Alert archive / Nebraska / Mesoscale Discussions in 2021
Mesoscale Discussion 1613
The Storm Prediction Center issued this mesoscale discussion at Aug 26, 2021, 5:34 PM CDT for 15 counties in Iowa; 30 counties in Nebraska; 5 counties in South Dakota. It was in force for 116 min.
The area
The outline as issued.
The facts
- Issued
- Aug 26, 2021, 5:34 PM CDT (22:34 UTC)
- Expired
- Aug 26, 2021, 7:30 PM CDT
- In force
- 116 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
All 50 counties
Buena Vista County, IA, Cherokee County, IA, Clay County, IA, Crawford County, IA, Harrison County, IA, Ida County, IA, Lyon County, IA, Monona County, IA, O'Brien County, IA, Osceola County, IA, Plymouth County, IA, Sac County, IA, Shelby County, IA, Sioux County, IA, Woodbury County, IA, Antelope County, NE, Boone County, NE, Burt County, NE, Butler County, NE, Cedar County, NE, Colfax County, NE, Cuming County, NE, Custer County, NE, Dakota County, NE, Dixon County, NE, Dodge County, NE, Douglas County, NE, Garfield County, NE, Greeley County, NE, Howard County, NE, Knox County, NE, Madison County, NE, Merrick County, NE, Nance County, NE, Pierce County, NE, Platte County, NE, Polk County, NE, Saunders County, NE, Sherman County, NE, Stanton County, NE, Thurston County, NE, Valley County, NE, Washington County, NE, Wayne County, NE, Wheeler County, NE, Clay County, SD, Lincoln County, SD, Turner County, SD, Union County, SD, Yankton County, SD
The radar
The Omaha radar (KOAX), 123 km from the middle of the area, began a volume at 22:35 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, 10.6 hours before the alert went out and 122 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
- 2002 J/kg
- Mixed-layer CIN
- -261 J/kg
- Mixed-layer LCL
- 1111 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 217 m²/s²
- 0-3 km storm-relative helicity
- 264 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.3
The text
As transmitted.
181
ACUS11 KWNS 262234
SWOMCD
SPC MCD 262234
IAZ000-MNZ000-NEZ000-SDZ000-270030-
Mesoscale Discussion 1613
NWS Storm Prediction Center Norman OK
0534 PM CDT Thu Aug 26 2021
Areas affected...portions of eastern NE...southeast SD and western
IA
Concerning...Severe potential...Watch possible
Valid 262234Z - 270030Z
Probability of Watch Issuance...60 percent
SUMMARY...Severe thunderstorm potential is increasing across parts
of eastern Nebraska into far southeast South Dakota and western
Iowa. Damaging gusts and large hail are possible this evening into
tonight. This area is being monitored for a possible severe
thunderstorm watch.
DISCUSSION...Isolated convection is developing along an
eastward-advancing boundary across northeast/central NE that extends
from roughly Holt County toward Custer County. Another west-to-east
oriented outflow boundary extends from southeast Holt County into
western IA. Stronger capping exists across southeast SD into
northern IA due to early day convection, persistent cloud cover and
periodic thunderstorms/showers. Near and south of the outflow
boundary, strong instability is in place with surface dewpoints in
the 70s F in a nearly uncapped environment. Large-scale forcing
remains modest across the region.
As a result of capping and weak forcing, uncertainty exists
regarding convective evolution across the region . However, as a low
level jet increases this evening, convection may be able to become
organized in the vicinity of these surface boundaries across
northeast NE into far southeast SD and western IA. Aided by the
developing south/southwesterly low level jet and effective shear
magnitudes around 35-45 kt, thunderstorm clusters may evolve into an
eastward-propagating line, posing a threat for damaging gusts this
evening into tonight. Strong instability and moderately steep
midlevel lapse rates also could support large hail with any
semi-discrete activity. Convective trends are being monitored and a
severe thunderstorm watch may be needed for portions of the MCD area
in the next couple of hours.
..Leitman/Bunting.. 08/26/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DMX...FSD...OAX...GID...LBF...
LAT...LON 42169923 43169760 43449686 43509630 43499559 43309516
42619481 42169487 41629515 41239584 41119672 41139787
41199942 41369988 41679973 41929942 42169923SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 26, 7:37 AM CDT | Mesoscale Discussion | SPC | Adair, Audubon, Boone, Buena Vista, Calhoun, Carroll and 20 more | 83 min |
| Aug 26, 9:40 AM CDT | Mesoscale Discussion | SPC | Adair, Adams, Appanoose, Benton, Boone, Clarke and 25 more | 95 min |
| Aug 26, 1:12 PM CDT | Mesoscale Discussion | SPC | Allamakee, Winneshiek | 93 min |
| Aug 26, 3:10 AM CDT | Mesoscale Discussion | SPC | Antelope, Boyd, Cedar, Dixon, Garfield, Holt and 6 more | 3 hr |
| Aug 26, 2:35 AM CDT | Mesoscale Discussion | SPC | Brown, Campbell, Corson, Dewey, Edmunds, Faulk and 6 more | 2 hr |
| Aug 26, 8:36 AM CDT | Mesoscale Discussion | SPC | Beadle, Brookings, Buffalo, Clark, Codington, Day and 10 more | 84 min |
| Aug 26, 9:05 AM CDT | Severe Thunderstorm Watch | SPC | Beadle, Brookings, Clark, Codington, Deuel, Grant and 7 more | 4 hr |
| Aug 26, 10:43 AM CDT | Mesoscale Discussion | SPC | Brookings, Deuel, Moody | 92 min |
Nearby
Mesoscale Discussions in Nebraska, 2021Mesoscale Discussions in Iowa, 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.