SWODY1
SPC AC 151920
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0120 PM CST TUE FEB 15 2011
VALID 152000Z - 161200Z
...NO SVR TSTM AREAS FORECAST...
...WA/ORE COAST...
LATEST VIS SATELLITE IMAGERY SUGGESTS A NOTABLE AMOUNT OF CONVECTION
JUST OFF THE WA/ORE COAST...WWD BENEATH THE MEAN TROUGH AXIS NEAR
135W. THIS CU/CB FIELD IS CONSIDERABLY CLUSTERED JUST DOWNSTREAM OF
TWO DISTINCT UPPER VORT MAXIMA...ONE NEAR 47N/129W...AND THE OTHER
ROUGHLY 43N/134W. LOW LEVEL CONVERGENCE AND VERTICAL ASCENT AHEAD
OF THESE FEATURES SHOULD CONTINUE TO ENCOURAGE CONVECTION AND
ISOLATED THUNDERSTORMS...ESPECIALLY INVOF MARINE BOUNDARY LAYER
INFLUENCES. LATEST RADAR IMAGERY SUPPORTS THIS WITH A FEW STRONGER
UPDRAFTS WITH EMBEDDED LIGHTNING APPROACHING THE COLUMBIA RIVER
BASIN ALONG THE WA/ORE BORDER. GIVEN THIS EVOLUTION WILL NOT MAKE
CHANGES TO 1630Z FORECAST AS THERE REMAINS AT LEAST A LOW
PROBABILITY FOR AN ISOLATED SEVERE WIND GUST OR PERHAPS A BRIEF WEAK
TORNADO.
..DARROW.. 02/15/2011
.PREV DISCUSSION... /ISSUED 1020 AM CST TUE FEB 15 2011/
...PACIFIC NW COAST...
SHORT-WAVE TROUGH AND ASSOCIATED 90-100 KT MIDLEVEL JET STREAK WILL
MOVE ONSHORE TODAY IN ADVANCE OF MORE INTENSE UPSTREAM SYSTEM WHICH
IS FORECAST TO APPROACH THE NRN CA COAST LATE TONIGHT INTO WED
MORNING. DYNAMIC COOLING/HEIGHT FALLS ALONG CYCLONIC SIDE OF
MIDLEVEL JET CORE COUPLED WITH SOME BOUNDARY LAYER WARMING AND
CONTINUED...MOIST ONSHORE FLOW IN THE LOW LEVELS WILL RESULT IN THE
DEVELOPMENT OF WEAK INSTABILITY LATER TODAY WITH SBCAPE APPROACHING
100-300 J/KG.
TSTMS ARE EXPECTED TO INCREASE IN AREAL COVERAGE TODAY IN ADVANCE OF
LEAD SHORT-WAVE TROUGH WITHIN KINEMATIC ENVIRONMENT CHARACTERIZED BY
A STRONG VERTICAL SHEAR PER CURRENT MEDFORD AND PORTLAND ORE VWP
DATA. AS SUCH...SOME POTENTIAL WILL EXIST FOR
ORGANIZED/LONGER-LIVED STORM STRUCTURES EMBEDDED WITHIN LARGER
PRECIPITATION SHIELD WITH A RISK FOR LOCALLY STRONG WIND GUSTS
AND/OR A BRIEF TORNADO. THIS SEVERE WEATHER THREAT IS EXPECTED TO
DIMINISH THROUGH THE EVENING AS THE BOUNDARY LAYER COOLS/STABILIZES.
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