SWODY1
SPC AC 131956
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0256 PM CDT FRI MAR 13 2009
VALID 132000Z - 141200Z
...NO SVR TSTM AREAS FORECAST...
...PARTS OF SRN LA/FAR SRN MS...
EARLY AFTERNOON SURFACE ANALYSIS SHOWED A PORTION OF A BOUNDARY
LOCATED OFFSHORE THE NWRN GULF COAST HAD MOVED INLAND ACROSS SERN LA
AND SERN MS...WHILE A SURFACE LOW WAS DEVELOPING ALONG THIS SAME
BOUNDARY OFF THE SRN/MIDDLE TX COAST. THIS SURFACE WAVE DEVELOPMENT
IS LIKELY IN RESPONSE TO A SHORT WAVE TROUGH APPROACHING N TX/OK
THIS FORECAST PERIOD...AND A WEAKER SRN STREAM IMPULSE EXPECTED TO
REACH E TX/LA THIS EVENING. MODELS SUGGEST THE SURFACE LOW WILL
MOVE INLAND ACROSS SRN LA THIS EVENING AND SHOULD REACH ERN MS/WRN
AL BY 12Z SATURDAY. RECENT SURFACE PRESSURE FALLS ALONG THE
BOUNDARY LOCATED ALONG AND OFFSHORE THE LA COAST MAY BE AN
INDICATION THAT THE LOW IS BEGINNING TO MOVE NEWD.
SO FAR TODAY...MUCH OF THE CONVECTION/EMBEDDED TSTMS HAVE BEEN
ELEVATED ATOP A COOL STABLE BOUNDARY LAYER LOCATED N OF THE SURFACE
BOUNDARY WITHIN WAA/ISENTROPIC ASCENT REGIME. HOWEVER...AS HIGHER
THETA-E AIR ADVECTS INLAND WITHIN THE SMALL WARM SECTOR OVER SERN
LA/SERN MS...THERE WILL BE A GREATER POTENTIAL FOR SURFACE BASED
TSTMS THIS EVENING INTO THE OVERNIGHT PERIOD. WEAK INSTABILITY IS
EXPECTED TO LIMIT THE SEVERE WEATHER THREAT THIS FORECAST PERIOD.
HOWEVER...STRENGTHENING LOW LEVEL WINDS AS THE SURFACE LOW TRACKS
THROUGH LA TO MS WILL INCREASE HODOGRAPH CURVATURE...AND MAY PROMOTE
A LOW TORNADO THREAT.
...AZ/WRN NM/SWRN CO...
SURFACE HEATING ACROSS WRN NM WWD INTO AZ AND BENEATH COLD MID LEVEL
TEMPERATURES ATTENDANT TO THE UPPER LOW LOCATED OVER WRN NM WILL
CONTINUE TO RESULT IN STEEP LAPSE RATES AND ADDITIONAL CONVECTIVE
DEVELOPMENT. THIS TREND HAS ALREADY BEEN NOTED ACROSS THIS REGION
PER SATELLITE/RADAR IMAGERY AND LIGHTNING DATA ACROSS NM WITH CU/CB
FORMATION.
..PETERS.. 03/13/2009
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