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URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 228

NWS STORM PREDICTION CENTER NORMAN OK

440 PM MDT THU MAY 27 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       EASTERN MONTANA

       WESTERN NORTH DAKOTA

       PART OF NORTH-CENTRAL WYOMING



EFFECTIVE THIS THURSDAY AFTERNOON AND FRIDAY MORNING FROM 440 PM

UNTIL 100 AM MDT.



TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 80 STATUTE

MILES EITHER SIDE OF A LINE FROM 110 MILES WEST SOUTHWEST OF

MILES CITY MONTANA TO 50 MILES EAST SOUTHEAST OF WILLISTON NORTH

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

WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).



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 227...



DISCUSSION...TSTMS ARE EXPECTED TO DEVELOP WITHIN THE NEXT ONE TO

TWO HOURS ALONG A QUASI-STATIONARY BOUNDARY PRESENT FROM S-CNTRL MT

INTO W-CNTRL ND.  DAYTIME HEATING COUPLED WITH DEW POINTS IN THE

LOW/MID 60S AND STEEP LAPSE RATES ARE CONTRIBUTING TO A MODERATELY

UNSTABLE AIR MASS WITH MLCAPE OF 2000-2500 J/KG AND A WEAKENING CAP.

THIS INSTABILITY IN CONJUNCTION WITH AROUND 50 KT OF DEEP LAYER

SHEAR AND EFFECTIVE SRH OF 200-250 M2/S2 INDICATE A VERY FAVORABLE

ENVIRONMENT FOR SUPERCELLS CAPABLE OF VERY LARGE HAIL AND TORNADOES.



AVIATION...TORNADOES AND 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 24025.





...MEAD

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