Alert archive / South Dakota / Mesoscale Discussions in 2021
Mesoscale Discussion 1580
The Storm Prediction Center issued this mesoscale discussion at Aug 22, 2021, 8:40 PM CDT for 8 counties in South Dakota. It was in force for 65 min.
The area
The outline as issued.
The facts
- Issued
- Aug 22, 2021, 8:40 PM CDT (01:40 UTC)
- Expired
- Aug 22, 2021, 9:45 PM CDT
- In force
- 65 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 457
Counties Aurora County, SD, Davison County, SD, Douglas County, SD, Hanson County, SD, Hutchinson County, SD, Jerauld County, SD, Miner County, SD, Sanborn County, SD
The radar
The Sioux Falls radar (KFSD), 117 km from the middle of the area, began a volume at 01:39 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, 1.7 hours before the alert went out and 125 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
- 166 J/kg
- Mixed-layer CIN
- -152 J/kg
- Mixed-layer LCL
- 1323 m above ground
- 0-6 km bulk shear
- 56 kt
- 0-1 km storm-relative helicity
- 245 m²/s²
- 0-3 km storm-relative helicity
- 282 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.4
The text
As transmitted.
836 ACUS11 KWNS 230141 SWOMCD SPC MCD 230140 SDZ000-230245- Mesoscale Discussion 1580 NWS Storm Prediction Center Norman OK 0840 PM CDT Sun Aug 22 2021 Areas affected...Southeast SD Concerning...Tornado Watch 457... Valid 230140Z - 230245Z The severe weather threat for Tornado Watch 457 continues. SUMMARY...Isolated supercell and tornado threat will continue for a couple more hours. DISCUSSION...Lead supercell that tracked southeast into the central part of ww457 has weakened considerably, and one primary supercell is now tracking across Hanson County toward southwest McCook County SD. Given the CINH observed on OAX sounding this evening, it's likely this contributed to the initial weakening. Even so, air mass remains adequately buoyant/sheared for potential tornado development, especially where surface dew points are holding in the upper 60s-near 70F. Boundary-layer decoupling and greater CINH toward the MN/IA border should lead to increasingly elevated updrafts. ..Darrow.. 08/23/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FSD... LAT...LON 44169885 44169765 43239712 43229830 44169885
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 23, 2:56 PM CDT | Mesoscale Discussion | SPC | Aurora, Brule, Buffalo, Charles Mix, Gregory, Jones and 4 more | 2 hr |
| Aug 23, 5:20 PM CDT | Severe Thunderstorm Watch | SPC | Aurora, Bon Homme, Brule, Buffalo, Charles Mix, Davison and 14 more | 8 hr |
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.