Mesoscale Discussion 1162

Issued

Jul 6, 2021, 1:06 PM CDT (18:06 UTC)

Expired

Jul 6, 2021, 3:00 PM CDT

In force

114 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

60%

The Sioux Falls radar (KFSD), 114 km from the middle of the area, began a volume at 18:07 UTC, the scan nearest the moment this went out.

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• Severe Thunderstorm Watch 338Jul 6, 2:00 PM CDT

109 
ACUS11 KWNS 061806
SWOMCD
SPC MCD 061806 
WIZ000-MNZ000-IAZ000-SDZ000-NEZ000-062000-

Mesoscale Discussion 1162
NWS Storm Prediction Center Norman OK
0106 PM CDT Tue Jul 06 2021

Areas affected...northeast Nebraska southeast South Dakota and
portions of  Minnesota Iowa and Wisconsin

Concerning...Severe potential...Watch possible 

Valid 061806Z - 062000Z

Probability of Watch Issuance...60 percent

SUMMARY...Strong/severe storms developing ahead of and along a
remnant MCV/stationary front through the upper Midwest may pose a
severe risk as they move northeast through the day. Severe hail and
damaging wind gusts appear to be the mean threats. Convective trends
are being monitored as a weather watch may be needed.

DISCUSSION...As observed by regional radar mosaics and midday
visible imagery, a cluster of elevated thunderstorms has shown signs
of organization/intensification this morning across portions of
Nebraska, and south Dakota. Likely driven by enhanced lift ahead of
the MCV and along the stationary front, these storms should
gradually become surface based as they track northeastward.
Downstream, clearing skies south of the front have allowed
temperatures to warm into the low to mid 80s F across southern
Minnesota and far northern Iowa. To the north, residual cloud cover
has limited heating so far, but breaks in the clouds should allow
some warming through the afternoon. With the warm temperatures and
dewpoints in the mid to upper 60s F, moderate buoyancy (1500-2000
J/kg MLCAPE) is forecast to materialize despite modest mid-level
lapse rates. As lift from the approaching MCV increases, additional
thunderstorm development appears likely along and north of the
stationary front through southern Minnesota and farther southwest
along the surging cold front in central Nebraska. Regional 12z
soundings and VWPs show enhanced mid-level shear associated with the
MCV across portions of South Dakota and northeastern Nebraska. 30-35
kts of effective shear should support organized short line segments
and a few supercells this afternoon. Hail and damaging wind gusts
appear to be the most likely threat, though a brief tornado will be
possible with greater low-level shear from backed surface flow along
the boundary through southern Minnesota and western Wisconsin.
Upscale growth into a forward propagating MCS appears likely later
this evening as storms congeal heading into southwestern Wisconsin.
A somewhat more organized wind threat may evolve there if a deeper
cold pool can become established. Given the favorable environment
and potential storm coverage, convective trends are being monitored.
A weather watch may be needed over portions of the area later this
afternoon/evening as convection becomes more organized.

..Lyons/Guyer.. 07/06/2021

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

ATTN...WFO...ARX...MPX...DMX...FSD...OAX...ABR...GID...LBF...

LAT...LON   44919120 44709061 43959055 43539122 43509241 43529407
            43489521 43099614 42439715 41199892 40960031 41070055
            41530058 42739936 44299773 44589661 45049479 45169276
            44919120

Mesoscale Discussions in Minnesota, 2021Mesoscale Discussions in South Dakota, 2021Mesoscale Discussions in Nebraska, 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.