Monday afternoon storm update: Isolated storms remain possible through the night

 

6:40pm Update: A line of showers and isolated thunderstorms have developed and are currently moving through northern Illinois, with a storm centered over Byron. The risk for severe weather remains low, but a few of the storms through 9pm could have some heavy downpours, frequent lightning, and small hail.

It feels more like mid-summer rather than late April as temperatures have soared into the 80s, with Rockford's 5pm temperature currently at 85 degrees. South winds have also been strong gusting to 45 mph throughout much of the afternoon.

Outside of the warmth and wind our afternoon has been fairly quiet with regards to any showers or thunderstorms. That's because the warmth - not only at the surface, but aloft - has put a cap, or lid, on our atmosphere. You may have noticed over the last few hours cumulus clouds developing but really struggling to grow in depth. This is a sign that the cap is in place and holding strong.

A weak disturbance moving through eastern Iowa has been trying to break the cap - as indicated by some of the clouds beginning to 'bubble' in eastern Iowa and southwest Wisconsin. A few light rain showers have also been trying to develop. So far, not much has grown with a lot of the activity falling apart. However, some of the showers southwest of Madison, WI have started to grow some, moving to the northeast. This activity will not impact the Stateline.

Over the next couple hours there remains an isolated thunderstorm chance, but the overall coverage isn't expected to be widespread. In fact, this looks to be at only about a 20% chance.

The next chance for storms will be with the arrival of the cold front itself which will move in well after Midnight. Ongoing severe weather near the Iowa/Minnesota border will continue to move east, further into Minnesota and northern/central Wisconsin later tonight. To the southwest, thunderstorms have started to develop west of Kansas City,
MO along the tail end of the cold front. As the front moves east through the night showers and thunderstorms may begin to fill in between the two ongoing areas of severe weather, moving into central Iowa and eventually into eastern Iowa. By this time, a lot of the instability we were able to build up during the day will have decreased, but instability aloft will remain somewhat sufficient for thunderstorms. If this line fills in and the storms are able to hold together through the night, then a few of the stronger storms would be capable of producing strong winds and hail locally.

On the other hand, it's also possible that the line doesn't fill in and we remain mostly dry, but warm, through the night. Overall - I think our risk for severe weather is on the lower end through the rest of the evening and overnight. But until the cold front passes it's best to remain weather aware and be prepared just in case.