Alert archive / South Dakota / Mesoscale Discussions in 2021
Mesoscale Discussion 1975
The Storm Prediction Center issued this mesoscale discussion at Dec 10, 2021, 1:39 AM MST for 8 counties in South Dakota. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Dec 10, 2021, 1:39 AM MST (08:39 UTC)
- Expired
- Dec 10, 2021, 5:45 AM MST
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Heavy snow
Counties Bennett County, SD, Custer County, SD, Fall River County, SD, Jackson County, SD, Mellette County, SD, Oglala Lakota County, SD, Todd County, SD, Tripp County, SD
The radar
The Rapid City radar (KUDX), 106 km from the middle of the area, began a volume at 08:39 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
Rapid City, SD (KUNR), launched 00:00Z, 8.7 hours before the alert went out and 104 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 799 m above ground
- 0-6 km bulk shear
- 74 kt
- 0-1 km storm-relative helicity
- 34 m²/s²
- 0-3 km storm-relative helicity
- 1 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
885
ACUS11 KWNS 100839
SWOMCD
SPC MCD 100839
SDZ000-NEZ000-101245-
Mesoscale Discussion 1975
NWS Storm Prediction Center Norman OK
0239 AM CST Fri Dec 10 2021
Areas affected...portions of southwest into south-central SD
Concerning...Heavy snow
Valid 100839Z - 101245Z
SUMMARY...A narrow corridor of moderate to heavy snow will continue
to slowly lift northward across parts of southwest into
south-central SD through early morning. Snowfall rates may briefly
reach 1 inch per hour within this narrow snow band.
DISCUSSION...A narrow snow band extending west to east from northern
Fall River to central Tripp County in southern SD will slowly shift
northward the next few hours. This snow band is being driven by
strong warm advection and frontogenesis around 700 mb. Moderate
ascent will continue to overspread the region as a mid/upper
shortwave trough ejects eastward toward the Four Corners and central
Rockies vicinity. However, the dendritic growth zone will remain
somewhat shallow within the area of stronger warm advection and
midlevel frontogenesis, limiting greater snowfall efficiency. This
should temper overall rates, but narrow/brief areas of heavy snow
are possible the next few hours.
..Leitman.. 12/10/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FSD...ABR...LBF...UNR...CYS...
LAT...LON 43010343 43040369 43140391 43270403 43530405 43650398
43680392 43790353 43890252 43760006 43679952 43589921
43309919 43169921 42979947 42940086 42990287 43010343SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Dec 9, 8:49 PM MST | Mesoscale Discussion | SPC | Bennett, Fall River, Gregory, Todd | 5 hr |
| Dec 10, 8:10 AM MST | Mesoscale Discussion | SPC | Aurora, Bon Homme, Brule, Charles Mix, Davison, Douglas and 11 more | 4 hr |
| Dec 10, 11:27 AM MST | Mesoscale Discussion | SPC | Bon Homme, Clay, Hanson, Hutchinson, Lake, Lincoln and 6 more | 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.