SEL0
SPC WW 221612
IAZ000-MNZ000-NEZ000-SDZ000-222300-
URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 680
NWS STORM PREDICTION CENTER NORMAN OK
1110 AM CDT WED SEP 22 2010
THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF
NORTHWEST IOWA
SOUTHWEST MINNESOTA
NORTHEAST NEBRASKA
SOUTHEAST SOUTH DAKOTA
EFFECTIVE THIS WEDNESDAY MORNING AND EVENING FROM 1110 AM UNTIL
600 PM CDT.
HAIL TO 2.5 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 65
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 45 MILES WEST OF
YANKTON SOUTH DAKOTA TO 25 MILES EAST NORTHEAST OF FAIRMONT
MINNESOTA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).
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...THE COMBINATION OF ENEWD-PROGRESSING MIDLEVEL IMPULSE
AND AN INFLUX OF A WARM/MOIST AIR MASS ALONG 40-50 KT LLJ SHOULD
SUSTAIN ELEVATED SEVERE TSTMS THROUGH THE DAY TO THE N OF SURFACE
WARM FRONT. STEEP MIDLEVEL LAPSE RATES...MUCAPE OF 2000-3000 J/KG
AND 45-55 KT OF EFFECTIVE BULK SHEAR WILL BE MORE THAN SUFFICIENT
FOR SUPERCELLS CAPABLE OF MAINLY LARGE HAIL.
AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 25030.
...MEAD
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