SWODY1
SPC AC 181918
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0118 PM CST MON JAN 18 2010
VALID 182000Z - 191200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTN ACROSS PARTS OF CNTRL
CALIFORNIA COASTAL AREAS AND THE INTERIOR VALLEYS...
...20Z UPDATE...
SLIGHT RISK PROBABILITIES ARE BEING MAINTAINED ALONG COASTAL AREAS
NORTH OF POINT CONCEPTION...NORTHWARD...EAST OF THE SAN FRANCISCO
BAY AREA...INTO PARTS OF THE SOUTHERN SACRAMENTO VALLEY...AND
EASTWARD...THROUGH PARTS OF THE SAN JOAQUIN VALLEY. THIS IS WHERE
LOW-LEVEL FLOW...JUST ABOVE GROUND LEVEL...REMAINS VERY
STRONG...NEAR A PRE-FRONTAL 50-60+ KT SOUTHERLY 850 MB JET AXIS.
ALTHOUGH CLOUD TO GROUND LIGHTNING HAS BEEN ALMOST NEGLIGIBLE...
PERIODIC INTENSIFICATION OF ELEMENTS WITHIN THE FRONTAL BAND COULD
STILL BE SUFFICIENT TO ENHANCE THE DOWNWARD TRANSFER OF HIGHER
MOMENTUM TO THE SURFACE. EVEN AHEAD OF THE FRONT...THIS POTENTIAL
MAY BEGIN TO DIMINISH BY 19/00Z...AS MODELS GENERALLY INDICATE
SUBSTANTIAL WEAKENING AND VEERING OF THE LOW-LEVEL FLOW FIELDS... AS
THE APPROACHING SHORT WAVE TROUGH CONTINUES TO SPLIT...AND THE
PRIMARY SURFACE CYCLONE LIFTS NORTHWARD TO THE WEST OF NORTHERN
PACIFIC COASTAL AREAS.
..KERR.. 01/18/2010
.PREV DISCUSSION... /ISSUED 0957 AM CST MON JAN 18 2010/
...CA...
ACTIVE WEATHER PATTERN WILL CONTINUE ACROSS THE WEST COAST TODAY
WITH A SERIES OF POTENT SYSTEMS APPROACHING THE REGION. LEADING
IMPULSE APPEARS TO BE WEAKENING/SPLITTING AS IT APPROACHES CA THIS
MORNING. PRECEDING MOIST PLUME WILL MAINTAIN ENHANCED QPF AND
CLOUDS OVER MUCH OF CA THROUGH THE DAY LIMITING HEATING AND
POTENTIAL INSTABILITY AS PORTION OF THIS IMPULSE PROGRESSES EWD
ACROSS THE SIERRAS. HOWEVER...REGION WILL REMAIN WITHIN FAVORABLE
EXIT REGION OF ENHANCED MID/UPPER LEVEL JET AS 100-150 KT H25 SPEED
MAX NOSES INTO FAR SRN CA/NRN BAJA REGION BY THE END OF THE PERIOD.
SMALL POCKETS OF WEAK INSTABILITY MAY EVOLVE INLAND INTO THE
INTERIOR VALLEYS OF CA THIS AFTERNOON...AND ALONG AND WEST OF THE
COASTAL RANGES WHERE SOME CLEARING MAY OCCUR IN WAKE OF LEADING
SYSTEM. THIS SHOULD PROVE FAVORABLE FOR A FEW TSTMS WITHIN BROADER
PRECIPITATION SHIELD. SHEAR WILL REMAIN QUITE STRONG AND MORE THAN
ADEQUATE FOR ORGANIZATION INTO SMALL LINES AND PERHAPS TRANSIENT LOW
LEVEL ROTATION IN STRONGER LOW TOPPED STORMS NEAR THE COAST.
ALTHOUGH...FORECAST SOUNDINGS INDICATE THAT NEAR MOIST ADIABATIC
THERMODYNAMIC PROFILES WILL REMAIN PREVALENT ACROSS THE AREA WHICH
WILL LIMIT INSTABILITY AND OVERALL POTENTIAL/COVERAGE OF STRONG TO
SEVERE TSTMS. THE THREAT OF AN ISOLATED DAMAGING WIND GUST AND/OR
ISOLATED TORNADO MAY ACCOMPANY ANY PERSISTENT/ORGANIZED UPDRAFT.
LATER TONIGHT...COOLING MID LEVELS AND MORE OPEN CELLULAR
DEVELOPMENT SHOULD INCREASE POTENTIAL FOR HAIL IN ISOLATED CORES
NEAR THE CENTRAL CA COAST AS NEXT IMPULSE APPROACHES.
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