Mere hours after achieving record warmth, Stateline temperatures plummet toward what will be the coldest weather of the season.
Wednesday morning, the National Weather Service issued a wind advisory for a large portion of the Midwest including for every county on the Illinois side of the Stateline. Through the morning and afternoon, most of the Stateline saw wind gusts north of 40mph with sustained wind speeds greater than 30mph. These winds are the result of a tight pressure gradient associated with a large storm system that made its way into the Midwest Tuesday night. To illustrate the strength of this pressure gradient, the Rockford Airport recorded a 24.8mb drop in pressure in 24 hours, something that does not occur often in this part of the country. This pressure gradient naturally resulted in a strong temperature gradient with a potent cold front dividing the two air masses. The Stateline is feeling the full effect of both.
As strong winds came through from the south and southwest through Wednesday morning and afternoon, temperatures managed to warm into the upper 50’s across most of the Stateline. Rockford recorded a high of 62°. This is the warmest temperature ever recorded on a December 23rd in Rockford. This surpasses the prior record of 59° which was set back in 2015. Shortly thereafter, however, the system’s cold front moved over the area and caused temperatures to plummet. In the one hour between 2:54PM and 3:54PM, the temperature in Rockford dropped 10° from 60° to 50°. Strong westerly winds will continue to pull cold air into the Stateline through the night and into Thursday.
As of 7:40PM on Wednesday, temperatures have dropped into the middle 20’s through middle 30’s with wind chills as low as the single digits. Temperatures are forecast to continue falling into the early morning hours of Thursday until bottoming out in the low teens. Gusts upwards of 30-35mph will pull wind chills down below zero through the night and likely keep them there through the entirety of Thursday as well. Overnight between Thursday and Friday, temperatures are forecast to drop into the single digits with wind chills as cold as -10°. This will be the first time this season that temperatures will have fallen into the single digits. Subzero wind chills are expected for much of Friday morning with single digits wind chills expected through the rest of the day despite a small warmup with highs on Christmas Day forecast in the lower 20’s. Temperatures should be back in the 30’s for the weekend with temperatures near 40 possible for Sunday.