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WWUS20 KWNS 061220

SEL5

SPC WW 061220

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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 255

NWS STORM PREDICTION CENTER NORMAN OK

720 AM CDT SUN MAY 6 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHERN IOWA



EFFECTIVE THIS SUNDAY MORNING AND AFTERNOON FROM 720 AM UNTIL 100

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 60

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

NORTHEAST OF DES MOINES IOWA TO 25 MILES EAST OF LAMONI IOWA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU5).



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.



DISCUSSION...OVERNIGHT TSTM N-S BAND OVER THE LWR MO VLY...WITH

SPORADIC STRONGER STORMS...RECENTLY HAS BECOME SOMEWHAT BETTER

ORGANIZED ACROSS SW IA...MOST LIKELY IN RESPONSE TO ACTIVITY HAVING

REACHED ZONE OF GREATER LOW LVL MOISTURE /PW AOA 1.25 INCHES/.

ORIENTATION OF THE SQLN LINE RELATIVE TO SELY SFC FLOW...AND ONSET

OF SFC HEATING...SUGGEST POSSIBILITY FOR A CONTINUED INCREASE IN

STORM STRENGTH/SUSTENANCE THROUGH LATER THIS MORNING...WITH AN

ATTENDANT INCREASED RISK FOR DMGG WIND/SVR HAIL DESPITE MODEST DEEP

SHEAR.



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 27030.





...CORFIDI

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