Severe Thunderstorm Watch 821

Issued

Aug 11, 2008, 1:58 PM MDT (19:58 UTC)

Expired

Aug 11, 2008, 9:00 PM MDT

In force

7 hr

Issued by

the Storm Prediction Center

Largest hail expected

2 in

Strongest gust expected

60 kt

The North Platte radar (KLNX), 84 km from the middle of the area, began a volume at 20:01 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

5%

One or more EF2 to EF5 tornadoes

2%

Ten or more severe wind reports

40%

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

20%

Six or more combined severe hail and wind reports

80%

• Mesoscale Discussion 2071Aug 11, 12:56 PM MDT
• Mesoscale Discussion 2073Aug 11, 4:04 PM MDT
• Mesoscale Discussion 2074Aug 11, 6:47 PM MDT

000
WWUS20 KWNS 112000
SEL1  
SPC WW 112000
NEZ000-SDZ000-120300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 821
NWS STORM PREDICTION CENTER NORMAN OK
300 PM CDT MON AUG 11 2008

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

       CENTRAL NEBRASKA
       CENTRAL SOUTH DAKOTA

EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 300 PM UNTIL
1000 PM 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 70
STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES SOUTHWEST OF
NORTH PLATTE NEBRASKA TO 50 MILES WEST NORTHWEST OF ABERDEEN
SOUTH 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.

DISCUSSION...THUNDERSTORM INCREASING LATE THIS AFTERNOON AHEAD OF
APPROACHING SHORTWAVE TROUGH AND ASSOCIATED MID LEVEL SPEED MAX. 
PRIMARY DEVELOPMENT SHOULD OCCUR ALONG AND EAST OF SURFACE FRONT
EXTENDING ACROSS CENTRAL NEB/SD...WHERE AXIS OF MODERATE INSTABILITY
IS IN PLACE.  SHEAR WILL BE MODERATE...BUT STILL SUFFICIENT FOR
ORGANIZED LINES/CLUSTERS AND BRIEF-LIVED SUPERCELLS.  LARGE HAIL
WILL BE PRIMARY SEVERE THREAT...ESPECIALLY WITH INITIAL DEVELOPMENT
GIVEN THE RELATIVELY COLD AIR ALOFT...ALTHOUGH ISOLATED WIND DAMAGE
IS ALSO EXPECTED.  SHOULD ONE OR MORE LINEAR CLUSTERS EVOLVE THIS
EVENING...WIND DAMAGE POTENTIAL WILL LIKEWISE INCREASE.

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 500. MEAN STORM
MOTION VECTOR 28020.


...EVANS

Severe Thunderstorm Watches in South Dakota, 2008Severe Thunderstorm Watches in Nebraska, 2008Every severe thunderstorm watch in 2008

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.