Mesoscale Discussion 320

Issued

Mar 21, 2003, 2:05 PM EST (19:05 UTC)

Expired

Mar 21, 2003, 4:30 PM EST

In force

2 hr

Issued by

the Storm Prediction Center

The Sterling radar (KLWX), 22 km from the middle of the area, began a volume at 19:08 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

607 
ACUS11 KWNS 211906
SWOMCD
SPC MCD 211905 COR
PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-212130-

MESOSCALE DISCUSSION 0320
NWS STORM PREDICTION CENTER NORMAN OK
0105 PM CST FRI MAR 21 2003

AREAS AFFECTED...NRN VA...PARTS OF CNTRL/ERN MD

CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

VALID 211905Z - 212130Z

CORRECTED  AREAS AFFECTED

SEVERE THREAT IS EXPECTED TO INCREASE LATE THIS AFTERNOON.  AREA
IS BEING MONITORED FOR POSSIBLE WW.



IN RESPONSE TO EVOLVING UPPER FLOW PATTERN ASSOCIATED WITH
APPROACH OF UPSTREAM SHORT WAVE TROUGHS...AREA OF STRONGER
SURFACE PRESSURE FALLS IS BEGINNING TO DEVELOP IN THE LEE OF THE
CENTRAL APPALACHIANS...NORTHWEST THROUGH NORTH OF CHARLOTTESVILLE
VA.  MODELS SUGGEST THIS AREA OF PRESSURE FALLS WILL BE
MAINTAINED... WITH PERHAPS A WEAK SURFACE LOW DEVELOPING LATE
THIS AFTERNOON... MIGRATING EAST NORTHEASTWARD ACROSS NORTHERN
VIRGINIA INTO CENTRAL/EASTERN MARYLAND.  THIS IS EXPECTED TO
PROVIDE FOCUS FOR PRIMARY CONVECTIVE DEVELOPMENT IN ENVIRONMENT
WITH STRONG SHEAR SUPPORTIVE OF SUPERCELLS.



DESTABILIZATION HAS BEEN SLOWED BY LOW CLOUDINESS ACROSS MUCH OF
EASTERN VIRGINIA AND THE DELMARVA PENINSULA...AND MID/HIGH CLOUDS
ASSOCIATED WITH WEAK CONVECTIVE BAND ALONG THE MID ATLANTIC
COAST.	  18Z SOUNDING FROM WASHINGTON D.C.
DOES...HOWEVER...ALREADY SUGGEST PRESENCE OF CAPE IN EXCESS OF
500 J/KG FOR PARCELS ABOVE STABLE BOUNDARY LAYER.  COMBINATION OF
MID-LEVEL COOLING...INCREASING LARGE-SCALE FORCING FOR UPWARD
VERTICAL MOTION AND WARMING OF BOUNDARY LAYER IS EXPECTED TO
CONTRIBUTE TO FURTHER DESTABILIZATION THROUGH THE REMAINDER OF
THE AFTERNOON HOURS.  AS THIS OCCURS...CONVECTIVE DEVELOPMENT NOW
BEGINNING TO OCCUR OFF THE MOUNTAINS OF WESTERN VIRGINIA LIKELY
WILL BEGIN TO INTENSIFY AS IT SPREADS EASTWARD.  A FEW SEVERE
THUNDERSTORMS APPEARS LIKELY...ESPECIALLY NORTH THROUGH NORTHEAST
OF THE D.C. AREA AFTER 21Z.

..KERR.. 03/21/2003

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

ATTN...WFO...PHI...CTP...LWX...

38847839 39387787 39967686 39787554 39007598 38797708
38247824

Mesoscale Discussions in Virginia, 2003Mesoscale Discussions in Maryland, 2003Mesoscale Discussions in Pennsylvania, 2003Every mesoscale discussion in 2003

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.