Alert archive / Nebraska / Tornado Watches in 2011

Tornado Watch 632

July 11, 20115 counties in Nebraska; Bennett County, Fall River County, South Dakota; Niobrara County, Wyoming

The Storm Prediction Center issued this tornado watch at Jul 11, 2011, 4:06 PM MDT for 5 counties in Nebraska; Bennett County, Fall River County, South Dakota; Niobrara County, Wyoming. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued
Jul 11, 2011, 4:06 PM MDT (22:06 UTC)
Expired
Jul 11, 2011, 9:00 PM MDT
In force
5 hr
Issued by
the Storm Prediction Center
Largest hail expected
2.5 in
Strongest gust expected
60 kt

Counties Box Butte County, NE, Cherry County, NE, Dawes County, NE, Sheridan County, NE, Sioux County, NE, Bennett County, SD, Fall River County, SD, Niobrara County, WY

The radar

The Rapid City radar (KUDX), 154 km from the middle of the area, began a volume at 22:07 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

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
40%
One or more hailstones of 2 inches or more
50%
Six or more combined severe hail and wind reports
70%

Warnings issued inside it

12 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Jul 11, 4:12 PM MDTSevere Thunderstorm WarningLBFSheridan63 min
Jul 11, 4:14 PM MDTSevere Thunderstorm WarningUNRFall River61 min
Jul 11, 4:24 PM MDTSevere Thunderstorm WarningCYSSioux51 min
Jul 11, 5:08 PM MDTSevere Thunderstorm WarningCYSDawes, Sioux26 min
Jul 11, 5:14 PM MDTSevere Thunderstorm WarningLBFCherry, Sheridan61 min
Jul 11, 6:14 PM MDTSevere Thunderstorm WarningLBFCherry, Sheridan61 min
Jul 11, 6:19 PM MDTTornado WarningLBFCherry41 min
Jul 11, 7:02 PM MDTTornado WarningLBFCherry41 min
Jul 11, 7:12 PM MDTSevere Thunderstorm WarningLBFCherry63 min
Jul 11, 7:17 PM MDTTornado WarningLBFCherry28 min
Jul 11, 7:55 PM MDTSevere Thunderstorm WarningLBFCherry50 min
Jul 11, 8:40 PM MDTSevere Thunderstorm WarningLBFCherry, Hooker, Thomas65 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Rapid City, SD (KUNR), launched 12:00Z, 10.1 hours before the alert went out and 147 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Rapid City, SD at 12:00Z on 2011-07-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Rapid City, SD at 12:00Z on 2011-07-11The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -49 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1860 m above ground
0-6 km bulk shear
23 kt
0-1 km storm-relative helicity
-49 m²/s²
0-3 km storm-relative helicity
74 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

038 
WWUS20 KWNS 112206
SEL2
SPC WW 112206
NEZ000-SDZ000-WYZ000-120300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 632
NWS STORM PREDICTION CENTER NORMAN OK
405 PM MDT MON JUL 11 2011

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

       NORTHWEST NEBRASKA
       SOUTHWEST SOUTH DAKOTA
       EAST-CENTRAL WYOMING

EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 405 PM UNTIL 900
PM 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 115 STATUTE
MILES EAST AND WEST OF A LINE FROM 30 MILES NORTH NORTHEAST OF
CHADRON NEBRASKA TO 20 MILES EAST OF ALLIANCE NEBRASKA.  FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU2).

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 628...WW 629...WW
630...WW 631...

DISCUSSION...MULTIPLE SUPERCELLS HAVE FORMED ALONG A WNW-ESE
ORIENTED BOUNDARY WHERE DEWPOINTS HAVE REMAINED IN THE 60S.
MOREOVER...LOCALLY BACKED SURFACE WINDS ARE RESULTING IN A CORRIDOR
OF ENHANCED LOW-LEVEL SHEAR.  AS SUCH...ONGOING STORMS WILL BE
CAPABLE OF A COUPLE TORNADOES IN ADDITION TO LARGE HAIL.

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
550. MEAN STORM MOTION VECTOR 28020.


...MEAD

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 10, 6:21 PM MDTMesoscale DiscussionSPCAdams, Blaine, Brown, Buffalo, Chase, Custer and 29 more84 min
Jul 10, 6:24 PM MDTSevere Thunderstorm WatchSPCAdams, Blaine, Boyd, Brown, Buffalo, Chase and 38 more6 hr
Jul 10, 9:27 PM MDTMesoscale DiscussionSPCAntelope, Boone, Buffalo, Burt, Butler, Cedar and 27 more63 min
Jul 10, 9:57 PM MDTSevere Thunderstorm WatchSPCAntelope, Boone, Burt, Butler, Cedar, Colfax and 14 more4 hr
Jul 10, 10:56 PM MDTSevere Thunderstorm WatchSPCDakota, Dixon4 hr
Jul 11, 1:50 PM MDTMesoscale DiscussionSPCArthur, Banner, Box Butte, Cheyenne, Dawes, Deuel and 8 more85 min
Jul 11, 2:07 PM MDTSevere Thunderstorm WatchSPCBanner, Box Butte, Cheyenne, Dawes, Deuel, Garden and 5 more7 hr
Jul 11, 4:01 PM MDTMesoscale DiscussionSPCCherry, Dawes, Sheridan29 min

Nearby

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

Sources

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.