

023 

WWUS20 KWNS 181802

SEL3

SPC WW 181802

IAZ000-ILZ000-INZ000-MNZ000-WIZ000-LMZ000-190100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 493

NWS STORM PREDICTION CENTER NORMAN OK

100 PM CDT WED JUL 18 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST AND EAST-CENTRAL IOWA

       NORTHERN ILLINOIS

       FAR NORTHWEST INDIANA

       FAR SOUTHEAST MINNESOTA

       SOUTHERN WISCONSIN

       LAKE MICHIGAN



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 100 PM UNTIL

800 PM CDT.



HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 40 MILES SOUTHWEST

OF ROCHESTER MINNESOTA TO 20 MILES SOUTH SOUTHEAST OF VALPARAISO

INDIANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).



REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.



OTHER WATCH INFORMATION...CONTINUE...WW 490...WW 491...WW 492...



DISCUSSION...TSTMS CURRENTLY DEVELOPING INVOF STATIONARY BOUNDARY

OVER SRN MN/NRN IA ARE LIKELY BEING FORCED BY MCV NE OF SUX.

UPSCALE GROWTH OF STORMS INTO A SEWD-MOVING MCS APPEARS POSSIBLE

LATER THIS AFTERNOON.  ELY INFLOW OF A VERY MOIST...

MODERATE-STRONGLY UNSTABLE AIR MASS INTO DEVELOPING CONVECTIVE

SYSTEM WILL ENHANCE UPDRAFT VIGOR WITH A RISK FOR DAMAGING WINDS AND

LARGE HAIL.  ADDITIONAL...MORE ISOLATED STORM FORMATION WILL OCCUR

SEWD ALONG SURFACE FRONT ACROSS NRN IL WITH THE STRONG INSTABILITY

PROMOTING STRONG UP/DOWNDRAFTS CAPABLE OF DAMAGING WINDS AND HAIL.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 31025.





...MEAD

