Mesoscale Discussion 952

Issued

Jun 13, 2021, 1:16 PM MDT (19:16 UTC)

Expired

Jun 13, 2021, 2:45 PM MDT

In force

89 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

60%

Counties Banner County, NE, Box Butte County, NE, Cheyenne County, NE, Dawes County, NE, Garden County, NE, Kimball County, NE, Morrill County, NE, Scotts Bluff County, NE, Sheridan County, NE, Sioux County, NE, Custer County, SD, Fall River County, SD, Lawrence County, SD, Oglala Lakota County, SD, Pennington County, SD, Goshen County, WY, Laramie County, WY, Niobrara County, WY, Platte County, WY, Weston County, WY

The Cheyenne radar (KCYS), 168 km from the middle of the area, began a volume at 19:18 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.

• Severe Thunderstorm Watch 268Jun 13, 3:05 PM MDT

236 
ACUS11 KWNS 131917
SWOMCD
SPC MCD 131916 
NEZ000-SDZ000-WYZ000-132045-

Mesoscale Discussion 0952
NWS Storm Prediction Center Norman OK
0216 PM CDT Sun Jun 13 2021

Areas affected...Eastern Wyoming...western Nebraska...and southwest
South Dakota

Concerning...Severe potential...Watch possible 

Valid 131916Z - 132045Z

Probability of Watch Issuance...60 percent

SUMMARY...A few severe thunderstorms may develop early this
afternoon and track eastward with a risk of hail and damaging wind
gusts. Upscale growth later this evening with the arrival of
stronger westerly flow aloft may promote a greater risk of damaging
winds across western Nebraska.

DISCUSSION...Early afternoon satellite and RADAR observations have
shown the development of isolated immature updrafts along the
southern Laramie Range of Wyoming and South Dakota Black Hills in
the last half hour. Strong solar heating is ongoing with surface
temperatures in the upper 70s to mid 80s noted across eastern
Wyoming. SPC mesoanalysis and regional observations show dewpoints
in the upper 50s and low 60s along with steep low and mid-level
lapse rates are contributing to large buoyancy of 2500-3500 J/kg of
MLCAPE. Weak inhibition remains in place, likely due to the lack of
strong forcing for ascent and weak mid-level height rises ahead of
the stronger southwesterly flow to the west. However, continued
heating and weak easterly upslope flow should gradually erode
inhibition and allow the development of thunderstorms as early as
20z. Given the degree of buoyancy and large CAPE (>1500 J/kg) in the
hail-growth layer suggests hail will be the primary severe threat
with initial storms. Some damaging wind potential may also exist
with storms as downdrafts mature and move into a warmer and better
mixed boundary layer to the east, but shear overall remains weak.

Later this afternoon and early this evening, hi-res cam guidance
hints at the possibility of a more organized storm mode (ie:
clusters and short line segments) evolving out of initial cellular
convection as stronger deep-layer flow ahead of weak shortwave
trough ejecting eastward. Should this occur, a greater threat for
damaging wind gusts may evolve across western Nebraska as cold pools
become deeper and better organized.

..Lyons/Grams.. 06/13/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...LBF...UNR...CYS...

LAT...LON   42880541 44420462 44420295 44270267 44130249 43360198
            42500194 41480200 41160206 41000313 41030451 41020468
            41040532 41340566 42300554 42880541

Mesoscale Discussions in Nebraska, 2021Mesoscale Discussions in South Dakota, 2021Mesoscale Discussions in Wyoming, 2021Every mesoscale discussion in 2021

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.