Severe Thunderstorm Warning 164, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE/WASHINGTON
205 PM EDT FRI AUG 2 2002

SHORT TERM...TNGT THRU SAT NIGHT...

HUGE SUBTROPICAL RIDGE EXTENDING FROM COAST TO COAST WILL ACTUALLY
STRENGTHEN AND BUILD EWD THROUGH FRI NIGHT. MEANWHILE...THE
WESTERLIES REMAIN AT THEIR SUMMER RETREAT ACROSS SRN CANADA AND THE
FAR NRN U.S.

MODELS IN DECENT AGREEMENT ON EVOLUTION OF THINGS OVR THE NEXT 3
PDS. CDFNT EXTENDING FM THE GTLKS THROUGH THE OH VLY WILL PRESS SEWD
JUST A BIT MORE TNGT. HOWEVER...WITH DYNAMICS/SUPPORT FOR THE FRONT
LIFTING OUT THRU ERN CANADA AND UPR LVL RIDGE STRENGTHENING AND
BUILDING EWD OVR THE AREA...DOUBT FRONT WILL EVER MAKE IT PASS THE
MASON/DIXON LINE. THIS IS SHOWN IN THE ETA LI FIELD WHICH SHOWS THE
STABLE AIR REMAINING N OF THE REGION THE NEXT 3 PDS. IN
ADDTN...PWATS REMAIN OVR 1.5 INCHES THRU SAT NIGHT INDICATING NONE
OF THE DRIER AIR IS ABLE TO PRESS SWD INTO THE AREA.

CAPES 2500-3500 J/KG AND LIS -6C TO -8C OVR THE AREA ATTM WITH
DESTABILIZATION INCREASING. IN ADDTN...500MB TEMPS A COUPLE DEG
COOLER TDA THAN YDA. NO SYNOPTIC SCALE BOUNDARY OR SHORTWAVE TO
FOCUS CONVECTION REMAINDER OF THE AFTRN. HOWEVER...AS WE SAW
YDA...SCT CONVECTION COULD FIRE ON MESOSCALE BOUNDARIES SUCH AS A
BAY BREEZE. IN ADDTN...SCT CONVECTION COULD FIRE OVR THE MTNS DUE TO
OROGRAPHIC LIFT. CONDITIONS APPEAR FAVORABLE FOR SCT CONVECTION
REMAINDER OF AFTRN INTO EARLY EVE.

ETA SHOWS A WIND SHIFT LINE DROPPING S THRU THE AREA TNGT. THIS IS
NOT THE FRONT BUT IS LIKELY A WIND SHIFT DUE TO A CONVECTIVE
BOUNDARY MOVING THRU THE REGION. CONVECTION MAY FIRE OVR PA THIS AFT
AND EVE THEN DROP SEWD THRU THE AREA. MODEL POPS NOT TOO THRILLED
ABOUT PROSPECTS OF PCPN. HOWEVER...AIR MASS IS UNSTABLE AND
850-500MB LAPSE RATES STEEPEN. GIVEN THIS AND PREFRONTAL BOUNDARY
MOVING THROUGH...WILL HAVE 30 POPS FOR TSRA REMAINDER OF AFTRN AND
OVRNGT.

AIR MASS CONTINUES MOIST AND UNSTABLE SAT AND SAT NGT AS WEAKENING
FRONT REMAINS ALG THE MASON/DIXON LINE. ETA BUFKIT CAPES AROUND 1500
J/KG SAT AFTRN AND LIS ARE NEGATIVE. WILL KEEP LOW CHC POPS IN FCST
SAT INTO SAT NGT. THINK CONVECTION WILL BE MAINLY DURING THE AFT AND
EARLY EVE SAT BUT WILL NOT PLAY WITH TIMING ATTM.

850MB TEMPS DO NOT CHG MUCH THRU SAT NGT. HOWEVER...CLOUDINESS WILL
CUT BACK ON HEATING JUST A FEW DEG ON SAT FROM TDAS READINGS.
OVRNGT HEAT INDICES SHOULD DROP BELOW 80F TNGT AND THEY WILL BE NEAR
OR ON THE THRESHOLD (100F) OF ADVISORY CRITERIA ON SAT. FOR
NOW...WILL LET THE HEAT ADVISORY EXPIRE AT 8 PM AND MID SHIFT CAN
RE-EVALUATE SITUATION FOR SAT AND RE-ISSUE IF NEEDED.

NGM/AVN MOS CLOSE. ETA MOS A BIT WARMER ON MAX TEMPS. WENT WITH A
BLEND OF GUIDANCE.

WALSTON

---------------------------------------------------------------------

LONG-TERM DISCUSSION

SUNDAY
UPPER RIDGE WILL DOMINATE THE CNTRL US TO THE MID ATLANTIC
REGION THRU MONDAY.  TEMPS WILL CONTINUE TO BE HOT WITH LITTLE IF
ANY CHANCE OF PRECIP.

(MON-FRI) MEDIUM RANGE MODELS CONTINUE TO ADVERTISE INCREASED
AMPLITUDE TO THE WRN TROF/CNTRL RIDGE BEGINNING MONDAY.  THIS
RESULTS IN DOWNSTREAM TROF AMPLIFICATION OVER ERN NOAM TUESDAY.
ASSOCIATED COLD FRONT WILL APPROACH THE AREA MONDAY EVENING AND MOVE
SOUTH OF THE AREA BY TUESDAY AFTERNOON. HAVE 30 POPS FOR NOW FOR
MONDAY AFTERNOON THRU TUESDAY. MORE PLEASANT WX WED-FRI WITH COOLER
AND DRIER AIR.

ROSA

.LWX...
DC...HEAT ADVISORY UNTIL 800 PM EDT FRIDAY FOR ZONE DCZ001.
MD...HEAT ADVISORY UNTIL 800 PM EDT FRIDAY FOR ZONES
     MDZ002>007...MDZ009>011...MDZ013>014...MDZ016>018.
VA...HEAT ADVISORY UNTIL 800 PM EDT FRIDAY FOR ZONES
     VAZ025>031...VAZ036>042...VAZ050>057.
WV...HEAT ADVISORY UNTIL 700 PM EDT FRIDAY FOR ZONES
     WVZ048>053...WVZ055.

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