SPC AC 161933
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0133 PM CST MON FEB 16 2009
VALID 162000Z - 171200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTN AND EARLY EVE ACROSS
THE L.A. BASIN AND ADJACENT SRN CA COASTAL AREAS....
THE MAIN MID-LEVEL CIRCULATION CENTER EMBEDDED WITHIN THE BROADER
SCALE UPPER TROUGH WEST OF PACIFIC COASTAL AREAS IS EXPECTED TO
REMAIN OFFSHORE OF NORTHERN CALIFORNIA THROUGH THE BALANCE OF THE
FORECAST PERIOD. BUT...IT APPEARS THAT A LOW AMPLITUDE WAVE...WITH
PERHAPS A COUPLE OF SMALLER SCALE PERTURBATIONS...IS NOW IN THE
PROCESS OF MIGRATING INLAND ACROSS SOUTHERN CALIFORNIA...
ACCOMPANIED BY A 70-90 KT 500 MB JET STREAK. AND...MODELS INDICATE
THAT MID-LEVEL FORCING FOR UPWARD VERTICAL ASSOCIATED WITH THIS
FEATURE WILL OVERSPREAD THE LOS ANGELES BASIN BETWEEN NOW AND EARLY
EVENING.
IT APPEARS THAT STRONGEST FORCING MAY COINCIDE WITH THE PEAK
AFTERNOON HEATING...ROUGHLY 22-00Z...WHEN MODEL FORECAST SOUNDINGS
INDICATE THAT A SHALLOW SURFACE-BASED STABLE LAYER MAY FINALLY
ERODE. SURFACE WARMING AND MOISTENING...COUPLED WITH MID-LEVEL
COOLING...MAY YIELD CAPE OF A FEW HUNDRED J/KG...EXTENDING THROUGH
THE FAVORABLE MIXED PHASE LAYER FOR CHARGE SEPARATION. A FEW LOW
TOPPED THUNDERSTORMS ARE POSSIBLE. WITH OROGRAPHICALLY BACKED NEAR
SURFACE FLOW CONTINUING TO SUPPORT SIZABLE CLOCKWISE CURVED
LOW-LEVEL HODOGRAPHS AND THE POTENTIAL FOR ROTATING UPDRAFTS...A
WINDOW OF OPPORTUNITY EXISTS FOR THE RISK OF TORNADOES...IN ADDITION
TO SOME HAIL AND GUSTY WINDS...LATE THIS AFTERNOON.
..KERR.. 02/16/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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