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WWUS20 KWNS 131907

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SPC WW 131907

MTZ000-WYZ000-140300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 309

NWS STORM PREDICTION CENTER NORMAN OK

105 PM MDT THU JUN 13 2013



THE NWS STORM PREDICTION CENTER HAS ISSUED A



* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

  EASTERN MONTANA

  CENTRAL AND NORTHERN WYOMING



* EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 105 PM UNTIL

  900 PM MDT.



* PRIMARY THREATS INCLUDE...

  SEVERAL LARGE HAIL EVENTS WITH A FEW VERY LARGE HAIL EVENTS TO 3

    INCHES IN DIAMETER POSSIBLE

  SEVERAL DAMAGING WIND GUSTS TO 70 MPH POSSIBLE



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 100

STATUTE MILES EITHER SIDE OF A LINE FROM 50 MILES NORTHWEST OF

GLASGOW MONTANA TO 30 MILES EAST SOUTHEAST OF LANDER WYOMING.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU9).



PRECAUTIONARY/PREPAREDNESS ACTIONS...



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 306...WW 307...WW 308...



DISCUSSION...EXPECT ISOLATED TO WIDELY SCATTERED STRONG TO SEVERE

STORMS TO CONTINUE TO POSE A THREAT OF POTENTIALLY VERY LARGE HAIL

AND LOCALLY HIGH WINDS ACROSS NRN WY AND PARTS OF CENTRAL AND ERN MT

THROUGH THE AFTERNOON AND INTO THIS EVENING. LOW AMPLITUDE IMPULSES

EMANATING FROM A STRONG LARGER SCALE TROUGH HAVE BEEN AIDING STORM

DEVELOPMENT ACROSS THE HIGH TERRAIN AND ADJACENT LOWER ELEVATIONS

WHERE INSTABILITY CONTINUES TO INCREASE WITH HEATING OF THE DAY.

SHEAR PROFILES ARE ALREADY ADEQUATE FOR SUPERCELLS WITH ABOUT 40KT

OF SWLY MID-LEVEL FLOW FORECAST TO INCREASE TO OVER 50KT THROUGH THE

LATE AFTERNOON. STORMS DEVELOPING IN THIS ENVIRONMENT WILL HAVE THE

TENDENCY TO ACQUIRE ROTATION WITH BOTH HAIL AND WIND HAZARDS

POSSIBLE. AN ISOLATED TORNADO CANNOT BE RULED OUT GIVEN BACKED LOW

LEVEL FLOW AND RELATIVELY MOIST BOUNDARY LAYER EAST OF THE HIGHER

TERRAIN.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 3 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450. MEAN STORM

MOTION VECTOR 22035.





...CARBIN

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