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139 

WWUS20 KWNS 131941

SEL1

SPC WW 131941

IAZ000-MNZ000-WIZ000-LSZ000-140300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 611

NWS STORM PREDICTION CENTER NORMAN OK

240 PM CDT FRI AUG 13 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       PART OF NORTH-CENTRAL AND NORTHEAST IOWA

       PART OF CENTRAL AND SOUTHERN MINNESOTA

       NORTHWEST WISCONSIN

       LAKE SUPERIOR



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 240 PM UNTIL

1000 PM 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 85

STATUTE MILES EAST AND WEST OF A LINE FROM 20 MILES SOUTH

SOUTHEAST OF MASON CITY IOWA TO 95 MILES NORTHEAST OF SAINT CLOUD

MINNESOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).



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 609...WW 610...



DISCUSSION...TSTMS ARE RAPIDLY DEVELOPING IN ADVANCE OF POTENT

MIDLEVEL TROUGH THIS AFTERNOON WITHIN A MOIST ENVIRONMENT WHERE

MLCAPE HAS INCREASED TO 1000-2000 J/KG.  40-50 KT MIDLEVEL JET

ATTENDING VORTICITY MAXIMUM IS RESULTING IN SUFFICIENT DEEP-LAYER

VERTICAL SHEAR FOR ORGANIZED STORMS...INCLUDING SUPERCELLS AND

BOWING STRUCTURES.  WHILE A BRIEF TORNADO OR TWO IS POSSIBLE WITH

ANY MORE INTENSE SUPERCELLS...THE STRONGEST LOW-LEVEL SHEAR HAS

SHIFTED TO THE E OF AREA WHICH SHOULD LIMIT THE POTENTIAL FOR A MORE

ROBUST THREAT.  AS SUCH...LARGE HAIL AND DAMAGING WIND GUSTS APPEAR

TO THE PRIMARY HAZARDS WITH THE MOST INTENSE STORMS.



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 500. MEAN STORM

MOTION VECTOR 26030.





...MEAD

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