Thunderstorms possible Monday night following record warmth

 

NEW: SEVERE THUNDERSTORM WARNING for Jo Daviess, western Stephenson and northern Carroll counties until 10pm. The storm is located south of Galena, moving east at 50 mph and capable of producing 60 mph wind gusts and half dollar sized hail.

There is another storm moving through DeKalb County, right along I-88. Had a report of quite a bit of hail in Creston (likely some smaller hail but coming down with the heavy rain). This storm is just south of Malta and DeKalb. No warning with this storm, but it is producing quite a bit of lightning, heavy rain, and small hail.

7:45PM UPDATE: Skies are mainly quiet for now, but the showers and thunderstorms developing out west are the ones we are keeping an eye for our risk of thunderstorms later tonight, most likely after 9pm near Rockford. There are some isolated thunderstorms that have developed between Davenport and Clinton, IA and those could impact parts of Carroll and Whiteside counties.

ORIGINAL POST: 

It's a little taste of summer at the end of March as temperatures area-wide warmed into the upper 70s and low 80s. In fact, Rockford made it to 82 degrees which tied our previous record for the 30th of March set back in 1910! And what's even more impressive is the fact we started out in the upper 30s! But the warmth we've experienced this afternoon could lead to a few stronger thunderstorms late tonight.

Rest of the evening/Overnight:

Cloud cover will slowly increase (you're already noticing the higher-level cirrus clouds overhead) through the evening as temperatures remain in the 70s. We should stay dry through at least sunset, if not an hour or two after. Thunderstorms are expected to develop over parts of northern Iowa, extending east towards southwest Wisconsin through 8pm. Between 8pm and 10pm those storms may then move into northwest Illinois, shifting east by Midnight. The storms will be developing along/near a warm front, that currently sits well north of the state line. This front will slowly sink south, likely staying very close to southern Wisconsin and northern Illinois.

The storms will move east along the warm front posing a large hail risk, feeding off the instability we will have aloft - known as elevated instability. However, there should be a gradual weakening trend in that instability the further east you travel of the Mississippi River. The highest potential for large hail tonight could end up in Iowa, far northwest Illinois and southwest Wisconsin. Regardless, our storm window appears to be from around 9pm to 2am. There may be some widely scattered showers and thunderstorms that continue through sunrise Tuesday. Because of the risk for large hail the Storm Prediction Center has highlighted southern Wisconsin and northern Illinois in a 'slight' risk for scattered severe storms late Monday night.

Tuesday:

What happens Tuesday afternoon will depend on what we see Tuesday morning. An area of low pressure will be approaching from the west during the early afternoon, dragging a cold front through with it. We hold on to some instability as the front moves through which could trigger some additional thunderstorms during the early afternoon and evening. Should those storms form, hail and damaging winds would again be our primary concerns.

Temperatures ahead of the front will warm into the low 70s but then are expected to quickly drop behind the front Tuesday evening. By Tuesday night the front will settle to our south and this could temporarily bring an end to our precipitation chances. However, it will be pulled back north ahead of another low that could bring more widespread and heavy rainfall Wednesday night and Thursday.