Mesoscale Discussion 2139

Issued

Aug 26, 2026, 1:43 PM MDT (19:43 UTC)

Expired

Aug 26, 2026, 4:15 PM MDT

In force

3 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

60%

The Denver radar (KFTG), 70 km from the middle of the area, began a volume at 19:43 UTC, the scan nearest the moment this went out.

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• Severe Thunderstorm Watch 629Aug 26, 3:50 PM MDT

813 
ACUS11 KWNS 261944
SWOMCD
SPC MCD 261943 
COZ000-NEZ000-WYZ000-262215-

Mesoscale Discussion 2139
NWS Storm Prediction Center Norman OK
0243 PM CDT Wed Aug 26 2026

Areas affected...southeast Wyoming...far southwest Nebraska
Panhandle...and eastern Colorado

Concerning...Severe potential...Watch possible 

Valid 261943Z - 262215Z

Probability of Watch Issuance...60 percent

SUMMARY...An initially isolated severe storm threat is expected to
develop by mid to late afternoon, mainly in the form of large hail
up to two inches. The potential for severe wind gusts up to 65-75
mph may increase this evening. A watch is possible by 21-22Z.

DISCUSSION...Visible satellite and lightning data indicate deepening
cumulus and early thunderstorm development from the Laramie
Mountains to the Sangre de Cristo Range, as well as along a subtle
boundary over east-central CO into northwest KS. The presence of
steep low/mid-level lapse rates, surface dewpoints in the 50 to low
60s, and considerable daytime heating are contributing to a
destabilizing air mass east of the mountains with MLCAPE expected to
increase to 1500-2000 J/kg later this afternoon with minimal
convective inhibition. As such, expect storms to gradually move off
the high terrain with greater uncertainty in the evolving convection
over east-central CO. The presence of 30-35 kt of deep-layer shear
may support a few supercells capable of large hail up to two inches
as the initial hazard. 

By this evening, there is some model signal for storms to merge into
clusters, at which point the threat for severe winds with gusts up
to 65-75 mph would increase.

..Mead/Mosier.. 08/26/2026

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

ATTN...WFO...GLD...PUB...BOU...CYS...

LAT...LON   38720513 40010526 40930528 41600496 41670414 40820286
            40100228 38980213 37880233 37310327 37230400 37460474
            38720513 

MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN

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The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; radar from the NEXRAD Level II archive.