Mesoscale Discussion 1114

Issued

Jun 26, 2021, 6:08 PM CDT (23:08 UTC)

Expired

Jun 26, 2021, 7:15 PM CDT

In force

67 min

Issued by

the Storm Prediction Center

Concerning

Tornado watch 321...322

The Northern Indiana radar (KIWX), 34 km from the middle of the area, began a volume at 23:09 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 325Jun 26, 6:45 PM CDT

273 
ACUS11 KWNS 262309
SWOMCD
SPC MCD 262308 
MIZ000-OHZ000-INZ000-ILZ000-270015-

Mesoscale Discussion 1114
NWS Storm Prediction Center Norman OK
0608 PM CDT Sat Jun 26 2021

Areas affected...east-central Illinois...northwest Indiana...and
much of Lower Michigan

Concerning...Tornado Watch 321...322...

Valid 262308Z - 270015Z

The severe weather threat for Tornado Watch 321, 322 continues.

SUMMARY...Thunderstorms continue to occur across Illinois northeast
into Lower Michigan. The overall environment will continue to
support strong, gusty thunderstorm winds and a couple of tornadoes
for a few more hours likely requiring a local extension to Tornado
Watch #321. The need for additional watches downstream, however,
remain uncertain.

DISCUSSION...Two main bands of convection remain ongoing across the
region, with one moving out of west-central Illinois into northwest
Indiana, and another moving across Lower Michigan. Although both
bands of thunderstorms have trended more linear in nature the last
hour, supercellular-like structures remain embedded within the line
-- especially across Lower Michigan. 

Across Lower Michigan, the kinematic environment ahead of the line
remains favorable for low-level rotation, as the KDTX VAD indicates
strong low-level shear (greater than 30 knots in the surface to 1km
layer) within a veering-with-height wind profile (0-1KM SRH 220
m2/s2). This favorable wind field will support at least transient
low-level circulations for the next couple of hours.

Farther south, thunderstorms continue to move east-northeast out of
Illinois into northwest Indiana. Although low-level wind fields are
less favorable than farther north, deep-layer wind shear remains
sufficient to support thunderstorm updraft organization and the
organizational low-level circulation. Over the next few hours, these
thunderstorms should move east of the better deep-layer shear and a
transition to a more outflow dominant/wind threat. However, given
the very moist airmass in place and low LCLs, a couple of tornadoes
will still be possible. Areas downstream of Tornado Watch 321 will
continue to be monitored for future watch needs.

..Marsh.. 06/26/2021

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

ATTN...WFO...CLE...DTX...APX...IWX...GRR...IND...LOT...ILX...

LAT...LON   41648738 43858548 44888309 44618210 43278211 41808332
            41018457 39708684 39238811 39278855 39588914 40728831
            41648738

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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.