Alert archive / Wyoming / Mesoscale Discussions in 2021
Mesoscale Discussion 967
The Storm Prediction Center issued this mesoscale discussion at Jun 14, 2021, 1:24 PM MDT for Sioux County, Nebraska; Custer County, Fall River County, Lawrence County, South Dakota; 7 counties in Wyoming. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 14, 2021, 1:24 PM MDT (19:24 UTC)
- Expired
- Jun 14, 2021, 4:00 PM MDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Sioux County, NE, Custer County, SD, Fall River County, SD, Lawrence County, SD, Campbell County, WY, Converse County, WY, Crook County, WY, Johnson County, WY, Niobrara County, WY, Sheridan County, WY, Weston County, WY
The radar
The Rapid City radar (KUDX), 190 km from the middle of the area, began a volume at 19:27 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, 7.4 hours before the alert went out and 184 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
- 234 J/kg
- Mixed-layer CIN
- -457 J/kg
- Mixed-layer LCL
- 1503 m above ground
- 0-6 km bulk shear
- 21 kt
- 0-1 km storm-relative helicity
- 32 m²/s²
- 0-3 km storm-relative helicity
- 57 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.3
The text
As transmitted.
055
ACUS11 KWNS 141924
SWOMCD
SPC MCD 141924
SDZ000-NEZ000-WYZ000-MTZ000-142200-
Mesoscale Discussion 0967
NWS Storm Prediction Center Norman OK
0224 PM CDT Mon Jun 14 2021
Areas affected...portions of eastern Wyoming...western South
Dakota...far northwest Nebraska
Concerning...Severe potential...Watch unlikely
Valid 141924Z - 142200Z
Probability of Watch Issuance...20 percent
SUMMARY...Isolated strong thunderstorms are expected to gradually
develop and intensify over the next few hours. Large hail and
damaging gusts appear to be the primary threats with these storms.
Storm coverage is expected to be too sparse to warrant a WW
issuance.
DISCUSSION...Visible satellite and MRMS mosaic radar data show
convective initiation underway in proximity to the Big Horn
Mountains in northern WY, and Lawrence County, SD. Across portions
of eastern WY into western SD and far northwest NE, diurnal heating
is gradually eroding MLCINH per 15-19Z mesoanalysis trends. Moist
upslope low-level flow should also support isolated thunderstorm
development through the afternoon/early evening hours. Upper
50s/near 60 F surface dewpoints have been advecting northwestward
beneath 7.5-8.5 C/km low and mid-level lapse rates, contributing to
1500+ J/kg MLCAPE. While wind speeds are rather weak in the
surface-500 mb layer, gradual veering with height, along with some
speed shear above 500 mb, are contributing to 30-45 kts of effective
bulk shear. Transient supercells may manifest from the longer
lasting storms given the expected isolated coverage and
aforementioned thermodynamic/kinematic environment.
The steep mid-level lapse rates will support large hail with any
robust updraft that can become established. Damaging gusts may also
occur with the stronger storm cores given the somewhat dry, mixed
boundary layer/steep low-level lapse rates. Still, a WW issuance
appears unlikely given the anticipated low storm coverage.
..Squitieri/Grams.. 06/14/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...UNR...CYS...BYZ...RIW...
LAT...LON 42300390 42260441 42290500 42460564 42620592 43270639
44010697 44680760 44990761 45040689 44930555 44760457
44470363 44250336 43670326 43000328 42830323 42300390SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 13, 6:15 PM MDT | Mesoscale Discussion | SPC | Arthur, Banner, Box Butte, Chase, Cherry, Cheyenne and 17 more | 2 hr |
| Jun 13, 8:39 PM MDT | Mesoscale Discussion | SPC | Arthur, Cherry, Garden, Grant, Hooker, McPherson and 1 more | 2 hr |
| Jun 14, 2:51 PM MDT | Mesoscale Discussion | SPC | Banner, Kimball, Scotts Bluff | 114 min |
Nearby
Mesoscale Discussions in Wyoming, 2021Mesoscale 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.