Severe Thunderstorm Warning 192, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
331 PM EDT THU JUN 9 2011

.SYNOPSIS...
BERMUDA HIGH OVER THE ATLANTIC WILL CONTINUE TO SUPPLY HOT AND HUMID
CONDITIONS. A SURFACE BOUNDARY WILL STALL NEAR THE REGION THROUGH
THE EARLY WEEKEND. A COLD FRONT WILL MOVE ACROSS SUNDAY AFTERNOON.
HIGH PRESSURE RETURNS MONDAY AND TUESDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
DEWPOINTS HAVE BEEN UP AND DOWN WITHIN THE U60-L70 RANGE SINCE
SOME AREAS HAVE BEEN EXPERIENCING MORE LOW-LEVEL MIXING THAN
OTHERS. HEAT INDICES ACROSS THE AREA ARE IN THE U90S AND 100S...AND
WE STILL HAVE AT LEAST A 3-4 HR WINDOW TO INCREASE THESE VALUES
EVEN FURTHER.

THE OTHER CONCERN TODAY IS SEVERE WEATHER...WHICH IS EVIDENT BY THE
SEVERE THUNDERSTORM WATCH BLANKETING NEARLY HALF THE CWA THROUGH
THIS EVENING. A STRONG CAP EXISTS OVER THE REGION WITH VERY LITTLE
SHEAR. IN ORDER TO OVERCOME THIS INVERSION...TEMPS DO NEED TO
INCREASE A BIT MORE AND CONVERGENCE OF SOME KIND WILL BE NEEDED TO
INITIATE CONVECTION. IN THESE TYPICAL MID-SUMMER-LIKE PATTERNS
WITH A BERMUDA HIGH OFF THE SRN ATLC COAST...THE NEARBY RIDGELINES
ARE FAVORED FOR INITIATION. THIS WAS THE CASE LAST NIGHT...IS THE
CASE TODAY AND LIKELY WILL BE THE CASE FOR FRI AND POSSIBLY SAT.

THROUGH THE REST OF THE AFTN/EVE...MORE CUMULUS WILL CONTINUE TO
DEVELOP ACROSS THE AREA...WHICH WILL LIMIT HEATING JUST A TAD.
STILL EXPECT TEMPS TO MAKE A RUN AT 100 OVER MANY AREAS EAST OF
THE BLUE RIDGE. POPS ARE HIGHEST ACROSS THE WRN HALF OF THE
CWA...ESPECIALLY ALONG THE RIDGELINES AND NEARBY MTN VALLEYS. IF
ENOUGH CONVECTIVE ACTIVITY DEVELOPS AND PRODUCES ORGANIZED COLD
POOLS...THEN THESE FEATURES COULD POTENTIALLY DEVELOP CELLS
FARTHER EAST AND OVER THE NRN VA/MD PIEDMONT.

NAM AND OTHER HI-RES GUIDANCE STILL PAINTING ANY NUMBER OF SOLUTIONS
THAT COLLECTIVELY BRING A LINE OF BROKEN LINE OF TSTMS ACROSS THE
AREA...AIDED BY EITHER A STRONG GUST FRONT OR LEE TROF THAT
EVENTUALLY WORKS ITS WAY ACROSS THE I-95 CORRIDOR AND SRN MD LATE
TONIGHT. ISOLATED POCKETS ALONG THE LINE MAY HAVE UPDRAFTS STRONG
ENOUGH TO PRODUCE SEVERE HAIL/DAMAGING WINDS...THOUGH LARGE HAIL IS
THE MAIN THREAT. SLOW-MOVING CELLS ALONG THE HIGHER TERRAIN MAY
ALSO PRODUCE FLASH FLOODING IF TRAINING OCCURS.

AFTER CONVECTION HAS DISSIPATED LATE TONIGHT ONCE THE INVERSION
HAS SET UP...CONDITIONS WILL CLEAR OUT FOR THE MOST PART. TEMPS
WILL RECOVER VERY LITTLE...ONLY A COUPLE DEGREES COOLER THAN LAST
NIGHT BUT ALSO A BIT LESS HUMID.

A COLD FRONT IS APPROACHING THE REGION FROM OHIO VLY AND WILL MAKE
ITS WAY INTO THE AREA OVERNIGHT. THE FRONT WILL STALL ONCE IT
REACHES THE AREA AS THE PARENT LOW PRESSURE SYSTEM SPEEDS OFF THE
NRN ATLC/NEW ENGLAND COAST. THE SUBSEQUENT LOW PRESSURE SYSTEM
WILL NOT ARRIVE UNTIL LATE SAT...SO UNTIL THEN...THE FRONT WILL
PROVIDE A FOCUS FOR LIFT FRI AFTN/EVE. EVEN WITH A LIGHT NLY FLOW
DURING THE AFTN HRS...DEWPOINTS ARE EXPECTED TO RECOVER BACK INTO
THE U60S/L70S JUST IN TIME FOR ANOTHER WARM AFTN. FRIDAY WILL NOT
BE AS HOT HOWEVER...WITH HIGHS BARELY TOPPING 90 ACROSS THE PIEDMONT
AND U80S OVER THE WRN ZONES. MORE INSTABILITY AND THE AFOREMENTIONED
CONDITIONS WILL CREATE ANOTHER SCENARIO FAVORABLE FOR CONVECTION
DURING THE AFTN/EVE HRS...AGAIN FOCUSING ON THE HIGHER TERRAIN FOR
INITIATION AND EVENTUAL MOVEMENT OFF THE MTNS.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
BARRING ARRIVAL OF ANY POTENT SHRTWV TROFS...CNVCTN GENLY SHUD BE
DIURNALLY DRIVEN FRI EVE...BUT MAY LAST INTO THE EVE HRS BFR
DISSIPATING. MSTR WILL LINGER AND MAINTAIN MINIMA IN THE MID 60S-
LWR 70S.

