Alert archive / Nebraska / Severe Thunderstorm Watches in 2011

Severe Thunderstorm Watch 404

May 30, 20114 counties in Colorado; 15 counties in Nebraska

The Storm Prediction Center issued this severe thunderstorm watch at May 30, 2011, 3:45 PM MDT for 4 counties in Colorado; 15 counties in Nebraska. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: May 30, 2011, 3:45 PM MDT (21:45 UTC)
Expired: May 30, 2011, 7:10 PM MDT
In force: 3 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 60 kt

Counties Logan County, CO, Phillips County, CO, Sedgwick County, CO, Yuma County, CO, Arthur County, NE, Chase County, NE, Cherry County, NE, Deuel County, NE, Dundy County, NE, Garden County, NE, Grant County, NE, Hayes County, NE, Hooker County, NE, Keith County, NE, Keya Paha County, NE, Logan County, NE, McPherson County, NE, Perkins County, NE, Thomas County, NE

The radar

The North Platte radar (KLNX), 136 km from the middle of the area, began a volume at 21:47 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: 10%
One or more EF2 to EF5 tornadoes: 2%
Ten or more severe wind reports: 50%
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: 20%
Six or more combined severe hail and wind reports: 70%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
May 30, 4:01 PM MDT	Severe Thunderstorm Warning	LBF	Blaine, Custer, Logan	44 min
May 30, 4:50 PM MDT	Severe Thunderstorm Warning	LBF	Arthur, Garden, Grant, Sheridan	40 min
May 30, 5:04 PM MDT	Severe Thunderstorm Warning	BOU	Sedgwick	22 min
May 30, 5:25 PM MDT	Severe Thunderstorm Warning	LBF	Cherry, Sheridan	50 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

N. Platte/Lee Bi, NE (KLBF), launched 12:00Z, 9.8 hours before the alert went out and 98 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 1099 J/kg
Mixed-layer CIN: -360 J/kg
Mixed-layer LCL: 2078 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 296 m²/s²
0-3 km storm-relative helicity: 302 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.

890 
WWUS20 KWNS 302142
SEL4
SPC WW 302142
COZ000-NEZ000-310300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 404
NWS STORM PREDICTION CENTER NORMAN OK
445 PM CDT MON MAY 30 2011

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

       PARTS OF NORTHEAST COLORADO
       PARTS OF WESTERN AND SOUTHWESTERN NEBRASKA

EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 445 PM UNTIL
1000 PM CDT.

HAIL TO 1.5 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 55 MILES EAST
SOUTHEAST OF AKRON COLORADO TO 10 MILES NORTH NORTHEAST OF
VALENTINE NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE
THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).

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 402...WW 403...

DISCUSSION...STRONG FRONTAL PUSH ASSOCIATED WITH EJECTING UPPER
TROUGH EXPECTED TO DEVELOP STRONG/SEVERE THUNDERSTORMS ACROSS THE
WATCH.  WITH BRN SHEAR OF 60-70 KTS...STEEP MID LEVEL LAPSE RATES
AND MLCAPE AOA 1000 J/KG...DAMAGING WINDS EXPECTED TO BE THE PRIMARY
THREAT AS THUNDERSTORMS EVOLVE INTO A LINE.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 23040.


...HALES

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 30, 1:19 PM MDT	Mesoscale Discussion	SPC	Logan, Phillips, Sedgwick, Weld	56 min
May 30, 4:47 PM MDT	Mesoscale Discussion	SPC	Logan, Phillips, Sedgwick, Yuma	58 min
May 29, 6:16 PM MDT	Tornado Watch	SPC	Cass, Douglas, Fillmore, Gage, Jefferson, Johnson and 11 more	4 hr
May 29, 8:24 PM MDT	Mesoscale Discussion	SPC	Antelope, Boone, Burt, Butler, Cass, Cedar and 31 more	96 min
May 30, 12:40 PM MDT	Mesoscale Discussion	SPC	Antelope, Blaine, Boone, Boyd, Buffalo, Cedar and 16 more	95 min
May 30, 1:08 PM MDT	Tornado Watch	SPC	Adams, Antelope, Blaine, Boone, Boyd, Brown and 29 more	7 hr
May 30, 5:17 PM MDT	Mesoscale Discussion	SPC	Adams, Antelope, Blaine, Boone, Boyd, Brown and 25 more	118 min

Nearby

Severe Thunderstorm Watches in Nebraska, 2011 Severe Thunderstorm Watches in Colorado, 2011 Every severe thunderstorm 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.