Mesoscale Discussion 1690

Issued

Sep 3, 2021, 1:20 PM MDT (19:20 UTC)

Expired

Sep 3, 2021, 2:15 PM MDT

In force

55 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

Counties Adams County, CO, Arapahoe County, CO, Elbert County, CO, Morgan County, CO, Washington County, CO, Weld County, CO, Banner County, NE, Kimball County, NE, Scotts Bluff County, NE, Sioux County, NE, Goshen County, WY, Laramie County, WY, Niobrara County, WY, Platte County, WY

The Cheyenne radar (KCYS), 53 km from the middle of the area, began a volume at 19:20 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.

303 
ACUS11 KWNS 031921
SWOMCD
SPC MCD 031920 
NEZ000-COZ000-WYZ000-032015-

Mesoscale Discussion 1690
NWS Storm Prediction Center Norman OK
0220 PM CDT Fri Sep 03 2021

Areas affected...southeast WY...northeast CO...western NE Panhandle

Concerning...Severe potential...Watch unlikely 

Valid 031920Z - 032015Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated strong to severe storms will be possible this
afternoon with a risk for large hail and strong/damaging gusts.  The
severe risk is expected to remain isolated in coverage, and a watch
is not currently expected.

DISCUSSION...Isolated/widely scattered thunderstorms have developed
across eastern WY as of 1915z, aided by ascent associated with a
departing upper-level trough.  Clouds have only recently begun to
clear over much of this area, and the delayed onset of stronger
diurnal heating has resulted in only weak instability (MLCAPE on the
order of 500 J/kg).  Farther south, a few storms have developed over
the higher terrain of north-central and central CO.  As the
afternoon progresses, some additional destabilization is expected
across the discussion area given heating in the presence of upper
50s/lower 60s surface dew points with MLCAPE locally approaching
1000 J/kg.  Westerly mid-level flow averaging 30 kts coupled with
low-level southeast flow will result in sufficient shear for storm
organization, and isolated supercells will be possible this
afternoon posing a risk for large hail and strong/possibly damaging
gusts.  A couple of clusters of storms may ultimately evolve by late
afternoon or early evening, with a continued severe risk as storms
move east across the adjacent plains.  

The overall severe risk is expected to remain isolated, and a watch
is not currently expected.

..Bunting/Grams.. 09/03/2021

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

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

LAT...LON   42750538 43280468 42920393 42270348 41000317 40130316
            39650320 39260327 39090356 39090428 39310470 41130492
            42310543 42750538

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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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.