Friday, February 18, 2011

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 181622
SWODY1
SPC AC 181620

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1020 AM CST FRI FEB 18 2011

VALID 181630Z - 191200Z

...NO SVR TSTM AREAS FORECAST...

...SRN CA COASTAL AREAS PRIMARILY AFTER 00Z...
COMPLEX TROUGH JUST OFF CA COAST THIS AM. ONE S/WV IMPULSE ROTATES
INLAND THRU CENTRAL CA THIS AFTERNOON...WHILE MORE SIGNIFICANT
SYSTEM NOW AROUND 130W IMPACTS SRN CA TONIGHT.

MODELS ALL MAINTAIN INSTABILITY SUFFICIENT FOR A SEVERE THUNDERSTORM
CONCERN CONFINED TO ALONG AND OFFSHORE SRN CA COAST. THIS SEEMS
REASONABLE WITH THE RATHER DRY ANTECEDENT CONDITIONS ACROSS SRN
CA...IT WILL BE DIFFICULT TO DEVELOP MUCH IN THE WAY OF INSTABILITY
INLAND EVEN WITH THE STRONG LARGE SCALE ASCENT EXPECTED TO SPREAD
ACROSS THE AREA OVERNIGHT.

A BAND OF CONVECTION...INCLUDING SCTD TSTMS...SHOULD FORM INVOF COLD
FRONT OVER THE OFFSHORE WATERS LATER TODAY AND MOVE TO THE COAST
DURING THE EVE. THE STRONGEST ACTIVITY MAY REMAIN OVER THE
WATER...WHERE LOW-LVL THETAE WILL BE GREATEST. MOISTURE INCREASE
AHEAD OF FRONT WILL BE MODEST AT BEST. GIVEN STRENGTH OF UPR
IMPULSE...AND MODEL FORECASTS SHOWING FAIRLY SUBSTANTIAL MID LVL
COOLING...EXPECT THAT DESTABILIZATION WILL BE SUFFICIENT TO YIELD
200-400 J/KG MUCAPE WITH NO CINH ALONG THE CST BY MID TO LATE EVE AS
THE CONVECTION MOVES ASHORE.

THERE WILL BE A CONDITIONAL RISK FOR LOW-LVL MESOCYCLONES WITH AND
AHEAD OF THE FRONT. THIS THREAT SHOULD BE GREATEST WHERE TERRAIN
FORCES NEAR-SFC FLOW TO RETAIN A SLY/SELY COMPONENT...I.E. ALONG THE
IMMEDIATE CST FROM NEAR KLAX S TO KSAN BETWEEN ABOUT 03-09Z SAT.
OVERALL...HOWEVER...WEAK INSTABILITY SUGGEST THAT SVR
POTENTIAL SHOULD REMAIN LIMITED. THE THREAT WILL INCLUDE A LOW
PROBABILISTIC RISK FOR A FEW STG/LOCALLY DMGG GUSTS...AND/OR A BRIEF
TORNADO OR TWO.

..HALES/STOPPKOTTE.. 02/18/2011

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