60’s are likely to make a much-anticipated appearance for the first time of 2021 during this upcoming week, but the Stateline’s first chances for thunderstorms are popping up in the forecast as well.
After a bitterly cold February, Rockford reached the 50’s for the first time this year just this past Wednesday on the 3rd when the high temperature hit 50° exactly. This comes over a month later than the climatological normal with the average for the first 50° day being February 1st. March 3rd was the longest Rockford had to wait for 50’s to return since 2015 (March 11th) and the first time the city had to wait any longer than January 10th since 2016 (February 19th). Rockford has not made it back into the 50’s since the 3rd having made it only into the lower 40’s on Thursday and Friday. However, 50’s will be back soon and the first 60° day appears to be right around the corner and it’s nearly right on time.
Midlevel and upper level ridging forming aloft on Sunday in addition to a shift in surface wind direction to southerly will begin our big warmup and pull the Stateline back into the 50’s for the latter half of the weekend. Continued warm air advection at all levels of the atmosphere will pull temperatures in the upper 50’s, possibly even lower 60’s, on Monday. March 5th is the average first 60° day in Rockford. Lower 60’s also appear likely on Tuesday and Wednesday as well before a cooldown is expected to begin late Wednesday.
While warming through the first half of the week, we will also see some added moisture being pulled into the Stateline and will result in a more even mix of clouds and clear sky for Sunday and Monday following a very sunny week. On the windward side of the ridge responsible in part for the warmup is a jet streak which will promote strong upward vertical motion and the quick formation of a low pressure system in the Central Plains on Tuesday. This system will quickly propagate northeastward and form quite a lot of rainfall around the storm’s center and along its frontal boundaries. The approaching system will bring the Stateline its next chance of rain as early as late Tuesday night. Scattered light showers appear likely through most of the day on Wednesday. The storm’s cold front is forecast to move through the Stateline late Wednesday night which brings the chance for some heavier rainfall and potentially a light thunderstorm or two. Plenty of dynamically forced lift through a saturated atmosphere and a melting layer only 3km above ground level could promote some lightning formation along the front though likely weak instability will keep any thunderstorms that do arise rather mild. This cold front will pull high temperatures back down into the lower 50’s for Thursday.