SWOMCD
SPC MCD 122249
MSZ000-LAZ000-ARZ000-130015-
MESOSCALE DISCUSSION 0459
NWS STORM PREDICTION CENTER NORMAN OK
0549 PM CDT SUN APR 12 2009
AREAS AFFECTED...ERN LA...SE AR...WRN MS
CONCERNING...TORNADO WATCH 145...
VALID 122249Z - 130015Z
THE SEVERE WEATHER THREAT FOR TORNADO WATCH 145 CONTINUES.
AN INCREASE IN TORNADIC POTENTIAL STILL APPEARS POSSIBLE WITHIN THE
NEXT HOUR OR TWO...AND TRENDS WILL HAVE TO BE MONITORED FOR THIS
RISK GRADUALLY SPREADING NORTH/EAST OF THE CURRENT WATCH THIS
EVENING.
THE BULK OF ONGOING CONVECTIVE DEVELOPMENT APPEARS ELEVATED... BASED
WITHIN A BROAD ZONE OF ISENTROPIC ASCENT SLOWLY SHIFTING EASTWARD
ACROSS THE LOWER MISSISSIPPI VALLEY...ABOVE AT LEAST A SHALLOW NEAR
SURFACE RAIN COOLED AIR MASS. HOWEVER...RAPID SURFACE PRESSURE
FALLS HAVE BECOME EVIDENT IN 22Z SURFACE DATA NEAR THE RIVER...
NORTH OF NATCHEZ THROUGH VICKSBURG AND GREENVILLE...ALONG A AXIS
WHICH A DEVELOPING SURFACE LOW APPEARS LIKELY TO TRACK BETWEEN NOW
AND 00-02Z. THIS FEATURE COULD BECOME A FOCUS FOR SURFACE BASED
DESTABILIZATION AND INTENSIFYING STORMS BENEATH STRONGLY DIFLUENT
AND...PROBABLY...AT LEAST WEAKLY DIVERGENT UPPER FLOW. LATEST RUC
GUIDANCE SUGGESTS THIS IS NEARLY COINCIDENT WITH A 60 KT SOUTHERLY
850 MB JET AXIS...ALONG WHICH LOW-LEVEL HODOGRAPHS ARE VERY LARGE
BENEATH STRONG SOUTHWESTERLY MID/HIGH LEVEL FLOW. THESE PROFILES
ARE VERY SUPPORTIVE OF SUPERCELLS WITH STRONG LOW-LEVEL MESOCYCLONES
CAPABLE OF PRODUCING TORNADOES...EVEN IN THE PRESENCE OF SOMEWHAT
WEAK LAPSE RATES AND CAPE.
..KERR.. 04/12/2009
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...MEG...JAN...LIX...LZK...LCH...SHV...
LAT...LON 31889195 32799167 33869100 33838971 32938936 31958984
31299026 30899126 31269204 31479201 31889195
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