Alert archive / South Dakota / Mesoscale Discussions in 2021
Mesoscale Discussion 1614
The Storm Prediction Center issued this mesoscale discussion at Aug 26, 2021, 7:25 PM CDT for 6 counties in Nebraska; 28 counties in South Dakota. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 26, 2021, 7:25 PM CDT (00:25 UTC)
- Expired
- Aug 26, 2021, 9:30 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 34 counties
Boyd County, NE, Brown County, NE, Cherry County, NE, Holt County, NE, Keya Paha County, NE, Rock County, NE, Aurora County, SD, Bennett County, SD, Bon Homme County, SD, Brule County, SD, Buffalo County, SD, Charles Mix County, SD, Custer County, SD, Davison County, SD, Douglas County, SD, Fall River County, SD, Gregory County, SD, Haakon County, SD, Hand County, SD, Hughes County, SD, Hutchinson County, SD, Hyde County, SD, Jackson County, SD, Jerauld County, SD, Jones County, SD, Lyman County, SD, Mellette County, SD, Oglala Lakota County, SD, Pennington County, SD, Sanborn County, SD, Stanley County, SD, Sully County, SD, Todd County, SD, Tripp County, SD
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Rapid City, SD (KUNR), launched 00:00Z, 0.4 hours before the alert went out and 138 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
- 1372 J/kg
- Mixed-layer CIN
- -139 J/kg
- Mixed-layer LCL
- 1154 m above ground
- 0-6 km bulk shear
- 43 kt
- 0-1 km storm-relative helicity
- 71 m²/s²
- 0-3 km storm-relative helicity
- 214 m²/s²
- Significant tornado parameter
- 0.5
- Supercell composite
- 2.7
The text
As transmitted.
530
ACUS11 KWNS 270026
SWOMCD
SPC MCD 270025
SDZ000-NEZ000-270230-
Mesoscale Discussion 1614
NWS Storm Prediction Center Norman OK
0725 PM CDT Thu Aug 26 2021
Areas affected...Parts of southern South Dakota and northern
Nebraska
Concerning...Severe potential...Watch possible
Valid 270025Z - 270230Z
Probability of Watch Issuance...40 percent
SUMMARY...Parts of western into central South Dakota and Nebraska
will see and increase in severe thunderstorm activity this evening.
Damaging wind gusts are likely the main threat, though large hail
will be possible with discrete storms. A severe thunderstorm watch
may be needed for parts of these areas.
DISCUSSION...Satellite and NLDN lightning data have shown an
increase in storm intensity near the Black Hills. Other thunderstorm
development is occurring in parts of central Nebraska near what
appears to be a remnant outflow boundary. Increasing height falls
and an increase in the low-level jet across the central and northern
Plains should support and greater storm coverage and intensity this
evening. How storms evolve this evening is still uncertain. Storms
near the Black Hills may progress along a quasi-stationary boundary
within northern South Dakota with additional development as warm
advection increases. Steep mid-level lapse rates were sampled by
this evening's regional soundings. With moderate flow aloft, 40-50
kts of effective shear will support organized storms capable of
damaging wind gusts as well as large hail with the more discrete,
supercellular activity. Even with the uncertainty, a severe
thunderstorm watch may be needed later this evening. Trends will
continue to be monitored.
..Wendt/Bunting.. 08/27/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FSD...OAX...ABR...LBF...UNR...CYS...
LAT...LON 44440328 44840166 44689905 44519844 43209748 42409844
42300000 42370173 42610251 42900355 43150395 44100389
44440328SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 26, 8:03 PM CDT | Severe Thunderstorm Watch | SPC | Antelope, Blaine, Boone, Boyd, Brown, Cedar and 20 more | 7 hr |
| Aug 26, 10:45 PM CDT | Mesoscale Discussion | SPC | Dakota | 2 hr |
| Aug 27, 6:28 PM CDT | Mesoscale Discussion | SPC | Douglas, Sarpy, Washington | 92 min |
| Aug 27, 3:55 PM CDT | Mesoscale Discussion | SPC | Butte, Harding, Perkins | 2 hr |
| Aug 27, 6:33 PM CDT | Mesoscale Discussion | SPC | Butte, Perkins, Ziebach | 117 min |
Nearby
Mesoscale Discussions in South Dakota, 2021Mesoscale Discussions in Nebraska, 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.