

577 

WWUS20 KWNS 132322

SEL1

SPC WW 132322

NEZ000-SDZ000-WYZ000-140700-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 401

NWS STORM PREDICTION CENTER NORMAN OK

520 PM MDT SAT JUN 13 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN AND WESTERN NEBRASKA

       SOUTHWEST SOUTH DAKOTA

       NORTHEAST WYOMING `



EFFECTIVE THIS SATURDAY AFTERNOON AND SUNDAY MORNING FROM 520 PM

UNTIL 100 AM MDT.



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 105

STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES NORTHWEST OF

RAPID CITY SOUTH DAKOTA TO 5 MILES EAST OF NORTH PLATTE 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 397...WW 398...WW

399...WW 400...



DISCUSSION...SCTD SUPERCELLS/STRONG STORM CLUSTERS EXPECTED TO

PERSIST THROUGH LATE TONIGHT FROM NE WY/BLACK HILLS SSE INTO

NEB...WHERE LOW LVL WARM/MOIST ADVECTION WILL PERSIST BENEATH AREA

OF UPR DIFFLUENCE ON CREST OF UPR RIDGE.  A LOW PROBABILITY RISK MAY

EVOLVE FOR A TORNADO OR TWO IN NEBRASKA...DEPENDING UPON STORM

MODE/CHARACTER OF DEVELOPMENT...BUT MAIN RISK IN WW SHOULD BE LARGE

HAIL.



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 500. MEAN STORM

MOTION VECTOR 31025.





...CORFIDI

