Not a lot has changed with regard to the late season/mid-April accumulating snow event that is one the way to portions of Illinois early tomorrow morning and through the afternoon but we are putting out a fresh update for you guys with some new thoughts and a new snowfall map will be out later tonight...
I dig into the latest below...
Our strong storm system and upper level low is still currently well to the southwest of us this evening, located across the southern plains in portions of Texas and Oklahoma. Over the next 12-18 hours, it will continue moving northeast and move into the Midwest and through portions of Illinois during the morning and afternoon hours tomorrow, as you can see by the track below.
As we look at current radar across the region, widespread rains have already moved into portions of southern Illinois this evening and these will continue to drift northward over the next several hours and into the overnight as well.
As mentioned in previous posts, moderate to heavy precipitation will come northward late tonight and overnight across much of the state, eventually getting all the way into portions of northern Illinois by early tomorrow morning. It is across this area (and back into portions of western Illinois) where there will be sufficient cold air at low levels along with dynamic cooling to changeover rain to snow. The loop below runs from late tonight through tomorrow evening, showing nearly the entire evolution of this system as it moves through the region. Snow could fall for quite the lengthy period across an axis tomorrow from the early morning hours with snow showers not ending till potentially late afternoon or early evening.
Given the impressive signal for heavy precipitation and strong frontogenesis being modeled, the threat for heavy snowfall rates, at least for a few hour period across portions of northern Illinois is fairly impressive. Below is one model depicting an area of snowfall rates of 1-2"/hr during the mid-morning hours tomorrow. This image itself is valid between 8-9am, showing one hour snowfall accumulations.
A new snowfall map/TAM will be out later tonight but we continue to highlight the axis below boxed in orange for the accumulating snow and any minor shift in the storm track could move that axis a bit further southeast or a bit further northwest. Stay tuned for updates later tonight...
Like mentioned above, a new snowfall map will be out later tonight but here is our previous map from earlier this afternoon for those interested...