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WWUS20 KWNS 072054

SEL6

SPC WW 072054

MTZ000-NDZ000-080300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 566

NWS STORM PREDICTION CENTER NORMAN OK

255 PM MDT TUE AUG 7 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EASTERN MONTANA

       WESTERN NORTH DAKOTA



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 255 PM UNTIL

900 PM MDT.



HAIL TO 2 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 100

STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES SOUTH

SOUTHEAST OF BAKER MONTANA TO 40 MILES NORTH OF WILLISTON NORTH

DAKOTA.  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 565...



DISCUSSION...THICKENING CU FIELD OVER EXTREME ERN MT INTO WRN ND

WITHIN LOW LEVEL MOISTURE INSTABILITY AXIS SUGGESTS THAT DEEP MOIST

CONVECTION WILL DEVELOP WITHIN THE NEXT 1-2 HOURS AS CAP CONTINUES

TO WEAKEN.  ALTHOUGH SURFACE DEW POINTS ARE IN THE 45-55F

RANGE...VERY WARM TEMPERATURES/STEEP LAPSE RATES ARE RESULTING IN

MLCAPE OF 1000-1500 J/KG. WIND PROFILES VEER AND INCREASE WITH

HEIGHT PROVIDING FAVORABLE FOR ENVIRONMENT FOR SEVERE STORMS

INCLUDING ISOLATED SUPERCELLS.  STORMS ARE LIKELY TO CONTINUE

THROUGH THE EVENING HOURS AS UPPER SHORT WAVE TROUGH MOVES EWD

TOWARD THE NRN ROCKIES...AND LOW LEVEL JET STRENGTHENS AFTER 00Z.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 24025.





...WEISS

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