DAY1SVR: Day 1 Convective Outlook Resent 1

ACUS01 KWNS 040610
SWODY1
SPC AC 040607

DAY 1 CONVECTIVE OUTLOOK RESENT 1
NWS STORM PREDICTION CENTER NORMAN OK
0107 AM CDT TUE SEP 04 2012

VALID 041200Z - 051200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE MID MO
VALLEY AND UPPER MS VALLEY...

...MID MO VALLEY/UPPER MS VALLEY...
WESTERLY FLOW WILL BE IN PLACE ACROSS THE NCNTRL STATES TODAY AS AN
UPPER-LEVEL TROUGH MOVES INTO THE NRN PLAINS. AHEAD OF THE
UPPER-LEVEL TROUGH...MODEL FORECASTS INDICATE THAT SEVERAL
DISTURBANCES WILL BE PRESENT IN THE FLOW MOVING ACROSS THE REGION
FROM WEST TO EAST. AT THE SFC...A COLD FRONT IS FORECAST TO ADVANCE
SEWD ACROSS THE NRN AND CNTRL PLAINS WITH A CORRIDOR OF LOW-LEVEL
MOISTURE IN PLACE FROM THE MID MO VALLEY NEWD INTO THE UPPER MS
VALLEY. AS SFC TEMPS WARM DURING THE DAY...SCATTERED THUNDERSTORMS
SHOULD INITIATE ALONG THE WRN EDGE OF THE MOIST CORRIDOR FROM WRN
UPPER MI SWWD ACROSS WI...IA INTO ERN NEB. SEVERAL CONVECTIVE
CLUSTERS ARE EXPECTED TO PERSIST ACROSS THE REGION FROM THE LATE
AFTERNOON INTO THE EVENING.

FORECAST SOUNDINGS ALONG THE CORRIDOR OF MODERATE INSTABILITY FROM
WI SWWD INTO IA AT 00Z/WED GENERALLY SHOW AROUND 40 KT OF DEEP LAYER
SHEAR. THIS SHEAR ENVIRONMENT SHOULD SUPPORT SEVERE STORM
DEVELOPMENT AS CELLS INITIATE DURING THE LATE AFTERNOON. LARGE-SCALE
ASCENT IS FORECAST TO REMAIN RELATIVELY WEAK AND SHOULD ENABLE
STORMS TO REMAIN DISCRETE. THIS FACTOR ALONG WITH STEEP LAPSE RATES
MAY BE FAVORABLE FOR ISOLATED LARGE HAIL ESPECIALLY WITH STORMS THAT
ROTATE. LARGE TEMP-DEWPOINT SPREADS MAY ALSO ENHANCE DOWNDRAFT
ACCELERATION AND DAMAGING WIND GUSTS WILL CERTAINLY BE POSSIBLE WITH
THE BETTER ORGANIZED STORM CLUSTERS. THE GREATEST SEVERE THREAT
COULD EXIST ACROSS THE NERN PART OF THE SLIGHT RISK AREA DURING THE
EARLY EVENING WHERE LOW-LEVEL FLOW IS FORECAST TO BE STRONGER.

...CNTRL GULF COAST STATES...
AN UPPER-LEVEL TROUGH WILL MOVE SLOWLY EWD ACROSS THE ERN GULF COAST
STATES TODAY. ON THE WRN EDGE OF THE UPPER-LEVEL TROUGH...A CORRIDOR
OF MODERATE INSTABILITY IS FORECAST TO DEVELOP THIS AFTERNOON ACROSS
MS AND WRN AL. AS SFC TEMPS WARM...SCATTERED TO NUMEROUS
THUNDERSTORMS SHOULD AGAIN INITIATE ALONG THE INSTABILITY CORRIDOR
THIS AFTERNOON. FORECAST SOUNDINGS ACROSS SE MS AND SRN AL AT 21Z
GENERALLY SHOW DEEP LAYER SHEAR IN THE 30 TO 35 KT SUGGESTING SEVERE
STORM DEVELOPMENT WILL BE POSSIBLE. LINE SEGMENTS THAT HAVE ACCESS
TO THE STRONGEST INSTABILITY MAY BE CAPABLE OF PRODUCING ISOLATED
DAMAGING WIND GUSTS ESPECIALLY AS LOW-LEVEL LAPSE RATES STEEPEN
DURING THE LATE AFTERNOON. AT THIS POINT...UNCERTAINTY REGARDING
WHERE THE STRONGEST INSTABILITY DEVELOPS PRECLUDES A SLIGHT RISK
ATTM.

..BROYLES/MOSIER.. 09/04/2012

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