Tornado Watch 766

Issued

Aug 11, 2011, 3:05 PM CDT (20:05 UTC)

In effect from

Aug 11, 2011, 3:10 PM CDT

Expired

Aug 11, 2011, 8:20 PM CDT

In force

5 hr

Issued by

the Storm Prediction Center

Largest hail expected

3 in

Strongest gust expected

65 kt

The Rapid City radar (KUDX), 165 km from the middle of the area, began a volume at 20:05 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

Two or more tornadoes

50%

One or more EF2 to EF5 tornadoes

10%

Ten or more severe wind reports

50%

One or more gusts of 65 knots or more

30%

Ten or more severe hail reports

50%

One or more hailstones of 2 inches or more

30%

Six or more combined severe hail and wind reports

80%

• Mesoscale Discussion 1943Aug 11, 1:49 PM CDT
• Mesoscale Discussion 1948Aug 11, 6:38 PM CDT

535 
WWUS20 KWNS 112009
SEL6
SPC WW 112009
SDZ000-120300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 766
NWS STORM PREDICTION CENTER NORMAN OK
310 PM CDT THU AUG 11 2011

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

       SOUTH DAKOTA

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 310 PM UNTIL
1000 PM CDT.

TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 75 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 140 STATUTE
MILES EAST AND WEST OF A LINE FROM 75 MILES NORTH NORTHEAST OF
PIERRE SOUTH DAKOTA TO 75 MILES SOUTH SOUTHEAST OF PHILIP SOUTH
DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED
WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).

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...STRONG STORMS HAVE DEVELOPED OVER WEST CENTRAL SD...AND
ADDITIONAL CONVECTION IS LIKELY TO DEVELOP AND INTENSIFY THIS
AFTERNOON AS A SHORT WAVE TROUGH MOVES EWD FROM MT.  IN RESPONSE TO
THE APPROACHING TROUGH...THE LOW LEVEL JET IS BEGINNING TO
STRENGTHEN /30 KT AT KLBF RDA/ AND THIS IS FORECAST BY MODELS TO
LIFT NWD INTO SRN SD BY LATE THIS AFTERNOON.  WINDS WILL INCREASE
AND VEER WITH HEIGHT PROVIDING A FAVORABLE KINEMATIC ENVIRONMENT FOR
SEVERE STORMS INCLUDING SUPERCELLS.  STRONGER CELLS WILL HAVE
POTENTIAL TO PRODUCE VERY LARGE HAIL...DAMAGING WIND...AND A FEW
TORNADOES.  THE CONVECTION IS EXPECTED TO GROW UPSCALE AND FORM INTO
A SEWD MOVING BOWING QLCS BY THIS EVENING WITH AN INCREASING THREAT
FOR DAMAGING WIND GUSTS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 65 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
550. MEAN STORM MOTION VECTOR 28025.


...WEISS

Tornado Watches in South Dakota, 2011Every tornado watch in 2011

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.