Alert archive / Iowa / Mesoscale Discussions in 2021
Mesoscale Discussion 1423
The Storm Prediction Center issued this mesoscale discussion at Aug 5, 2021, 9:34 PM CDT for 13 counties in Iowa; Nobles County, Rock County, Minnesota; 5 counties in South Dakota. It was in force for 86 min.
The area
The outline as issued.
The facts
- Issued
- Aug 5, 2021, 9:34 PM CDT (02:34 UTC)
- Expired
- Aug 5, 2021, 11:00 PM CDT
- In force
- 86 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
Counties Buena Vista County, IA, Cherokee County, IA, Clay County, IA, Dickinson County, IA, Ida County, IA, Lyon County, IA, O'Brien County, IA, Osceola County, IA, Plymouth County, IA, Pocahontas County, IA, Sac County, IA, Sioux County, IA, Woodbury County, IA, Nobles County, MN, Rock County, MN, Clay County, SD, Lincoln County, SD, Minnehaha County, SD, Turner County, SD, Union County, SD
The radar
The Sioux Falls radar (KFSD), 74 km from the middle of the area, began a volume at 02:33 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
Aberdeen, SD (KABR), launched 00:00Z, 2.6 hours before the alert went out and 271 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
- 835 J/kg
- Mixed-layer CIN
- -42 J/kg
- Mixed-layer LCL
- 1549 m above ground
- 0-6 km bulk shear
- 24 kt
- 0-1 km storm-relative helicity
- 41 m²/s²
- 0-3 km storm-relative helicity
- 259 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
159
ACUS11 KWNS 060234
SWOMCD
SPC MCD 060234
IAZ000-MNZ000-NEZ000-SDZ000-060400-
Mesoscale Discussion 1423
NWS Storm Prediction Center Norman OK
0934 PM CDT Thu Aug 05 2021
Areas affected...Southeastern South Dakota northwest Iowa and far
southwestern Minnesota
Concerning...Severe potential...Watch unlikely
Valid 060234Z - 060400Z
Probability of Watch Issuance...5 percent
SUMMARY...A cluster of thunderstorms with a history of severe hail
may continue to pose a risk for hail/damaging winds over the next
few hours. Storms should gradually weaken with time, diminishing the
severe threat.
DISCUSSION...Over the last 90 minutes, the cluster of strong/severe
thunderstorms in the vicinity of Sioux Falls, South Dakota has
produced several reports of severe hail and strong wind gusts.
Contrary to earlier day model guidance, radar and satellite trends
suggest weakening of the storm cluster is evolving slower than
anticipated. Some severe threat in the form of hail and damaging
wind gusts will likely linger across portions of northwestern Iowa
and far southeastern South Dakota as storms continue to move south
and east over the next few hours. Despite boundary-layer cooling and
increasing inhibition, SPC mesoanalysis indicates a moderate
unstable environment (2000-3000 J/kg of MLCAPE) remains in place.
Effective shear is somewhat limited with regional VWPs indicating
only 20-25 kts. Limited vertical shear but favorable thermodynamics
suggest a few organized multicells and perhaps a supercell or two
may persist for another few hours before being overcome by
increasing nocturnal inhibition. Until then, severe hail and
occasional damaging wind gusts will remain possible with the
strongest storms.
..Lyons/Hart.. 08/06/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DMX...FSD...
LAT...LON 43719727 43929670 43899575 43479488 42629463 42339490
42309573 42369625 42679668 43069727 43719727SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 6, 2:43 PM CDT | Severe Thunderstorm Watch | SPC | Butte, Custer, Fall River, Harding, Lawrence, Meade and 3 more | 6 hr |
| Aug 6, 6:07 PM CDT | Mesoscale Discussion | SPC | Bennett, Jackson, Mellette, Oglala Lakota, Todd | 113 min |
Nearby
Mesoscale Discussions in Iowa, 2021Mesoscale Discussions in South Dakota, 2021Mesoscale Discussions in Minnesota, 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.