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956 

WWUS20 KWNS 221923

SEL1

SPC WW 221923

MTZ000-230300-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 671

NWS STORM PREDICTION CENTER NORMAN OK

125 PM MDT FRI JUL 22 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       EASTERN MONTANA



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 125 PM UNTIL 900

PM MDT.



TORNADOES...HAIL TO 4 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 90 STATUTE

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

GLASGOW MONTANA TO 35 MILES SOUTHWEST OF BROADUS MONTANA.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU1).



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.



OTHER WATCH INFORMATION...CONTINUE...WW 670...



DISCUSSION...POTENT UPPER TROUGH AND UNSTABLE AIRMASS WILL

CONTRIBUTE TO AN INCREASE IN SEVERE THUNDERSTORMS ACROSS ERN MT THIS

AFTERNOON. DEEP SHEAR WILL INITIALLY SUPPORT SUPERCELLS WITH THE

POTENTIAL FOR VERY LARGE HAIL. TORNADO THREAT WILL ALSO EXIST

ALTHOUGH MIXING OF DRIER AIR THROUGH DEEP HEATED BOUNDARY LAYER MAY

KEEP THIS POTENTIAL FOCUSED MOSTLY NEAR THE LOW/TROUGH AND ALONG THE

FRONTAL ZONE EXTENDING FROM THE LEE LOW/TROUGH SEWD ACROSS ECNTRL

MT. GGW VWP INDICATIVE OF STRONG DIRECTIONAL SHEAR SUPPORTIVE OF

INTENSE LOW LEVEL UPDRAFT ROTATION. EXPECT A TRANSITION TO MORE

LINEAR/WIND DAMAGE STORM MODE LATER THIS AFTERNOON AS FORCING WITH

THE UPPER TROUGH AND COLD FRONT MOVE INTO STRONG INSTABILITY...

CELLS AND STORMS MERGE/CONGEAL...AND CONVECTIVE COLD POOLS

MATURE...ALL IN THE PRESENCE OF INCREASINGLY STRONG DEEP LAYER FLOW

AND FORCING.



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

SURFACE AND ALOFT TO 4 INCHES. EXTREME TURBULENCE AND SURFACE

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

450. MEAN STORM MOTION VECTOR 24030.





...CARBIN

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