DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 281232
SWODY1
SPC AC 281230

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0630 AM CST FRI FEB 28 2014

VALID 281300Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF SRN CA...

...SYNOPSIS...
SPLIT FLOW PATTERN WILL PREVAIL THROUGH EARLY SAT FROM THE EASTERN
PACIFIC EWD INTO THE CNTRL U.S...SOUTH OF PERSISTENT BLOCK OVER ERN
AK. POTENT UPR LOW IN THE SRN STREAM...NOW LOCATED ABOUT 600 MILES W
OF SFO...SHOULD CONTINUE SLOWLY SEWD TODAY/TNGT AND REACH A POINT
ABOUT 250 MILES SW OF SFO BY 12Z SAT. IN THE SAME BELT OF
FLOW...DOWNSTREAM IMPULSE NOW ENTERING SW OK EXPECTED TO FURTHER
WEAKEN AS IT SHEARS ESE ACROSS THE LWR MS VLY THROUGH THIS EVE...AND
CONTINUES ESE TO THE S ATLANTIC CST BY THE END OF THE PERIOD.

AT LWR LVLS...DEEPLY OCCLUDED /PER SATELLITE/ SFC LOW ASSOCIATED
WITH PACIFIC UPR LOW SHOULD MOVE SEWD IN TANDEM WITH THE UPR SYSTEM.
ATTENDANT WARM CONVEYOR BELT WILL AFFECT MUCH OF CA EARLY THIS
MORNING...WHILE INCREASINGLY COLD/CYCLONIC FLOW OVERSPREADS CNTRL
AND SRN SECTIONS OF THE STATE LATER TODAY THROUGH TNGT. FALLING
HEIGHTS...SUFFICIENT MOISTURE...AND ANTECEDENT MILD CONDITIONS
SUGGEST A GOOD CHANCE FOR TSTMS OVER MUCH OF CA TODAY...WITH THE
THREAT LIKELY TO SPREAD E/SE INTO THE LWR CO VLY EARLY SAT. GIVEN
THE ACCOMPANYING WIND FIELD AND POTENTIAL FOR TOPOGRAPHICALLY-FORCED
LOW-LVL FLOW...SOME OF THE STORMS COULD BECOME STRONG TO SVR.

...CA TO LWR CO VLY TODAY/TNGT...
MODEST LOW-LVL MOISTURE INFLOW...AND MOISTENING FROM ONGOING WARM
CONVEYOR BELT RAINFALL...COUPLED WITH MID-LVL COOLING ASSOCIATED
WITH THE CONTINUED SE MOTION OF E PACIFIC UPR LOW...SHOULD FOSTER
SUFFICIENT DESTABILIZATION/DEEPENING OF EXISTING CONVECTION TO YIELD
THUNDER OVER MUCH OF CNTRL AND SRN CA LATER TODAY INTO TNGT.
DESTABILIZATION OVER SRN SECTIONS MAY BE LOCALLY ENHANCED BY PARTIAL
CLEARING IN WAKE OF PASSING WARM CONVEYOR BELT CLOUDS. THE STRONGEST
MID-LVL COOLING/DESTABILIZATION...HOWEVER...LIKELY WILL NOT OCCUR S
OF THE PT CONCEPTION/VANDENBERG AREA UNTIL THE ARRIVAL OF OFFSHORE
VORT LOBE /MARKED BE LEADING EDGE OF DEEPER CONVECTION OFF THE CNTRL
CA CST/ AFTER 17-18Z.

WHILE SBCAPE LIKELY WILL REMAIN AOB ABOUT 750 J/KG...COMBINATION OF
EVEN MODEST BUOYANCY WITH INCREASING ASCENT AND STRONG /60 KT/ SSW
TO SWLY DEEP SHEAR IN EXIT REGION OF 80+ KT 500 MB JET STREAK
ACCOMPANYING THE VORT LOBE SHOULD PROMOTE SOME DEGREE OF LOW TO
MID-LVL ROTATION IN ANY LONGER-LIVED UPDRAFTS. COUPLED WITH
OROGRAPHIC BACKING OF THE LOW-LVL FLOW...ESPECIALLY IN THE LOS
ANGELES BASIN...SETUP MAY YIELD A FEW STORMS WITH TORNADOES IN
ADDITION TO MARGINALLY SVR HAIL. A MORE CONDITIONAL SVR THREAT MAY
DEVELOP IN THE SAN JOAQUIN VLY...WHERE MOISTURE AND HEATING ARE
EXPECTED TO BE MORE LIMITED.

STRENGTH OF FORCING FOR ASCENT AND PROGRESSIVE NATURE OF UPR SYSTEM
SUGGEST THAT THE CONVECTION/STORMS ULTIMATELY WILL MERGE INTO ONE OR
MORE BROKEN LINES BY LATE AFTN. THIS ACTIVITY MAY MOVE OR REDEVELOP
E INTO THE LWR CO VLY TNGT AND EARLY SAT...WHERE STRONG LOW-LVL
WINDS/SHEAR IN A SOMEWHAT DRIER LOW-LVL ENVIRONMENT COULD POSE A
CONTINUED RISK FOR SVR WIND AND POSSIBLY A BRIEF TORNADO INTO THE
NIGHT.

..CORFIDI/MARSH.. 02/28/2014

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