

385 

WWUS20 KWNS 042252

SEL8

SPC WW 042252

MTZ000-NDZ000-050400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 728

NWS STORM PREDICTION CENTER NORMAN OK

450 PM MDT THU AUG 4 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EXTREME EASTERN MONTANA

       WESTERN NORTH DAKOTA



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 450 PM UNTIL

1000 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 70

STATUTE MILES EAST AND WEST OF A LINE FROM 60 MILES WEST

NORTHWEST OF MINOT NORTH DAKOTA TO 40 MILES SOUTHEAST OF BAKER

MONTANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).



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 727...



DISCUSSION...STORMS ARE SLOWING INCREASING OVER ERN MT WITH ONE

SPLITTING SUPERCELL EVIDENT OVER DAWSON COUNTY.  ACTIVITY IS FOCUSED

NEAR AN EAST/WEST FRONT AND WEAK LOW LEVEL CONVERGENCE ZONE

EXTENDING ACROSS THE AREA.  STEEP LAPSE RATES AND SURFACE DEW POINTS

IN THE UPPER 50S ARE CONTRIBUTING TO MLCAPE AROUND 1500 J/KG.

WESTERLY MID/UPPER LEVEL WINDS OF 30-50 KT ARE PROVIDING SUFFICIENT

VERTICAL SHEAR...PARTICULARLY ALONG/NORTH OF THE BOUNDARY...FOR

ORGANIZED STORMS INCLUDING POTENTIAL FOR ADDITIONAL SUPERCELLS.

ACTIVITY IS EXPECTED TO SPREAD EWD INTO WRN ND THIS EVENING BEFORE

WEAKENING AFTER SUNSET.



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 500. MEAN STORM

MOTION VECTOR 27020.





...WEISS

