Mesoscale Discussion 1190

Issued

Jul 7, 2021, 7:15 PM MDT (01:15 UTC)

Expired

Jul 7, 2021, 9:15 PM MDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

40%

Counties Dawes County, NE, Custer County, SD, Fall River County, SD, Lawrence County, SD, Crook County, WY, Niobrara County, WY, Weston County, WY

The Rapid City radar (KUDX), 124 km from the middle of the area, began a volume at 01:16 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.

250 
ACUS11 KWNS 080115
SWOMCD
SPC MCD 080115 
SDZ000-NEZ000-WYZ000-080315-

Mesoscale Discussion 1190
NWS Storm Prediction Center Norman OK
0815 PM CDT Wed Jul 07 2021

Areas affected...Northeast Wyoming...far southwest South
Dakota...and far northwest Nebraska

Concerning...Severe potential...Watch possible 

Valid 080115Z - 080315Z

Probability of Watch Issuance...40 percent

SUMMARY...A developing line of storms may continue to intensify for
the next 1-2 hours and pose a severe wind risk. Confidence in the
longevity of this threat is low, and conditions will be monitored
for the need for a watch.

DISCUSSION...Recent regional radar and GOES IR imagery show
re-intensification of convection across northeast WY associated with
the remnants of an earlier cluster that moved out of southern MT.
This line of storms is developing along an instability gradient that
stretches from northeast WY into far western NE. Deep layer flow
across this region is oriented in a similar manner with 40-50 knots
of effective bulk shear along the boundary. With sunset still around
one hour away, a brief window will likely exist where the line of
storms can intensify and pose a severe wind risk across northeast WY
into adjacent areas of SD and NE. The longevity of this threat is
uncertain after 02z when diurnal cooling of a modestly moist air
mass (dewpoints in the upper 40s/low 50s noted) augments surface and
mixed-layer inhibition. Trends will continue to be monitored for the
need for a watch.

..Moore/Thompson.. 07/08/2021

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

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

LAT...LON   43930566 44420518 44740475 44650401 44260358 44030329
            43490287 43020271 42660291 42590356 42700434 43090507
            43610558 43930566

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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.