WATCHES: Severe Thunderstorm Watch Number 815

WWUS20 KWNS 091814
SEL5
SPC WW 091814
IDZ000-MTZ000-100200-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 815
NWS STORM PREDICTION CENTER NORMAN OK
1215 PM MDT SAT AUG 9 2008

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

CENTRAL IDAHO
WESTERN MONTANA

EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 1215 PM UNTIL
800 PM 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 85
STATUTE MILES EITHER SIDE OF A LINE FROM 25 MILES WEST OF SALMON
IDAHO TO 55 MILES EAST SOUTHEAST OF CUT BANK MONTANA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU5).

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...THUNDERSTORMS EXPECTED TO CONTINUE INCREASING AND
INTENSIFYING ACROSS WW THIS AFTERNOON AHEAD OF NEGATIVELY-TILTED
SHORTWAVE TROUGH CURRENTLY EJECTING ACROSS THE PAC NW. CONTINUED
HEATING WITHIN SEASONABLY MOIST AIR MASS IS EXPECTED TO SUPPORT
MARGINAL TO MODERATE INSTABILITY AND STEEP LOW LEVEL LAPSE RATES
AHEAD OF CONVECTION MOVING NEWD. DAMAGING WINDS AND LARGE HAIL CAN
BOTH BE EXPECTED AS SHEAR REMAINS SUPPORTIVE OF LINES/BRIEF
SUPERCELLS.

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 400. MEAN STORM
MOTION VECTOR 24035.

...EVANS

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