MESO: Mesoscale Discussion 0103

ACUS11 KWNS 151939
SWOMCD
SPC MCD 151939
ORZ000-WAZ000-152115-

MESOSCALE DISCUSSION 0103
NWS STORM PREDICTION CENTER NORMAN OK
0139 PM CST TUE FEB 15 2011

AREAS AFFECTED...SWRN WA / ORE COASTS

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 151939Z - 152115Z

TSTMS ARE EXPECTED TO INCREASE IN COVERAGE THIS AFTERNOON ALONG THE
IMMEDIATE COAST WITH SOME RISK FOR ISOLATED SEVERE WEATHER. A WW IS
NOT ANTICIPATED.

LATEST TRENDS IN LIGHTNING AND REGIONAL RADAR DATA INDICATE A
NOTABLE INCREASE IN TSTM DEVELOPMENT OFF THE ORE COAST SW OF AST.
INSPECTION OF WATER VAPOR IMAGERY SUGGESTS THAT THIS ACTIVITY IS
OCCURRING WITHIN A ZONE OF DEEP-LAYER FORCING FOR ASCENT ASSOCIATED
WITH SHORT-WAVE TROUGH LIFTING NEWD TOWARD NWRN WA AND VANCOUVER
ISLAND. BREAKS IN COVER OBSERVED NEAR THE MOUTH OF THE COLUMBIA
RIVER SHOULD ALLOW FOR LOCALLY STRONGER DIABATIC HEATING TO OCCUR
THIS AFTERNOON. WHEN COUPLED WITH THE DYNAMIC MIDLEVEL COOLING
ATTENDANT TO VORTICITY MAXIMUM...EXPECT FURTHER STEEPENING OF LAPSE
RATES TO OCCUR...SUPPORTING SBCAPE VALUES OF 100-200 J/KG.

ISALLOBARIC RESPONSE TO PRIMARY SURFACE LOW OFF THE WA COAST IN
CONJUNCTION WITH OROGRAPHICALLY BACKED LOW-LEVEL FLOW ALONG THE
COLUMBIA RIVER VALLEY ARE EXPECTED TO MAINTAIN A VERTICALLY VEERING
WIND PROFILE THIS AFTERNOON WITH MORE THAN SUFFICIENT LOW AND
DEEP-LAYER SHEAR FOR UPDRAFT ROTATION. THE MARGINAL INSTABILITY
WILL REMAIN A LIMITING INGREDIENT FOR A MORE ROBUST SEVERE WEATHER
EPISODE. HOWEVER...ANY MORE PERSISTENT STORMS WILL BE CAPABLE OF
LOCALLY STRONG WIND GUSTS...SOME SMALL HAIL AND PERHAPS A BRIEF
TORNADO/WATERSPOUT.

..MEAD.. 02/15/2011

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

ATTN...WFO...MFR...SEW...PQR...

LAT...LON 42632429 43252469 44722426 45802429 46622442 47092393
46462346 45172332 43762361 42912390 42632429

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