Several severe‑weather days ahead for northern Illinois

Monday:

Severe weather potential today remains rather low and isolated, largely due to a the capped atmosphere across the Stateline region. 

This is a layer of warm up that develops a few thousand feet above the surface that acts as a "lid" on the atmosphere, preventing storm development. Normally, you want temperatures to cool the further up you go into the atmosphere. 

But with a warm layer sitting overhead, storms can't bubble up and become mature or severe. That is why the better environment will be focused along the incoming surface low and the associated warm front up in the southern Minnesota and central Wisconsin. If anything were to bubble up this afternoon and evening, the main concerns would be hail, gusty winds and heavy rainfall.   

Tuesday:

Monday night's storms will play a primary role into Tuesday's potential as they will likely produce an outflow boundary which will track south towards our area by Tuesday morning. 

That boundary might be the primary initiating point for storms Tuesday afternoon. Once those storms develop, the environment Tuesday will be particularly volatile for severe weather. With higher instability and much less of a cap, all hazards of severe weather will be possible Tuesday, including a threat for tornadoes. The main timing for storms will be after 4-5PM. The Storm Prediction Center has highlighted a large area where severe weather may be a bit more numerous, including the entire Stateline under a Level 3 of 5 Enchained Risk. 

Wednesday:

This multi-day stretch of severe potential continues into Wednesday, though the overall setup won't be as volatile as what we're watching for Tuesday. Storm fuel looks lower, especially if we do end up seeing a batch of showers push through during the midday and early afternoon hours. For now, most of the area sits under a level 2 of 5 Slight Risk with damaging winds and hail being the primary concerns. 

Severe Weather Recap:

Monday: A "cap" will keep a "lid" on the atmosphere for much of the day. Any thunderstorm that does break the cap will be capable of producing large hail, winds, and heavy rainfall. 

Tuesday: Storm coverage will be more scattered and numerous with all hazard on the table. Mainly during the late afternoon and early evening. 

Wednesday: Showers will be more widespread, lowering storm fuel in the atmosphere. A few stronger storms will be possible with hail and wind being the main concerns.  

Late-Week Threat:

Friday is also a day that we've been monitoring. But with recent trends, it seems the Storm Prediction Center has left the best potential for strong to severe storms for areas west of the Mississippi River. Still, I would keep an eye on this as the forecast will likely change within the coming days.