Mesoscale Discussion 1205

Issued

Jul 8, 2021, 4:56 PM MDT (22:56 UTC)

Expired

Jul 8, 2021, 7:00 PM MDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 352...353...354

The Bismarck radar (KBIS), 160 km from the middle of the area, began a volume at 22:58 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

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• Severe Thunderstorm Watch 355Jul 8, 8:30 PM MDT

636 
ACUS11 KWNS 082256
SWOMCD
SPC MCD 082256 
SDZ000-NDZ000-MTZ000-090100-

Mesoscale Discussion 1205
NWS Storm Prediction Center Norman OK
0556 PM CDT Thu Jul 08 2021

Areas affected...Northeast Montana...Western North Dakota...Western
South Dakota

Concerning...Severe Thunderstorm Watch 352...353...354...

Valid 082256Z - 090100Z

The severe weather threat for Severe Thunderstorm Watch 352, 353,
354 continues.

SUMMARY...The severe threat across the northern High Plains is
expected to increase in coverage over the next couple of hours. Very
large hail and wind damage will be possible. A brief tornado could
also occur.

DISCUSSION...The latest radar imagery from Glasgow, Montana shows
two short line segments ongoing across northeast Montana and far
northwestern North Dakota. The eastern most line in far northwest
North Dakota is the most vigorous with a several embedded
supercells. The RAP is analyzing a pocket of moderate to strong
instability just ahead of this line, with MLCAPE estimated in the
2000 to 2500 J/kg range. This line of strong to severe storms is
being supported by a shortwave trough evident on water vapor imagery
over eastern Montana. As large-scale ascent moves eastward across
the northern High Plains this evening, cell coverage is expected to
increase. The instability combined with 40 to 50 kt of deep-layer
shear will be favorable for large hail and wind damage associated
with supercells and organized line segments. A brief tornado may
also occur with supercells that remain dominant.

Further to the south, the Rapid City, South Dakota high resolution
radar shows an isolated supercell about 40 statute miles to the
north of Rapid City. The Rapid City WSR-88D VWP has 0-6 km shear
near 60 kt which will continue to support the supercell early this
evening. The shear combined with steep mid-level lapse rates of 8.0
C/km according to the RAP, will support a threat for large hail.
Isolated very large hail (hailstones greater than 2 inches in
diameter) will be possible. A wind-damage threat will also exist.

..Broyles.. 07/08/2021

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

ATTN...WFO...ABR...BIS...UNR...BYZ...GGW...

LAT...LON   44370208 45110145 46770129 48200156 48640189 48890247
            48900362 48760401 48400420 47960423 46550411 44570386
            44230320 44370208

Mesoscale Discussions in North Dakota, 2021Mesoscale Discussions in South Dakota, 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.