

249 

WWUS20 KWNS 021743

SEL8

SPC WW 021743

MTZ000-SDZ000-WYZ000-030100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 538

NWS STORM PREDICTION CENTER NORMAN OK

1145 AM MDT THU JUL 2 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST MONTANA

       WESTERN SOUTH DAKOTA

       NORTHEAST WYOMING



EFFECTIVE THIS THURSDAY MORNING AND EVENING FROM 1145 AM UNTIL

700 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 50 MILES SOUTHWEST OF

RAPID CITY SOUTH DAKOTA TO 60 MILES NORTH NORTHWEST OF MILES CITY

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.



DISCUSSION...THUNDERSTORMS ARE ALREADY INCREASING ACROSS S-CENTRAL

MT/N-CENTRAL WY AND THE BLACK HILLS OF SD LATE THIS MORNING.  THESE

WILL LIKELY CONTINUE INCREASING/INTENSIFYING THROUGH THE DAY AHEAD

OF SHORTWAVE TROUGH CRESTING UPPER RIDGE AS AIR MASS DESTABILIZES

OVER THE PLAINS.  MODEST WLY FLOW ALOFT WILL SUSTAIN SUFFICIENT DEEP

LAYER SHEAR FOR SUPERCELLS...ALONG WITH PERSISTENT CLUSTERS/SMALL

LINES OF STORMS SPREADING ESEWD.  LARGE HAIL AND DAMAGING WINDS WILL

BE PRIMARY SEVERE THREATS...ALTHOUGH AN ISOLATED TORNADO COULD OCCUR

WITH ANY PERSISTENT SUPERCELL.



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 28015.





...EVANS

