Monday, June 8, 2009

MESO: Mesoscale Discussion 0987

ACUS11 KWNS 081655
SWOMCD
SPC MCD 081654
INZ000-ILZ000-WIZ000-MOZ000-081830-

MESOSCALE DISCUSSION 0987
NWS STORM PREDICTION CENTER NORMAN OK
1154 AM CDT MON JUN 08 2009

AREAS AFFECTED...NORTHERN/WEST CENTRAL IL INTO ADJACENT SOUTHERN
WI/NORTHWEST INDIANA/EASTERN MO

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 081654Z - 081830Z

SEVERE RISK MAY DEVELOP/INCREASE ACROSS NORTHERN/WEST CENTRAL IL AND
ADJACENT PORTIONS OF SOUTHERN WI/NORTHWEST INDIANA/EASTERN MO
THROUGH EARLY/MID AFTERNOON. WHEN INITIATION OF DEEP CONVECTION
BECOMES APPARENT...A WATCH MAY BE NEEDED FOR PORTIONS OF THE REGION.


WATER VAPOR IMAGERY FEATURES A NORTHEAST ADVANCING SHORTWAVE TROUGH
OVER EASTERN IA AT MIDDAY...WITH ASSOCIATED MID LEVEL JET STREAK /50
KT AT 500 MB/ CROSSING THE MIDDLE MISSISSIPI VALLEY. ALTHOUGH THIS
SHORTWAVE TROUGH WILL BEGIN TO SPREAD NORTHEASTWARD AWAY FROM THE
REGION WITH POTENTIAL FOR LARGE SCALE HEIGHT RISES BY MID/LATE
AFTERNOON...IT SEEMS PROBABLE THAT TSTMS WILL DEVELOP ALONG A
SURFACE COLD FRONT/PREFRONTAL TROUGH ADVANCING INTO/ACROSS NORTHERN
IL THIS AFTERNOON. WITH CLOUD COVER TENDING TO CLEAR ACROSS FAR
EASTERN IA/NORTHERN IL AT MIDDAY...SOME SIGNS OF INCIPIENT DEEP
CONVECTIVE DEVELOPMENT PER VISIBLE SATELLITE IMAGERY MAY ALREADY BE
OCCURRING IN VICINITY OF THE COLD FRONT AND/OR SUBTLE PREFRONTAL
TROUGH...AND OVERALL IT SEEMS PROBABLE THAT TSTMS SHOULD
DEVELOP/INCREASE THROUGH EARLY/MID AFTERNOON. AS THE PREFRONTAL
BOUNDARY LAYER CONTINUES TO HEAT/DESTABILIZE...AFOREMENTIONED
MODERATELY STRONG MID LEVEL FLOW WOULD SUPPORT SUFFICIENT VERTICAL
SHEAR FOR SOME SUPERCELLS AND WELL-ORGANIZED MULTICELLS. DAMAGING
WINDS AND SEVERE HAIL SHOULD THE PRIMARY THREATS. WHILE AN ISOLATED
TORNADO RISK CANNOT BE RULED OUT...WEAKENING/VEERING LOW LEVEL FLOW
ACROSS THE WARM SECTOR SHOULD KEEP SUCH A THREAT LOW.

THE TIMING/EXTENT OF THE SEVERE THREAT SEEMS A BIT MORE QUESTIONABLE
WITH SOUTHWESTWARD EXTENT TO WEST CENTRAL IL/EASTERN MO...GIVEN
EARLY DAY TSTMS/RESIDUAL CLOUD COVER...IN ADDITION TO BEING MORE
REMOVED FROM THE INFLUENCE OF THE PARENT SHORTWAVE TROUGH.
NEVERTHELESS...A SEVERE THREAT MAY INCREASE ACROSS THIS CORRIDOR
LATER THIS AFTERNOON.

..GUYER.. 06/08/2009

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

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

LAT...LON 39928832 38468988 39559124 42888869 41138646 39928832

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