Alert archive / Nebraska / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 506
The Storm Prediction Center issued this severe thunderstorm watch at Sep 16, 2021, 8:16 PM CDT for 22 counties in Nebraska; 8 counties in South Dakota. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 16, 2021, 8:16 PM CDT (01:16 UTC)
- Expired
- Sep 17, 2021, 2:05 AM CDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 30 counties
Blaine County, NE, Boyd County, NE, Brown County, NE, Cherry County, NE, Custer County, NE, Dawson County, NE, Garfield County, NE, Grant County, NE, Greeley County, NE, Holt County, NE, Hooker County, NE, Keya Paha County, NE, Lincoln County, NE, Logan County, NE, Loup County, NE, McPherson County, NE, Rock County, NE, Sheridan County, NE, Sherman County, NE, Thomas County, NE, Valley County, NE, Wheeler County, NE, Aurora County, SD, Brule County, SD, Charles Mix County, SD, Davison County, SD, Douglas County, SD, Gregory County, SD, Todd County, SD, Tripp County, SD
The radar
The North Platte radar (KLNX), 61 km from the middle of the area, began a volume at 01:18 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
- 5%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 20%
- 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
4 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 16, 8:21 PM CDT | Severe Thunderstorm Warning | LBF | Cherry | 39 min |
| Sep 16, 8:35 PM CDT | Severe Thunderstorm Warning | LBF | Blaine, Custer, Hooker, Lincoln, Logan, McPherson and 1 more | 55 min |
| Sep 16, 10:20 PM CDT | Severe Thunderstorm Warning | FSD | Charles Mix, Gregory | 25 min |
| Sep 16, 11:31 PM CDT | Severe Thunderstorm Warning | FSD | Bon Homme, Charles Mix, Hutchinson, Yankton | 29 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 00:00Z, 1.3 hours before the alert went out and 143 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
- 1601 J/kg
- Mixed-layer CIN
- -38 J/kg
- Mixed-layer LCL
- 2561 m above ground
- 0-6 km bulk shear
- 30 kt
- 0-1 km storm-relative helicity
- 106 m²/s²
- 0-3 km storm-relative helicity
- 153 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 4.7
The text
As transmitted.
341
WWUS20 KWNS 170114
SEL6
SPC WW 170114
NEZ000-SDZ000-170800-
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 506
NWS Storm Prediction Center Norman OK
815 PM CDT Thu Sep 16 2021
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Central and western Nebraska
Southern South Dakota
* Effective this Thursday night and Friday morning from 815 PM
until 300 AM CDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Scattered damaging wind gusts to 70 mph possible
SUMMARY...Growing clusters of thunderstorms on either side of a
slow-moving cold front should pose a severe hail/wind threat, as
they access a strengthening low-level jet, and move east-
northeastward across the watch area tonight.
The severe thunderstorm watch area is approximately along and 90
statute miles north and south of a line from 30 miles south
southwest of Mullen NE to 30 miles northeast of Oneill NE. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU6).
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 504...WW 505...
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 550. Mean storm motion vector
24030.
...EdwardsSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 16, 7:15 PM CDT | Mesoscale Discussion | SPC | Blaine, Box Butte, Boyd, Brown, Cherry, Garden and 10 more | 2 hr |
| Sep 16, 7:57 PM CDT | Mesoscale Discussion | SPC | Buffalo, Custer, Dawson, Keith, Lincoln, Logan and 4 more | 2 hr |
Nearby
Severe Thunderstorm Watches in Nebraska, 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.