Severe Thunderstorm Warning 261, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
329 PM EDT THU AUG 16 2007

.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH THE AREA TONIGHT. THE FRONT WILL
MOVE INTO CENTRAL VIRGINIA AND STALL LATE FRIDAY AND EARLY
SATURDAY. THIS BOUNDARY WILL MOVE NORTH INTO THE AREA AS A WARM
FRONT ON MONDAY AND LINGER INTO TUE. THE FRONT WILL MOVE NORTH OF
THE REGION BY MID WEEK. UNSETTLED WEATHER IS EXPECTED FOR THE FIRST
PART OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...CHALLENGING FCST FOR TONIGHT AS
MODELS HAVE NOT HAD A GOOD HANDLE ON CONVECTIVE COMPLEXES
RECENTLY. MCV THAT MOVED THRU THE AREA EARLIER HAS STABILIZED
THINGS ESPECIALLY IN THE NORTH BUT A WEAK BOUNDARY HAS SET UP ACROSS
THE SOUTHERN HALF OF THE FORECAST AREA SEPARATING HOT HUMID AIR WHERE TEMPS
ARE 100 DEGREES AND LOW TO MID 80S IN THE NORTH. THINK THAT ISOLATED
TSRA IS A POSSIBILITY OVER THE FAR SOUTH WHERE VISIBLE IMAGERY SHOWS
CUMULUS BUBBLING UP.

ALSO WATCHING CONVECTIVE COMPLEX NEAR THE IL/IN BORDER WHICH HAS
BEEN MOVING RAPIDLY EASTWARD AT APPROX. 40 KTS. THIS IS MORE THAN 500
MILES AWAY BUT BEST ESTIMATION IF IT HOLDS UP IT WILL MOVE ACROSS
THE SOUTHERN HALF OF FORECAST AREA AROUND DAYBREAK. 12Z GFS SHOWS AN MCS
MOVING ACROSS THE AREA EARLY TOMORROW BUT ITS LOCATION IS PROBABLY
TOO FAR NORTH. IN THE NORTH...IT WILL PROBABLY BE DRY BUT DID NOT
FEEL COMFORTABLE GOING COMPLETELY DRY GIVEN A WEAK FRONT WILL BE
CROSSING THE AREA OVERNIGHT.

&&

.SHORT TERM /FRIDAY/...POTENTIAL FOR MCS TO ROLL ACROSS THE AREA
EARLY TOMORROW. 15Z WRF-ARW INDICATES COMPLEX MOVING ACROSS THE
CHARLOTTESVILLE AREA WHILE GFS IS FURTHER NORTH. PREFER THE WRF-
ARW SOLUTION. ISOLD TSTMS ALSO POSSIBLE IN THE AFTERNOON MAINLY SE
OF DCA WHERE MODELS SHOW A LEE-TROF (CONVERGENCE LINE) SETTING UP.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
FOR FRI NIGHT...CLEARING SKIES AND DRYING OF THE AIRMASS AS THE
CANADIAN HIGH BUILDS OVER THE REGION.

FOR SAT...PLEASANT SUMMER DAY WITH SUNNY SKIES LOW HUMIDITIES AND
BELOW NORMAL MAX TEMPS ASSOCIATED WITH AREA OF CANADIAN HIGH PRES.
THE FRONTAL BOUNDARY REMAINS WELL SOUTH OF THE REGION.

FOR SUN...HIGH PRESSURE BEGINS TO RETREAT EAST AND OFFSHORE AS A
WEAK SOUTHERLY RETURN FLOW SETS UP. MOISTURE VALUES AND SURFACE DEW
POINTS BEGIN TO EDGE UP BUT REMAIN WITHIN THE COMFORTABLE RANGE
THROUGH MOST OF THE DAY.

BY SUN EVENING...WEAK ISENTROPIC LIFT ASSOCIATED WITH RETURNING WARM
FRONT THAT SLOWLY MOVES NORTH INTO THE REGION. 12Z GFS SUGGESTS LOTS
OF CLOUDS AS MCV REMNANTS APPROACH THE MID-ATLANTIC REGION FROM THE
NORTHWEST. HOWEVER...TIMING OF ANY MCV-LIKE MOISTURE/PRECIP
DIFFICULT. STILL...WITH FRONTAL BOUNDARY IN THE AREA AND SOUTHERLY
RETURN FLOW BRINGING MORE MOISTURE...WILL KEEP MENTION OF CHANCE
POPS FOR SUN NIGHT.

FOR MON AND TUE...FOLLOWED HPC GUIDANCE AND ENSEMBLES SUGGESTING A
CONTINUED PRESENCE OF A FRONT IN THE AREA. TEMPS ON MON WILL BE WARM
WITH LOWER CLOUD AMOUNT. HPC GUIDANCE IS ABOVE GUIDANCE FOR
MON...BUT THAT APPEARS REASONABLE BASED ON LESS CLOUD COVER. THEN ON
TUE...TEMPERATURE EXPECTED TO BE BELOW NORMAL WITH LOTS OF CLOUDS
AND PRECIP CHANCES. ABOVE NORMAL CHANCES FOR PRECIP.

FOR WED AND THU...THE FRONT SHOULD HAVE MOVED NORTH OF THE REGION BY
EARLY WED. EXPECT SEASONABLE TO SLIGHTLY ABOVE NORMAL TEMPS AND ONLY
MINIMAL CHANCES FOR PRECIP.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
STORMS THIS MORNING HAVE STABILIZED ATMOSPHERE FOR THIS AFTERNOON
ACROSS THE NORTHERN HALF OF THE AREA. THUS ONLY KCHO MOST SUSCEPTIBLE
TO DIURNAL CONVECTION...SINCE THATS THE ONLY TERMINAL PREVIOUSLY
UNAFFECTED. THERE WILL COVER THREAT WITH VICINITY REMARK. HIGH
CLOUDS WILL BLOW OFF FROM MIDWEST CONVECTION...COMBINED W/WEAK
UPGLIDE/LIFT PRODUCING A POTENTIAL MID DECK. SWLY FLOW WILL VEER
NW W/ CDFROPA OVERNIGHT. THERE MAY BE ANOTHER MCS PREDAWN...BUT
UNCERTAINTY TOO GREAT TO INCLUDE IN TAFS ATTM.

ONCE CDFNT THRU...QUIET VFR CONDS THRU WEEKEND. AS WARM FRONT APPROACHES
EARLY NEXT WEEK...SCATTERED TSRA MAY PRODUCE LOCAL CIG/VSBY
RESTRICTIONS.

&&

.MARINE...WINDS BELOW SCA TONIGHT AND TOMORROW. PRES SURGE FCST
TOMORROW NIGHT WITH GOOD PRES RISES. HAVE RAISED SCA FOR TOMORROW
NIGHT ON NW WINDS. MAIN SURGE OF NORTHERLY WINDS ON SAT EXPECTED
TO BE SOUTH OF THE WATERS BY EARLY SAT...BUT STILL COULD BE SOME
NEAR-SCA GUSTS FROM THE NW ON SAT MORNING.

FOR SAT THROUGH MID WEEK...EXPECT WINDS TO BE BELOW SCA AS A WEAK
WARM FRONT MOVES INTO THE REGION LATE SUN NIGHT AND LINGERS
THROUGH TUE.

&&

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

&&

SYNOPSIS...LFR
NEAR TERM...LFR
SHORT TERM...LFR
LONG TERM...SMZ
AVIATION...HTS
MARINE...LFR

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