

000 

WWUS20 KWNS 212215

SEL8

SPC WW 212215

MNZ000-NDZ000-220500-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 158

NWS STORM PREDICTION CENTER NORMAN OK

515 PM CDT SAT APR 21 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHWESTERN MINNESOTA

       SOUTHEASTERN NORTH DAKOTA



EFFECTIVE THIS SATURDAY AFTERNOON FROM 515 PM UNTIL MIDNIGHT 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 EAST AND WEST OF A LINE FROM 65 MILES SOUTH

SOUTHWEST OF FARGO NORTH DAKOTA TO 50 MILES NORTHWEST OF BEMIDJI

MINNESOTA.  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.



OTHER WATCH INFORMATION...CONTINUE...WW 154...WW 155...WW

156...WW 157...



DISCUSSION...SURFACE COLD FRONT AND OUTFLOW BOUNDARIES FROM EARLIER

STORMS WILL MAINTAIN FOCUS FOR STRONG TO SEVERE THUNDERSTORM

DEVELOPMENT THIS EVENING.  AIR MASS REMAINS MODERATELY UNSTABLE WITH

EFFECTIVE BULK SHEAR FROM 35-45 KT SUPPORTING SUPERCELLS.  PRIMARY

THREATS ARE EXPECTED TO BE LARGE HAIL AND DAMAGING WINDS.



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 24020.





...EVANS

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