Mesoscale Discussion 1069

Issued

Jul 17, 2018, 5:49 PM MDT (23:49 UTC)

Expired

Jul 17, 2018, 7:45 PM MDT

In force

116 min

Issued by

the Storm Prediction Center

The Cheyenne radar (KCYS), 154 km from the middle of the area, began a volume at 23:51 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.

348 
ACUS11 KWNS 172349
SWOMCD
SPC MCD 172349 
NEZ000-SDZ000-COZ000-MTZ000-WYZ000-180145-

Mesoscale Discussion 1069
NWS Storm Prediction Center Norman OK
0649 PM CDT Tue Jul 17 2018

Areas affected...Northeast Wyoming...far northwest
Nebraska...Western South Dakota

Concerning...Severe Thunderstorm Watch 279...

Valid 172349Z - 180145Z

The severe weather threat for Severe Thunderstorm Watch 279
continues.

SUMMARY...Isolated severe threat continues, with a slow weakening
trend noted. Marginally severe hail/wind remain the primary threats.

DISCUSSION...Earlier discrete storms along the Wyoming/Montana
border have begun to grow upscale into a more loosely organized
convective complex. These storms are expected to progress slowly
eastward/southeastward over the next few hours, aided by modest
larger scale lift associated with an approaching mid-level shortwave
trough and left-exit region of a weak upper-level jet streak. 

An outflow boundary is oriented roughly along a line from CUT to
ECS, with more stable air located just to the east of the boundary.
Storms that may traverse the boundary have the best chance at
ingesting more buoyant surface based parcels and maintaining their
intensity, perhaps producing marginally severe hail/wind. As
nocturnal cooling sets in, the boundary layer will stabilize and any
remaining storms are expected to decrease in intensity, given that
effective bulk shear remains non-supportive of updraft organization.
 
Elsewhere across Severe Thunderstorm Watch 0279, the trend has been
for storms to weaken, and this trend will likely continue for the
remainder of the evening.

..Squitieri.. 07/17/2018

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

ATTN...WFO...LBF...UNR...GLD...BOU...CYS...BYZ...

LAT...LON   42490602 43350601 44790595 45000584 45160559 45250499
            45160396 45090355 44730274 44270230 43840216 43640211
            42690205 42130209 41220205 40160209 39640212 39550251
            39590339 39650360 40010383 40120456 40290484 40810480
            41080497 42450525 42550553 42550589 42490602

Mesoscale Discussions in Nebraska, 2018Mesoscale Discussions in Wyoming, 2018Mesoscale Discussions in Colorado, 2018Every mesoscale discussion in 2018

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.