(10:15PM - 1/19/19) Now that the significant winter storm has departed Illinois tonight to the east, attention turns to the bitterly cold arctic air that will be moving into the Midwest, including Illinois tonight and Sunday night. This is going to lead to some very cold temperatures and even colder wind chills across portions of the state.
As you can see in the loop below, very cold temperatures advect southeast this evening and overnight into most of Illinois. Due to clear skies and fresh snow cover across the northern portion of Illinois, some areas could even drop to near or below 0 degrees by early tomorrow morning.
These cold temperatures coupled with still gusty north and northwest winds across much of Illinois (as seen in the loop below) will lead to dangerously cold wind chills across the northern half of Illinois, especially where temperatures get well into the single digits and winds remain gusty.
Taking a look at high resolution model guidance, we can see that places across northern and central Illinois will see wind chill values get down to -10 to -20 degrees below 0 by the predawn hours and into the morning tomorrow.
Cold temperatures are likely once again for Sunday night, with low temps near or below 0 over the snow-pack in Northern and Central Illinois. However, with lighter winds expected, wind chills should not be as low as Saturday night.