Flash Flood Warning 44, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
248 PM EDT MON JUN 17 2013

.SYNOPSIS...
A WEAK COLD FRONT APPROACHING FROM THE NORTH WILL STALL OVER THE
MID ATLANTIC THROUGH TUESDAY...THEN MOVE SOUTH OF THE REGION EARLY
WEDNESDAY. AN AREA OF LOW PRESSURE WILL TRACK SOUTH OF THE AREA
TUESDAY NIGHT. HIGH PRESSURE WILL RETURN FOR THE REMAINDER OF THE
WEEK.

&&

.NEAR TERM /THROUGH TUESDAY/...
COLD FRONT REMAINS LOCATED OVER THE LOWER GREAT LAKES THIS
AFTERNOON...HOWEVER A SURFACE TROUGH AND OTHER SMALLER MESOSCALE
BOUNDARIES WERE OBSERVED OVER THE CWA. SCATTERED SHOWERS AND
THUNDERSTORMS WERE INITIATING ALONG/NEAR THESE BOUNDARIES EARLY THIS
AFTERNOON.

PER MOST GUIDANCE...BELIEVE THE BULK OF THE ACTIVITY WILL BE LOCATED
FROM NORTHEAST MARYLAND SOUTHWARD THROUGH CENTRAL AND SOUTHERN
MARYLAND AND INTO CENTRAL VIRGINIA. THIS IS WHERE CHANCE POPS FOR
SCATTERED CONVECTION WILL RESIDE DURING THE AFTERNOON...WITH ONLY
ISOLATED ACTIVITY FURTHER TO THE NORTHWEST.

DESPITE THE PRESENCE OF SURFACE BOUNDARIES...LARGER SCALE FORCING IS
FAIRLY WEAK AND INSTABILITY APPEARS TO BE ON THE WEAK SIDE TOO WITH
MODIFIED 12Z SOUNDING REVEALING ONLY ABOUT 1000 J/KG. SPC
MESOANALYSIS PAGE INDICATES A LITTLE MORE THAN THAT BUT AM NOT
EXPECTING WIDESPREAD SEVERE ACROSS THE CWA. PERHAPS A COUPLE CELLS
WIND UP PULSING UP AND BECOMING STRONG ENOUGH TO PRODUCE LOCALLY
GUSTY WINDS DURING THE AFTERNOON.

MOST ACTIVITY SHOULD WEAKEN/DIMINISH IN THE EVENING...WITH ANY
LINGERING ACTIVITY LIKELY ACROSS THE EXTREME SOUTHERN PORTION OF THE
CWA.

COLD FRONT WILL ALSO START TO SINK SOUTHWARD INTO PENNSYLVANIA
TONIGHT BUT IT LOOKS LIKE ACTIVITY NEAR THAT BOUNDARY WILL REMAIN TO
THE NORTH TONIGHT.

BOUNDARY LOOKS TO RESIDE OVER THE CWA ON TUESDAY. CLOUDS AROUND THE
BOUNDARY MAY HINDER DESTABILIZATION SOME...BUT MODELS SUGGEST 1-2K
J/KG OF CAPE AND WITH THE BOUNDARY OVERHEAD EXPECT SCATTERED
THUNDERSTORMS. IF SHEAR WINDS UP BEING A LITTLE BETTER...THEN A FEW
STORMS COULD PRODUCE LOCALLY DAMAGING WIND GUSTS.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/...
BOUNDARY IS FORECAST TO STALL OUT JUST SOUTH OF THE CWA TUESDAY
NIGHT/WEDNESDAY. BOTH NAM/GFS INDICATE A WAVE OF LOW PRESSURE RIDING
ALONG THE FRONT...SPILLING SOME SHOWERS TO THE NORTH INTO THE CWA.
BUT THE MODELS DISAGREE WITH TIMING...WITH THE GFS BEING FASTER AND
FAVORING A MOSTLY DRY WEDNESDAY WHILE THE NAM INDICATES SHOWERS.

GIVEN TIMING UNCERTAINTY...AND BLENDING THE ECMWF IN THE MIX HAVE
FOCUSED HIGHEST POPS ACROSS THE CWA TUESDAY NIGHT BUT CONTINUE
CHANCE POPS INTO THE FIRST PART OF WEDNESDAY. WILL HAVE TO FINE TUNE
TIMING AS WE GET CLOSER.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
HIGH PRESSURE BUILDS IN TO END THE WEEK...THEN MOVES OFFSHORE OVER
THE WEEKEND. EXPECT DRY CONDITIONS MUCH OF THE TIME HOWEVER ISOLATED
DIURNAL THUNDERSTORMS MAY BE POSSIBLE OVER THE HIGHER TERRAIN FRIDAY
INTO THE WEEKEND. THERE MAY ALSO BE A SHORTWAVE SOMETIME LATE SUNDAY
INTO MONDAY WHICH COULD BRING A CHANCE OF THUNDERSTORMS TO THE
ENTIRE CWA.

NEAR NORMAL TEMPERATURES AT THE END OF THE WEEK COULD MODERATE A
LITTLE ABOVE CLIMO OVER THE WEEKEND INTO THE FIRST PART OF NEXT
WEEK.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
WILL HAVE SCATTERED THUNDERSTORMS DEVELOPING DURING PEAK HEATING
ALONG A TROUGH THIS AFTERNOON. BUT GIVEN LOW CONFIDENCE IN DIRECT
IMPACT AT INDIVIDUAL SITES HAVE FOCUSED ON VCTS IN TAFS ATTM. IF
BASED ON RADAR IT APPEARS ANY TERMINAL WILL HAVE MORE DIRECT
IMPACT...AMENDMENTS WILL BE ISSUED.

COLD FRONT SAGS SOUTHWARD TONIGHT INTO TUESDAY. EXPECT MORE
SCATTERED CONVECTION TUESDAY AND PERHAPS EVEN INTO WEDNESDAY UNTIL
HIGH PRESSURE PUSHES THE FRONT FAR ENOUGH SOUTH FOR DRY WX.

&&

.MARINE...
NO SCA FLAGS EXPECTED IN THE NEXT 24 HOURS WITH RELATIVELY WEAK
GRADIENT. WILL HAVE TO WATCH LOCALLY GUSTY WINDS IN THUNDERSTORMS
THIS AFTERNOON AND AGAIN TUESDAY.

COLD FRONT MAKES IT WAY SOUTHWARD ACROSS THE WATERS ON
TUESDAY...WITH A WAVE OF LOW PRESSURE RIDING ALONG THE FRONT TUESDAY
NIGHT OR WEDNESDAY. HIGH PRESSURE BUILDS FOR THE END OF THE WEEK.

&&

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

&&

BPP

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