WATCHES: Tornado Watch Number 637

WWUS20 KWNS 310444
SEL7
SPC WW 310444
IAZ000-MNZ000-SDZ000-311200-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 637
NWS STORM PREDICTION CENTER NORMAN OK
1145 PM CDT MON AUG 30 2010

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

FAR NORTHWEST IOWA
SOUTHWEST INTO CENTRAL MINNESOTA
SOUTHEAST SOUTH DAKOTA

EFFECTIVE THIS MONDAY NIGHT AND TUESDAY MORNING FROM 1145 PM
UNTIL 700 AM CDT.

TORNADOES...HAIL TO 1.5 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 60 STATUTE
MILES EAST AND WEST OF A LINE FROM 5 MILES SOUTH OF YANKTON SOUTH
DAKOTA TO 85 MILES NORTHEAST OF REDWOOD FALLS MINNESOTA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU7).

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.

OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES TORNADO
WATCH NUMBER 636. WATCH NUMBER 636 WILL NOT BE IN EFFECT AFTER
1145 PM CDT.

DISCUSSION...FORCED BAND OF TSTMS ALONG COLD FRONT AND A DOWNSTREAM
CORRIDOR OF MORE DISCRETE STORM ACTIVITY ARE EXPECTED TO SPREAD NEWD
ACROSS AREA OVERNIGHT IN CONCERT WITH A MIDLEVEL VORTICITY MAXIMUM
TRANSLATING NEWD THROUGH NERN SD. ANOMALOUS INFLOW AIR MASS EXISTS
FOR THE TIME OF YEAR...CHARACTERIZED BY 70 F BOUNDARY LAYER DEW
POINTS AND 0-1 KM SRH OF 400-500 J/KG. THUS...DESPITE THE PRESENCE
OF MODEST CONVECTIVE INHIBITION...THE OVERALL SETUP WILL REMAIN
FAVORABLE FOR EMBEDDED BOWING AND SUPERCELL STRUCTURES WITH THE
THREAT FOR A COUPLE OF TORNADOES AND DAMAGING WINDS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 24035.

...MEAD

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