Flash Flood Warning 168, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
257 PM EDT FRI SEP 23 2011

.SYNOPSIS...

A WEAK COLD FRONT OVER WEST VIRGINIA IS SLOWLY APPROACHING THE AREA
AND WILL MOVE INTO THE MID-ATLANTIC REGION TONIGHT AND EARLY
SATURDAY. THE FRONT WILL STALL OUT NEAR THE MID-ATLANTIC COAST
OVER THE WEEKEND. MEANWHILE...AN UPPER LOW WILL REMAIN OVER THE
OHIO VALLEY INTO THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...

THE NEXT SVRL HRS SHOULD BE THE MOST INTERESTING AS A LARGE COMMA
SHAPED SYSTEM XTNDG FM SW PA TO SC IS TRACKING NNE TOWARDS THE
CST. AS HAS BEEN CHRONICLED IN THE PAST SVRL DSCNS WE RMN MOST
CONCERNED ABT HVY RAFL ESPECIALLY IN THE I-95 CORRIDOR AND OVR TO
THE DELMARVA. AREAS OF VERY HVY RAIN OCCURRING E OF THE BNDRY
WHERE PCPBL WATER VALUES ARE OVER 2". HRRR/RUC SEEMS TO HV A GOOD
HANDLE ON THE PROGRESSION OF THE LN...W/ THE HVY RAFL MOVG ONTO
THE ERN SHORE DURG THE MID EVENG HRS. THE FLSH FLD WTCH GOES THRU
02Z...WHICH SEEMS LK A GOOD END TIME.

WHAT'S ALSO INTERESTING IS THE DRY SLOT MOVG INTO SWRN VA BEHIND
THE PRINCIPAL SHRT WV. HV DONE A LTL TWEAKING OF THE SKY CVR IN
THE CENTRAL SHEN VLLY THIS EVE...BUT STILL XPTCG M CLDY CONDS.
NEXT QUSTN WL BE HOW MUCH FOG WL DVLP LATE TNGT THERE - WL LV THAT
FOR THE EVE SHIFT TO INVESTIGATE FURTHER.

AM GOING ABV GDNC ON TEMPS TNGT - U60S IN THE CITIES TO THE U50S
IN THE HIGHLANDS.

&&

.SHORT TERM /SATURDAY/...

THE IT'LL-SEEMINGLY-NEVER GO-AWAY UPR LVL PATTERN OF THE CLOSED
UPR LOW IN THE UPPER MIDWEST AND HIGH PRES IN THE WRN ALTANTIC WL
BE MAINTAINED THRU SAT. THIS WL KEEP SKIES M CLDY W/ CHCS OF RW
BUT NOT VIA A WELL ORGRANIZED SYSTEM LK TDA. PCPN IS XPCTD TO BE SCT.

AFTN TEMPS WL BE IN THE 70S OVR THE MAJORITY OF THE CWA. ONLY
HIGHLANDS WL TOP OUT IN U60S.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...

STAGNANT WX OVR WKEND...AS SFC TROF STALLS ALONG ERN SEABOARD AND
CLOSED UPR LOPRES CNTRD NEAR CHICAGO SPINS. MOSTLY CLOUDY AND SHWRY
CONDS ACRS MID-ATLC...WITH BEST RAIN CHCS/HIGHEST QPF THRU SUN NGT
ACRS ERN ZONES. SIGNIFICANT VORT LOBE ROTATES THRU OH VLY AROUND UPR
LOPRES ERY NEXT WEEK...CAUSING ANOTHER FRONT TO SLOWLY DRAG ACRS
MID-ATLC MON THRU WED. GOOD CHC SHWRS CONT UNTIL UPR LOPRES OPENS
AND LIFTS INTO SE CANADA...ALLOWING SURGE OF DRIER AIR TO MOVE INTO
CWA. MODELS NOW PROJECT THIS TO OCCUR WED. ATTM...QPF THRU XTDD
LOOKS RELATIVELY LOW...SO FLOODING PROBLEMS APPEAR UNLIKELY.

LITTLE/NO COLD AIR SPILLING S/E TWD AREA...SO TEMPS RMN ABV NRML.
ONLY MAXIMA TEMPS WILL BE SOMEWHAT CURBED BY ABUNDANT CLOUDS/PRECIP.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...

THE ERN TAF SITES - DCA/BWI/MTN WL SEE THE MOST PROBLEMS OVR THE
RMDR OF DAYLGT HRS AND THRU MID EVE AS PDS OF HVY RA TRACK NNE FM
THE CAROLINAS CREATING PDS OF IFR/LIFR CIGS AND VSBY. SOME
IMPRVMNT XPCTD AFTR MID EVENING.

LATER TNGT FOG MAY BECOME A PROBLEM...ESPECIALLY AT CHO...BUT ALL
TAF SITES COULD XPRND IFR VSBYS B4 SUNRISE.

IFR CIGS LIKELY OVNGTS SAT AND SUN...WITH MVFR CIGS SUN/MON. VSBY
RESTRICTIONS PSBL IN FG BOTH ERY MRNGS...AND AGAIN DURING PERIODS OF
SHWRS...WHICH SHUD BE SCATTERED THRU THE PERIOD. SCATTERED SHWRS AND
THREAT FOR FLIGHT RESTRICTIONS PERSIST THRU ERY NEXT WEEK...AS
LOPRES RMNS NEARLY STATIONARY WEST OF THE TERMINALS.

&&

.MARINE...

WINDS/WAVES NOT A PRBLM TNGT OR SAT. HVY RW WL REDUCE VSBY BLO 1SM
THRU MID EVE.

SFC TROF IN VICINITY OF WATERS THRU MON WILL LEAD TO LGT WINDS AND
LIKELY SHWRS. DEGRADED VSBYS ARE PSBL THRU THE PERIOD. A COLD FRONT
WILL SLOWLY MOVE TWD WATERS TUE AND CROSS ON WED. UNTIL
FROPA...LGT/MOSTLY SLY WINDS AND SCATTERED SHWRS XPCD. BY LT WED
INTO THU...WESTERLY WINDS WILL BEGIN TO PREVAIL.

&&

.TIDES/COASTAL FLOODING...

WATER LEVELS MAY APPROACH MINOR COASTAL FLOODING THRESHOLDS BY
THE HIGH TIDE CYCLE LATE TNGT.

WITH LOPRES NEAR THE BAY AND PERSISTENT SE FLOW...THE THREAT OF
MINOR COASTAL FLOODING WILL CONTINUE INTO SAT AND SUN.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...FLASH FLOOD WATCH UNTIL 10 PM EDT THIS EVENING FOR DCZ001.
MD...FLASH FLOOD WATCH UNTIL 10 PM EDT THIS EVENING FOR MDZ004>007-
     009>011-013-014-016>018.
VA...FLASH FLOOD WATCH UNTIL 10 PM EDT THIS EVENING FOR VAZ042-
     052>057.
WV...NONE.
MARINE...NONE.

&&

PRODUCTS...WOODY!/SBK

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