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WWUS20 KWNS 272045

SEL4

SPC WW 272045

IAZ000-MNZ000-NEZ000-SDZ000-280500-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 304

NWS STORM PREDICTION CENTER NORMAN OK

345 PM CDT SUN MAY 27 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHWEST IOWA

       SOUTHWEST MINNESOTA

       EASTERN NEBRASKA

       EXTREME SOUTHEAST SOUTH DAKOTA



EFFECTIVE THIS SUNDAY AFTERNOON FROM 345 PM UNTIL MIDNIGHT CDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 75

STATUTE MILES EAST AND WEST OF A LINE FROM 55 MILES WEST

NORTHWEST OF MANKATO MINNESOTA TO 45 MILES SOUTH SOUTHWEST OF

HASTINGS NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).



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 303...



DISCUSSION...ALL INDICATIONS POINT TO THE INITIATION OF DEEP

CONVECTION WITHIN ANOTHER HOUR OR SO. DEEP-LAYER VERTICAL SHEAR

MAGNITUDES ON THE ORDER OF 40KT AND MLCAPE IN THE 1200-1800 J/KG

RANGE WILL CONTRIBUTE TO ROBUST AND ORGANIZED STORM DEVELOPMENT.

REMOVAL OF REMAINING INHIBITION ALONG THE FRONT WILL OCCUR AS

DEEP-LAYER ASCENT OVERSPREADS THE REGION THROUGH THE EVENING. THIS

SHOULD RESULT IN A SIGNIFICANT INCREASE IN STORMS ALONG THE FRONT

AND NEAR THE TRIPLE LOW. AREAL COVERAGE OF THIS ROBUST DEVELOPMENT

LENDS CONFIDENCE IN SEVERE WEATHER...ESPECIALLY LARGE HAIL AND

DAMAGING WINDS. TORNADO PROBABILITY...WHILE NOT ZERO...DOES APPEAR

LOW ACROSS THE BULK OF THE WATCH. GIVEN RELATIVELY HIGH CLOUD

BASES....VEERED LOW LEVEL FLOW AHEAD OF THE FRONT...AND DEEP-LAYER

UNIDIRECTIONAL WIND PROFILES EVIDENT IN SOUNDINGS AND VWP/PROFILER

DATA ACROSS THE REGION TORNADO POTENTIAL SEEMS LOW. ONE POSSIBLE

EXCEPTION WILL BE NEAR THE TRIPLE POINT LOW/FRONT WAVE IN THE SWRN

PORTION OF THE WATCH. UPDRAFT STRETCHING...STORM INTERACTIONS...AND

THE POTENTIAL FOR VERY LOCALIZED AREAS OF ENHANCED SR FLOW/HELICITY

NEAR THE TRIPLE POINT LOW COULD FAVOR A BETTER CHANCE AT A TORNADO

IN THIS AREA. IF THIS APPEARS MORE LIKELY...A TORNADO WATCH MAY

REPLACE PARTS OF THIS WATCH LATER.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 23035.





...CARBIN

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