Alert archive / Nebraska / Mesoscale Discussions in 2021
Mesoscale Discussion 1220
The Storm Prediction Center issued this mesoscale discussion at Jul 9, 2021, 8:21 PM CDT for 50 counties in Nebraska; Gregory County, South Dakota. It was in force for 114 min.
The area
The outline as issued.
The facts
- Issued
- Jul 9, 2021, 8:21 PM CDT (01:21 UTC)
- Expired
- Jul 9, 2021, 10:15 PM CDT
- In force
- 114 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 356
All 51 counties
Adams County, NE, Antelope County, NE, Arthur County, NE, Blaine County, NE, Boone County, NE, Boyd County, NE, Brown County, NE, Buffalo County, NE, Butler County, NE, Cedar County, NE, Cherry County, NE, Clay County, NE, Colfax County, NE, Cuming County, NE, Custer County, NE, Dawson County, NE, Dodge County, NE, Fillmore County, NE, Garfield County, NE, Grant County, NE, Greeley County, NE, Hall County, NE, Hamilton County, NE, Holt County, NE, Hooker County, NE, Howard County, NE, Kearney County, NE, Keya Paha County, NE, Knox County, NE, Logan County, NE, Loup County, NE, Madison County, NE, McPherson County, NE, Merrick County, NE, Nance County, NE, Pierce County, NE, Platte County, NE, Polk County, NE, Rock County, NE, Saline County, NE, Saunders County, NE, Seward County, NE, Sherman County, NE, Stanton County, NE, Thomas County, NE, Thurston County, NE, Valley County, NE, Wayne County, NE, Wheeler County, NE, York County, NE, Gregory County, SD
The radar
The North Platte radar (KLNX), 77 km from the middle of the area, began a volume at 01:21 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 00:00Z, 1.4 hours before the alert went out and 110 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
- 2799 J/kg
- Mixed-layer CIN
- -162 J/kg
- Mixed-layer LCL
- 1859 m above ground
- 0-6 km bulk shear
- 47 kt
- 0-1 km storm-relative helicity
- 30 m²/s²
- 0-3 km storm-relative helicity
- 117 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 4.9
The text
As transmitted.
325
ACUS11 KWNS 100121
SWOMCD
SPC MCD 100121
NEZ000-SDZ000-100315-
Mesoscale Discussion 1220
NWS Storm Prediction Center Norman OK
0821 PM CDT Fri Jul 09 2021
Areas affected...Central/eastern Nebraska
Concerning...Severe Thunderstorm Watch 356...
Valid 100121Z - 100315Z
The severe weather threat for Severe Thunderstorm Watch 356
continues.
SUMMARY...As activity in WW 356 increase, storms will continue to
move east into a strongly unstable airmass. A new downstream WW is
likely by 02Z for parts of eastern Nebraska.
DISCUSSION...Convection has increased along the cold front in
central Nebraska with a small line segment also developing farther
east of earlier supercells in western Nebraska. As this activity
continues to the east, driven by lift associated with the low-level
jet as well as an approaching shortwave, storms will encounter a
strongly unstable environment sampled by the 00Z OAX sounding.
Effective bulk shear of 50-55 kts will favor storm organization,
though the mode is likely to be predominantly linear. As such,
severe wind gusts are expected to be the primary threat, though
mid-level lapse rates would favor large hail in any more discrete
storms.
Activity in southern South Dakota has also increased over the last
hour. These storms are forming in an environment that has remained
cooler. These multicell storms may produce large hail, but will
similarly congeal as they move toward the southeast where better
buoyancy exists.
A new WW downstream is likely by 02Z.
..Wendt.. 07/10/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FSD...OAX...GID...LBF...UNR...
LAT...LON 42250183 42640119 43010081 43180021 43219914 42889762
42159642 41129652 40419691 40199738 40439892 40940013
41130114 41530219 42010243 42250183SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 9, 8:45 PM CDT | Severe Thunderstorm Watch | SPC | Adams, Antelope, Boone, Buffalo, Cedar, Clay and 28 more | 8 hr |
| Jul 9, 9:06 PM CDT | Severe Thunderstorm Watch | SPC | Arthur, Blaine, Boyd, Brown, Cherry, Custer and 15 more | 6 hr |
| Jul 9, 9:12 PM CDT | Mesoscale Discussion | SPC | Burt, Cass, Cuming, Dodge, Douglas, Gage and 13 more | 2 hr |
| Jul 9, 9:58 PM CDT | Severe Thunderstorm Watch | SPC | Burt, Butler, Cass, Cuming, Dodge, Douglas and 14 more | 7 hr |
| Jul 9, 10:20 PM CDT | Mesoscale Discussion | SPC | Butler, Clay, Fillmore, Gage, Hamilton, Jefferson and 7 more | 115 min |
| Jul 9, 10:44 PM CDT | Mesoscale Discussion | SPC | Box Butte, Garden, Grant, Sheridan | 91 min |
| Jul 10, 1:37 AM CDT | Mesoscale Discussion | SPC | Custer, Dawson, Lincoln, Logan, Thomas | 53 min |
| Jul 10, 1:45 AM CDT | Mesoscale Discussion | SPC | Custer, Dawson, Lincoln, Logan, Thomas | 60 min |
| Jul 10, 1:20 PM CDT | Mesoscale Discussion | SPC | Butler, Cass, Douglas, Fillmore, Gage, Jefferson and 12 more | 115 min |
| Jul 10, 2:18 PM CDT | Severe Thunderstorm Watch | SPC | Cass, Douglas, Gage, Johnson, Lancaster, Nemaha and 4 more | 7 hr |
| Jul 10, 3:44 PM CDT | Mesoscale Discussion | SPC | Gage, Johnson, Nemaha, Pawnee, Richardson | 91 min |
| Jul 10, 5:27 PM CDT | Mesoscale Discussion | SPC | Richardson | 2 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.