WATCHES: Severe Thunderstorm Watch Number 686

WWUS20 KWNS 092047
SEL6
SPC WW 092047
IAZ000-KSZ000-MOZ000-NEZ000-100400-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 686
NWS STORM PREDICTION CENTER NORMAN OK
345 PM CDT SUN AUG 9 2009

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

SOUTHWEST AND CENTRAL IOWA
NORTHEAST KANSAS
NORTHWEST MISSOURI
SOUTHEAST NEBRASKA

EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 345 PM UNTIL
1100 PM CDT.

HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 55
STATUTE MILES EITHER SIDE OF A LINE FROM 50 MILES SOUTHWEST OF
BEATRICE NEBRASKA TO 50 MILES NORTH OF OTTUMWA IOWA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU6).

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 682...WW 683...WW
684...WW 685...

DISCUSSION...INITIALLY ELEVATED CONVECTION IN A BAND FROM CENTRAL KS
INTO SWRN IA IS BEGINNING TO INTENSIFY BASED ON REMOTE SENSING DATA.
ACTIVITY IS EXPECTED TO FURTHER INTENSIFY WITH INCREASING
LIKELIHOOD OF A FEW SURFACE-BASED STORMS DEVELOPING WITHIN VERY
UNSTABLE AIR MASS /MLCAPE 2000-3000 J PER KG/. THE BAND IS ALONG
THE SERN EDGE OF STRONGER FLOW ALOFT WITH SUFFICIENT VERTICAL SHEAR
TO PROMOTE DEVELOPMENT OF SEVERE STORMS INCLUDING SUPERCELLS.
THREAT FOR DAMAGING WINDS AND LARGE HAIL WILL INCREASE THROUGH THE
EVENING HOURS AS ACTIVITY MOVES NEWD/ENEWD 30-35 KT.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM
MOTION VECTOR 24035.

...WEISS

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