Mesoscale Discussion 0309
NWS Storm Prediction Center Norman OK
0244 PM CDT Tue Mar 31 2026
Areas affected...parts of northern and central Illinois...northern
Indiana
Concerning...Severe potential...Watch possible
Valid 311944Z - 312215Z
Probability of Watch Issuance...40 percent
SUMMARY...Isolated to widely scattered strong thunderstorm
development, including a couple supercells, appears possible late
this afternoon. It remains unclear if a new severe weather watch
will be needed, but trends are being monitored for this possibility.
DISCUSSION...In the wake of early day convection, substantive
pre-cold frontal boundary-layer destabilization appears ongoing in a
corridor across northern/central Illinois through northern Indiana.
This is occurring beneath 40-50 kt westerly flow around 500 mb, near
the southern fringe of the stronger westerlies, but in the wake of
one low-amplitude short wave migrating toward the lower Great Lakes
and generally well south of broad mid-level troughing overspreading
the Upper Midwest and adjacent upper Great Lakes region. Models
indicate at least subtly building mid-level heights across the
region into this evening.
However, low-level warm advection may be contributing to ongoing
renewed thunderstorm development southeast of Davenport IA toward
southern portions of the Greater Chicago area. And, at least some
convection allowing guidance suggests that a subtle linger mid-level
perturbation, now progressing west-northwest through north of the
Greater St. Louis area, may support additional storm development
during the next few hours.
While it remains unclear how widespread or organized convection may
become, the environment appears at least conditionally supportive of
supercells with potential to produce large hail, locally damaging
wind gusts, and perhaps a brief tornado.
..Kerr/Hart.. 03/31/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...IND...LOT...ILX...LSX...DVN...
LAT...LON 40249098 41189006 41518512 40618530 39258855 38889022
40249098
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
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