Mesoscale Discussion 0291
NWS Storm Prediction Center Norman OK
0248 PM CDT Thu Mar 26 2026
Areas affected...Portions of Illinois...northern Indiana...into
southern lower Michigan and northwest Ohio
Concerning...Severe potential...Watch likely
Valid 261948Z - 262145Z
Probability of Watch Issuance...80 percent
SUMMARY...Thunderstorm development appears likely over the next
couple of hours along a surface cold front and various lake breeze
boundaries. Ample buoyancy and vertical shear for supercells and
line segments will support an increasing severe risk for all
hazards. A WW is likely.
DISCUSSION...As of 1945 UTC, visible imagery showed a deepening
cumulus field across portions of northern IL into northern IN, Lower
MI and northwestern OH. Mid-level ascent from a shortwave trough and
strong flow aloft north of a subtropical ridge has begun to erode
remnant inhibition from west to east. Amid strong diurnal heating,
dewpoints in the upper 50s to low 60s F are supporting 500-1500 J/kg
of MLCAPE. Continued destabilization is likely over the next couple
of hours, with a favorable cape/shear parameter space for supercells
and line segments. Hail, some very large, is likely with
supercellular elements, given steep mid-level lapse rates > 8 C/km.
A fairly quick transition to more linear structures appears likely
given the frontal forcing. This would favor a risk for
severe/damaging gusts as well.
The tornado threat, especially to the west, remains more uncertain.
Stronger heating/mixing has resulted in nearly 30 degree
temperature/dewpoint spreads over parts of IL, with veered low-level
flow. Still, elongated hodographs will favor supercells along the
frontal zone with hail and damaging gusts likely. The tornado threat
appears highest where low 60s F surface dewpoints hold, and stronger
low-level hodograph curvature is present. Primarily across IN/OH,
closer to the front.
Storms may develop across multiple areas of the surface front and
lake breeze this afternoon into this evening before rapidly
increasing in coverage. Given the expected increase in severe
potential a WW is likely needed this afternoon.
..Lyons/Smith.. 03/26/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ILN...DTX...IWX...GRR...IND...LOT...ILX...LSX...
DVN...
LAT...LON 42148522 42108469 41668423 41218419 40118451 39658502
39608510 38858825 38999023 39439082 39889086 40629010
41298926 41638787 41768688 42088590 42148522
MOST PROBABLE PEAK TORNADO INTENSITY...100-130 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN
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