MESO: Mesoscale Discussion 1041

ACUS11 KWNS 121750
SWOMCD
SPC MCD 121749
WIZ000-ILZ000-IAZ000-MNZ000-121845-

MESOSCALE DISCUSSION 1041
NWS STORM PREDICTION CENTER NORMAN OK
1249 PM CDT WED JUN 12 2013

AREAS AFFECTED...PORTIONS OF CENTRAL/ERN IA...SWRN WI...NWRN IL

CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY

VALID 121749Z - 121845Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...A TORNADO WATCH WILL BE COORDINATED WITH LOCAL NWS WEATHER
FORECAST OFFICES PRIOR TO 19Z. SVR TSTMS ARE EXPECTED TO DEVELOP
OVER PORTIONS OF NORTHERN/EASTERN IA AND NORTHWEST ILLINOIS THIS
AFTERNOON AND QUICKLY BECOME SEVERE WITH A RISK FOR
TORNADOES...LARGE HAIL AND DAMAGING WINDS.

DISCUSSION...SURFACE MESOANALYSIS AT 17Z INDICATES AN AREA OF LOW
PRESSURE OVER CENTRAL IOWA AND A FRONTAL BOUNDARY EXTENDING EASTWARD
ALONG THE ILLINOIS/WISCONSIN BORDER. LATEST VISIBLE SATELLITE
IMAGERY SHOWS A DEVELOPING CU FIELD AS DIABATIC HEATING REDUCES
MLCINH. TOWERING CU EVIDENT WEST/NW OF DES MOINES SUGGESTS THAT
CONVECTIVE INITIATION MAY OCCUR WITHIN THE NEXT FEW HOURS. THE
ENVIRONMENT IS CHARACTERIZED BY MODERATE/STRONG INSTABILITY WITH
MLCAPES RANGING FROM 2000 J/KG OVER CENTRAL IOWA TO NEAR 4000 J/KG
OVER EASTERN IOWA/NORTHWEST ILLINOIS. STRONG DEEP-LAYER SHEAR IS
PREVALENT WITH 50-60 KNOTS OVER THE DISCUSSION AREA. LOW-LEVEL /0-3
KM/ SRH FROM THE DAVENPORT VWP OF NEAR 300 M2/S2 SUGGESTS THAT
LOW-LEVEL ROTATION IS POSSIBLE WITH ANY DISCRETE STORM THAT DOES
DEVELOP.

AS AN UPPER LEVEL IMPULSE APPROACHES FROM THE WEST THIS AFTERNOON
AND PROVIDES ADDITIONAL FORCING FOR ASCENT...SEVERE THUNDERSTORMS
ARE EXPECTED TO DEVELOP RAPIDLY NEAR THE SURFACE FRONT AND
INTENSIFYING SURFACE LOW PRESSURE. LOW-LEVEL FLOW WILL BACK WITH
TIME LATER THIS AFTERNOON NORTHEAST OF THE SURFACE LOW...FURTHER
AUGMENTING LOW-LEVEL SRH.

TORNADOES...LARGE HAIL AND DAMAGING WINDS WILL BE POSSIBLE WITH
SUPERCELLS DEVELOPING IN THE DISCUSSION AREA...WITH THE POSSIBILITY
FOR A STRONG TORNADO DURING THE FIRST FEW HOURS AFTER INITIATION.
WITH TIME...UPSCALE GROWTH IS ANTICIPATED AS THE STORMS MOVE EAST
WITH ENHANCED DAMAGING WIND/EMBEDDED MESOVORTEX TORNADO THREATS.

A TORNADO WATCH WILL BE COORDINATED WITH LOCAL NWS WEATHER FORECAST
OFFICES PRIOR TO 19Z.

..BUNTING/CARBIN.. 06/12/2013

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

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

LAT...LON 42718972 42368975 41968980 41648993 41559022 41439071
41519144 41559217 41669317 41819403 42539398 42939364
43549311 43729241 43629112 43189045 42718972

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