Mesoscale Discussion 1446

Issued

Aug 8, 2021, 5:04 PM CDT (22:04 UTC)

Expired

Aug 8, 2021, 6:30 PM CDT

In force

86 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

The Sioux Falls radar (KFSD), 157 km from the middle of the area, began a volume at 22:06 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.

497 
ACUS11 KWNS 082204
SWOMCD
SPC MCD 082204 
IAZ000-MNZ000-082330-

Mesoscale Discussion 1446
NWS Storm Prediction Center Norman OK
0504 PM CDT Sun Aug 08 2021

Areas affected...Portions of Southwestern Minnesota and northern
Iowa

Concerning...Severe potential...Watch unlikely 

Valid 082204Z - 082330Z

Probability of Watch Issuance...20 percent

SUMMARY...Beneath an upper level trough, a few storms may pose an
isolated severe risk this evening. Storm coverage is expected to
remain low, but isolated severe hail or a brief tornado cannot be
ruled out.

DISCUSSION...Afternoon water vapor imagery showed a well-defined
vort max centered over southern Minnesota and the upper Midwest.
Daytime heating and ascent near the center of the vort max has
resulted in isolated convective development along the backside of
the low near the Iowa Minnesota border. SPC mesoanalysis indicates
1000-1500 J/kg of SBCAPE is present along with weak vertical shear
near 30 kts. While not overly supportive of severe weather, a few
stronger multicells or weak supercell structures may evolve as
convection moves southeastward into north-central Iowa. Moderate
buoyancy and cool temperatures beneath the upper low may support
severe hail with the strongest updrafts. Enhanced vertical vorticity
beneath the vort max and buoyancy concentrated near the ground may
also support the potential for a brief non-supercell tornado given
enhanced updraft/vorticity stretching. Convective trends are being
monitored, but high uncertainty on storm coverage/severity suggests
a weather watch is unlikely.

..Lyons/Hart.. 08/08/2021

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

ATTN...WFO...MPX...DMX...FSD...

LAT...LON   44179574 44069490 43829433 43649407 43509387 43369370
            43209366 42759349 42519371 42219419 42249498 42559542
            42779570 43649620 43989620 44169585 44179574

Mesoscale Discussions in Iowa, 2021Mesoscale Discussions in Minnesota, 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.