SWOMCD
SPC MCD 152000
WAZ000-ORZ000-152100-
MESOSCALE DISCUSSION 0228
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT TUE MAR 15 2011
AREAS AFFECTED...NWRN/N CNTRL ORE...SWRN/S CNTRL WA
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 152000Z - 152100Z
THUNDERSTORMS WILL GRADUALLY INCREASE IN COVERAGE OVER PORTIONS OF
THE PACIFIC NORTHWEST THIS AFTERNOON...WITH ISOLATED DMGG
WINDS...SMALL HAIL...AND PERHAPS A BRIEF TORNADO POSSIBLE.
20Z WV IMAGERY SHOWS THE LEADING EDGE OF STRONGER ASCENT JUST
BEGINNING TO IMPINGE OF THE PACIFIC NORTHWEST COAST. THUNDERSTORM
COVERAGE IS GRADUALLY INCREASING OFFSHORE AND ALONG THE IMMEDIATE
COAST AS ASSOCIATED LAPSE RATES BEGIN TO INCREASE. PATCHES OF
CLEARING EVIDENT OF VISIBLE IMAGERY HAS LED TO WEAK DESTABILIZATION
AS WEAK SURFACE HEATING OCCURS...AND AFOREMENTIONED LAPSE RATES
CONTINUE TO STEEPEN...PARTICULARLY IN A CORRIDOR FROM NWRN ORE/SWRN
WA INTO CNTRL WA. CONVERGENT SURFACE WIND FIELDS ALONG THE COAST AND
WEAK SURFACE PRESSURE FALLS SUGGEST A SURFACE TROUGH THAT WILL FAVOR
THUNDERSTORM DEVELOPMENT...WITH ADDITIONAL DEVELOPMENT POSSIBLE IN
UPSLOPE FLOW. ALTHOUGH INSTABILITY IS WEAK...STRONG UNIDIRECTIONAL
SHEAR PROFILES /50 KTS JUST ABOVE THE SURFACE IN AREA VAD WIND
PROFILE DATA/ WILL SUPPORT SMALL BOWING SEGMENTS CAPABLE OF DMGG
WINDS...WHILE COMPLEX TERRAIN AND LOCALIZED BACKED SURFACE WINDS MAY
SUPPORT BRIEFLY ROTATING STORMS/AN ISOLATED TORNADO. AS LAPSE RATES
CONTINUE TO STEEPEN...SMALL HAIL MAY BECOME POSSIBLE. GIVEN THE WEAK
INSTABILITY AND ISOLATED NATURE OF EXPECTED SEVERE STORMS...A WW IS
NOT ANTICIPATED. HOWEVER...TRENDS WILL CONTINUE TO BE MONITORED.
..HURLBUT.. 03/15/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...PDT...MFR...SEW...PQR...
LAT...LON 46772111 45042108 43862302 43892424 44752454 46302426
47002372 47142288 46772111
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