

539 

WWUS20 KWNS 262018

SEL8

SPC WW 262018

MTZ000-NDZ000-270300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 688

NWS STORM PREDICTION CENTER NORMAN OK

220 PM MDT TUE JUL 26 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST MONTANA

       EXTREME NORTHWEST NORTH DAKOTA



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 220 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 80

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

NORTHWEST OF WILLISTON NORTH DAKOTA TO 100 MILES SOUTH OF GLASGOW

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 686...WW 687...



DISCUSSION...DISCRETE STORMS HAVE DEVELOPED OVER VALLEY AND

PETROLEUM COUNTIES IN MT...AND POTENTIAL EXISTS FOR ADDITIONAL CELLS

TO FORM THIS AFTERNOON.  ACTIVITY IS ASSOCIATED WITH UPPER VORTICITY

MAX MOVING EWD JUST NORTH OF THE MT BORDER...AND WILL BE MOVING INTO

AN INCREASINGLY MOIST AND UNSTABLE AIR MASS.  40-50 KT WSWLY MID

LEVEL FLOW IS RESULTING IN FAVORABLE SHEAR FOR SEVERE STORMS

INCLUDING POSSIBLE SUPERCELLS.



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 25030.





...WEISS

