Alert archive / South Dakota / Mesoscale Discussions in 2021
Mesoscale Discussion 1680
The Storm Prediction Center issued this mesoscale discussion at Sep 1, 2021, 10:36 PM MDT for 6 counties in Nebraska; 11 counties in South Dakota. It was in force for 84 min.
The area
The outline as issued.
The facts
- Issued
- Sep 1, 2021, 10:36 PM MDT (04:36 UTC)
- Expired
- Sep 2, 2021, 12:00 AM MDT
- In force
- 84 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 485
Counties Arthur County, NE, Cherry County, NE, Garden County, NE, Grant County, NE, Hooker County, NE, Sheridan County, NE, Bennett County, SD, Haakon County, SD, Hughes County, SD, Jackson County, SD, Jones County, SD, Lyman County, SD, Mellette County, SD, Oglala Lakota County, SD, Stanley County, SD, Todd County, SD, Tripp County, SD
The radar
The North Platte radar (KLNX), 135 km from the middle of the area, began a volume at 04:38 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, 4.6 hours before the alert went out and 165 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
- 549 J/kg
- Mixed-layer CIN
- -82 J/kg
- Mixed-layer LCL
- 1203 m above ground
- 0-6 km bulk shear
- 55 kt
- 0-1 km storm-relative helicity
- -34 m²/s²
- 0-3 km storm-relative helicity
- 71 m²/s²
- Significant tornado parameter
- -0.0
- Supercell composite
- -0.7
The text
As transmitted.
516
ACUS11 KWNS 020436
SWOMCD
SPC MCD 020436
SDZ000-NEZ000-020600-
Mesoscale Discussion 1680
NWS Storm Prediction Center Norman OK
1136 PM CDT Wed Sep 01 2021
Areas affected...portions of northwest Nebraska and southwest South
Dakota
Concerning...Severe Thunderstorm Watch 485...
Valid 020436Z - 020600Z
The severe weather threat for Severe Thunderstorm Watch 485
continues.
SUMMARY...Although an isolated hail and wind threat will persist for
another hour or so, overall trends suggest the severe potential
should sufficiently diminish by 01 AM CDT to allow Severe
Thunderstorm Watch #485 to expire on time.
DISCUSSION...Showers and thunderstorms continue to develop and move
slowly east across Severe Thunderstorm Watch #485. A largely
unstable and sheared airmass remains along and ahead of these
thunderstorms and thus the potential for isolated hail and wind will
continue. However, continued storm interactions and upscale growth
will tend to favor an overall weakening trend with time. Barring
more robust, discrete initiation ahead of the existing line of
thunderstorms, all indications are that the watch will be allowed to
expire at 06Z/01 AM CDT.
..Marsh.. 09/02/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FSD...ABR...LBF...UNR...CYS...
LAT...LON 43070302 44680139 44309928 42989960 41210207 41220258
43070302SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 1, 8:20 PM MDT | Mesoscale Discussion | SPC | Box Butte, Cherry, Dawes, Garden, Morrill, Scotts Bluff and 2 more | 85 min |
| Sep 2, 12:28 PM MDT | Mesoscale Discussion | SPC | Blaine, Brown, Buffalo, Custer, Dawson, Franklin and 13 more | 2 hr |
| Sep 2, 4:27 PM MDT | Tornado Watch | SPC | Adams, Buffalo, Butler, Clay, Dawson, Fillmore and 23 more | 5 hr |
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; radar from the NEXRAD Level II archive.