SWODY1
SPC AC 181246
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0646 AM CST SAT DEC 18 2010
VALID 181300Z - 191200Z
...NO SVR TSTM AREAS FORECAST...
...PACIFIC NW COAST...
POTENT VORTICITY MAXIMUM JUST OFFSHORE OF NWRN CA/ORE WILL PIVOT
NNEWD THROUGH ORE/WA IN ADVANCE OF VERY STRONG MID AND UPPER-LEVEL
JET STREAKS MOVING ONSHORE ACROSS NRN PARTS OF CA/NV. THIS PATTERN
EVOLUTION WILL RESULT IN SUBSTANTIAL HEIGHT FALLS AND ASSOCIATED
STEEPENING OF MIDLEVEL LAPSE RATES ACROSS THE REGION TODAY. WHEN
COUPLED WITH THE MOIST...ONSHORE FLOW IN THE LOW LEVELS...LOCAL
ENVIRONMENT W OF THE COASTAL RANGES IS EXPECTED TO BECOME MARGINALLY
UNSTABLE WITH MUCAPE OF A COUPLE HUNDRED J/KG.
LATEST MESOANALYSIS INDICATES A WELL-DEFINED PRESSURE RISE-FALL
COUPLET FROM THE NRN CA/SRN ORE COASTS NNEWD THROUGH THE LOWER
COLUMBIA RIVER VALLEY INTO WRN WA...INDICATIVE OF THE STRONG DYNAMIC
FORCING FOR ASCENT ATTENDANT TO THE ABOVE-MENTIONED SHORT WAVE
TROUGH. WIDELY SCATTERED TSTMS ARE BEGINNING TO AFFECT COASTAL
LOCATIONS AROUND CEC OWING TO THE ONSHORE FLUX OF A WARMER...MORE
MOIST AIR MASS WITHIN THE VEERED LOW-LEVEL WIND FIELD.
EXPECT A SIMILAR TREND TO CONTINUE NWD ALONG THE ORE COAST TODAY AS
ONSHORE FLOW IS ENHANCED IN WAKE OF LEAD SHORT WAVE TROUGH. GIVEN
THE COLD THERMODYNAMIC PROFILES AND STEEPENING LAPSE RATES SOME HAIL
WILL BE POSSIBLE WITH THE MOST INTENSE STORMS. VERTICAL SHEAR WILL
REMAIN RATHER STRONG AND SUPPORTIVE OF SOME UPDRAFT ROTATION. AS
SUCH...A RISK FOR LOCALLY STRONG WIND GUSTS AND PERHAPS A BRIEF
TORNADO WILL EXIST THROUGH THIS AFTERNOON.
...CNTRL/SRN FL PENINSULA...
SHORT WAVE TROUGH CURRENTLY TRANSLATING EWD THROUGH THE LOWER MS
VALLEY AND N-CNTRL GULF BASIN WILL CONTINUE EWD THIS
PERIOD...EVENTUALLY MOVING THROUGH THE SERN STATES...INCLUDING THE
FL PENINSULA LATE TONIGHT INTO SUNDAY MORNING. AN ASSOCIATED
SURFACE LOW WILL CONCURRENTLY CONSOLIDATE OVER THE ERN GULF BEFORE
MOVING ACROSS THE CNTRL PENINSULA LATER THIS AFTERNOON INTO
EVENING.
THE 12Z MIA SOUNDING AND SATELLITE-DERIVED PW IMAGERY INDICATE THAT
THE AIR MASS ACROSS THE SRN PENINSULA HAS MOISTENED CONSIDERABLY
OVER THE PAST 12-HRS WITH BOUNDARY LAYER DEW POINTS IN THE MID/UPPER
60S AND PW VALUES APPROACHING 1.2 INCHES. EXPECT THIS MORE MOIST
AIR MASS/EFFECTIVE WARM FRONT TO DEVELOP NWD TODAY IN ADVANCE OF
SURFACE LOW WITH ENVIRONMENT GRADUALLY DESTABILIZING WITH AFTERNOON
MLCAPE VALUES APPROACHING 500-1000 J/KG.
BAND OF TSTMS APPROXIMATELY 80 NM W OF EYW WILL LIKELY BEGIN TO
AFFECT THE KEYS AND SWRN PENINSULA BY LATE MORNING/AFTERNOON WITH
ADDITIONAL STORMS FORMING DURING THE PEAK OF THE DIURNAL HEATING
CYCLE ALONG AND S OF SURFACE LOW TRACK WHERE LOW-LEVEL CONVERGENCE
AND INSTABILITY WILL BE MAXIMIZED. FORECAST SOUNDINGS SUGGEST THAT
LOW-LEVEL WIND FIELD WILL REMAIN BACKED MOST NOTABLY INVOF
DEVELOPING E COAST SEA-BREEZE...RESULTING IN MODEST LOW-LEVEL SHEAR
AND AROUND 35 KT OF EFFECTIVE BULK SHEAR. GIVEN SETUP APPEARS AT
LEAST SUPPORTIVE OF A FEW STRONG STORMS LATER TODAY WITH A THREAT
FOR LOCALLY STRONG WIND GUSTS AND PERHAPS A BRIEF TORNADO.
..MEAD/STOPPKOTTE.. 12/18/2010
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