ACUS11 KWNS 181732
SWOMCD
MESOSCALE DISCUSSION 1464
NWS STORM PREDICTION CENTER NORMAN OK
1231 PM CDT SAT JUL 18 2015
AREAS AFFECTED...EASTERN IOWA...NORTHERN ILLINOIS...AND SOUTHERN
WISCONSIN
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 181731Z - 181930Z
PROBABILITY OF WATCH ISSUANCE...60 PERCENT
SUMMARY...THUNDERSTORMS ARE EXPECTED TO DEVELOP/INTENSIFY THIS
AFTERNOON. VERY LARGE HAIL AND DAMAGING THUNDERSTORM WIND GUSTS WILL
BE THE MAIN THREATS...BUT ONE OR TWO TORNADOES CANNOT BE RULED OUT.
DISCUSSION...THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER THE NEXT
SEVERAL HOURS AS ASCENT ASSOCIATED WITH A MID-LEVEL VORTICITY
MAXIMUM /CURRENTLY ACROSS NORTH-CENTRAL IOWA/ OVERSPREADS THE AREA.
INITIAL THUNDERSTORMS SHOULD DEVELOP ALONG OR SOUTH OF A DECAYING
OUTFLOW BOUNDARY LEFT OVER FROM OVERNIGHT CONVECTION...WHERE THE
ATMOSPHERE HAS BECOME MODERATELY UNSTABLE AND IS WEAKLY CAPPED.
EFFECTIVE DEEP-LAYER SHEAR IS SUFFICIENT FOR ORGANIZED MULTI-CELL
CLUSTERS AND/OR SUPERCELLS...ALTHOUGH THE LACK OF WIDESPREAD
CONVECTIVE INHIBITION SUGGESTS THUNDERSTORMS SHOULD EVENTUALLY GROW
UPSCALE. THUNDERSTORMS SOUTH OF THE OUTFLOW BOUNDARY WILL HAVE THE
POTENTIAL TO PRODUCE LARGE HAIL AND DAMAGING THUNDERSTORM
WINDS...AND A TORNADO OR TWO CANNOT BE RULED OUT...ESPECIALLY IN THE
VICINITY OF THE REMNANT OUTFLOW BOUNDARY AND/OR LAKE BREEZE...WHERE
LOW-LEVEL VORTICITY MAY BE LOCALLY AUGMENTED. NORTH OF THE OUTFLOW
BOUNDARY...THUNDERSTORMS MAY EXHIBIT CHARACTERISTICS OF ELEVATED
CONVECTION OWING TO THE WORKED-OVER AIRMASS. HERE...THE MAIN THREAT
SHOULD BE LARGE HAIL...ALTHOUGH GIVEN THE STRONGER DEEP-LAYER SHEAR
AND LOWER CLOUD BASES...ISOLATED DAMAGING WIND GUSTS AND A TORNADO
OR TWO WILL BE POSSIBLE.
ONE COMPLICATING FACTOR WILL BE THE EVOLUTION OF THE CLOUD SHIELD
DEVELOPING ACROSS NORTHERN MISSOURI AND NORTHWESTERN ILLINOIS.
SHOULD THIS DEVELOP FARTHER NORTHWARD...OVERSPREADING NORTHERN
ILLINOIS AND SOUTHERN WISCONSIN...THUNDERSTORM DEVELOPMENT MAY END
UP BEING MORE ISOLATED IN NATURE...DELAYING POTENTIAL UPSCALE
GROWTH.
..MARSH/CORFIDI.. 07/18/2015
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...GRB...LOT...ILX...MKX...DVN...ARX...DMX...
LAT...LON 41489297 42669244 43869038 44178849 43758740 42268754
41358799 41048894 40688998 40689197 41489297
S����
http://goo.gl/Cr2Yhn
------------------------------------------------
(c) Copyleft 2015 WxNotify. All wrongs reserved.
