

000 

WWUS20 KWNS 262208

SEL3

SPC WW 262208

MNZ000-NDZ000-270400-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 653

NWS STORM PREDICTION CENTER NORMAN OK

505 PM CDT SUN AUG 26 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       NORTHWEST MINNESOTA

       EASTERN NORTH DAKOTA



EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 505 PM UNTIL

1100 PM CDT.



TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 80 STATUTE

MILES EAST AND WEST OF A LINE FROM 25 MILES NORTHEAST OF HALLOCK

MINNESOTA TO 70 MILES SOUTH SOUTHWEST OF JAMESTOWN NORTH DAKOTA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU3).



REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND 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.



DISCUSSION...VISIBLE SATELLITE IMAGERY SHOWS GROWING CUMULUS ALONG

THE SURFACE BOUNDARY FROM BIS TO DVL...AND MODIFIED SOUNDINGS

SUGGEST THAT THE CAP IS BECOMING SUFFICIENTLY WEAK TO ALLOW

THUNDERSTORM DEVELOPMENT.  STRONG INSTABILITY /MLCAPE IN EXCESS OF

3000 J/KG/ IS PRESENT E OF THE BOUNDARY IN ND...WHILE DEEP LAYER

VERTICAL SHEAR IS FAVORABLE FOR SUPERCELLS.  THE INITIAL STORM

DEVELOPMENT SHOULD BE DISCRETE SUPERCELLS WITH THE THREAT FOR VERY

LARGE HAIL AND DAMAGING WINDS.  A COUPLE OF TORNADOES WILL BE

POSSIBLE THIS EVENING GIVEN THE MODEST LOW-LEVEL SHEAR AND BOUNDARY

LAYER DEWPOINTS NEAR 70 F.  BY EARLY TONIGHT...STORMS MAY GROW INTO

LINE SEGMENTS/MIXED MODES ALONG THE FRONT AS A SHORTWAVE TROUGH

MOVES EWD ALONG THE ND/CANADIAN BORDER...WITH A CONTINUED THREAT FOR

DAMAGING WINDS AND HAIL.



AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

550. MEAN STORM MOTION VECTOR 28020.





...THOMPSON

