Alert archive / South Dakota / Mesoscale Discussions in 2021
Mesoscale Discussion 1206
The Storm Prediction Center issued this mesoscale discussion at Jul 8, 2021, 6:08 PM MDT for 8 counties in South Dakota. It was in force for 97 min.
The area
The outline as issued.
The facts
- Issued
- Jul 8, 2021, 6:08 PM MDT (00:08 UTC)
- Expired
- Jul 8, 2021, 7:45 PM MDT
- In force
- 97 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 354
Counties Bennett County, SD, Haakon County, SD, Jackson County, SD, Meade County, SD, Oglala Lakota County, SD, Pennington County, SD, Perkins County, SD, Ziebach County, SD
The radar
The Rapid City radar (KUDX), 65 km from the middle of the area, began a volume at 00:10 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 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, 0.1 hours before the alert went out and 72 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
- 1357 J/kg
- Mixed-layer CIN
- -133 J/kg
- Mixed-layer LCL
- 2075 m above ground
- 0-6 km bulk shear
- 73 kt
- 0-1 km storm-relative helicity
- 111 m²/s²
- 0-3 km storm-relative helicity
- 272 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 3.3
The text
As transmitted.
812
ACUS11 KWNS 090008
SWOMCD
SPC MCD 090008
NEZ000-SDZ000-NDZ000-090145-
Mesoscale Discussion 1206
NWS Storm Prediction Center Norman OK
0708 PM CDT Thu Jul 08 2021
Areas affected...Southwestern South Dakota
Concerning...Severe Thunderstorm Watch 354...
Valid 090008Z - 090145Z
The severe weather threat for Severe Thunderstorm Watch 354
continues.
SUMMARY...Hailstones greater than 2 inches in diameter will be
possible with a supercell moving southeastward across western South
Dakota over the next couple of hours. Wind driven hail and damaging
wind gusts exceeding 70 knots will also be possible.
DISCUSSION...High resolution radar from Rapid City shows a
well-developed intense supercell located about 20 statute miles to
the east of Rapid City. Another supercell is located in far
southwestern North Dakota. The environment ahead of the storms is
characterized by moderate instability with MLCAPE near 2000 J/kg,
strong deep-layer shear and steep mid-level lapse rates. The 00Z
sounding from Rapid City shows 0-6 km near 75 kt with 700-500 mb
lapse rate of 8.0 C/km. This will continue to support intense
supercell development over the next couple of hours. Hailstones of
greater than 2 inches in diameter will be possible within the
strongest part of each storm. Wind driven hail and wind gusts
exceeding 70 knots will also be possible. These two storms are
expected to produce swaths of large hail and wind damage, oriented
to the southeast across parts of western South Dakota.
..Broyles/Thompson/Smith.. 07/09/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ABR...BIS...LBF...UNR...
LAT...LON 45980219 45670186 45070145 44270123 42930133 42760158
42720191 42920247 43400289 44610321 45420329 45880312
45950284 45980219SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 8, 7:54 PM MDT | Mesoscale Discussion | SPC | Aurora, Beadle, Brule, Buffalo, Campbell, Corson and 16 more | 2 hr |
| Jul 8, 8:33 PM MDT | Severe Thunderstorm Watch | SPC | Aurora, Beadle, Bon Homme, Brule, Buffalo, Charles Mix and 24 more | 5 hr |
| Jul 9, 1:41 AM MDT | Mesoscale Discussion | SPC | Aurora, Beadle, Bon Homme, Brule, Buffalo, Charles Mix and 27 more | 34 min |
| Jul 9, 5:33 PM MDT | Severe Thunderstorm Watch | SPC | Custer, Fall River, Lawrence, Oglala Lakota, Pennington | 4 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.