262 ACUS11 KWNS 152149 SWOMCD SPC MCD 152149 ILZ000-WIZ000-IAZ000-152315- Mesoscale Discussion 0454 NWS Storm Prediction Center Norman OK 0449 PM CDT Wed Apr 15 2026 Areas affected...portions of northern Illinois and southern Wisconsin Concerning...Severe potential...Watch possible Valid 152149Z - 152315Z Probability of Watch Issuance...40 percent SUMMARY...Some severe risk may develop along and north of a warm front this afternoon/evening. There remains uncertainty about the coverage/intensity of severe storms. A WW is possible. DISCUSSION...As of 2145 UTC, regional mesoanalysis showed a warm front was slowly lifting northward across northern IL and southern WI. To the south of the front, temperatures have warmed into the mid 70s with lower 60s F dewpoints supporting moderate destabilization. While thus far to the north of the front, instability has been more limited, area RAP soundings and subtle warming/moistening is likely supporting 500-1000 J/kg of MLCAPE, that will gradually expand northward with time. Deep-layer shear (40-50 kt EBWD) over much of the western Great Lakes region will remain supportive of organized convective modes with line segments and supercells possible. Damaging gust and hail could be possible with any stronger storms. While low-level moisture is somewhat limited, it should increase with time as the front lifts slowly north. Low-level shear is also fairly robust and expected to intensify this evening. This could support a risk for a couple tornadoes with any stronger line segment mesovorticies or with any supercells able to remain semi-discrete. With adequate destabilization taking place, ongoing storms over northeast IA will likely continue eastward. These storms have shown some organization into linear segments and at least weak storm scale rotation already. Additional storm development (possibly more discrete) is likely ongoing across northern IL. With storm coverage expected to increase with time, a severe risk appears plausible. A WW may be needed. ..Lyons/Hart.. 04/15/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LOT...MKX...DVN...ARX... LAT...LON 43318786 42608769 42168774 41988808 42028914 42189048 42359104 42629125 43159105 43409053 43608924 43588856 43498812 43318786 MOST PROBABLE PEAK TORNADO INTENSITY...85-115 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN