

710 

WWUS20 KWNS 212047

SEL1

SPC WW 212047

MTZ000-WYZ000-220400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 511

NWS STORM PREDICTION CENTER NORMAN OK

250 PM MDT WED JUL 21 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST MONTANA

       CENTRAL AND NORTHEASTERN WYOMING



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 250 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 95

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

ROCK SPRINGS WYOMING TO 10 MILES EAST NORTHEAST OF BROADUS

MONTANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).



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 507...WW 508...WW

509...WW 510...



DISCUSSION...SCATTERED THUNDERSTORMS HAVE DEVELOPED ALONG THE BIG

HORN MTNS...AND FARTHER SOUTHWEST ACROSS CENTRAL WY.  THESE STORMS

ARE IN AN ENVIRONMENT OF STEEP LAPSE RATES AND SUFFICIENT

INSTABILITY FOR STRONG UPDRAFTS.  FAVORABLE VERTICAL SHEAR WILL

PROMOTE ORGANIZED/SUPERCELL STORMS CAPABLE OF LARGE HAIL AND

DAMAGING WINDS THROUGH THE EVENING.



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 27030.





...HART

