Tornado Watch 706

Issued

Jul 31, 2011, 4:44 PM MDT (22:44 UTC)

Expired

Aug 1, 2011, 12:00 AM MDT

In force

7 hr

Issued by

the Storm Prediction Center

Largest hail expected

2.5 in

Strongest gust expected

60 kt

The Bismarck radar (KBIS), 116 km from the middle of the area, began a volume at 22:46 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

40%

One or more EF2 to EF5 tornadoes

20%

Ten or more severe wind reports

30%

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

50%

Six or more combined severe hail and wind reports

80%

• Mesoscale Discussion 1807Jul 31, 7:16 PM MDT
• Mesoscale Discussion 1808Jul 31, 11:35 PM MDT

922 
WWUS20 KWNS 312246
SEL6
SPC WW 312246
NDZ000-SDZ000-010600-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 706
NWS STORM PREDICTION CENTER NORMAN OK
445 PM MDT SUN JUL 31 2011

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

       SOUTHWEST AND SOUTH CENTRAL NORTH DAKOTA
       NORTHWEST AND NORTH CENTRAL SOUTH DAKOTA

EFFECTIVE THIS SUNDAY AFTERNOON FROM 445 PM UNTIL MIDNIGHT MDT.

TORNADOES...HAIL TO 2.5 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 80 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 25 MILES WEST NORTHWEST OF
BUFFALO SOUTH DAKOTA TO 90 MILES EAST NORTHEAST OF MOBRIDGE 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...THUNDERSTORMS HAVE DEVELOPED OFF THE N SIDE OF THE
BLACK HILLS...AND SOME FORM OF THIS CONVECTION MAY CONTINUE WHILE
SPREADING EWD/NEWD THROUGH THE EVENING.  OTHER ISOLATED STORM
DEVELOPMENT WILL BE POSSIBLE ALONG THE SURFACE WARM FRONT IN ND.
EXTREME INSTABILITY /MLCAPE AOA 5000 J PER KG/ AND EFFECTIVE BULK
SHEAR OF 40-50 KT WILL FAVOR SUPERCELLS CAPABLE OF PRODUCING VERY
LARGE HAIL AND DAMAGING WINDS.  LOW-LEVEL MOISTURE/SHEAR ARE
SUFFICIENT FOR SOME TORNADO RISK ALONG THE WARM FRONT...ESPECIALLY
IN ND.  OTHERWISE...STORM COULD EVENTUALLY EVOLVE INTO A LARGER
CLUSTER BY EARLY TONIGHT...WITH A CONTINUING HAIL/WIND RISK.

AVIATION...TORNADOES AND 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
650. MEAN STORM MOTION VECTOR 26020.


...THOMPSON

Tornado Watches in North Dakota, 2011Tornado 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.