WATCHES: Severe Thunderstorm Watch Number 281

WWUS20 KWNS 202040
SEL1
SPC WW 202040
MTZ000-SDZ000-WYZ000-210600-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 281
NWS STORM PREDICTION CENTER NORMAN OK
230 PM MDT SUN MAY 20 2007

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

SOUTHERN AND EASTERN MONTANA
WESTERN SOUTH DAKOTA
NORTHEAST WYOMING

EFFECTIVE THIS SUNDAY AFTERNOON FROM 230 PM UNTIL MIDNIGHT MDT.

HAIL TO 2.5 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 100
STATUTE MILES EAST AND WEST OF A LINE FROM 50 MILES SOUTH
SOUTHEAST OF MOORCROFT WYOMING TO 80 MILES NORTH NORTHWEST OF
MILES CITY MONTANA. 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.

DISCUSSION...TSTMS/POSSIBLE SUPERCELLS EXPECTED TO CONTINUE FORMING
OVER THE ERN SLOPES OF THE HIGHER TERRAIN IN CNTRL/S CNTRL MT AND N
CNTRL WY THIS AFTERNOON. STRENGTHENING DEEP SHEAR WITH APPROACH OF
ID UPR DISTURBANCE AND CONTINUED ENELY LOW LEVEL FLOW IN WAKE OF
OVERNIGHT CONVECTION WILL CREATE INCREASINGLY FAVORABLE SETUP FOR
SUSTAINED SUPERCELLS WITH LARGE HAIL/HIGH WIND. FARTHER SE...OTHER
STRONG TO SVR STORMS WITH LARGE HAIL EXPECTED TO PERSIST INVOF THE
BLACK HILLS.
THE THREAT FOR TORNADOES MAY INCREASE A BIT LATER THIS AFTERNOON OR
EARLY THIS EVENING IN S CNTRL MT...WHERE ENELY NEAR-SFC FLOW WILL BE
COLLOCATED WITH LOW LEVEL MOISTURE AXIS. IF STORMS FORMING IN THE
REGION W AND S OF BILLINGS REMAIN DISCRETE...PART OF PRESENT WATCH
MAY REQUIRE UPGRADE TO TORNADO.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 24025.

..CORFIDI

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