SWODY1
SPC AC 181247
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0647 AM CST WED NOV 18 2009
VALID 181300Z - 191200Z
...NO SVR TSTM AREAS FORECAST...
...CAROLINAS TO THE UPPER OH VALLEY THROUGH TONIGHT...
THE CLOSED/OCCLUDED LOW CENTERED NEAR STL AS OF 12Z WILL DRIFT NNEWD
OVER WRN/NWRN IL IN RESPONSE TO MODEST UPSTREAM HEIGHT FALLS OVER
THE HIGH PLAINS WITH THE INLAND PROGRESSION OF A WEAKENING PACIFIC
SHORTWAVE TROUGH. AT THE SURFACE...A DIFFUSE OCCLUDED FRONT ARCS
EWD FROM THE CYCLONE CENTER TO SRN INDIANA...AND THEN SSEWD ACROSS
KY/TN/GA/N FL. AN ELEVATED WAA REGIME IS ONGOING FROM THE SRN
APPALACHIANS INTO THE OH VALLEY...AND THIS WILL CONTRIBUTE TO
GRADUAL DESTABILIZATION AND SUPPORT A RISK FOR ISOLATED
THUNDERSTORMS THROUGH TONIGHT FROM THE CAROLINAS NWD INTO ERN OH/WRN
PA.
THE INTENSITY AND COVERAGE OF DEEP CONVECTION IS IN QUESTION AS A
RESULT OF MARGINAL MID LEVEL LAPSE RATES AND ONLY WEAK LARGE SCALE
ASCENT WELL SE OF THE OCCLUDED CYCLONE. THE WEAK FORCING AND A LACK
OF SUBSTANTIAL CYCLOGENESIS SUGGEST THAT EROSION OF THE COOL AIR
WEDGE ACROSS THE CAROLINAS MAY BE SLOWER TO OCCUR THAN SHOWN IN
SHORT TERM MODEL FORECASTS...AS CLOUDS AND LIGHT RAIN INHIBIT
SURFACE HEATING INLAND TODAY. IF THE LOW LEVELS CAN WARM/MOISTEN
SUFFICIENTLY FOR SURFACE-BASED INSTABILITY /SURFACE TEMPERATURES OF
68-72 F AND DEWPOINTS IN THE LOW-MID 60S/...THERE WILL BE A SMALL
CHANCE FOR ROTATING STORMS ALONG THE REMNANT COASTAL FRONT. THIS
AREA WILL CONTINUE TO BE MONITORED...BUT THE OVERALL SEVERE STORM
THREAT APPEARS TOO SMALL TO WARRANT INCLUSION OF ANY PROBABILITIES
IN THIS UPDATE.
..THOMPSON/HURLBUT.. 11/18/2009
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