Tornado Watch 438

Issued

Jun 21, 2007, 3:37 PM MDT (21:37 UTC)

Expired

Jun 21, 2007, 11:00 PM MDT

In force

7 hr

Issued by

the Storm Prediction Center

Largest hail expected

4 in

Strongest gust expected

70 kt

The Rapid City radar (KUDX), 112 km from the middle of the area, began a volume at 21:37 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

50%

One or more gusts of 65 knots or more

30%

Ten or more severe hail reports

80%

One or more hailstones of 2 inches or more

50%

Six or more combined severe hail and wind reports

70%

• Mesoscale Discussion 1238Jun 21, 1:13 PM MDT
• Mesoscale Discussion 1239Jun 21, 1:43 PM MDT
• Mesoscale Discussion 1242Jun 21, 2:40 PM MDT
• Mesoscale Discussion 1245Jun 21, 5:33 PM MDT
• Mesoscale Discussion 1248Jun 21, 8:45 PM MDT

000
WWUS20 KWNS 212137
SEL8  
SPC WW 212137
NEZ000-SDZ000-220500-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 438
NWS STORM PREDICTION CENTER NORMAN OK
340 PM MDT THU JUN 21 2007

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

       MUCH OF WESTERN NEBRASKA
       MUCH OF WESTERN SOUTH DAKOTA

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 340 PM UNTIL
1100 PM MDT.

TORNADOES...HAIL TO 4 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 95 STATUTE
MILES EAST AND WEST OF A LINE FROM 80 MILES NORTH NORTHEAST OF
RAPID CITY SOUTH DAKOTA TO 45 MILES SOUTH OF NORTH PLATTE
NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).

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.

OTHER WATCH INFORMATION...CONTINUE...WW 434...WW 435...WW
436...WW 437...

DISCUSSION...VERY TO EXTREMELY UNSTABLE AIR MASS ACROSS WATCH AREA. 
STORMS ARE RAPIDLY DEVELOPING ON WRN EDGE OF MOSTLY STILL CAPPED AIR
MASS.  WITH 30-40 KT OF SHEAR AND 3000PLUS J/KG CAPE...SUPERCELLS
WILL QUICKLY FORM WITH VERY LARGE HAIL AND TORNADOES LIKELY.  STORMS
WILL EVOLVE INTO CLUSTERS BY EVENING WITH INCREASING WIND DAMAGE
POTENTIAL AS THEY DEVELOP COLD POOLS AND SPREAD SEWD.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 4 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
550. MEAN STORM MOTION VECTOR 30020.


...HALES

Tornado Watches in Nebraska, 2007Tornado Watches in South Dakota, 2007Every tornado watch in 2007

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.