

821 

WWUS20 KWNS 201023

SEL6

SPC WW 201023

MNZ000-NDZ000-201800-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 666

NWS STORM PREDICTION CENTER NORMAN OK

525 AM CDT WED JUL 20 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHWEST MINNESOTA

       NORTHERN AND CENTRAL NORTH DAKOTA



EFFECTIVE THIS WEDNESDAY MORNING AND AFTERNOON FROM 525 AM UNTIL

100 PM CDT.



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 60

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 70 MILES WEST

NORTHWEST OF GARRISON NORTH DAKOTA TO 25 MILES EAST OF THIEF

RIVER FALLS MINNESOTA.  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.



DISCUSSION...TSTMS ARE INCREASING IN COVERAGE AND INTENSITY THIS

MORNING WITHIN LOW-LEVEL WAA REGIME WHICH HAS BECOME ESTABLISHED IN

ADVANCE OF COLD FRONT MOVING INTO WRN ND.  AMBIENT...PRE-FRONTAL AIR

MASS IS VERY MOIST WITH DEWPOINTS IN THE 70S...AND STEEP MIDLEVEL

LAPSE RATES ARE CONTRIBUTING TO AN EXTREMELY UNSTABLE ENVIRONMENT

WITH MUCAPE ESTIMATED TO BE UPWARDS OF 4000-5000 J/KG.  WHEN COUPLED

WITH AROUND 40 KT OF DEEP SWLY SHEAR...SETUP WILL FAVOR THE

DEVELOPMENT OF SUPERCELLS AND BOWING STRUCTURES WITH THE PRIMARY

HAZARDS BEING DAMAGING WINDS AND HAIL.



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 26030.





...MEAD

