Severe Thunderstorm Warning 196, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE/WASHINGTON
200 PM EDT SUN AUG 18 2002

SHORT TERM...TNGT THRU MON NGT...

MODELS ARE IN PRETTY GOOD AGREEMENT CONSIDERING THE COMPLEXITY OF
THE WEATHER FEATURES THAT WILL AFFECT THE AREA DURING THE NEXT 48
HRS.

ZONAL FLOW ACRS THE NRN PART OF THE COUNTRY WITH SUBTROPICAL RIDGE
OVR THE SRN STATES THROUGH MON NIGHT. OUR AREA WILL BE ON THE SRN
EDGE OF THE WESTERLIES IN THE SHORT TERM. SFC TROF/LEESIDE TROF OVR
THE AREA WILL MOVE E THIS EVENING. MEANWHILE SHORTWAVE OVR ONTARIO
WILL MOVE EWD INTO QUEBEC TNGT. IN RESPONSE...AT THE SFC...CDFNT NOW
ALG THE GTLKS WILL DROP SWD. HOWEVER...CDFNT WILL STALL AS IT
BECOMES PARALLEL TO THE UPR LVL FLOW...ON THE SRN EDGE OF THE
WESTERLIES. USING LIS...CDFNT WILL GET AS FAR S AS THE MASON/DIXON
LINE OR PERHAPS SNEAK INTO OUR NRN ZNS LATE TNGT. AS SHORTWAVE LIFTS
OUT THRU QUEBEC AND NEXT SHORTWAVE MOVES INTO THE GTLKS...HEIGHTS
WILL RISE JUST ENOUGH TO CAUSE THE FRONT TO RETREAT BACK TO THE N
INTO SRN PA ON MON. MEANWHILE...MESOETA SFC PRES/SFC WIND FIELD
SUGGESTS ANOTHER SFC TROF/LEESIDE TROF MOVING ACRS THE AREA LATE
MON. FOR MON NGT...THE SHORTWAVE MOVES FM THE GTLKS INTO NEW ENG AND
HGTS DROP JUST ENOUGH TO ALLOW THE FRONT TO SLIDE BACK TO THE S INTO
THE AREA. IN ADDTN...MODELS HINT AT A SFC WAVE ALG THE FNT MON NGT.

WITH SFC TROF/LEESIDE TROF OVR ERN ZNS....COULD SEE A FEW CELLS FIRE
ALG THE BOUNDARY FOR THE REMAINDER OF THE AFTRN INTO EARLY EVE. IN
ADDTN...MAY SEE A FEW CELLS OVR THE MTNS DUE TO OROGRAPHIC LIFT.
ALSO...COULD SEE SOME ISOLD ACTIVITY ALG CDFNT ACRS THE NRN ZNS LATE
IN THE NGT. TO KEEP IT SIMPLE...PLAN ON GOING SLGT CHC OF TSTM TNGT
ALL ZNS...OTHERWISE P/CLDY SKIES.

ON MON...AIR MASS WILL BE UNSTABLE AND WE WILL HAVE TWO BOUNDARIES
TO DEAL WITH. 1ST BOUNDARY WILL BE THE CDFNT NEAR THE MASON/DIXON
LINE WHICH SHOULD MOVE A BIT TO THE N DURING THE AFTRN. SECOND
BOUNDARY WILL BE THE LEESIDE TROF/SFC TROF THAT WILL BE MOVING ACRS
THE AREA DURING THE AFT/EVE HOURS. DYNAMICS ARE LACKING AND THERE
IS VERY LITTLE FORCING. HOWEVER...WITH UNSTABLE AIR MASS AND
BOUNDARIES PRESENT...HAVE TO GO WITH LOW CHC POPS ALL ZNS.

MON NGT...FNT DROPS BACK INTO THE AREA WITH HINT OF SFC WAVE ALG THE
FNT. ALL THE MODELS GENERATING SOME QPF OVR THE AREA. FEEL THE CHC
OF CONVECTION WILL INCREASE A BIT SO WILL GO WITH 50 POPS.

ETA/NGM/AVN MOS TEMPS ARE ALL SURPRISINGLY CLOSE CONSIDERING THE
COMPLEXITY OF THE SITUATION. WILL STICK CLOSE TO THE MOS GUIDANCE.

HEAT ADVISORY WILL BE IN EFFECT UNTIL 8 PM. SOME AREAS ALREADY HAVE
REACHED ADVISORY CRITERIA WITH ANOTHER HOUR OR SO OF HEATING.

WALSTON

LONG-TERM (TUE-SUN)

RELATIVELY QUIET WX. THE WEAK FRONT AND A WEAK SFC WAVE WILL BE OVER
THE REGION TUESDAY. SO WILL RAISE POPS...AND LOWER TEMPS SLIGHTLY
DUE TO CLOUD COVER. WEDNESDAY...THE FRONT IS PROGED TO THE MOVE
SOUTH OF AREA WI WITH FALLING TEMPS AND DEWPOINTS. SEASONABLE TEMPS
AND DRY WX CONTINUE FOR THUR. FRIDAY RETURN FLOW WILL ALLOW TEMPS
AND DEW PT TO RISE AHEAD OF NEXT TROUGH PROGED BY THE MRF. WI THIS
PATTERN WL KEEP THINGS DRY THROUGH FRI. BY DAY SIX AND SEVEN THERE
IS SOME QUESTION ON WHERE THE TROUGH AXIS WL BE...FOR NOW WL GO WITH
WI POPS ON SAT...WITH THE AXIS SHIFTING TO THE EAST OF THE REGION WI
COOLER AND DRIER AIR ADVECTING IN BEHIND IT ON SUNDAY.

.LWX...
DC...HEAT ADVISORY UNTIL 800 PM EDT SUNDAY FOR ZONE DCZ001.
MD...HEAT ADVISORY UNTIL 800 PM EDT SUNDAY FOR ZONES
     MDZ004>007...MDZ009>011...MDZ013>014...MDZ016>018.
VA...HEAT ADVISORY UNTIL 800 PM EDT SUNDAY FOR ZONES
     VAZ036>042...VAZ050>057.
WV...NONE.