Alert archive / Nebraska / Severe Thunderstorm Watches in 2021

Severe Thunderstorm Watch 114

April 27, 20217 counties in Kansas; 8 counties in Nebraska

The Storm Prediction Center issued this severe thunderstorm watch at Apr 27, 2021, 6:36 PM CDT for 7 counties in Kansas; 8 counties in Nebraska. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued
Apr 27, 2021, 6:36 PM CDT (23:36 UTC)
Expired
Apr 28, 2021, 12:00 AM CDT
In force
5 hr
Issued by
the Storm Prediction Center
Largest hail expected
1.5 in
Strongest gust expected
60 kt

Counties Cheyenne County, KS, Decatur County, KS, Rawlins County, KS, Sheridan County, KS, Sherman County, KS, Thomas County, KS, Wallace County, KS, Chase County, NE, Dundy County, NE, Frontier County, NE, Hayes County, NE, Hitchcock County, NE, Lincoln County, NE, Perkins County, NE, Red Willow County, NE

The radar

The Goodland radar (KGLD), 94 km from the middle of the area, began a volume at 23:36 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
20%
One or more EF2 to EF5 tornadoes
2%
Ten or more severe wind reports
20%
One or more gusts of 65 knots or more
10%
Ten or more severe hail reports
40%
One or more hailstones of 2 inches or more
10%
Six or more combined severe hail and wind reports
60%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Apr 27, 7:23 PM CDTSevere Thunderstorm WarningGLDCheyenne, Sherman67 min
Apr 27, 7:55 PM CDTSevere Thunderstorm WarningGLDCheyenne50 min
Apr 27, 8:21 PM CDTSevere Thunderstorm WarningGLDCheyenne, Rawlins, Sherman39 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, 11.6 hours before the alert went out and 123 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, N. Platte/Lee Bi, NE at 12:00Z on 2021-04-27Temperature 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, N. Platte/Lee Bi, NE at 12:00Z on 2021-04-27The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -72 square meters per square second.1939587897117Sfc1 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
592 m above ground
0-6 km bulk shear
46 kt
0-1 km storm-relative helicity
-72 m²/s²
0-3 km storm-relative helicity
132 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.6

Open this sounding in Storm Lab

The text

As transmitted.

590 
WWUS20 KWNS 272333
SEL4  
SPC WW 272333
KSZ000-NEZ000-280500-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 114
NWS Storm Prediction Center Norman OK
535 PM MDT Tue Apr 27 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Northwest Kansas
  Southwest Nebraska

* Effective this Tuesday afternoon and evening from 535 PM until
  1100 PM MDT.

* Primary threats include...
  Scattered large hail events to 1.5 inches in diameter possible
  Isolated damaging wind gusts to 70 mph possible
  A tornado or two possible

SUMMARY...Ongoing severe thunderstorms are likely to continue
develop east-northeastward into northwest Kansas and southwest
Nebraska this evening, with the strongest storms expected generally
be Interstates 70 (Kansas) and 80 (Nebraska). Severe hail and
severe-caliber winds will both be possible, and a brief tornado is
also possibly mainly early this evening.

The severe thunderstorm watch area is approximately along and 75
statute miles north and south of a line from 35 miles north
northwest of Goodland KS to 20 miles east southeast of Mccook NE.
For a complete depiction of the watch see the associated watch
outline update (WOUS64 KWNS WOU4).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 112...WW 113...

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 450. Mean storm motion vector
23025.

...Guyer

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 27, 5:24 PM CDTMesoscale DiscussionSPCCheyenne, Decatur, Graham, Norton, Rawlins, Sheridan and 2 more2 hr

Nearby

Severe Thunderstorm Watches in Nebraska, 2021Severe Thunderstorm Watches in Kansas, 2021Every severe thunderstorm watch in 2021

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.