Over the last 24 hours, confidence has increased regarding the threat of a wintry system across the Midwest, including here in Illinois later this week and potentially continuing into the weekend as well. If all things go right (if you're a snow lover), the possibility is there for this to be a long duration event and someone seeing continuous snow for quite a long period. But....we are still a ways away from figuring out finer details but an update follows below...
Early this evening our system of interest is located still out over the Pacific Ocean, off the Pacific Northeast coast and will eventually come ashore that area and into British Columbia, cresting the ridging and then diving southeast while crossing the Northern Rockies. Numerical model guidance continues to agree on this but differences remain on the exact evolution on this upper level low once it gets into the northern and central plains.
As mentioned above, this has the potential to be a long lived event for some across the Midwest and the animation below shows some of that potential. The loop below runs from early Wednesday morning till Midnight Thursday night/early Friday morning. Broad warm air advection from the lower Mississippi Valley into the Midwest will aid in precipitation generation initially to our west. As the upper level low and surface low inch closer, a broad area of precipitation, will begin to invade Illinois. As mentioned yesterday, temperatures both at the surface and aloft are decently marginal for snow but model guidance is showing it to be cold enough for snow but cannot rule out some areas of mixed precipitation or even rain. As things stand now, expect snow and mixed precipitation to move into Illinois from the west by Wednesday evening and crawling east at a snails pace after that. Snow could then fall across much of Illinois on Thursday, leading to several inches of snow accumulation. Beyond Thursday, guidance remains a bit more muddled but we could easily see snow and mixed precipitation continue on into much of Friday as well.
Stay tuned for continued updates as this system gets closer and we should be able to begin pinning down more details, potentially as early as tomorrow.