Alert archive / Wyoming / Mesoscale Discussions in 2021
Mesoscale Discussion 1277
The Storm Prediction Center issued this mesoscale discussion at Jul 13, 2021, 7:35 PM MDT for Custer County, Fall River County, Lawrence County, South Dakota; 5 counties in Wyoming. It was in force for 85 min.
The area
The outline as issued.
The facts
- Issued
- Jul 13, 2021, 7:35 PM MDT (01:35 UTC)
- Expired
- Jul 13, 2021, 9:00 PM MDT
- In force
- 85 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 376
Counties Custer County, SD, Fall River County, SD, Lawrence County, SD, Campbell County, WY, Converse County, WY, Crook County, WY, Niobrara County, WY, Weston County, WY
The radar
The Rapid City radar (KUDX), 167 km from the middle of the area, began a volume at 01:37 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, 1.6 hours before the alert went out and 163 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
- 35 J/kg
- Mixed-layer CIN
- -271 J/kg
- Mixed-layer LCL
- 1660 m above ground
- 0-6 km bulk shear
- 46 kt
- 0-1 km storm-relative helicity
- 8 m²/s²
- 0-3 km storm-relative helicity
- 227 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
170
ACUS11 KWNS 140135
SWOMCD
SPC MCD 140135
SDZ000-NEZ000-MTZ000-WYZ000-140300-
Mesoscale Discussion 1277
NWS Storm Prediction Center Norman OK
0835 PM CDT Tue Jul 13 2021
Areas affected...Eastern WY...Southwest SD...Western NE Panhandle
Concerning...Severe Thunderstorm Watch 376...
Valid 140135Z - 140300Z
The severe weather threat for Severe Thunderstorm Watch 376
continues.
SUMMARY...Damaging wind gusts remain possible within Severe
Thunderstorm Watch 376 over northeast/east-central WY, southwest SD,
and the western NE Panhandle.
DISCUSSION...Two distinct storm clusters have developed within
Severe Thunderstorm Watch 376. The northernmost cluster is moving
southeastward through northern Campbell and Crook Counties in
northeast WY. Storms within this cluster have produced measured wind
gusts of 62 and 72 mph. Downstream air mass into southwest SD is not
overly buoyant but continued low-level southeasterly flow should
provide some low-level moisture advection as well as increase
convergence on the leading edge of the cold pool. These factors
should allow the cluster to persist as it moves southeastward, with
an attendant threat for damaging wind gusts.
The southernmost cluster is moving into Converse County in
east-central WY. Storms within this cluster have weakened over the
past hour or so. However, buoyancy increases modestly downstream
into more of southeast WY and adjacent western NE Panhandle. Like
the areas farther north, some increase in low-level moisture is
possible here as well, contributing to enough buoyancy for
additional updrafts within this cluster. Damaging wind gusts remain
possible with this cluster.
..Mosier.. 07/14/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...UNR...CYS...BYZ...RIW...
LAT...LON 44690565 45030509 45000367 44150274 42050410 42780628
43710612 44690565SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 13, 10:30 PM MDT | Mesoscale Discussion | SPC | Bennett, Custer, Fall River, Jackson, Lawrence, Meade and 2 more | 90 min |
Nearby
Mesoscale Discussions in Wyoming, 2021Mesoscale 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.