MESO: Mesoscale Discussion 2039

ACUS11 KWNS 280215
SWOMCD
SPC MCD 280214
MIZ000-INZ000-280415-

MESOSCALE DISCUSSION 2039
NWS STORM PREDICTION CENTER NORMAN OK
0914 PM CDT SUN SEP 27 2009

AREAS AFFECTED...SWRN LOWER MI THROUGH NRN IND

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 280214Z - 280415Z

STORMS WILL CONTINUE DEVELOPING EWD INTO SWRN LOWER MI AND NRN IND
LATER THIS EVENING. AT LEAST A MODEST THREAT WILL EXIST FOR MAINLY
ISOLATED DAMAGING WIND AND MARGINALLY SEVERE HAIL. HOWEVER...THE
MARGINAL THERMODYNAMIC ENVIRONMENT COULD POTENTIALLY SERVE AS A
LIMITING FACTOR FOR A MORE ROBUST SEVERE THREAT...AND WW ISSUANCE
WILL ULTIMATELY DEPEND ON CONVECTIVE TRENDS.

THIS EVENING A BAND OF CONVECTION EXTENDS FROM S CNTRL LAKE MI INTO
SWRN WI AND NERN IL MOVING EAST AT 35 KT. THE STORMS ARE DEVELOPING
IN ZONE OF DEEP ASCENT ALONG AND JUST AHEAD OF AN EWD MOVING COLD
FRONT AND WITHIN EXIT REGION OF A STRONG PROGRESSIVE UPPER JET.
OBJECTIVE DATA INDICATE AN AXIS OF MARGINAL INSTABILITY /300-500
J/KG MLCAPE/ FROM WI SWWD THROUGH IL WHERE PLUME OF STEEP MID LEVEL
LAPSE RATES HAS OVERSPREAD MOIST AXIS CONTAINING MID TO UPPER 50S
DEWPOINTS. THE STRENGTHENING SWLY LOW LEVEL JET AND EWD ADVANCE OF
MID-UPPER LEVEL THERMAL TROUGH WILL CONTRIBUTE TO EWD
DESTABILIZATION WITH TIME...BUT INSTABILITY WILL REMAIN MARGINAL DUE
TO NOCTURNAL COOLING AND ONLY MODEST MOISTURE ADVECTION. VERTICAL
SHEAR PROFILES AND HODOGRAPHS ATTENDING THE COUPLED JET STRUCTURE
ARE MORE THAN ADEQUATE FOR ORGANIZED SEVERE STORMS INCLUDING
SUPERCELLS AND LINES WITH BOWING SEGMENTS. HOWEVER...THE MARGINAL
THERMODYNAMIC ENVIRONMENT INCLUDING THE STABILIZING BOUNDARY LAYER
REMAINS A POTENTIAL LIMITING FACTOR.

..DIAL.. 09/28/2009

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...IWX...GRR...

LAT...LON 43208628 43638521 43358440 42428439 41368542 41258663
41868660 42708613 43208628

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