

522 

WWUS20 KWNS 142139

SEL5

SPC WW 142139

IAZ000-MNZ000-NEZ000-150300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 475

NWS STORM PREDICTION CENTER NORMAN OK

440 PM CDT WED JUL 14 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL AND NORTHWEST IOWA

       CENTRAL AND SOUTHERN MINNESOTA

       EXTREME NORTHEAST NEBRASKA



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 440 PM UNTIL

1000 PM CDT.



HAIL TO 2.5 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 35 MILES NORTH

NORTHWEST OF MINNEAPOLIS MINNESOTA TO 25 MILES SOUTH SOUTHWEST OF

STORM LAKE 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.



OTHER WATCH INFORMATION...CONTINUE...WW 473...WW 474...



DISCUSSION...THUNDERSTORM DEVELOPMENT IS EXPECTED TO PROCEED SWWD

ALONG THE SYNOPTIC FRONT ACROSS CENTRAL MN...AND ADDITIONAL STORM

DEVELOPMENT WILL OCCUR NEWD FROM ERN NEB TOWARD NW IA.  INSTABILITY

IS STRONG ACROSS THE WATCH AREA...WHILE DEEP-LAYER VERTICAL SHEAR

WEAKENS FROM N TO S FROM MN INTO IA.  THE NET RESULT IS AN

ENVIRONMENT SUPPORTIVE OF BOTH SUPERCELLS AND BOWING SEGMENTS.  AN

ISOLATED TORNADO CANNOT BE RULED OUT GIVEN THE STRONG

INSTABILITY...BUT LARGE HAIL AND DAMAGING WINDS SHOULD BE THE

PRIMARY THREATS GIVEN THE SOMEWHAT VEERED LOW-LEVEL FLOW AND

STRAIGHT HODOGRAPH STRUCTURES.



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

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

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

MOTION VECTOR 27035.





...THOMPSON

