Alert archive / Nebraska / Mesoscale Discussions in 2021
Mesoscale Discussion 1577
The Storm Prediction Center issued this mesoscale discussion at Aug 22, 2021, 3:38 PM CDT for 39 counties in Nebraska; Gregory County, Tripp County, South Dakota. It was in force for 97 min.
The area
The outline as issued.
The facts
- Issued
- Aug 22, 2021, 3:38 PM CDT (20:38 UTC)
- Expired
- Aug 22, 2021, 5:15 PM CDT
- In force
- 97 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 41 counties
Adams County, NE, Blaine County, NE, Boone County, NE, Boyd County, NE, Brown County, NE, Buffalo County, NE, Chase County, NE, Custer County, NE, Dawson County, NE, Dundy County, NE, Franklin County, NE, Frontier County, NE, Furnas County, NE, Garfield County, NE, Gosper County, NE, Greeley County, NE, Hall County, NE, Hamilton County, NE, Harlan County, NE, Hayes County, NE, Hitchcock County, NE, Holt County, NE, Howard County, NE, Kearney County, NE, Keya Paha County, NE, Lincoln County, NE, Logan County, NE, Loup County, NE, McPherson County, NE, Merrick County, NE, Nance County, NE, Perkins County, NE, Phelps County, NE, Red Willow County, NE, Rock County, NE, Sherman County, NE, Thomas County, NE, Valley County, NE, Wheeler County, NE, Gregory County, SD, Tripp County, SD
The radar
The North Platte radar (KLNX), 80 km from the middle of the area, began a volume at 20:41 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.
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
N. Platte/Lee Bi, NE (KLBF), launched 12:00Z, 8.6 hours before the alert went out and 94 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
- 26 J/kg
- Mixed-layer CIN
- -584 J/kg
- Mixed-layer LCL
- 1143 m above ground
- 0-6 km bulk shear
- 41 kt
- 0-1 km storm-relative helicity
- 537 m²/s²
- 0-3 km storm-relative helicity
- 608 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
196
ACUS11 KWNS 222039
SWOMCD
SPC MCD 222038
NEZ000-SDZ000-KSZ000-222215-
Mesoscale Discussion 1577
NWS Storm Prediction Center Norman OK
0338 PM CDT Sun Aug 22 2021
Areas affected...central NE into far southern SD and extreme
northern KS
Concerning...Severe potential...Watch possible
Valid 222038Z - 222215Z
Probability of Watch Issuance...40 percent
SUMMARY...A damaging wind and hail risk may develop if thunderstorms
are able to organize late this afternoon and into this evening. A
weather watch is possible but uncertainty on the nature of any
severe threat remains high.
DISCUSSION...As of 2015 UTC, visible satellite imagery showed
towering cumulus deepening east of a lee trough/dryline and along a
diffuse differential heating axis through central Nebraska. On the
southern fringes of a compact upper low across the western Dakotas,
large-scale synoptic lift will continue to overspread a rapidly
warming airmass this afternoon. With additional heating and surface
dewpoints climbing into the 60s and 70s F, regional RAP soundings
develop 2000-3000 J/kg of MLCAPE by late this afternoon. Moderate
deep-layer shear will be augmented by stronger flow aloft ahead of
the approaching upper low. SPC mesoanalysis shows 40-50 kt of
effective shear co-located with favorable buoyancy across much of
Nebraska and northern Kansas.
Satellite trends and recent CAM guidance suggests storm development
along the dryline and differential heating axis is possible by
22-23z. Storm coverage is uncertain as forcing for ascent will be
quite subtle from the glancing of the upper low. However, given the
favorable thermodynamic and kinematic variables at play, any storms
that do develop will likely become supercells with the potential for
damaging wind gusts and large hail. CAM guidance suggests additional
storm development may also support upscale growth later in the
evening across east-central Nebraska. Convective trends will be
monitored for a possible weather watch, but storm coverage and the
resulting severe threat remains uncertain.
..Lyons/Kerr.. 08/22/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FSD...OAX...ABR...GID...LBF...UNR...GLD...
LAT...LON 41169785 40689802 40309851 40119883 39929967 39840070
39920138 40060171 40480195 40850174 41740108 42360070
42950060 43170053 43380044 43480030 43609975 43489909
42949839 42509822 42109807 41509787 41169785SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 22, 5:01 PM CDT | Severe Thunderstorm Watch | SPC | Adams, Buffalo, Clay, Custer, Dawson, Franklin and 17 more | 5 hr |
| Aug 22, 2:21 PM CDT | Mesoscale Discussion | SPC | Beadle, Brown, Buffalo, Campbell, Edmunds, Faulk and 8 more | 2 hr |
| Aug 22, 3:36 PM CDT | Severe Thunderstorm Watch | SPC | Aurora, Beadle, Brookings, Brown, Brule, Buffalo and 24 more | 5 hr |
| Aug 22, 5:59 PM CDT | Mesoscale Discussion | SPC | Beadle, Brookings, Brown, Campbell, Clark, Codington and 11 more | 91 min |
| Aug 22, 6:31 PM CDT | Tornado Watch | SPC | Aurora, Davison, Douglas, Hanson, Hutchinson, Jerauld and 4 more | 3 hr |
Nearby
Mesoscale Discussions in Nebraska, 2021Mesoscale Discussions in South Dakota, 2021Every mesoscale discussion 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.