Alert archive / Nebraska / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 192
The Storm Prediction Center issued this severe thunderstorm watch at May 21, 2021, 4:17 PM MDT for 9 counties in Colorado; 15 counties in Nebraska; Bennett County, Oglala Lakota County, Todd County, South Dakota. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- May 21, 2021, 4:17 PM MDT (22:17 UTC)
- Expired
- May 21, 2021, 10:00 PM MDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 27 counties
Cheyenne County, CO, Kit Carson County, CO, Logan County, CO, Morgan County, CO, Phillips County, CO, Sedgwick County, CO, Washington County, CO, Weld County, CO, Yuma County, CO, Arthur County, NE, Banner County, NE, Box Butte County, NE, Cherry County, NE, Cheyenne County, NE, Dawes County, NE, Deuel County, NE, Garden County, NE, Grant County, NE, Hooker County, NE, Keith County, NE, Kimball County, NE, Morrill County, NE, Scotts Bluff County, NE, Sheridan County, NE, Bennett County, SD, Oglala Lakota County, SD, Todd County, SD
The radar
The North Platte radar (KLNX), 121 km from the middle of the area, began a volume at 22:18 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
- 5%
- 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
- 40%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
5 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 21, 4:38 PM MDT | Severe Thunderstorm Warning | CYS | Box Butte, Dawes | 52 min |
| May 21, 5:26 PM MDT | Severe Thunderstorm Warning | CYS | Box Butte, Morrill, Scotts Bluff, Sioux | 49 min |
| May 21, 5:32 PM MDT | Severe Thunderstorm Warning | CYS | Dawes | 43 min |
| May 21, 5:44 PM MDT | Severe Thunderstorm Warning | UNR | Oglala Lakota | 27 min |
| May 21, 9:57 PM MDT | Tornado Warning | GLD | Yuma | 33 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, 10.3 hours before the alert went out and 120 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.
- Mixed-layer CAPE
- 177 J/kg
- Mixed-layer CIN
- -372 J/kg
- Mixed-layer LCL
- 633 m above ground
- 0-6 km bulk shear
- 25 kt
- 0-1 km storm-relative helicity
- 361 m²/s²
- 0-3 km storm-relative helicity
- 395 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
211
WWUS20 KWNS 212215
SEL2
SPC WW 212215
COZ000-NEZ000-SDZ000-220400-
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 192
NWS Storm Prediction Center Norman OK
415 PM MDT Fri May 21 2021
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
northeast Colorado
western Nebraska
southern South Dakota
* Effective this Friday afternoon and evening from 415 PM until
1000 PM MDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Isolated damaging wind gusts to 70 mph possible
A tornado or two possible
SUMMARY...Scattered storms developing over the central High Plains
this evening will become capable of producing large to very large
hail, downburst winds and a couple of tornadoes.
The severe thunderstorm watch area is approximately along and 70
statute miles east and west of a line from 65 miles northwest of
Valentine NE to 50 miles south southeast of Limon CO. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU2).
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.
&&
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
20035.
...DialSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 21, 2:54 PM MDT | Mesoscale Discussion | SPC | Logan, Morgan, Phillips, Sedgwick, Washington, Yuma | 3 hr |
Nearby
Severe Thunderstorm Watches in Nebraska, 2021Severe Thunderstorm Watches in Colorado, 2021Severe Thunderstorm Watches in South Dakota, 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.