We are continuing to keep a close eye out west as the system of interest is still slowly spinning it's was off the Pacific Northwest coast early this morning and this is the upper level that eventually shed a piece of itself that makes its way in our direction by later this coming weekend. As we talked about in our last post regarding this system, it will have the potential to drop a swath of accumulating snow across portions of the Midwest including here in Illinois. This also could be quite the long duration event too, snowing all day Sunday and into the evening hours.
We look at the latest on this system, including timing and expected amounts below...
As mentioned above, our system of interest is still offshore this morning but will begin to come onshore tomorrow afternoon and evening, eventually making its trek across the western and central United States.
As our system crosses the Rockies on Saturday afternoon and evening, a cyclone will develop at low levels of the atmosphere across the central plains and take a favorable track for accumulating snow across the northern half of Illinois (shown below)
As this system develops on Saturday afternoon and evening to our west across the plains, the strong low level flow (warm air advection) on the east side of the developing area of low pressure will aid in developing a fairly widespread area of snow.
As mentioned at the beginning of this post, this could be a fairly long duration snow event across portions of the state, even though snow will most likely be falling at fairly light to briefly moderate rates as things stand now. Timing wise, snow looks to move into western Illinois during the late night hours on Saturday and slowly continue in from the west and southwest overnight heading into Sunday morning. Model guidance is in fairly good agreement that by 6am on Sunday, most of northern and central Illinois will be seeing snow. It then looks to continue through the afternoon and into the evening hours across those locations while southern Illinois looks to see mostly rain or a mix out of this system given the warmer surface temperatures. The loop below runs from 6pm Saturday night till late Sunday night, showing the snow slowly moving in from the west and southwest early Sunday morning and continuing through all day on Sunday.
Below is one models take on how things will look at noon on Sunday, showing the northern half of Illinois seeing snowfall during that time as the weak area of low pressure tracks up northeast through the Ohio River Valley. Circled in orange is the area that looks to receive the highest snow totals as of now.
Below is our first TAM snowfall forecast this event.