WATCHES: Severe Thunderstorm Watch Number 410

WWUS20 KWNS 112156
SEL0
SPC WW 112156
MTZ000-NDZ000-SDZ000-120500-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 410
NWS STORM PREDICTION CENTER NORMAN OK
450 PM CDT THU JUL 11 2013

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF
FAR EASTERN MONTANA
WESTERN NORTH DAKOTA
NORTHWEST SOUTH DAKOTA

* EFFECTIVE THIS THURSDAY AFTERNOON FROM 450 PM UNTIL MIDNIGHT
CDT.

* PRIMARY THREATS INCLUDE...
SEVERAL DAMAGING WIND GUSTS WITH A FEW SIGNIFICANT GUSTS TO 75
MPH POSSIBLE
SEVERAL LARGE HAIL EVENTS WITH A FEW VERY LARGE HAIL EVENTS TO 2
INCHES IN DIAMETER POSSIBLE
A FEW TORNADOES POSSIBLE

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 75
STATUTE MILES EAST AND WEST OF A LINE FROM 65 MILES NORTH
NORTHEAST OF WILLISTON NORTH DAKOTA TO 40 MILES SOUTH OF BUFFALO
SOUTH DAKOTA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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...TSTM DEVELOPMENT IS UNDERWAY OVER ERN MT AT THE
INTERSECTION OF AN EWD-MOVING COLD FRONT AND A QUASI-STATIONARY
BOUNDARY WHERE A LOCAL EROSION OF THE CAP HAS OCCURRED. THE
PRESENCE OF STEEP LAPSE RATES AND A RELATIVELY MOIST PBL --NAMELY
ALONG AND E OF THE QUASI-STATIONARY BOUNDARY-- HAVE CONTRIBUTED TO A
MODERATE TO STRONGLY UNSTABLE AIR MASS WITH MLCAPE VALUES OF
2000-4000 J/KG. WHEN COUPLED WITH A VERTICALLY VEERING WIND PROFILE
WITH 35-45 KT OF EFFECTIVE BULK SHEAR...THE SETUP WILL BE SUPPORTIVE
OF SUPERCELLS AS THE INITIAL STORM MODE WITH A RISK FOR PRIMARILY
LARGE HAIL AND DAMAGING WIND GUSTS. THE GREATEST RISK FOR A TORNADO
WILL EXIST WITH ANY MATURE SUPERCELLS WHICH CROSS THE NNW-SSE
ORIENTED STATIONARY FRONT INTO WRN ND WHERE A LOWER LCL-STRONGER
LOW-LEVEL SHEAR ENVIRONMENT EXISTS. OTHERWISE...EXPECT UPSCALE
GROWTH OF STORMS INTO CLUSTERS WITH A DAMAGING WIND AND HAIL THREAT
SPREADING EWD ACROSS WRN ND THIS EVENING INTO TONIGHT.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 65
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM
MOTION VECTOR 24020.


...MEAD

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