MESO: Mesoscale Discussion 0698

ACUS11 KWNS 071933
SWOMCD
SPC MCD 071932
INZ000-ILZ000-072130-

MESOSCALE DISCUSSION 0698
NWS STORM PREDICTION CENTER NORMAN OK
0232 PM CDT SAT MAY 07 2011

AREAS AFFECTED...PARTS OF NRN/CNTRL ILLINOIS INTO NORTHWESTERN
INDIANA

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 071932Z - 072130Z

TRENDS ARE BEING MONITORED FOR THE DEVELOPMENT OF SEVERE STORMS THAT
PROBABLY WILL REQUIRE A WW LATE THIS AFTERNOON AND EVENING.

A SURFACE FRONTAL ZONE CONTINUES TO BECOME BETTER DEFINED ACROSS
PARTS OF NORTHERN ILLINOIS AND INDIANA...WITH SOUTHEASTWARD
DEVELOPMENT OF A LOW CENTER ALONG IT ONGOING ACROSS UPPER PORTIONS
OF THE MIDDLE MISSISSIPPI VALLEY INTO NORTHWESTERN ILLINOIS. UPPER
RIDGING IS BUILDING TO THE WEST...BUT ENHANCED MID-LEVEL FORCING FOR
ASCENT ASSOCIATED WITH A LOW AMPLITUDE SHORT WAVE IMPULSE STILL
APPEARS LIKELY TO OVERSPREAD THE FRONT...AND PORTIONS OF THE WARM
SECTOR TO THE IMMEDIATE SOUTHEAST OF THE LOW...ROUGHLY ALONG/BETWEEN
THE INTERSTATE 74 AND INTERSTATE 80 CORRIDORS...BETWEEN NOW AND
22-23Z.

INCREASING LIFT COUPLED WITH ONGOING WEAK TO MODERATE BOUNDARY LAYER
DESTABILIZATION PROBABLY WILL BE ACCOMPANIED BY VIGOROUS CONVECTIVE
DEVELOPMENT. NEAR INTERSECTING LOW-LEVEL THERMAL AND MOISTURE AXES
EMANATING FROM THE PLAINS /WHERE SURFACE TEMPS ARE APPROACHING 80F
AND DEW POINTS NEAR 60F/...MIXED LAYER CAPE APPEARS LIKELY TO REACH
1000 J/KG BY PEAK HEATING. IN THE PRESENCE OF STRONG SHEAR BENEATH
THE NORTHERN EDGE OF A 50+ KT 500 MB JET AXIS...ISOLATED SUPERCELL
DEVELOPMENT APPEARS POSSIBLE ...PERHAPS GROWING UPSCALE INTO A SMALL
CONVECTIVE CLUSTER CAPABLE OF PRODUCING DAMAGING WIND GUSTS...IN
ADDITION TO LARGE HAIL. TORNADIC POTENTIAL IS MORE UNCERTAIN...BUT
A TORNADO OR TWO MAY NOT BE OUT OF THE QUESTION...PARTICULARLY IN
RELATIVELY EARLY STAGES OF STORM DEVELOPMENT.

..KERR.. 05/07/2011

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

ATTN...WFO...IWX...IND...LOT...ILX...DVN...

LAT...LON 41748996 41318732 40748639 39908686 39688760 39658819
39888956 40458963 41059003 41748996

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