WATCHES: Severe Thunderstorm Watch Number 436

WWUS20 KWNS 011943
SEL6
SPC WW 011943
IDZ000-MTZ000-020400-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 436
NWS STORM PREDICTION CENTER NORMAN OK
140 PM MDT THU JUL 1 2010

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

A SMALL PART OF EAST CENTRAL IDAHO
SOUTHWEST...CENTRAL...AND NORTHEAST MONTANA

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 140 PM UNTIL
1000 PM 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 135
STATUTE MILES EAST AND WEST OF A LINE FROM 50 MILES EAST
SOUTHEAST OF DILLON MONTANA TO 55 MILES NORTH NORTHEAST OF
GLASGOW MONTANA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).

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 435...

DISCUSSION...LIKE PREVIOUS DAYS...THUNDERSTORMS ARE BEGINNING TO
DEVELOP OVER THE HIGH TERRAIN NEAR AND NE OF THE ID/SW MT BORDER.
CONTINUED SURFACE HEATING ACROSS CENTRAL MT WILL CONTRIBUTE TO
ADDITIONAL DESTABILIZATION IN AN ENVIRONMENT WITH BOUNDARY LAYER
DEWPOINTS IN THE LOW-MID 50S. THIS AREA IS ALSO DOWNSTREAM FROM A
MIDLEVEL TROUGH OVER THE PAC NW...WITH A SUBTLE/EMBEDDED VORTICITY
LOBE EJECTING NEWD OVER WRN MT. THE COMBINATION OF WEAK BACKGROUND
ASCENT AND DEEP-LAYER VERTICAL SHEAR WITH THIS EJECTING WAVE WILL
SUPPORT A FEW SUPERCELLS CAPABLE OF PRODUCING ISOLATED VERY LARGE
HAIL AND DAMAGING WINDS. AN ISOLATED TORNADO CANNOT BE RULED
OUT...THOUGH LOW-LEVEL MOISTURE/SHEAR ARE MARGINAL FOR A TORNADO
THREAT. OTHERWISE...CONVECTION MAY MERGE INTO LARGER CLUSTERS
DURING THE EVENING AND SPREAD NEWD INTO NE MT WITH A CONTINUED
DAMAGING WIND/HAIL THREAT.

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 25030.

...THOMPSON

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