Thursday, July 23, 2009

WATCHES: Severe Thunderstorm Watch Number 615

WWUS20 KWNS 232152
SEL5
SPC WW 232152
MNZ000-NDZ000-240500-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 615
NWS STORM PREDICTION CENTER NORMAN OK
450 PM CDT THU JUL 23 2009

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

NORTHWEST MINNESOTA
EASTERN NORTH DAKOTA

EFFECTIVE THIS THURSDAY AFTERNOON FROM 450 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 115
STATUTE MILES EAST AND WEST OF A LINE FROM 15 MILES NORTHWEST OF
HALLOCK MINNESOTA TO 75 MILES SOUTH SOUTHEAST OF JAMESTOWN NORTH
DAKOTA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED
WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).

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 614...

DISCUSSION...THUNDERSTORM DEVELOPMENT IS UNDERWAY ALONG A
PRE-FRONTAL TROUGH IN CENTRAL ND WHERE STRONG SURFACE HEATING HAS
REDUCED CONVECTIVE INHIBITION AND CONTRIBUTED TO MODERATE
INSTABILITY. ADDITIONAL STORMS WILL FORM DURING THE EVENING INTO NE
ND AND NW MN AS A PRONOUNCED MID LEVEL TROUGH DIGS SEWD FROM
MANITOBA. THE COMBINATION OF MODERATE INSTABILITY AND STRONG DEEP
LAYER NWLY SHEAR WILL BE SUPPORTIVE OF BOTH SUPERCELLS AND BOWING
SEGMENTS CAPABLE OF PRODUCING DAMAGING WINDS AND LARGE HAIL THROUGH
EARLY TONIGHT.

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 30030.


...THOMPSON

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