DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 131940
SWODY1
SPC AC 131938

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0238 PM CDT THU SEP 13 2007

VALID 132000Z - 141200Z

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF ERN LA AND SW
MS...

..LOWER MS VALLEY...
THE CENTER OF TROPICAL STORM HUMBERTO IS CURRENTLY JUST WEST OF
ALEXANDRIA LA WITH RAINBAND MAINLY IN THE ERN QUADRANT. THE
STRONGEST CONVECTION IS LOCATED FROM CNTRL MS EXTENDING SEWD INTO
SRN AL WITH ANOTHER BAND LOCATED FROM NORTHEAST OF THE CENTER SSEWD
ACROSS SE LA. THE INNER BAND IS LOCATED ACROSS ERN LA EXTENDING SWD
INTO SCNTRL LA. LOW-LEVEL VERTICAL SHEAR IS STRONGEST WITH THE INNER
RAINBAND AS SHOWN BY FORECAST SOUNDINGS WHERE SFC WINDS ARE BACKED
AND SUBSTANTIAL DIRECTIONAL SHEAR IS PRESENT. AS INSTABILITY
CONTINUES TO INCREASE ACROSS ERN LA AND SW MS...NEW THUNDERSTORM
DEVELOPMENT MAY OCCUR. THE LOW-LEVEL SHEAR SHOULD BE SUPPORTIVE OF A
TORNADO THREAT WITH ROTATING CELLS IN THE INNER BANDS OF HUMBERTO.
AN ISOLATED TORNADO THREAT WILL ALSO BE POSSIBLE WITH THE
CONVECTION.

..TX PANHANDLE/OK PANHANDLE/FAR SW KS...
THE LATEST SFC ANALYSIS SHOWS A COLD FRONT EXTENDING SWWD ACROSS WRN
KS INTO FAR SE CO. A SFC LOW IS LOCATED ACROSS THE WRN OK PANHANDLE
WITH A MOIST AXIS WITH DEWPOINTS NEAR 60 F EXTENDING NNEWD FROM WEST
TX INTO SW KS. A WEAKENING CAPPING INVERSION AND CONTINUED
DESTABILIZATION SHOULD ALLOW FOR STORM INITIATION ALONG THE BOUNDARY
LATE THIS AFTERNOON. ALTHOUGH VERTICAL SHEAR IS NOT THAT
STRONG...LAPSE RATES HAVE BECOME VERY STEEP FROM NE NM EXTENDING EWD
ACROSS THE OK PANHANDLE. THIS MAY SUPPORT A THREAT FOR HAIL AND
STRONG GUSTY WINDS WITH THE MORE INTENSE CELLS.

..UPPER MIDWEST...
WATER VAPOR IMAGERY CURRENTLY SHOWS AN UPPER-LEVEL TROUGH OVER THE
NRN PLAINS. AT THE SFC...A COLD FRONT EXTENDS SWWD FROM LAKE
SUPERIOR INTO SE MN AND NRN IA. LARGE-SCALE FORCING WITH THE
UPPER-LEVEL TROUGH AND LOW-LEVEL CONVERGENCE ALONG THE BOUNDARY IS
SUPPORTING SCATTERED THUNDERSTORMS ONGOING IN WRN WI. ADDITIONAL
DEVELOPMENT MAY OCCUR SWWD ACROSS FAR SE MN AND NE IA THIS
AFTERNOON. ALTHOUGH OBJECTIVE ANALYSIS SUGGESTS INSTABILITY IS
WEAK...STRONG VERTICAL SHEAR IS PRESENT ASSOCIATED WITH A 90 KT
MID-LEVEL JET OVER NE MN AND SRN ONTARIO. THIS COMBINED WITH COLD
AIR ALOFT WITH 500 MB TEMPS AROUND -14 C SHOULD BE SUFFICIENT FOR AN
ISOLATED HAIL THREAT LATE THIS AFTERNOON FROM WRN WI SWWD INTO NE
IA.

.BROYLES.. 09/13/2007

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