[MCD] SWOMCD

[MCD at goshenarc.org]

ACUS11 KWNS 180201
SWOMCD
SPC MCD 180158 
VAZ000-MDZ000-PAZ000-NCZ000-DCZ000-WVZ000-180400-

MESOSCALE DISCUSSION 2241
NWS STORM PREDICTION CENTER NORMAN OK
0858 PM CDT FRI SEP 17 2004

AREAS AFFECTED...DC...MD...NERN NC...SCNTRL PA...ERN VA...EXTREME
ERN WV PNHDL

CONCERNING...TORNADO WATCH 836...

VALID 180158Z - 180400Z

ISOLD TORNADOES OR DAMAGING WIND GUSTS WILL CONTINUE TO BE THREATS
THROUGH 04Z...BUT SEVERE THREATS ARE GRADUALLY DIMINISHING THIS
EVENING.

THE NUMBER OF DISCRETE LONG-LIVED SUPERCELLS IS BEGINNING TO
DECREASE THIS EVENING. DIURNAL COOLING IS TAKING A TOLL ON THE
BUOYANCY OBSERVED IN THE 00Z KIAD SOUNDING AND AIR MASS IS BECOMING
LESS FAVORABLE TO SUSTAIN UPDRAFTS.  SUFFICIENT INSTABILITY DOES
EXIST TO SUPPORT A LINE OF TSTMS ASSOCIATED WITH A VORT LOBE
ROTATING CYCLONICALLY AROUND THE REMNANTS OF IVAN. THIS LINE OF
STORMS WILL TRANSLATE INTO THE LOWER MD SHORE BY 04Z.  ISOLD CELLS
MAY CONTINUE TO DEVELOP AHEAD OF THIS LINE AS WELL.

STRONGEST LOW LEVEL HELICITY HAS CONTRACTED TO A SMALL PART OF
CNTRL/ERN MD INTO SCNTRL PA AND SUGGESTS THAT THE HIGHEST RISK OF A
TORNADO HAS SHIFTED IN AREAS NORTH/EAST OF THE WASHINGTON D.C. AREA.
 WAKEFIELD VWP SHOWS THAT THE FLOW HAS VEERED IN THE LOWEST GATES
AND IS RESULTING IN A DEEP SLY UNIDIRECTIONAL REGIME THROUGH THE
COLUMN...EFFECTIVELY DECREASING SRH.  LINE SEGMENTS HAVE BECOME
ALIGNED MORE NORMAL TO THIS MEAN WIND AND DAMAGING WIND SEEMS MORE
OF A RISK FARTHER SOUTH ACROSS SERN VA INTO FAR ERN NC.

GIVEN CONTINUED SURFACE COOLING...PROBABILITIES FOR SEVERE WEATHER
WILL DECREASE. AFTER 04Z...ANOTHER WEATHER WATCH MAY NOT BE NEEDED
AS SEVERE WEATHER THREATS SHOULD BECOME ISOLD AT BEST.

..RACY.. 09/18/2004

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PHI...AKQ...MHX...CTP...LWX...

35917687 37377719 38597699 39717815 40097812 40137605
36007540 

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