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002 

WWUS20 KWNS 082028

SEL3

SPC WW 082028

MTZ000-NDZ000-SDZ000-WYZ000-090400-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 563

NWS STORM PREDICTION CENTER NORMAN OK

220 PM MDT WED JUL 8 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       EXTREME EASTERN MONTANA

       WESTERN NORTH DAKOTA

       WESTERN SOUTH DAKOTA

       NORTHEAST WYOMING



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 220 PM UNTIL

1000 PM MDT.



TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 100 STATUTE

MILES EAST AND WEST OF A LINE FROM 55 MILES EAST NORTHEAST OF

WILLISTON NORTH DAKOTA TO 35 MILES SOUTH SOUTHWEST OF RAPID CITY

SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).



REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND 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.



DISCUSSION...THUNDERSTORMS ARE EXPECTED TO DEVELOP AND INTENSIFY

ALONG FRONTAL BOUNDARY OVER EXTREME ERN MT AND NERN WY DURING THE

NEXT 1-2 HRS.  AIR MASS HAS DESTABILIZED THIS AFTERNOON WITH MLCAPE

OF 1000-1500 J/KG AS STRONG HEATING TAKES PLACE SOUTH OF EARLIER

CONVECTION OVER NERN MT AND NWRN ND.  DYNAMIC FORCING FOR LARGE

SCALE ASCENT WILL INCREASE THROUGH THE EVENING HAS A SHORT WAVE

TROUGH PROGRESSES ENEWD ACROSS MT...IN CONJUNCTION WITH A VERY

STRONG MID/UPPER LEVEL JET STREAK.  THIS IS CONTRIBUTING TO 40-50 KT

DEEP LAYER SHEAR SUPPORTIVE OF SUPERCELLS...WHILE STRENGTHENING LOW

LEVEL JET AND VEERING PROFILES IN LOWEST 2-3 KM INDICATE POTENTIAL

FOR A FEW TORNADOES WITH INITIAL STORM DEVELOPMENT.  STORMS ARE

EXPECTED TO GROW UPSCALE BY THE EVENING HOURS WITH A

FORWARD-PROPAGATING LINEAR MCS MOVING ACROSS WRN ND AND PARTS OF WRN

SD AND INCREASING THREAT FOR MORE WIDESPREAD WIND DAMAGE.



AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

500. MEAN STORM MOTION VECTOR 26035.





...WEISS

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