

620 

WWUS20 KWNS 192020

SEL6

SPC WW 192020

MTZ000-SDZ000-WYZ000-200400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 496

NWS STORM PREDICTION CENTER NORMAN OK

220 PM MDT MON JUL 19 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST MONTANA

       WESTERN SOUTH DAKOTA

       NORTHEAST WYOMING



EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 220 PM UNTIL

1000 PM MDT.



HAIL TO 2.5 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 65

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 80 MILES NORTH

NORTHWEST OF SHERIDAN WYOMING TO 20 MILES EAST OF PHILIP SOUTH

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 494...WW 495...



DISCUSSION...ISOLATED SUPERCELL THUNDERSTORMS HAVE FORMED OVER

SOUTHEAST MT.  OTHER ACTIVITY IS LIKELY TO FORM THROUGH THE

AFTERNOON OVER NORTHEAST WY AND WESTERN SD AHEAD OF APPROACHING

SHORTWAVE TROUGH.  COOLING TEMPERATURES ALOFT AND STEEP LAPSE RATES

WILL PROMOTE A RISK OF LARGE HAIL IN STRONGER STORMS.  BOWING

SEGMENTS MAY ALSO POSE A RISK OF DAMAGING WINDS.



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

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 29030.





...HART

