WWUS20 KWNS 012202
SEL1
SPC WW 012202
IAZ000-NEZ000-SDZ000-020600-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 221
NWS STORM PREDICTION CENTER NORMAN OK
500 PM CDT TUE MAY 1 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF 

       NORTHWEST IOWA
       CENTRAL THROUGH NORTHEASTERN NEBRASKA
       SOUTHEAST SOUTH DAKOTA

EFFECTIVE THIS TUESDAY AFTERNOON AND WEDNESDAY MORNING FROM 500
PM UNTIL 100 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 115
STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES NORTH
NORTHEAST OF YANKTON SOUTH DAKOTA TO 35 MILES SOUTHEAST OF
BURWELL NEBRASKA.  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 217...WW 218...WW
219...WW 220...

DISCUSSION...TSTMS EXPECTED TO DEVELOP SWD ALONG NE-SE COLD FRONT
NOW CROSSING SE SD/CNTRL SD AS SFC HEATING CONTINUES TO DESTABILIZE
REGION TO ITS SE.  DEEP SHEAR AND INSTABILITY SHOULD BE SUFFICIENT
FOR A FEW SUSTAINED STORMS/SUPERCELLS WITH LARGE HAIL AND DMGG WIND.
ADDITIONAL...POSSIBLY SEPARATE STORM DEVELOPMENT MAY OCCUR LATER
THIS EVE OVER S CNTRL AND ERN NEB AS SLY LLJ BROADENS AND
STRENGTHENS IN RESPONSE TO DIURNAL CYCLE AND APPROACH OF CNTRL RCKYS
UPR IMPULSE.

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 550. MEAN STORM
MOTION VECTOR 26030.


...CORFIDI