Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 030757
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
357 AM EDT THU SEP 3 2015

.SYNOPSIS...LOW PRES WILL REMAIN ALONG THE COAST THROUGH TODAY.
BACKDOOR CDFNT WILL CROSS THE AREA FRI AFTERNOON AND NIGHT. HIGH
PRES WILL BUILD FOR THE LABOR DAY WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...A SHORTWAVE TROUGH IS LOCATED ACROSS
COASTAL NC THIS MORNING WHILE RIDGING MOVES INTO THE MID-
ATLANTIC. HIGH PRESSURE PERSISTS AT THE SURFACE.

A WARM AND HUMID AIRMASS CONTINUES ACROSS THE MID-ATLANTIC THIS CLEAR
MORNING. DEWPTS ARE IN THE UPPER 60S TO LOW 70S WITH TEMPS WITHIN A
FEW DEGREES. ELEVATED INSTABILITY PERSISTS ACROSS MUCH OF THE REGION
INCLUDING THE OHIO VALLEY THIS MORNING. A FEW STORMS HAVE FORMED IN
OH/W PA AND ARE MOVING SOUTHWARD. THESE STORMS ARE IN A FAVORABLE
ENVIRONMENT WITH DECENT INSTABILITY. THE TRACK BRINGS THEM ALONG THE
APPALACHIANS SKIRTING THE WESTERN EDGE OF THE CWA THIS MORNING.
PATCHY FOG HAS DEVELOPED ACROSS MUCH OF THE AREA THAT RECEIVED RAIN
FROM WEDNESDAY. VISIBILITIES HAVE BEEN REDUCED TO LESS THAN A MILE
ALONG PORTIONS OF I-81/I-68 AS WELL AS VALLEYS IN THE POTOMAC
HIGHLANDS. FOG WILL CONTINUE THROUGH SUNRISE.

NO CHANGE IN AIRMASS IS EXPECTED TODAY AND WARM AND HUMID CONDITIONS
WILL CONTINUE. TEMPS WILL REACH THE UPPER 80S ALONG AND WEST OF THE
BLUE RIDGE TO THE LOW TO MID 90S NEAR THE I-95 CORRIDOR. A
DISTURBANCE WILL MOVE INTO THE OHIO VALLEY TODAY. INSTABILITY WILL
BE PRESENT AGAIN TODAY WITH MLCAPE VALUES REACHING 1-1.5 J/KG EVEN
TOUCHING 2K IN SOME SPOTS. AN UPPER LEVEL RIDGE WILL KEEP THE WIND
FLOW WEAK BUT THUNDERSTORMS ARE STILL EXPECTED TO FORM THIS
AFTERNOON. COVERAGE WILL LIKELY BE MORE WIDESPREAD ACROSS THE OHIO
VALLEY NEAR THE BETTER FORCING BUT STORMS SHOULD START TO PULSE
ALONG THE HIGHER ELEVATIONS WEST OF THE BLUE RIDGE THIS AFTERNOON.
STORMS SHOULD BE SLOW MOVING AND PRODUCE LOCALLY HEAVY
RAIN. OTHER THAN SCATTERED SPOTS THAT SAW HEAVY RAIN WEDNESDAY...THE
REGION SHOULD BE ABLE TO WITHSTAND THE HEAVY RAIN. LOCALIZED URBAN
FLOODING CAN NOT BE RULED OUT BUT CHANCE IS LOW. FCST SOUNDINGS
DEPICT DRY AIR IN THE MID-LEVELS THIS AFTERNOON AND THIS MAY CAUSE
STRONG WINDS. AN ISOLATED SVR STORM CAN NOT BE RULED OUT TODAY
MAINLY WEST OF THE BLUE RIDGE.

ACTIVITY WILL MOVE EASTWARD INTO THE EVENING. ELEVATED INSTABILITY
WILL STILL BE PRESENT TONIGHT AND SHOWERS AND THUNDERSTORMS CAN NOT
BE RULED OUT. TEMPS IN THE UPPER 60S TO LOW 70S. PATCHY FOG IS
POSSIBLE ESPECIALLY IN AREAS THAT RECEIVE RAIN TODAY.

