SWODY1
SPC AC 151906
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0106 PM CST SUN FEB 15 2009
VALID 152000Z - 161200Z
...NO TSTM AREAS FORECAST...
TSTMS ARE NOT EXPECTED CONUS-WIDE THROUGH TONIGHT AS STABLE
CONDITIONS GENERALLY PREVAIL. A FEW TSTMS COULD REACH COASTAL CA
LATE TONIGHT...BUT 10% TSTM PROBABILITIES DO NOT APPEAR TO BE
WARRANTED.
...PREVIOUS DISCUSSION...
COLD SFC/UPPER LOW OFF NRN CA COAST EXPECTED TO MOVE LITTLE THRU THE
FORECAST PERIOD WITH SLOW FILLING. DOWNSTREAM MORE PROGRESSIVE
PATTERN AS RIDGING SHIFTS INTO THE PLAINS AND STRONG WIND MAX/TROUGH
MOVES ACROSS TN VALLEY TO MID ATLANTIC STATES.
AT THE SURFACE HIGH PRESSURE CENTRAL U.S. HAS PUSHED ANY THREAT OF
MOISTURE SUFFICIENT FOR THUNDERSTORMS SWD INTO NRN GULF OF MEXICO.
WEAK FRONTAL BAND STRETCHES E/W ACROSS NRN FL PENINSULA WILL SHIFT
SLOWLY SWD...HOWEVER GIVEN THE WEAK LAPSE RATES COUPLED WITH
EXTENSIVE CLOUD COVER BOTH SIDES OF FRONT...PRECLUDES SUFFICIENTLY
DEEP UPDRAFTS FOR CHARGE SEPARATION AND LIGHTNING STRIKES OVER LAND.
BETTER CHANCE OF THUNDERSTORMS SHOULD REMAIN OFF SHORE IN AREA OF
GREATER LOW LEVEL MOISTURE...PARTICULARLY OVER THE GULF STREAM
TONIGHT OFF E COAST AS A WEAK SURFACE LOW DEVELOPS.
ALONG THE CA COAST WITH THE COLD UPPER LOW OFFSHORE MAKING LITTLE
PROGRESS...CONDITIONS FOR SUFFICIENTLY DEEP CONVECTION TO PRODUCE A
LIGHTNING THREAT OVER LAND NOT EXPECTED THIS FORECAST PERIOD. WITH
LIMITED ONSHORE TRAJECTORIES IN THE BOUNDARY LAYER AND STEEPER LAPSE
RATES OFFSHORE...ANY THUNDERSTORM THREAT SHOULD BE DELAYED UNTIL
AFTER 12Z MON WHEN UPPER LOW/TROUGH MOVES INLAND.
..GUYER/HALES.. 02/15/2009
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