MESO: Mesoscale Discussion 1852

ACUS11 KWNS 072102
SWOMCD
SPC MCD 072101
ILZ000-WIZ000-IAZ000-072300-

MESOSCALE DISCUSSION 1852
NWS STORM PREDICTION CENTER NORMAN OK
0401 PM CDT SAT SEP 07 2013

AREAS AFFECTED...IA...WI...IL

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 072101Z - 072300Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...A SEVERE TSTM WATCH IS POSSIBLE IN THE NEXT FEW HOURS FROM
EXTREME SRN WI AND ERN IA TO NRN IL. CHANCES FOR ISOLATED TO
SCATTERED TSTMS WILL INCREASE OVER THESE AREAS INTO THE EVENING.

DISCUSSION...VERY WARM AND UNSTABLE CONDITIONS HAVE DEVELOPED ON THE
EDGE OF PLAINS CAPPING INVERSION FROM ERN IA ACROSS SRN WI AND NRN
IL. THE AREA IS BISECTED BY A WEAK SURFACE TROUGH FROM ERN IA TO SRN
WI. MEANWHILE A MODERATE COLD FRONT WAS MOVING TOWARD THE AREA FROM
CNTRL WI AND A CONVECTIVELY REINFORCED LAKE BREEZE BOUNDARY WAS
SITUATED FROM THE SOUTH SHORE OF LM NWD TO SERN WI. LARGE SCALE LIFT
ACROSS THE AREA THROUGH THE EVENING WILL REMAIN RELATIVELY WEAK BUT
A LOW AMPLITUDE IMPULSE APPEARS TO BE APPROACHING THE AREA FROM IA
ATTM.

ANOTHER HOUR OR SO OF HEATING MAY BE SUFFICIENT TO OVERCOME THE
CAPPING INVERSION AND SUPPORT AT LEAST ISOLATED CONVECTIVE
DEVELOPMENT. NWLY MID LEVEL FLOW OF 30-35KT WILL BE ADEQUATE TO
CONTRIBUTE TO STORM ORGANIZATION AND MAGNITUDE OF AVAILABLE
INSTABILITY AND MID-LEVEL LAPSE RATES WOULD FAVOR LARGE HAIL. IF
STORM COVERAGE INCREASES INTO THE EVENING...COLD POOL EVOLUTION AND
ANY DEVELOPMENT ALONG THE ADVANCING FRONT MOVING INTO SRN WI...IN
ADDITION TO MODEST STRENGTHENING OF DEEP-LAYER NWLY FLOW...COULD
RESULT IN THE DEVELOPMENT OF A FORWARD PROPAGATING SYSTEM WITH
SCATTERED WIND DAMAGE. UNCERTAINTY IN THIS SCENARIO REMAINS TOO
GREAT FOR A WATCH AT THIS TIME BUT THE AREA WILL CONTINUE TO BE
MONITORED.

..CARBIN/MEAD.. 09/07/2013

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

ATTN...WFO...LOT...ILX...MKX...DVN...ARX...

LAT...LON 40598910 40709072 41339094 42459145 43179116 43049011
42818887 41998801 40738800 40598910

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