Alert archive / Nebraska / Mesoscale Discussions in 2021
Mesoscale Discussion 995
The Storm Prediction Center issued this mesoscale discussion at Jun 18, 2021, 12:27 PM MDT for Box Butte County, Dawes County, Sioux County, Nebraska; Goshen County, Wyoming. It was in force for 93 min.
The area
The outline as issued.
The facts
- Issued
- Jun 18, 2021, 12:27 PM MDT (18:27 UTC)
- Expired
- Jun 18, 2021, 2:00 PM MDT
- In force
- 93 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
Counties Box Butte County, NE, Dawes County, NE, Sioux County, NE, Goshen County, WY
The radar
The Cheyenne radar (KCYS), 171 km from the middle of the area, began a volume at 18:27 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, 6.5 hours before the alert went out and 190 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
- 2289 m above ground
- 0-6 km bulk shear
- 40 kt
- 0-1 km storm-relative helicity
- -52 m²/s²
- 0-3 km storm-relative helicity
- 47 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
339
ACUS11 KWNS 181827
SWOMCD
SPC MCD 181827
NEZ000-SDZ000-WYZ000-182000-
Mesoscale Discussion 0995
NWS Storm Prediction Center Norman OK
0127 PM CDT Fri Jun 18 2021
Areas affected...East-central Wyoming...far northwest Nebraska...and
far southwest South Dakota
Concerning...Severe potential...Watch unlikely
Valid 181827Z - 182000Z
Probability of Watch Issuance...5 percent
SUMMARY...A storm or two, capable of mostly large hail, will be
possible across mostly western Nebraska through the afternoon.
DISCUSSION...A storm has developed rather quickly near the border of
WY/SD/NE in Sioux county, Nebraska in a region of weak upslope flow.
Visible satellite imagery shows cumulus clustered in this small
region with some hints at additional towers forming to the west.
Therefore, another storm or two cannot be ruled out. SPC
mesoanalysis indicated MLCAPE around 1000 to 1500 J/kg in this
region with effective shear around 40 knots. This is sufficient for
storm organization including supercells. Given the nebulous forcing
and relatively small region with favorable conditions, do not
anticipate this threat being great enough, or lasting long enough to
warrant a severe thunderstorm watch.
..Bentley.. 06/18/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LBF...UNR...CYS...
LAT...LON 42360474 42860451 43140396 43070308 42750270 42300277
42040317 41950375 42120453 42360474SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 18, 5:34 PM MDT | Mesoscale Discussion | SPC | Banner, Kimball, Scotts Bluff | 86 min |
Nearby
Mesoscale Discussions in Nebraska, 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.