SAT XPCD TO BE A REPEAT PERFORMANCE OF FRI WITH BNDRY STALLED VCTY
FCST AREA...LEE TROF DVLPMT AND CONTD INSTBY. PRIMARY CNVCTV FOCUS
WILL BE SUN AFTN...AS CDFNT CROSSES FCST AREA. MAXIMA IN 80S-LWR
90S XPCD SAT AND SUN...LEADING TO HIGHLY UNSTABLE ENVIRONMENT AND
POTENTIAL FOR SVR WX DESPITE RELATIVELY WEAK MID-LVL FLOW.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
HIPRES WILL DOMINATE THE MID-ATLC WX MON-TUE AS THE SFC REFLECTION
OF THE UPR SHRTWV RDG MOVES FROM PA TWD CAROLINAS. AMPLIFYING
SHRTWV TROF OVER NRN PLNS ON WED WILL INDUCE LOPRES OVER GRTLKS
RGN. RESULT WILL BE INCRG SLY/SWLY FLOW AND A RETURN TO A VERY
HUMID AMS IN THE MID-ATLC RGN. SVR WX POTENTIAL WILL BE MONITORED
LATE NEXT WK.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
VFR CONDITIONS GENLY EXPECTED THRU THE TAF PERIOD...BUT ISOLD
TSTMS ARE THE CONCERN FOR THE MID-ATLC AREA. STILL DRY ACROSS THE
REGION...BUT A FEW MTN STORMS ARE EXPECTED TO DEVELOP IN THE
COMING HRS...WITH CUMULUS FIELD FILLING IN OVER THE REGION.
CONVECTION THAT DOES DEVELOP ACROSS THE REGION COULD AFFECT THE
METRO DC/BALTIMORE AREAS LATER THIS EVE...CLOSER TO SUNSET.
DIFFICULT TO SAY HOW FAR EAST ANY OF THE MTN INITIATED CONVECTION
WILL MOVE...THOUGH A CHANCE EXISTS FOR A LINE OF STORMS TO MOVE
ACROSS THE AREA LATE TONIGHT. UNCERTAINTY IN EWD EXTENT OF STORMS
IS HIGH.

THIS ACTIVITY IS EXPECTED TO DISSIPATE OVERNIGHT AND REDEVELOP ON
FRI AFTN/EVE. LITTLE MORE THAN A WIND SHIFT AND SOME GROUND FOG
REFLECTED IN THE LATTER PART OF THE CURRENT TAF CYCLE.

DAILY EPISODES OF AFTN/EVE TSTMS XPCD THRU SUN AS AMS STAGNATES IN
MID-ATLC RGN. MOIST BNDRY LYR AMS COULD LEAD TO MVFR FOG OVNGT.
CDFNT CLEARS FCST AREA SUN EVE...LEADING TO HIPRES...LIGHT WINDS
AND VFR CONDS.

&&

.MARINE...
FAIRLY QUIET OVER THE WATERS WITH HARDLY ANY WIND OTHER THAN
BRIEF GUSTS IN THE 10-15KT RANGE. LATER TONIGHT...SCATTERED
SHOWERS/TSTMS MAY MOVE EAST OF THE MOUNTAINS TOWARD/OVER THE
WATERS...ALTHOUGH CONFIDENCE IN THIS EWD PROGRESSION IS LOW.
CONDITIONS WILL SUBSIDE AGAIN OVERNIGHT BEFORE A SIMILAR SCENARIO
ON FRI AS A COLD FRONT STALLS ACROSS THE REGION AND ALLOWS FOR
MORE SHOWERS/TSTMS TO DEVELOP.

WITH SFC BNDRY BCMG STATIONARY ACRS MID-ATLC RGN...DAILY EPISODES
OF TSTMS XPCD. EWD PROGRESSION OF CNVCTN RMNS UNCERTAIN OWING TO
CONTD CAP...BUT SLOW EWD MVMT OF BNDRY MAY LEAD TO INCRG CHCS OF
TSTMS REACHING WATERS.

CDFNT CROSSES THE WATERS SUN AFTN/EVE. HIPRES DOMINATES WX MON-TUE
WITH NO MARINE HEADLINES ANTICIPATED ATTM.

&&

.CLIMATE...
THE CLIMAX OF THIS TWO-DAY HOT STRETCH IS UPON US. BWI HAS ALREADY
BROKEN ITS RECORD HIGH TEMP...WITH DCA AND IAD REACHING FOR THEIR
RESPECTIVE RECORDS. DCA/S RECORD IS QUITE HIGH...AT 102 SET IN 1874
/102 IS ALSO THE ALL-TIME RECORD FOR THE MONTH OF JUNE/.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR DCZ001.
MD...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR MDZ003>007-
     009>011-013-014-016>018.
VA...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR VAZ028-030-031-
     036>040-042-050>057-501-502.
WV...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR WVZ051>053.
MARINE...NONE.

&&

GMS/KRAMAR

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