Alert archive / South Dakota / Mesoscale Discussions in 2021
Mesoscale Discussion 1692
The Storm Prediction Center issued this mesoscale discussion at Sep 3, 2021, 2:59 PM MDT for 5 counties in South Dakota; Campbell County, Crook County, Weston County, Wyoming. It was in force for 91 min.
The area
The outline as issued.
The facts
- Issued
- Sep 3, 2021, 2:59 PM MDT (20:59 UTC)
- Expired
- Sep 3, 2021, 4:30 PM MDT
- In force
- 91 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Custer County, SD, Fall River County, SD, Lawrence County, SD, Oglala Lakota County, SD, Pennington County, SD, Campbell County, WY, Crook County, WY, Weston County, WY
The radar
The Rapid City radar (KUDX), 143 km from the middle of the area, began a volume at 20:59 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 12:00Z, 9.0 hours before the alert went out and 139 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
- 1231 m above ground
- 0-6 km bulk shear
- 34 kt
- 0-1 km storm-relative helicity
- 0 m²/s²
- 0-3 km storm-relative helicity
- 15 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
065
ACUS11 KWNS 032059
SWOMCD
SPC MCD 032059
SDZ000-MTZ000-WYZ000-032230-
Mesoscale Discussion 1692
NWS Storm Prediction Center Norman OK
0359 PM CDT Fri Sep 03 2021
Areas affected...Northeast WY...western SD
Concerning...Severe potential...Watch unlikely
Valid 032059Z - 032230Z
Probability of Watch Issuance...20 percent
SUMMARY...Isolated severe thunderstorms will be possible through
this evening. Large hail and damaging winds will be the primary
severe threats. A watch is not currently expected, however trends
will be monitored.
DISCUSSION...Latest visible satellite imagery shows towering cumulus
across the higher terrain of northeast WY, where strong heating of
lower to mid 50s surface dew points has resulted in MLCAPE of
500-locally 750 J/kg. Westerly mid-level flow above low-level
southerly winds has resulted in a favorable environment for
supercells, with effective shear averaging 50 kts. Isolated severe
thunderstorms are expected to develop the remainder of this
afternoon across northeast WY, posing a risk for large hail and
strong/possibly damaging gusts. Storms may evolve into a cluster
with time, although diminishing instability will limit the severe
risk with eastward extent.
A watch is not expected given the anticipated isolated coverage,
however convective trends will be monitored.
..Bunting/Grams.. 09/03/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...UNR...CYS...BYZ...RIW...
LAT...LON 44150603 45100509 45080401 44710326 44330271 43960259
43320249 43130391 43210530 42970603 43250616 43560618
44150603SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 3, 1:20 PM MDT | Mesoscale Discussion | SPC | Goshen, Laramie, Niobrara, Platte | 55 min |
Nearby
Mesoscale Discussions in South Dakota, 2021Mesoscale Discussions in Wyoming, 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.