We continue to watch what looks to be a strong and impressive storm system coming into the Midwest as early as late tomorrow night/Wednesday morning and lasting through Thursday evening. A potpourri of precipitation types is expected with this system over its entire duration, including accumulating snow across portions of Illinois. I dig into the latest details and thoughts below...
The system of interest is still up over southwest Canada late this afternoon but is about to enter the U.S. across the Pacific northwest and eventually dig southward into the central Rockies region by late tomorrow night and early Wednesday morning. It will then eventually come east and ENE across the plains and into the heart of our region during the day on Thursday.
A period of strong warm air advection across the plains due to a strengthening low level jet late tomorrow night east of the developing area of low pressure will aid in precipitation developing along and north of the frontal boundary (circled area in orange) front across the plains. This will mean snow as well, developing across the state of Kansas and ENE from there into Illinois.
Precipitation, possibly in the form of snow or a wintry mix will become likely at onset late tomorrow night/overnight across northern Illinois given surface temperatures in the low to mid 30's and cannot rule out snow sticking with that initial band of precipitation here or close by. As temperatures warm into the upper 30's and low 40's during the heart of the day on Wednesday, rain will become the dominant precipitation type across most of Illinois for the afternoon and evening hours and even into Thursday given the warmer temperatures aloft. However, as you can see in the included loop below, portions of the northern part of the state could remain mostly or all snow if temperatures remain cold enough. As we go into Thursday afternoon and evening, questions continue to remain given a muddled model guidance picture regarding the track and strength of the area of low pressure. Some recent guidance has trended further southeast which could mean a a larger area of accumulating snow across the mentioned area.
The biggest takeaway from reading this article/forecast is that **the location of the swath of accumulating snow is still yet to be determined**. As we get closer, we will pin that down along with talking expected snowfall amounts across portions of the state. Anyone within the outlined area below could receive accumulating snow from this.