

638 

WWUS20 KWNS 111955

SEL2

SPC WW 111955

IAZ000-NEZ000-120000-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 282

NWS STORM PREDICTION CENTER NORMAN OK

255 PM CDT WED MAY 11 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       SOUTHWEST IOWA

       EASTERN NEBRASKA



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 255 PM UNTIL

700 PM CDT.



TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 155 STATUTE

MILES EAST AND WEST OF A LINE FROM 10 MILES NORTH OF DENISON IOWA

TO 20 MILES WEST SOUTHWEST OF SHENANDOAH IOWA.  FOR A COMPLETE

DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE

(WOUS64 KWNS WOU2).



REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND 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.



OTHER WATCH INFORMATION...CONTINUE...WW 278...WW 279...WW

280...WW 281...



DISCUSSION...INTENSE STORMS EXPECTED TO CONTINUE TO SPREAD NWD

ACROSS DESTABILIZING AIRMASS ALONG THE MISSOURI RIVER VALLEY. WHILE

SPEED SHEAR IN THE CLOUD-BEARING LAYER IS NOT PARTICULARLY CONDUCIVE

TO ROBUST ORGANIZATION...DEGREE OF INSTABILITY...DIRECTIONAL

SHEAR...AND STORM SCALE INTERACTIONS ARE EXPECTED TO COMPENSATE FOR

THIS SHORTCOMING AND LEAD TO AN INCREASING CHANCE FOR ENHANCED LOW

LEVEL STORM ROTATION AND POSSIBLE TORNADOES. EXPECT THIS POTENTIAL

TO UNFOLD AS STRONGER UPDRAFTS ALONG THE LEADING EDGE OF MCS COLD

POOL ENCOUNTER BACKED LOW LEVEL FLOW ACROSS ERN NEB AND SWRN IA.



AVIATION...TORNADOES AND 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 20035.





...CARBIN

