Flash Flood Warning 42, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE/WASHINGTON
205 PM EDT SAT AUG 11 2001

WESTERLIES REMAIN JUST N OF THE AREA OVR THE NEXT 24 HOURS. BY SUN
AND MON...UPR LVL RDG DEVELOPS OVR THE WRN U.S. WITH A DOWNSTREAM
TROF DEVELOPING OVR THE ERN U.S.

FNT REMAINS STALLED JUST TO OUR N SEPARATING THE COOL DRY AIR TO THE
N OF THE FNT FROM THE VERY MOIST/HUMID AIR MASS OVR OUR AREA. WITH
THE FNT ON THE SRN EDGE OF THE WESTERLIES...PARALLEL TO THE UPR LVL
FLOW...IT WILL NOT MOVE MUCH THROUGH SUN. MEANWHILE...WEAK WAVES OF
LOW PRES WILL MOVE EWD ALG THE FNT. BY SUN NGT AND MON...WITH HGTS
FALLING OVR THE ERN U.S. AND THE UPR LVL TROF DEEPENING...THE FNT
WILL FINALLY START TO MOVE SWD THRU THE AREA WITH THE FNT THRU THE
CWA BY 00Z TUE.

PWS IN EXCESS OF 2 INCHES OVR THE AREA THRU MON MORNING WITH PWS
SLOWLY COMING DOWN LATE MON AS THE FNT PUSHES THRU THE AREA. PLENTY
OF MOISTURE TO WORK WITH THE NEXT COUPLE OF DAYS. THIS COMBINED WITH
AFTRN HEATING/INSTABILITY WILL RESULT IN THE DVLPMT OF CONVECTION
ESP ALG THE RDGS AND ALG VARIOUS MESOSCALE BOUNDARIES. IN ADDTN...AS
THE FNT SAGS SWD SUN NGT AND MON...THE FNT WILL ACT AS AN ADDITIONAL
FOCUS FOR CONVECTION.

WILL GO WITH LIKELY POPS THIS EVE (MAINLY BFR MIDNIGHT) AND LIKELY
POPS AGAIN ON SUN BUT SAY MAINLY AFTRN.  WITH FNT SLOWLY SAGGING
SWD INTO THE AREA MON NGT WILL CONTINUE WITH LIKELY POPS. FNT SHOULD
BE THRU THE NWRN ZNS BY 18Z MON SO WILL ONLY MENTION CHC MORNING
SHRA NW ZNS. ELSEWHERE...WILL GO WITH 60 POPS FOR SHRA/TSRA.

WITH HIGH PWS AND SLOW MOVEMENT OF CELLS...BIGGEST THREAT THE NEXT
DAY OR SO FROM CONVECTION WILL BE FOR HEAVY RAIN AND SCT FLASH
FLOODING. HOWEVER...CAN NOT PIN POINT ONE AREA THAT IS MORE
VULNERABLE THAN THE REST OF THE AREA SO NO WATCH WILL BE ISSUED.

AS FAR AS SVR POTENTIAL IS CONCERNED THE NEXT COUPLE OF DAYS...WET
BULB ZERO HEIGHTS REMAIN HIGH SO A VERY LOW THREAT OF LARGE HAIL.
AS FAR AS STRONG WINDS ARE CONCERNED...WE WILL HAVE WEAK SHEAR AND
LGT WINDS ALOFT SO NOTHING MORE THAN AN ISOLD PULSE TYPE SVR
EXPECTED (IF THAT).

FNT CLEARS THE AREA BY 00Z TUE AND DRIER AIR MAKES ITS WAY INTO THE
AREA TUE/WED AS HIGH PRES BUILDS INTO THE AREA.

NEXT CDFNT THRU HERE ON FRI W/ SHRA/TSRA.

FCSTID = 15 / DMW

DCA   75  89  76  87 /  60  60  60  60
BWI   72  88  72  86 /  60  60  60  60
MRB   72  86  70  85 /  60  60  60  40
IAD   73  89  72  86 /  60  60  60  60
CHO   73  87  72  86 /  60  60  60  60
HGR   69  85  68  84 /  60  60  60  40
NHK   75  88  75  86 /  60  60  60  60
W99   72  86  70  85 /  60  60  60  40

.LWX...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

DCZ001-MDZ004>007-009>011-013-014-016>018-VAZ021-025>031-036>042-
050>057-WVZ048-054-055-112300-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE-WASHINGTON
410 PM EDT SAT AUG 11 2001

...NUMEROUS THUNDERSTORMS WITH TORRENTIAL RAINS...

AT 410 PM EDT DOPPLER RADAR SHOWED NUMEROUS SLOW MOVING STRONG
THUNDERSTORMS OVER A WIDE AREA OF NORTHERN AND CENTRAL VIRGINIA AND
CENTRAL AND SOUTHERN MARYLAND. MANY OF THE STORMS WERE CONCENTRATED
IN AN AREA FROM HOWARD AND MONTGOMERY COUNTIES SOUTH ACROSS THE
DISTRICT PRINCE-GEORGES CHARLES FAIRFAX PRINCE-WILLIAM FAUQUIER
COUNTIES AND THROUGH THE CENTRAL PIEDMONT COUNTIES OF MADISON ORANGE
AND ALBEMARLE.

THE GENERAL MOVEMENT OF THESE STORMS WAS A SLOW DRIFT TOWARD THE
NORTHEAST BUT MANY WERE SHOWING ERRATIC MOVEMENT OR WERE NEARLY
STATIONARY. THE PRIMARY THREAT FROM THESE IS LOCALLY VERY HEAVY
RAINS CAPABLE OF PRODUCING RAINFALL RATES OF 2 TO 3 INCHES PER HOUR.
LOCALIZED FLOODING OF SMALL STREAMS CREEKS AND PONDING OF WATER ON
ROADWAYS UNDERPASSES AND OTHER LOW LYING AREAS IS A DISTINCT
POSSIBILTY INTO THIS EVENING UNTIL AT LEAST 6 TO 8 PM.

RESIDENTS IN FLOOD PRONE AREAS SHOULD BE ALERT FOR HEAVY RAINS IN
THEIR AREA AND BE PREPARED TO SEEK HIGHER GROUND SHOULD FLOODING BE
OBSERVED. MOTORISTS SHOULD UNDER NO CIRCUMSTANCE ATTEMPT TO DRIVE
INTO FLOOD WATERS.

LOCALLY GUSTY WINDS AND HAIL ARE ALSO POSSIBLE IN THE STRONGER
THUNDERSTORMS. STAY TUNED TO NOAA WEATHER RADIO AND OTHER LOCAL
MEDIA FOR FURTHER DETAILS OR UPDATES. FOR ADDITIONAL WEATHER
INFORMATION, CHECK OUR WEB SITE AT HTTP://WWW.NWS.NOAA.GOV/ER/LWX

JLW