Saturday, June 20, 2009

MESO: Mesoscale Discussion 1254

ACUS11 KWNS 201755
SWOMCD
SPC MCD 201755
VAZ000-MDZ000-PAZ000-DCZ000-WVZ000-201930-

MESOSCALE DISCUSSION 1254
NWS STORM PREDICTION CENTER NORMAN OK
1255 PM CDT SAT JUN 20 2009

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

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 201755Z - 201930Z

SHOULD STORMS BECOME SUSTAINED E OF THE BLUE RIDGE...A THREAT FOR
DAMAGING WIND GUSTS WILL EXIST. CONVECTIVE TRENDS ARE BEING
MONITORED FOR A POSSIBLE WW.

LATEST MESOANALYSIS INDICATED DEEPENING SURFACE LOW OVER N-CNTRL PA
WITH ATTENDANT WARM FRONT EXTENDING SEWD THROUGH S-CNTRL PA AND ERN
MD. MEANWHILE...COLD FRONT WAS MOVING THROUGH WRN PA AND THE BLUE
RIDGE OF VA. 3-HR TEMPERATURE/DEWPOINT TRENDS INDICATE THE
STRONGEST BOUNDARY LAYER DESTABILIZATION OCCURRING WITHIN NARROW
WARM SECTOR OVER S-CNTRL PA INTO NRN VA WHERE CONSIDERABLE
WARMING/MOISTENING IS OCCURRING. FARTHER S OVER CNTRL/SRN VA...WARM
SECTOR IS CONSIDERABLY WIDER WITH TEMPERATURES IN THE MID 80S TO
LOWER 90S AND DEWPOINTS IN THE LOWER 70S...CONTRIBUTING TO MLCAPE OF
1000-2000 J/KG.

THUS FAR TODAY...CONVECTION HAS STRUGGLED TO DEVELOP E OF THE BLUE
RIDGE. HOWEVER...RECENT RADAR/VISIBLE SATELLITE TRENDS INDICATE
DEEPENING CUMULUS IN THE IMMEDIATE LEE OF THE HIGHER TERRAIN WITH AN
ISOLATED TSTM DEVELOPING OVER KING WILLIAM COUNTY VA AS OF 1745Z.
AREA VWPS INDICATE CONSIDERABLE STRENGTHENING TO WNWLY WIND FIELDS
/REF. CURRENT ROANOKE VA PROFILE/ WITH ARRIVAL OF SHORTWAVE TROUGH
FROM THE W...RESULTING IN 40-45 KT OF UNIDIRECTIONAL SHEAR THROUGH
THE LOWEST 2-3 KM AGL. THIS STRONG FLOW COUPLED WITH THE PRESENCE
OF STEEP LOW-LEVEL LAPSE RATES INDICATE A HIGH LIKELIHOOD OF
DAMAGING WINDS SHOULD STORMS BECOME SUSTAINED.

..MEAD.. 06/20/2009

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

ATTN...WFO...PHI...AKQ...CTP...LWX...RNK...

LAT...LON 36667963 37497898 39137786 39587759 39757685 39637623
38837590 37697606 36837631 36627699 36557879 36667963

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