Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 021409
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1009 AM EDT WED SEP 2 2015

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

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...
MUCH OF CWFA IS MOCLDY ATTM. THERE EVEN HV BEEN A CPL BRIEF SHRA
IN VA. THIS ASSOCD W/ A WEAK VORT AHD OF THE MAIN EVENT. THE
LATTER AND STRONGER S/WV EVIDENT ON WATER VAPOR IMGRY IN THE UPR
OHVLY ATTM...AND WL BE TRACKING ACRS THE AREA TAFTN.

MODIFIED LWX RAOB DEPCITS PLENTY OF INSTBY BUT VERY LTL SHEAR.
OVERALL AMS FAIRLY TYPICAL FOR LT SUMMER. PWAT HIGH BUT NOT
EXTRAVAGENT...1.5 IN. THEREFORE XPCT NMRS TSRA TO DVLP...AND THEN
COLLAPSE. SVR THREAT NIL. IF ANYTHING...PERHAPS A WEAK WET
MICROBURST POTL. EUNF MVMT SUCH THAT A FLASH FLOOD THREAT NOT
ANTICIPATED EITHER.

&&

.SHORT TERM /7 PM THIS EVENING THROUGH THURSDAY NIGHT/...
THE SHORTWAVE TROUGH WILL DIVE INTO NC TONIGHT AND ACTIVITY WILL
MOVE TO THE SOUTH BY MIDNIGHT. DRY CONDITIONS WILL MOVE INTO THE
REGION OVERNIGHT HOWEVER DUE TO NO AIRMASS CHANGE...WARM AND
HUMID CONDITIONS WILL PERSIST WITH OVERNIGHT TEMPS IN THE 60S/LOW
70S AND MID 70S IN THE METROS.

THE SFC TROUGH WILL MOVE EAST THURSDAY AND BE LOCATED ALONG THE
EAST COAST. NRLY FLOW IS EXPECTED ACROSS THE REGION. 850MB TEMPS
ARE EXPECTED TO INCREASE FROM TUE/WED AND THEREFORE THURSDAY HAS
THE POTENTIAL TO BE THE HOTTEST DAY OF THE WEEK. SEVERAL
DISTURBANCES WILL BE UPSTREAM AND CLOUD COVER MAY CUT DOWN ON THE
TEMPS THURSDAY. A FEW SHOWERS ARE POSSIBLE THURSDAY AFTERNOON
MAINLY WEST OF THE BLUE RIDGE. AN ISOLATED THUNDERSTORM IS ALSO
POSSIBLE.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
A BACKDOOR COLD FRONT WILL ENTER NORTHEAST MD LATE FRI AND MOVE
SWD ACROSS THE REST OF THE AREA FRI NIGHT. SCT SHOWERS AND/OR
T-STORMS CAN BE EXPECTED ALONG AND AHEAD OF THE FRONT FRI EVENING
WITH ACTIVITY LINGERING LONGER ALONG THE I-64 CORRIDOR AND
CHARLOTTESVILLE AREA.

HIGH PRESSURE SFC AND ALOFT BUILDS QUICKLY LATE FRI NIGHT THROUGH
SUN LEADING TO VERY DRY CONDITIONS AND COOLER TEMPERATURES. WHILE
IT IS EXPECTED TO BE SUNNY MUCH OF THE WEEKEND...AEROSOL OPTICAL
DEPTH (AOD) OUTPUT FROM THE INTERNATIONAL COOPERATIVE FOR AEROSOL
PREDICTION MULTI-MODEL ENSEMBLE (ICAP MME) SHOWS REMNANT SMOKE
FROM THE GREAT LAKES REGION GETTING SHUNTED SOUTHEASTWARD INTO THE
MID-ATLC FRI INTO THE WEEKEND AS STEERING WINDS BECOME MORE
NORTHEASTERLY. SO...POTENTIAL FOR AIR QUALITY ISSUES OVER THE
WEEKEND UNDER STAGNANT HIGH PRESSURE SYSTEM.

&&

.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDITIONS ACRS THE TERMINALS ATTM...ALSO SOME HZ NOTED.
OVERALL...DO NOT XPCT WIDESPREAD FLGT RESTRICTIONS...ALTHO
SHRA/VCTS POSSIBLE AT MRB-CHO THIS AFTERNOON. IF AIRFIELD DOES
RECEIVE DIRECT IMPACT FM A CELL THEN POTL FOR BRIEF IFR. THE RISK
MUCH TOO LOW TO INCL IN TAF. SOME ACTIVITY MAY MOVE INTO IAD-DCA
LT DAY BUT CONFIDENCE IN THIS OUTCOME IS LOW.

ACTIVITY WILL MOVE TO THE SOUTH TONIGHT. SUB-VFR VSBYS ARE
POSSIBLE AGAIN INTO THURS MORNING DUE TO FOG. VFR CONDITIONS
EXPECTED THURSDAY.

BACKDOOR CFDNT WILL CROSS THE AREA FRI NIGHT WITH SHIFTING WINDS.
RISK OF SHOWERS AND T-STORMS WILL BE ENDING FROM NORTHEAST TO
SOUTHWEST FRI NIGHT. ALSO...POTENTIAL FOR VISBILITY RESTRICTIONS
FRI INTO THE WEEKEND AS AEROSOL MODELS SUGGEST SMOKE GETTING
SHUNTED SOUTHEASTWARD FROM THE GREAT LKS REGION INTO THE MID-ATLC.
BUILDING HIGH PRES SFC AND ALOFT AND STRENGTHENING SUBSIDENCE
INVERSION COULD FURTHER COMPLICATE THINGS.

&&

.MARINE...
A SFC TROUGH IS EXPECTED TO FORM LATER TODAY AND A FEW
SHOWERS MAY POP UP THIS AFTERNOON. WINDS SHOULD STAY LIGHT BELOW
10KTS THROUGH THURSDAY. SFC TROUGH MOVES EAST OF THE WATERS
THURSDAY.

FRONTAL PASSAGE EXPECTED FRI NIGHT WITH SHIFTING WINDS. WINDS
COULD APPROACH SCA CRITERIA FRI AFTERNOON AND SATURDAY. REMNANT
SMOKE EXPECTED TO GET TRANSPORTED INTO THE REGION OVER THE WEEKEND
COULD RESULT IN VISIBILITY RESTRICTIONS.

&&

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

&&

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



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