Alert archive / Nebraska / Tornado Watches in 2010

Tornado Watch 200

May 21, 20104 states

The Storm Prediction Center issued this tornado watch at May 21, 2010, 2:26 PM MDT for 4 states. It was in force for 8 hr.

The area

The outline as issued.

The facts

Issued
May 21, 2010, 2:26 PM MDT (20:26 UTC)
Expired
May 21, 2010, 10:00 PM MDT
In force
8 hr
Issued by
the Storm Prediction Center
Largest hail expected
2 in
Strongest gust expected
60 kt

Counties Larimer County, CO, Logan County, CO, Morgan County, CO, Weld County, CO, Banner County, NE, Box Butte County, NE, Cheyenne County, NE, Dawes County, NE, Kimball County, NE, Morrill County, NE, Scotts Bluff County, NE, Sioux County, NE, Custer County, SD, Fall River County, SD, Converse County, WY, Goshen County, WY, Laramie County, WY, Niobrara County, WY, Platte County, WY, Weston County, WY

The radar

The Cheyenne radar (KCYS), 125 km from the middle of the area, began a volume at 20:26 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
30%
Six or more combined severe hail and wind reports
70%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
May 21, 4:42 PM MDTSevere Thunderstorm WarningCYSGoshen, Niobrara, Platte29 min
May 21, 5:00 PM MDTSevere Thunderstorm WarningCYSNiobrara60 min
May 21, 5:06 PM MDTTornado WarningCYSGoshen, Niobrara, Platte54 min
May 21, 5:45 PM MDTSevere Thunderstorm WarningUNRCuster, Fall River60 min
May 21, 5:55 PM MDTTornado WarningCYSSioux65 min
May 21, 6:08 PM MDTSevere Thunderstorm WarningCYSNiobrara67 min
May 21, 6:40 PM MDTSevere Thunderstorm WarningUNRCuster, Pennington28 min
May 21, 6:52 PM MDTTornado WarningCYSDawes, Sioux42 min
May 21, 7:11 PM MDTSevere Thunderstorm WarningUNRCuster33 min
May 21, 8:45 PM MDTSevere Thunderstorm WarningCYSConverse, Niobrara, Platte45 min
May 21, 8:49 PM MDTSevere Thunderstorm WarningCYSNiobrara26 min
May 21, 9:36 PM MDTSevere Thunderstorm WarningCYSSioux39 min
May 21, 9:40 PM MDTSevere Thunderstorm WarningCYSGoshen, Niobrara, Platte28 min
May 21, 9:59 PM MDTSevere Thunderstorm WarningUNRCuster, Fall River61 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, 8.4 hours before the alert went out and 242 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 2010-05-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 6 joules per kilogram.LCLEL10008507005003002001001 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 2010-05-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 21 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
6 J/kg
Mixed-layer CIN
0 J/kg
Mixed-layer LCL
504 m above ground
0-6 km bulk shear
64 kt
0-1 km storm-relative helicity
21 m²/s²
0-3 km storm-relative helicity
178 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 21, 1:30 PM MDTMesoscale DiscussionSPCAdams, Arapahoe, Boulder, Broomfield, Denver, Larimer and 5 more60 min
May 21, 5:12 PM MDTMesoscale DiscussionSPCLarimer, Weld2 hr

Nearby

Tornado Watches in Nebraska, 2010Tornado Watches in Wyoming, 2010Tornado Watches in Colorado, 2010Every tornado watch in 2010

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.