Alert archive / South Dakota / Mesoscale Discussions in 2021
Mesoscale Discussion 893
The Storm Prediction Center issued this mesoscale discussion at Jun 8, 2021, 8:50 PM MDT for 7 counties in South Dakota. It was in force for 85 min.
The area
The outline as issued.
The facts
- Issued
- Jun 8, 2021, 8:50 PM MDT (02:50 UTC)
- Expired
- Jun 8, 2021, 10:15 PM MDT
- In force
- 85 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 249
Counties Butte County, SD, Custer County, SD, Harding County, SD, Lawrence County, SD, Meade County, SD, Pennington County, SD, Perkins County, SD
The radar
The Rapid City radar (KUDX), 51 km from the middle of the area, began a volume at 02:50 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
Rapid City, SD (KUNR), launched 00:00Z, 2.8 hours before the alert went out and 54 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
- 2269 J/kg
- Mixed-layer CIN
- -7 J/kg
- Mixed-layer LCL
- 2498 m above ground
- 0-6 km bulk shear
- 26 kt
- 0-1 km storm-relative helicity
- 49 m²/s²
- 0-3 km storm-relative helicity
- 162 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 9.2
The text
As transmitted.
939 ACUS11 KWNS 090251 SWOMCD SPC MCD 090250 SDZ000-090415- Mesoscale Discussion 0893 NWS Storm Prediction Center Norman OK 0950 PM CDT Tue Jun 08 2021 Areas affected...Western South Dakota Concerning...Severe Thunderstorm Watch 249... Valid 090250Z - 090415Z The severe weather threat for Severe Thunderstorm Watch 249 continues. SUMMARY...Severe threat will spread from west to east across ww249. DISCUSSION...Large-scale forcing for ascent appears to influencing Black Hills convection this evening. Over the last hour or so, a squall line has emerged along the leading edge of forcing ahead of the MT/WY short-wave trough. This activity is spreading east at roughly 25kt and should approach the eastern edge of ww249 around 05z. While the squall line is the primary convection of concern, an outflow boundary continues to sag southwest toward this approaching squall line. This boundary may serve as the focus for new development, both along and north of the wind shift. Primary severe risk continues to be hail, though damaging wind threat may increase just east of the Black Hills if this portion of the squall line begins to surge along the aforementioned outflow boundary. ..Darrow.. 06/09/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ABR...UNR... LAT...LON 43540404 45910403 45910195 43540204 43540404
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 8, 6:37 PM MDT | Mesoscale Discussion | SPC | Butte, Custer, Fall River, Lawrence, Meade, Pennington | 83 min |
| Jun 8, 7:00 PM MDT | Severe Thunderstorm Watch | SPC | Butte, Custer, Fall River, Harding, Lawrence, Meade and 2 more | 5 hr |
| Jun 8, 10:41 PM MDT | Mesoscale Discussion | SPC | Corson, Dewey, Haakon, Jackson, Oglala Lakota, Ziebach | 94 min |
Nearby
Mesoscale 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.