WATCHES: Severe Thunderstorm Watch Number 487

WWUS20 KWNS 162058
SEL7
SPC WW 162058
MTZ000-NDZ000-SDZ000-170400-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 487
NWS STORM PREDICTION CENTER NORMAN OK
255 PM MDT MON JUL 16 2012

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

EXTREME SOUTHEAST MONTANA
SOUTHWEST NORTH DAKOTA
NORTHWEST SOUTH DAKOTA

EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 255 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 55
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 50 MILES SOUTH
SOUTHWEST OF BAKER MONTANA TO 30 MILES EAST NORTHEAST OF MOBRIDGE
SOUTH DAKOTA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).

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...SEVERE STORMS ARE EXPECTED TO INCREASE AND DEVELOP EAST
OFF THE HIGHER TERRAIN OF SERN MT AND WRN SD OVER THE NEXT COUPLE OF
HOURS. DOWNSTREAM AIR MASS IS CHARACTERIZED BY STRONG INSTABILITY
WHERE MOIST POST-FRONTAL LOW LEVEL ELY FLOW IS TOPPED BY 25-30KT
SWLY FLOW ALOFT. RESULTING SHEAR AND THERMODYNAMIC REGIME SHOULD
SUPPORT SUPERCELLS IF STORMS CAN PERSIST AND OVERCOME REMAINING
INHIBITION EAST OF THE HIGHER TERRAIN. DESPITE WARM TEMPERATURES
ALOFT...PERSISTENT LOW LEVEL CONVERGENCE ALONG THE FRONT AND
THERMAL/TRIPLE-POINT LOW...AND MAGNITUDE OF HEATING ALONG AND SOUTH
OF THE FRONTAL ZONE...SHOULD ACT TO OVERCOME REMAINING INHIBITION
AND FAVOR AT LEAST A FEW SEVERE STORMS PRODUCING LARGE HAIL AND HIGH
WINDS SPREADING EAST NEAR THE SD/ND BORDER AREA INTO THIS EVENING.

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 27025.


...CARBIN

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