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420 

WWUS20 KWNS 200048

SEL8

SPC WW 200048

IAZ000-ILZ000-MOZ000-200700-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 498

NWS STORM PREDICTION CENTER NORMAN OK

745 PM CDT MON JUL 19 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHERN IOWA

       WESTERN ILLINOIS

       NORTHEASTERN MISSOURI



EFFECTIVE THIS MONDAY NIGHT AND TUESDAY MORNING FROM 745 PM UNTIL

200 AM CDT.



HAIL TO 2 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 65

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 30 MILES WEST

SOUTHWEST OF DES MOINES IOWA TO 10 MILES EAST OF SPRINGFIELD

ILLINOIS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).



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 495...WW 496...WW 497...



DISCUSSION...INTENSE STORMS HAVE RECENTLY DEVELOPED IN SERN

IA...WITHIN ZONE OF INCREASING LOW LEVEL WARM ADVECTION. AS LOW

LEVEL JET CONTINUES TO STRENGTHEN AND PROVIDES LIFT NORTH OF SURFACE

BOUNDARY... STRETCHING ACROSS NRN MO...STORMS ARE EXPECTED TO

CONTINUE DEVELOPING OVERNIGHT. EFFECTIVE SHEAR AT 50 KT AND STRONG

ELEVATED INSTABILITY WILL BE SUFFICIENT FOR ROTATING STORMS. SINCE

THE STORMS ARE LIKELY TO DEVELOP IN LINES OR BANDS...BOWING

STRUCTURES AND WIND DAMAGE ARE EXPECTED TO BE THE PRIMARY THREAT.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 600. MEAN STORM

MOTION VECTOR 30025.





...IMY

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