO KEEP TEMPERATURES A FEW
DEGREES LESS THAN PREVIOUS DAYS. HOWEVER...STILL EXPECT TEMPERATURES
A FEW DEGREES AOA NORMAL. PRECIP CHANCES SHOULD DWINDLE QUICKLY
AFTER DUSK FRIDAY NIGHT WITH LOSS OF INSTABILITY.

VERY LITTLE DAY-TO-DAY VARIABILITY IN SENSIBLE WEATHER THROUGH THE
REMAINDER OF THE EXTENDED...AS HIGH PRESSURE BUILDS IN SATURDAY AND
REMAINS THROUGH THE MIDDLE OF NEXT WEEK. WITH WARM MID-LEVEL
TEMPERATURES...LAPSE RATES WILL BE VERY POOR...CONSEQUENTLY CHANCES
FOR PRECIP DURING THIS PERIOD APPEAR VERY LOW AND GENERALLY WOULD
ONLY BE CONFINED TO THE HIGHER TERRAIN IN THE WEST.
ELSEWHERE...EXPECT HIGH TEMPERATURES NEAR NORMAL THROUGH THE
WEEKEND...WITH DEWPOINTS FALLING INTO THE U50S BY SUNDAY. BY
MONDAY...TEMPERATURES START CREEPING BACK ABOVE NORMAL AND BY
TUESDAY SOME AREAS COULD BE BACK INTO L90S.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
NMRS TSRA INVOF MRB/CHO...AND THESE STORMS APPCHG IAD. DCA SHUD BE
ON THE EDGE OF THE ACTIVITY. XPCT BRIEF IFR W/IN ANY STORM. SOME
STRONG WIND GUSTS PSBL.

ONCE STORMS CLR...SHUD BE PLENTY OF RESIDUAL LLVL MSTR AS SKIES
CLR. MVFR FOG POTL...SPCLY MRB/CHO. WL NEED TO EVALUATE EXTENT OF
IFR POTL.

FCST SHUD BE RELATIVELY SIMLR TMRW...EXCEPT ALL ACTIVITY SHUD BE
SVRL HRS LATER. LT DAY/ELY EVE TSRA...PRODUCING LCL RESTRICTIONS.

SUB-VFR POSSIBLE FRIDAY AFTERNOON AS BACKDOOR COLD FRONT MOVES
THROUGH THE REGION. VFR CONDITIONS RETURN SATURDAY THROUGH THE
EXTENDED UNDER HIGH PRESSURE.

&&

.MARINE...
NMRS TSRA ACRS THE LAND ATTM. THESE SHUD STAY W OF THE
WATERS...BUT WONT COMPLETELY RULE OUT A STORM OR TWO REACHING THE
PTMC. STRONG WIND GUST POTL W/IN A FEW OF THESE STORMS.

NW FLOW THRU THU. ANOTHER ROUND OF SCT TSRA PSBL LATE DAY INTO THE
EVNG...MOSTLY STAYING W OF THE MARINE AREA BUT THE PTMC RIVER WL
BE ON THE EDGE OF THE HIEST POTL RGN.

WINDS EXPECTED NEAR SCA FRIDAY AFTERNOON THROUGH SATURDAY
EVENING...AS BACKDOOR COLD FRONT MOVES THROUGH THE REGION. COLD
FRONT WILL ALSO BRING CHANCE FOR SHOWERS AND THUNDERSTORMS OVER THE
WATERS FRIDAY AFTERNOON AND EVENING. WINDS SHOULD SUBSIDE BELOW SCA
LATE SATURDAY INTO SUNDAY MORNING AND THROUGH THE EXTENDED.

&&

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

&&

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


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