MESO: Mesoscale Discussion 0537

ACUS11 KWNS 221708
SWOMCD
SPC MCD 221707
ILZ000-WIZ000-IAZ000-MNZ000-221900-

MESOSCALE DISCUSSION 0537
NWS STORM PREDICTION CENTER NORMAN OK
1207 PM CDT SUN APR 22 2007

AREAS AFFECTED...IA...SERN MN....NRN IL...SWRN WI

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 221707Z - 221900Z

SEVERE STORM POTENTIAL MAY INCREASE ACROSS CNTRL/ERN IA OVER THE
NEXT FEW HOURS. HAIL AND POSSIBLE SEVERE WIND THREAT MAY SPREAD FROM
PARTS OF ERN IA TO SRN/SERN MN...NRN IL...AND PERHAPS SWRN
WI...THROUGH LATER TODAY. A WATCH COULD BE ISSUED WITHIN AN HOUR OR
TWO.

LEADING ARC OF VIGOROUS TSTMS MOVING INTO CNTRL IA ATTM APPEARS
LINKED TO ASCENT WITHIN WARM CONVEYOR BELT ASSOCIATED WITH LARGER
SCALE CYCLONE ACROSS THE CNTRL PLAINS. DESPITE LIMITED LOW LEVEL
MOISTURE...STRONG SHEAR AND POCKETS OF STEEPER MID LEVEL LAPSE RATES
HAVE OCCASIONALLY SUPPORTED BRIEF UPDRAFT INTENSIFICATION... AND
HAIL PRODUCTION...WITH THIS ACTIVITY THROUGH THE MORNING.

ANOTHER BAND OF STORMS WAS GRADUALLY INCREASING TO THE WEST OF THE
LEADING CONVECTION AND COULD EVOLVE SIMILARLY AS FIRST BAND...INTO
SECTIONS OF CNTRL IA...OVER THE NEXT 1-2 HOURS.

PROSPECTS FOR SURFACE-BASED STORM DEVELOPMENT WITHIN THESE BANDS
COULD IMPROVE AS AIR MASS BETWEEN THE CONVECTION GRADUALLY
DESTABILIZES THIS AFTERNOON. IN ADDITION...MUCH OF CNTRL/ERN
IA...SERN MN AND NRN IL CONTINUE TO EXPERIENCE STRONG SURFACE
HEATING AND STEEPENING BOUNDARY LAYER LAPSE RATES UNDER SUNNY SKIES.
COUPLED WITH INCREASING FORCING AND STRONGER MID LEVEL FLOW WITH
APPROACHING PLAINS SYSTEM...ONGOING ACTIVITY COULD POSE AN
INCREASING THREAT FOR DAMAGING SURFACE WINDS AS CONVECTIVE COLD POOL
MOVES INTO WARM/DRY DOWNSTREAM AIR MASS. THE POTENTIAL FOR THIS
TRANSITION WILL BE MONITORED OVER THE NEXT HOUR OR SO...AND A WATCH
MAY BE NEEDED IF THIS SCENARIO APPEARS INCREASINGLY LIKELY.

.CARBIN.. 04/22/2007

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

ATTN...WFO...MKX...DVN...ARX...MPX...DMX...

43279455 43669471 44209424 44299344 44229220 43679118
42409004 41879002 41479026 41129100 40869229 40719348
41059434 41369457 41629467

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