Mesoscale Discussion 1421

Issued

Jul 1, 2026, 2:34 PM CDT (19:34 UTC)

Expired

Jul 1, 2026, 4:30 PM CDT

In force

116 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch likely

Chance of a watch

80%

The Quad Cities radar (KDVN), 64 km from the middle of the area, began a volume at 19:33 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.

523 
ACUS11 KWNS 011934
SWOMCD
SPC MCD 011934 
ILZ000-WIZ000-IAZ000-012130-

Mesoscale Discussion 1421
NWS Storm Prediction Center Norman OK
0234 PM CDT Wed Jul 01 2026

Areas affected...south-central ad eastern Iowa...northern
Illinois...and southern Wisconsin.

Concerning...Severe potential...Watch likely 

Valid 011934Z - 012130Z

Probability of Watch Issuance...80 percent

SUMMARY...The severe storm threat is expected to increase this
afternoon and into the evening.

DISCUSSION...A cluster of cumulus has had several initiation
attempts with intermittent lightning across northeast Iowa. These
initial attempts are likely struggling with the remaining
mixed-layer inhibition observed by the 18Z DVN RAOB. Thus far, no
storms have become rooted, but given the expansive nature of the
cumulus cluster and repeated attempts in this region as well as
additional boundary layer heating, expect eventual storm development
from this activity. In addition, storms are likely across central
and south-central Iowa this evening within the same maximum
instability axis as ascent increases across this area. 50+ knots of
mid-level flow (per DMX VWP) will support supercell storm mode and a
threat for large hail and severe winds. As the low-level jet
intensifies this evening, low-level shear will increase. Shear will
be mostly unidirectional, but the strong speed shear, and any
additional low-level vorticity along the boundary from earlier
convection, could lead to some tornado threat this evening. 

A watch will likely be needed at some point this afternoon/evening.
However, the timing remains somewhat uncertain. If the storm
attempts across northeast Iowa become rooted, the watch may be
issued soon, but if they continue to struggle, it may be later this
afternoon before one is needed.

..Bentley/Guyer.. 07/01/2026

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

ATTN...WFO...LOT...MKX...DVN...ARX...DMX...

LAT...LON   40789292 40719462 41099473 41559435 42059358 43029144
            43588950 43598767 43208784 42778769 42258772 41528934
            40889169 40819262 40789292 

MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN

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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.