&&

.SHORT TERM /FRIDAY/...HIGH PRESSURE BUILDS IN FROM THE NORTHEAST
FRIDAY AS A BACKDOOR COLD FRONT MOVES INTO N MD FRIDAY MORNING.
THIS WILL BRING AN AIRMASS CHANGE FOR THE WEEKEND. THE FRONT WILL
SAG SOUTHWARD FRIDAY AND SHOWERS ARE EXPECTED TO FORM FRIDAY
MORNING AND INTO THE AFTERNOON. THUNDERSTORMS ARE ALSO POSSIBLE
FRIDAY AFTERNOON. EASTERLY FLOW BEHIND THE FRONT WILL LEAD TO
ONSHORE FLOW AND SHOWERS AND THUNDERSTORMS MAY INCREASE IN
COVERAGE. EASTERN SLOPES SUCH AS THE BLUE RIDGE FOOTHILLS MAY
EXPERIENCE RAINFALL ENHANCEMENT DUE TO UPSLOPE CONDITIONS. AT THIS
TIME DUE TO RECENT DRY CONDITIONS NO FLOOD THREAT IS IMMINENT
HOWEVER THIS WILL NEED TO BE WATCHED CLOSELY.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...BACKDOOR CDFNT WILL
BE CROSSING THE AREA FRI NIGHT WITH SCT SHOWERS/T-STORMS ENDING
FROM EAST TO WEST LATE FRI NIGHT. LOW CLOUDS ARE EXPECTED TO GET
BANK UP AGAINST THE BLUE RIDGE AND APPALACHIANS MTNS ON EASTERLY
FLOW. LOW CLOUDS WILL THEN GRADUALY MIX OUT SAT MORNING.

HIGH PRES BUILDS FOR THE WEEKEND GIVING WAY TO FAIR WEATHER THROUGH
LABOR DAY. HOWEVER...GFS IS SUGGESTING SOME MOISTURE WILL BE
ADVECTED FROM THE ATLC INTO THE CHESAPEAKE BAY AS A WEAK LOW PRES
(POSSIBLE REMNANT LOW OF ERIKA) LIFTS NORTHEAST. FOR NOW WILL
CONTINUE TO KEEP FCST DRY AS THIS SEEMS A LOW PROBABILITY OUTCOME
ACCORDING TO GEFS ENSEMBLE DATA.

SFC HIGH PRES WEAKENS FURTHER MID NEXT WEEK WHILE MOISTURE
GRADUALLY INCREASES INCREASING THE RISK OF SHOWERS AND T-STORMS.
TEMPERATURES WILL ALSO BE ON THE RISE THROUGH MID NEXT WEEK WITH
90S MAKING A RETURN. WEAK FRONTAL PASSAGE INDICATED BY GFS AND
ECMWF IN THE WED-THU TIME FRAME BUT ENSEMBLES SHOW A HIGH DEGREE
OF UNCERTAINTY WITH RESPECT TO TIMING. ALSO...HIGH PRES BUILDING
BEHIND FRONT LOOKS PRETTY WEAK SO FRONT MAY NOT GET ENOUGH PUSH TO
MAKE IT THROUGH THE AREA.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...SUB-VFR POSSIBLE AT CHO-MRB
DUE TO PATCHY FOG THIS MORNING. SHRA/VCTS POSSIBLE THIS AFTERNOON
BUT CHANCE OF IT REACHING THE TERMINALS IS LOW AT THIS TIME. BEST
CHANCE WILL BE 18-00Z AT MRB- CHO. SHRA MAY MOVE EASTWARD INTO
IAD-DCA THIS EVENING. SOME THUNDERSTORMS MAY CAUSE SUB-VFR VSBYS
AND GUSTY WINDS. A COLD FRONT MOVES FROM NE TO SW FRIDAY.
SHRA/VCTS EXPECTED MAINLY IN THE AFTERNOON. SOME TS MAY PRODUCE
HEAVY RAIN.

LOW CLOUDS EXPECTED FRI NIGHT ALONG AND WEST OF THE BLUE RIDGE FRI
NIGHT INTO SAT MORNING WITH IFR CIGS LIKELY AT KCHO. SOME REMNANT
SMOKE FROM THE GREAT LKS MAY ALSO BE ADVECTED INTO THE REGION FROM
NEW ENGLAND.

&&

.MARINE...W-NW 5-10KTS ON THE WATERS THIS MORNING. HIGH PRESSURE IN
CONTROL TODAY. A FEW SHOWERS MAY PULSE UP TODAY INTO THIS
EVENING. A COLD FRONT WILL MOVE INTO THE WATERS FROM THE NE FRIDAY
MORNING. WINDS WILL BECOME NE FROM N TO S ON THE WATERS. WINDS
WILL ALSO BEGIN TO GUST NEAR SCA CONDITIONS BY FRIDAY AFTERNOON. A
SCA IS POSSIBLE FRIDAY AFTERNOON INTO FRIDAY NIGHT.

SCA CONDITIONS APPEAR LIKELY SAT INTO SAT EVENING ESPECIALLY ON
THE CHESAPEAKE BAY. SCA POSSIBLE AGAIN ON MONDAY.

&&

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

&&

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



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