Alert archive / Nebraska / Mesoscale Discussions in 2021
Mesoscale Discussion 920
The Storm Prediction Center issued this mesoscale discussion at Jun 11, 2021, 7:28 AM CDT for 4 counties in Iowa; 24 counties in Nebraska. It was in force for 92 min.
The area
The outline as issued.
The facts
- Issued
- Jun 11, 2021, 7:28 AM CDT (12:28 UTC)
- Expired
- Jun 11, 2021, 9:00 AM CDT
- In force
- 92 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 257
All 28 counties
Harrison County, IA, Mills County, IA, Monona County, IA, Pottawattamie County, IA, Boone County, NE, Burt County, NE, Butler County, NE, Cass County, NE, Colfax County, NE, Cuming County, NE, Dakota County, NE, Dixon County, NE, Dodge County, NE, Douglas County, NE, Lancaster County, NE, Madison County, NE, Merrick County, NE, Nance County, NE, Pierce County, NE, Platte County, NE, Polk County, NE, Sarpy County, NE, Saunders County, NE, Seward County, NE, Stanton County, NE, Thurston County, NE, Washington County, NE, Wayne County, NE
The radar
The Omaha radar (KOAX), 65 km from the middle of the area, began a volume at 12:28 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
Omaha, NE (KOAX), launched 12:00Z, 0.5 hours before the alert went out and 65 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
- 2132 J/kg
- Mixed-layer CIN
- -90 J/kg
- Mixed-layer LCL
- 899 m above ground
- 0-6 km bulk shear
- 29 kt
- 0-1 km storm-relative helicity
- 81 m²/s²
- 0-3 km storm-relative helicity
- 162 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.7
The text
As transmitted.
987
ACUS11 KWNS 111228
SWOMCD
SPC MCD 111228
IAZ000-NEZ000-SDZ000-111400-
Mesoscale Discussion 0920
NWS Storm Prediction Center Norman OK
0728 AM CDT Fri Jun 11 2021
Areas affected...portions of eastern NE and western IA
Concerning...Severe Thunderstorm Watch 257...
Valid 111228Z - 111400Z
The severe weather threat for Severe Thunderstorm Watch 257
continues.
SUMMARY...Damaging wind gusts are possible for another couple of
hours across parts of eastern Nebraska and perhaps far southwest
Iowa
DISCUSSION...A south/southeastward-advancing bow is producing
near-severe level wind speeds this morning across northeast NE.
Recently, a 49 kt gust was measured at KOFK. Velocity data from KOAX
also shows strong inbound signatures while the VWP from KFSD
indicated a rear-inflow jet up to 65 kt around 1-2 km. The bowing
segment will tracking along a stronger instability gradient amid
modest shear and strong low level inhibition. Nevertheless, wind
gusts around 45-55 kt appear possible at least in the short term,
and could persist another 1-2 hours. A local extension of WW 257 or
a new downstream watch is being considered.
..Leitman.. 06/11/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FSD...OAX...GID...
LAT...LON 41889827 42339792 42489730 42539660 42469629 42249595
41459549 40809553 40729609 40809734 41179816 41889827SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 11, 5:36 AM CDT | Severe Thunderstorm Watch | SPC | Harrison, Monona, Pottawattamie, Shelby | 5 hr |
| Jun 11, 8:30 AM CDT | Severe Thunderstorm Watch | SPC | Fremont, Mills, Montgomery, Page | 7 hr |
| Jun 11, 9:35 AM CDT | Mesoscale Discussion | SPC | Boone, Bremer, Butler, Calhoun, Cerro Gordo, Chickasaw and 19 more | 115 min |
| Jun 10, 8:28 PM CDT | Mesoscale Discussion | SPC | Arthur, Banner, Blaine, Box Butte, Brown, Cherry and 12 more | 92 min |
| Jun 10, 9:08 PM CDT | Severe Thunderstorm Watch | SPC | Arthur, Banner, Blaine, Box Butte, Brown, Cherry and 12 more | 6 hr |
| Jun 10, 11:07 PM CDT | Mesoscale Discussion | SPC | Box Butte, Dawes, Sheridan, Sioux | 83 min |
| Jun 11, 12:52 AM CDT | Mesoscale Discussion | SPC | Antelope, Boyd, Cedar, Holt, Keya Paha, Knox and 4 more | 53 min |
| Jun 11, 2:15 AM CDT | Severe Thunderstorm Watch | SPC | Dakota, Dixon | 5 hr |
| Jun 11, 10:28 AM CDT | Mesoscale Discussion | SPC | Gage, Johnson, Nemaha, Otoe, Pawnee, Richardson | 2 hr |
Nearby
Mesoscale Discussions in Nebraska, 2021Mesoscale Discussions in Iowa, 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.