Severe Thunderstorm Watch 421

Issued

Jun 2, 2011, 7:22 PM CDT (00:22 UTC)

Expired

Jun 3, 2011, 3:00 AM CDT

In force

8 hr

Issued by

the Storm Prediction Center

Largest hail expected

2 in

Strongest gust expected

60 kt

The Rapid City radar (KUDX), 120 km from the middle of the area, began a volume at 00:23 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

20%

One or more EF2 to EF5 tornadoes

5%

Ten or more severe wind reports

30%

One or more gusts of 65 knots or more

30%

Ten or more severe hail reports

40%

One or more hailstones of 2 inches or more

40%

Six or more combined severe hail and wind reports

80%

• Mesoscale Discussion 1071Jun 2, 5:37 PM CDT
• Mesoscale Discussion 1073Jun 2, 6:03 PM CDT
• Mesoscale Discussion 1076Jun 2, 10:07 PM CDT
• Mesoscale Discussion 1077Jun 3, 1:11 AM CDT

913 
WWUS20 KWNS 030023
SEL1
SPC WW 030023
NDZ000-SDZ000-030800-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 421
NWS STORM PREDICTION CENTER NORMAN OK
720 PM CDT THU JUN 2 2011

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

       CENTRAL NORTH DAKOTA
       WESTERN AND CENTRAL SOUTH DAKOTA

EFFECTIVE THIS THURSDAY NIGHT AND FRIDAY MORNING FROM 720 PM
UNTIL 300 AM CDT.

HAIL TO 2 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 60
STATUTE MILES EAST AND WEST OF A LINE FROM 80 MILES SOUTH
SOUTHWEST OF PHILIP SOUTH DAKOTA TO 50 MILES NORTHEAST OF
BISMARCK NORTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE
THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).

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 419...WW 420...

DISCUSSION...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY THIS EVENING ALONG COLD FRONT PUSHING EWD ACROSS THE WATCH
AREA.  00Z RAP/BIS SOUNDINGS SHOWED THE PRESENCE OF A VERY STEEP
LAPSE RATE ENVIRONMENT...WHICH WHEN COUPLED WITH MODEST BOUNDARY
LAYER MOISTURE...WAS RESULTING IN MLCAPE VALUES OF 2000-3000 J/KG.
MOREOVER...THESE OBSERVATIONS SAMPLED THE PRESENCE OF 30-50 KT SWLY
WINDS ABOVE 3 KM AGL WHICH WILL FAVOR ORGANIZED STORM MODES
INCLUDING SUPERCELLS AND BOWING STRUCTURES.  THOUGH A BRIEF TORNADO
IS POSSIBLE...DAMAGING WINDS AND LARGE HAIL APPEAR TO BE THE PRIMARY
HAZARDS.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM
MOTION VECTOR 24030.


...MEAD

Severe Thunderstorm Watches in South Dakota, 2011Severe Thunderstorm Watches in North Dakota, 2011Every severe thunderstorm 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.