SPC AC 291256
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0656 AM CST TUE JAN 29 2008
VALID 291300Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LWR/MID MS VLY INTO
THE OH VLY/CNTRL AND NRN APLCNS...
...SYNOPSIS...
VERY ACTIVE AND PROGRESSIVE PATTERN WILL CONTINUE OVER THE CONUS
THROUGH WEDNESDAY. STRONG SHORTWAVE TROUGH /WITH 500 MB WIND SPEEDS
AROUND 100 KTS/ NOW OVER THE CNTRL/SRN HI PLNS EXPECTED SWEEP
RAPIDLY NE TO THE LWR GRT LKS BY THE END OF THE PERIOD AS UPSTREAM
SPEED MAXIMA DROP SE INTO MEAN TROUGH OVER THE FAR WEST. INTENSE
COLD FRONT ASSOCIATED WITH PLNS TROUGH WILL CONTINUE E/SE ACROSS THE
MS RVR LATE TODAY/EARLY TONIGHT...BEFORE ACCELERATING E TO THE
CNTRL/NRN APLCNS EARLY WEDNESDAY AS UPR SYSTEM ASSUMES A NEGATIVE
TILT. WEAK WAVE NOW DEVELOPING ALONG THE FRONT IN SE KS SHOULD
REACH THE STL AREA THIS AFTN...BEFORE DEEPENING SUBSTANTIALLY AS IT
TURNS N ACROSS MI AND SRN ONTARIO TONIGHT/EARLY WEDNESDAY.
...MID MS/TN/LWR OH VLYS...
ELEVATED CONVECTION/TSTMS ARE DEVELOPING ATTM IN CONFLUENCE AXIS
ALONG WRN EDGE OF SWLY LLJ FROM E TX INTO THE LWR/MID MS VLY. THIS
ACTIVITY LIKELY WILL CONTINUE TO SLOWLY INCREASE IN COVERAGE AND
INTENSITY THROUGH THE DAY AS REGION FURTHER MOISTENS AND LARGE SCALE
ASCENT STRENGTHENS WITH APPROACH OF PLNS TROUGH.
RAPID EWD MOVEMENT OF UPR SYSTEM AND COLD FRONT WILL PREVENT
WIDESPREAD INFLUX OF TRUE MARITIME AIR INTO THE LWR MS/TN VLY
REGION. NEVERTHELESS...BY AFTERNOON...EXPECT THAT DEWPOINTS IN THE
LOW 50S F WILL HAVE REACHED SRN IL...WITH READINGS AOA 60 F NORTH TO
NEAR MEM. WITH SKIES REMAINING MOSTLY CLOUDY...THIS SHOULD SUPPORT
AT LEAST MODEST DESTABILIZATION. WARM SECTOR MLCAPE SHOULD RANGE
FROM 250 TO 500 J/KG FROM LA AND WRN MS INTO CNTRL/ERN AR...SE
MO...WRN TN AND WRN KY.
AS AFOREMENTIONED TSTMS GRADUALLY BECOME MORE NEARLY SFC-BASED
...THE STORMS WILL BE ABLE TO TAKE ADVANTAGE OF VERY STRONG LOW TO
MID LEVEL ENVIRONMENTAL SHEAR ACROSS REGION. WHILE LIMITED
INSTABILITY WILL TEMPER OVERALL SVR THREAT...PRESENCE OF 70+ KT DEEP
WSWLY SHEAR WILL SUPPORT EMBEDDED SUPERCELLS. 40 KT 0-1 KM SHEAR
COULD ALSO YIELD A FEW STORMS WITH LOW-LEVEL ROTATION AND
POTENTIALLY A TORNADO OR TWO...MAINLY ON SRN EDGE OF ACTIVITY.
FARTHER NW...ONSET OF STRONG FORCING FOR ASCENT AND FRONTAL UPLIFT
SHOULD SUPPORT A SEPARATE BAND OF STORMS BY MID AFTN ALONG COLD
FRONT FROM CNTRL IL SSW INTO SE MO AND AR. WHILE THESE STORMS
SHOULD EVOLVE RAPIDLY INTO A SQUALL LINE...INTENSITY OF SHEAR AND
PROXIMITY OF MAIN AXIS OF LARGE SCALE ASCENT SHOULD SUPPORT EMBEDDED
SUSTAINED/SEMI-DISCRETE STRUCTURES. THESE COULD YIELD BOWING
SEGMENTS WITH HIGH WIND AND ISOLATED TORNADOES AS THE LINE SWEEPS E
INTO PARTS OF IND/KY AND TN THIS EVENING.
...UPR OH VLY...
PROGRESSIVE NATURE OF LARGE SCALE PATTERN...INTENSITY OF HI PLNS
SPEED MAX AND LIKELY ASSUMPTION OF NEGATIVE TILT SUGGEST THAT OH VLY
COLD FRONT WILL SHARPEN AS IT ACCELERATES E ACROSS THE OH VLY LATER
TONIGHT. ASSOCIATED INTENSIFICATION OF FRONTAL CIRCULATION AND
MID-LEVEL COOLING LEND CONFIDENCE TO IDEA THAT A LOW-TOPPED
CONVECTIVE BAND...POSSIBLY WITH THUNDER...WILL SURGE E/NE ACROSS
OH/NRN WV/WRN PA AND WRN NY EARLY WEDNESDAY. WHILE THE BOUNDARY
LAYER ACROSS THIS REGION WILL NOT BE QUITE AS WARM AS IT WAS FOR THE
9 JANUARY EVENT...TEMPERATURES WILL BE ABOVE NORMAL. IT APPEARS
THAT AT LEAST SOME THREAT WILL EXIST FOR DOWNWARD MIXING ALONG
CONVECTIVE BAND...POSSIBLY WITH DAMAGING WINDS.
..CORFIDI.. 01/29/2008
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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