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MESOSCALE DISCUSSION 1601
NWS STORM PREDICTION CENTER NORMAN OK
1209 PM CDT THU JUL 26 2012
AREAS AFFECTED...PORTIONS WI...EXTREME NRN IL...WRN LM.
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 261709Z - 261915Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...TSTMS FCST TO INCREASE IN COVERAGE AND INTENSIFY OVER WRN
PORTIONS DISCUSSION AREA AND MOVE ESEWD TO SEWD...WITH POTENTIAL FOR
LARGE HAIL AND OCNL DAMAGING GUSTS.
DISCUSSION...16Z SFC MESOANALYSIS SHOWS OCCLUSION TRIPLE POINT OVER
N-CENTRAL/NWRN WI W RHI...WITH DIFFUSE COLD FRONT SSWWD ACROSS
EXTREME SERN MN. WARM FRONT WAS DRAWN FROM TRIPLE POINT SEWD ACROSS
CENTRAL LM THEN EWD AND QUASISTATIONARY OVER CENTRAL LOWER MI. WARM
FRONT SHOULD DRIFT NEWD WHILE COLD FRONT PROCEEDS SEWD 15-20 KT.
VIS IMAGERY SHOWS WELL-DEFINED WRN LOW-CLOUD EDGE NEAR OR JUST AHEAD
OF SFC COLD FRONT...WITH THICKEST CU/TCU AND A FEW SMALL CB OVER SFC
MOIST AXIS. THAT CORRESPONDS TO AREA OF HIGHEST BUOYANCY AND
WEAKEST CAPPING...MLCAPE RANGING FROM NEARLY 2000 J/KG OVER SWRN WI
TO AROUND 500 J/KG ALONG WARM FRONT. CONVERGENCE SHOULD REMAIN WEAK
ALONG/AHEAD OF COLD FRONT...INDICATING
1. GREATEST POTENTIAL FOR ADDITIONAL DEVELOPMENT TO ITS E NEAR MOIST
AXIS AND
2. THREAT EVOLUTION SHOULD BE GRADUAL...NOT EXPLOSIVE IN NATURE.
AIR MASS SHOULD CONTINUE TO DESTABILIZE IN WARM SECTOR...WITH
DIABATIC HEATING AND UPPER 60S TO LOW 70S F SFC DEW POINTS BOOSTING
MLCAPE ANOTHER 500-1000 J/KG ABOVE PRESENT VALUES THROUGH MID-AFTN.
STRONGEST DEEP-LAYER SHEAR WILL BE OVER SRN WI...PERHAPS SHIFTING
SWD TOWARD IL BORDER WITH TIME...IN STEP WITH MID-UPPER LEVEL JET
AXIS. EFFECTIVE SHEAR MAGNITUDES 40-50 KT SUPPORT POTENTIAL FOR A
FEW SUPERCELLS...ENHANCING HAIL/WIND RISK ON STORM SCALE.
..EDWARDS/HART.. 07/26/2012
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"INFORMS YOU ON WEATHER" THIS BLOG WILL INFORM ON WEATHER MOSTLY FOR NORTHERN ILLINOIS AND SURROUNDING AREAS. ALSO MOST AREAS DURRING SEVERE WEATHER.
Thursday, July 26, 2012
WATCH POSSIBLE FOR PORTIONS WI...EXTREME NRN IL...WRN LM
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