WATCHES: Severe Thunderstorm Watch Number 618

WWUS20 KWNS 192334
SEL8
SPC WW 192334
MTZ000-WYZ000-200600-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 618
NWS STORM PREDICTION CENTER NORMAN OK
530 PM MDT SUN AUG 19 2007

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

SOUTHEAST MONTANA
EASTERN WYOMING

EFFECTIVE THIS SUNDAY AFTERNOON FROM 530 PM UNTIL MIDNIGHT MDT.

HAIL TO 1.5 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 95
STATUTE MILES EAST AND WEST OF A LINE FROM 25 MILES NORTH
NORTHWEST OF MILES CITY MONTANA TO 55 MILES SOUTH SOUTHWEST OF
DOUGLAS WYOMING. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).

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 617...

DISCUSSION...TSTMS...INCLUDING SOME SUSTAINED CELLS AND HIGHER-BASED
SUPERCELLS...HAVE FORMED OVER THE MOUNTAINS OF NRN/WRN WY AND SRN
MT. THIS ACTIVITY IS IN ZONE OF INSTABILITY/UPLIFT ON SERN FRINGE
OF SHORTWAVE TROUGH ROTATING NE ACROSS THE NRN RCKYS. BELT OF DEEP/
MODERATELY STRONG WLY FLOW OVERSPREADING WY WITH THE TROUGH SHOULD
MAINTAIN FAVORABLE ENVIRONMENT FOR SUSTAINED STORMS EWD INTO THE ERN
WY/SE MT PLNS. GIVEN DEEPLY MIXED ENVIRONMENT PRESENT THERE...SOME
STORMS COULD YIELD HIGH WIND AND POSSIBLY HAIL THROUGH AT MID/LATE
EVENING.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450. MEAN STORM
MOTION VECTOR 26035.

..CORFIDI

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