Mesoscale Discussion 1033

Issued

Jun 20, 2021, 1:10 PM CDT (18:10 UTC)

Expired

Jun 20, 2021, 2:45 PM CDT

In force

95 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

60%

The Des Moines radar (KDMX), 174 km from the middle of the area, began a volume at 18:13 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.

• Severe Thunderstorm Watch 293Jun 20, 1:45 PM CDT
• Severe Thunderstorm Watch 294Jun 20, 4:00 PM CDT

348 
ACUS11 KWNS 201811
SWOMCD
SPC MCD 201810 
WIZ000-MNZ000-IAZ000-201945-

Mesoscale Discussion 1033
NWS Storm Prediction Center Norman OK
0110 PM CDT Sun Jun 20 2021

Areas affected...central and north-central IA...southeast
MN...west-central WI

Concerning...Severe potential...Watch possible 

Valid 201810Z - 201945Z

Probability of Watch Issuance...60 percent

SUMMARY...Isolated to scattered damaging gusts and some risk for
large hail with the stronger cores are expected this afternoon.

DISCUSSION...Visible-satellite imagery shows a cumulus field over
northern IA and southern MN in wake of an eastward-moving MCV
located near La Crosse, WI.  At the surface, a low was analyzed at
1pm over west-central MN with a cold front extending southward into
eastern NE.  Temperatures have warmed into the lower 80s across
west-central IA northeastward to the I-35 corridor near the MN/IA
border.  Overlapping the thermal ridge, a moist axis extends from
southwest to northeast with dewpoints ranging from mid 70s in
southwest IA to the mid 60s in north-central IA.  RAP forecast
soundings show around 1000 J/kg MLCAPE near the IA/MN border at 1pm
but additional heating/destabilization will result in 2000 J/kg in a
few hours.  

Water-vapor imagery shows a mid-level disturbance moving into
eastern SD early this afternoon.  Increasing large-scale ascent with
this feature and a weakening cap will lead to thunderstorms
developing over southern MN into western portions of IA this
afternoon.  Strong to severe multicells and a few supercells will be
possible with the stronger activity.  A coalescing into a band of
storms is expected with time, especially with farther north extent. 
It remains uncertain how far and how quickly the severe risk will
develop eastward into west-central WI and far southeast MN/northeast
IA given the recovery/destabilization needed to occur in wake of the
early day convection.

..Smith/Hart.. 06/20/2021

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

ATTN...WFO...ARX...MPX...DMX...

LAT...LON   42419492 43809467 44859357 45029257 44769188 43779135
            43399224 41939305 41859384 41909463 42419492

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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.