SPC AC 281942
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0242 PM CDT THU AUG 28 2008
VALID 282000Z - 291200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE UPPER MIDWEST
INTO CNTRL PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER NERN MN AND FAR NWRN WI...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF CNTRL/SRN AZ...
...UPPER GREAT LAKES INTO CNTRL PLAINS...
SURFACE COLD FRONT CURRENTLY FROM NERN WI SWWD INTO CNTRL KS WILL
CONTINUE EWD/SEWD THIS AFTERNOON AND TONIGHT IN ADVANCE OF STRONG
SHORT WAVE TROUGH MOVING THROUGH THE UPPER MS VALLEY. PRE-FRONTAL
AIR MASS IS MOIST WITH DEWPOINTS IN THE 60S TO LOWER 70S. THIS
MOISTURE COINCIDES WITH AN EML/STEEP LAPSE RATE PLUME ACCOMPANYING
MIDLEVEL TROUGH WITH ENVIRONMENT OVER SRN IA...WRN/CNTRL MO AND
CNTRL/ERN KS ALREADY MODERATELY UNSTABLE WITH MLCAPES OF 2000-2500
J/KG. FARTHER N...MORE PERSISTENT/WIDESPREAD CLOUDINESS OVER WI/MI
HAS LIMITED DIABATIC HEATING AND RESULTANT DESTABILIZATION
ALONG/AHEAD OF FRONT. THE EXCEPTION IS OVER NRN/CNTRL MN INTO WRN
WI WHERE STRONG DAYTIME HEATING COMBINED WITH COLD MIDLEVEL
TEMPERATURES OF AROUND -20 C AT 500 MB ARE RESULTING IN STEEP LAPSE
RATES AND MLCAPES OF 500-1000 J/KG.
A SHORT BAND OF ELEVATED STORMS HAS DEVELOPED OVER THE PAST COUPLE
OF HOURS ACROSS SERN NEB WITHIN ZONE OF ENHANCED MESOSCALE LIFT
ALONG SLOPED FRONTAL ZONE. WITH TIME...ADDITIONAL SURFACE-BASED
STORM DEVELOPMENT IS EXPECTED ALONG THE FRONT OVER FAR SRN IA...NRN
MO INTO NERN/CNTRL KS. REGIONAL PROFILERS INDICATE A NOTABLE
GRADIENT IN MIDLEVEL WIND SPEEDS WITH 50-60 KT FLOW ACROSS CNTRL
IA...DECREASING TO 30 KT OVER CNTRL MO AND 10-15 KT IN CNTRL KS. AS
SUCH...THE GREATEST POTENTIAL FOR ORGANIZED/ROTATING STORMS APPEARS
TO BE ALONG FRONTAL SEGMENT OVER SRN IA/NRN MO...AND MORE N-S
ORIENTED OUTFLOW BOUNDARY OVER SERN IA INTO NERN MO. LARGE HAIL AND
DAMAGING WINDS APPEAR TO BE THE PRIMARY HAZARDS WITH THE MOST
INTENSE STORMS.
OVER WI/MI...LARGE-SCALE FORCING FOR ASCENT ASSOCIATED WITH MIDLEVEL
TROUGH OVERSPREADING FRONTAL ZONE WILL LIKELY SUPPORT SCATTERED TSTM
DEVELOPMENT THIS AFTERNOON INTO EVENING. DESPITE THE LIMITED
HEATING/INSTABILITY...ANY MORE SUSTAINED STORMS WILL BE CAPABLE OF
HIGH WINDS AND HAIL GIVEN THE RELATIVELY STRONG DEEP-LAYER SPEED
SHEAR. ELSEWHERE...STORMS DEVELOPING OVER NRN MN IN STEEP LAPSE
RATE ENVIRONMENT WILL POSE A SEVERE HAIL THREAT GIVEN THE RELATIVELY
COOL THERMODYNAMIC PROFILE. FOR ADDITIONAL NEAR TERM GUIDANCE ON
THIS AREA...SEE MCD 2181.
...SRN AZ/SERN CA...
CLUSTERS OF TSTMS ARE IN PROGRESS EARLY THIS AFTERNOON ALONG THE
INTERNATIONAL BORDER S OF GBN APPARENTLY IN ASSOCIATION WITH
MIDLEVEL SHEAR ZONE SITUATED OVER THE AREA. OTHER STORMS ARE LIKELY
TO DEVELOP TODAY ALONG THE MOGOLLON RIM WITHIN A STEEP LAPSE RATE
AND RELATIVELY MOIST ENVIRONMENT WHERE MLCAPES HAVE INCREASED TO
1000-2000 J/KG. CURRENT VWPS INDICATE MODEST ENELY WINDS ABOVE 2 KM
WHICH MAY SUPPORT THE WWD/SWWD PROPAGATION OF ANY TSTM CLUSTERS
DEVELOPING OVER THE HIGH TERRAIN. LOCALLY DAMAGING WIND GUSTS WILL
BE THE PRIMARY SEVERE THREAT...THOUGH SOME HAIL IS POSSIBLE.
..MEAD.. 08/28/2008
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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