

881 

WWUS20 KWNS 300400

SEL0

SPC WW 300400

IAZ000-MNZ000-SDZ000-301000-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 400

NWS STORM PREDICTION CENTER NORMAN OK

1100 PM CDT SUN MAY 29 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHWESTERN IOWA

       SOUTHWESTERN MINNESOTA

       EAST-CENTRAL AND SOUTHEASTERN SOUTH DAKOTA



EFFECTIVE THIS SUNDAY NIGHT AND MONDAY MORNING FROM 1100 PM UNTIL

500 AM CDT.



HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 60

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 35 MILES WEST

NORTHWEST OF MITCHELL SOUTH DAKOTA TO 40 MILES EAST OF REDWOOD

FALLS MINNESOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).



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 399...



DISCUSSION...GROWING COMPLEX OF STG-SVR CONVECTION WITH RISK OF

LARGE HAIL SHOULD SPREAD/DEVELOP NEWD ACROSS WW AREA...IN

ENVIRONMENT OF STEEP MIDLEVEL LAPSE RATES...ISENTROPIC ASCENT TO LFC

ALONG NWRN LIMB OF 50-60 KT LLJ...45-55 KT EFFECTIVE SHEAR...AND STG

ELEVATED BUOYANCY SUPPORTING STORM ORGANIZATION.



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

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 50

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 21030.





...EDWARDS/HALES

