Alert archive / Nebraska / Mesoscale Discussions in 2021
Mesoscale Discussion 1656
The Storm Prediction Center issued this mesoscale discussion at Aug 30, 2021, 11:35 PM CDT for Harrison County, Iowa; 16 counties in Nebraska. It was in force for 85 min.
The area
The outline as issued.
The facts
- Issued
- Aug 30, 2021, 11:35 PM CDT (04:35 UTC)
- Expired
- Aug 31, 2021, 1:00 AM CDT
- In force
- 85 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 479
Counties Harrison County, IA, Burt County, NE, Butler County, NE, Cass County, NE, Colfax County, NE, Cuming County, NE, Dodge County, NE, Douglas County, NE, Madison County, NE, Pierce County, NE, Platte County, NE, Sarpy County, NE, Saunders County, NE, Stanton County, NE, Thurston County, NE, Washington County, NE, Wayne County, NE
The radar
The Omaha radar (KOAX), 57 km from the middle of the area, began a volume at 04:38 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 nearest sounding before it
Omaha, NE (KOAX), launched 00:00Z, 4.6 hours before the alert went out and 57 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
- 1443 J/kg
- Mixed-layer CIN
- -31 J/kg
- Mixed-layer LCL
- 1305 m above ground
- 0-6 km bulk shear
- 35 kt
- 0-1 km storm-relative helicity
- 4 m²/s²
- 0-3 km storm-relative helicity
- 143 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 3.5
The text
As transmitted.
220
ACUS11 KWNS 310435
SWOMCD
SPC MCD 310435
IAZ000-NEZ000-310600-
Mesoscale Discussion 1656
NWS Storm Prediction Center Norman OK
1135 PM CDT Mon Aug 30 2021
Areas affected...portions of eastern NE and extreme western IA
Concerning...Severe Thunderstorm Watch 479...
Valid 310435Z - 310600Z
The severe weather threat for Severe Thunderstorm Watch 479
continues.
SUMMARY...A threat of large hail and gusty winds continues across WW
479. Local watch extension may be needed for a small portions of
eastern Nebraska.
DISCUSSION...A couple of intense supercells, potentially producing
very large hail, are ongoing in the vicinity of Pierce and Stanton
counties in northeast NE near a stationary surface boundary draped
across eastern NE. The 00z RAOB from OAX indicated very steep
midlevel lapse rates amid strong instability. This will help
maintain well-organized cells amid 35-40 kt 0-6 km shear, and an
increasing southerly low-level jet (per latest OAX VWP data). While
these supercells are moving rather slow at around 15-20 kt, a local
aerial extension of the watch may be needed for portions of eastern
NE in the Omaha CWA given potential for a continued hail threat just
downstream from WW 479.
..Leitman.. 08/31/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FSD...OAX...GID...
LAT...LON 42479739 42399673 42169613 41509552 41039565 40879600
40819663 41059731 41459773 41879790 42209773 42479739SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 31, 3:02 AM CDT | Mesoscale Discussion | SPC | Adams, Cass, Fremont, Harrison, Mills, Montgomery and 5 more | 118 min |
| Aug 30, 7:25 PM CDT | Mesoscale Discussion | SPC | Antelope, Boyd, Brown, Cedar, Cherry, Holt and 5 more | 3 hr |
| Aug 30, 9:57 PM CDT | Severe Thunderstorm Watch | SPC | Antelope, Boone, Boyd, Brown, Burt, Butler and 24 more | 7 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.