(12:30PM - 1/11/19) Afternoon update on the approaching major snowstorm for the state this weekend... The storm system is currently developing in the Plains, with precipitation approaching Southwest Illinois at this time. Model guidance from this morning has continued to stay fairly consistent with the forecast for most of the state.
A mix of rain/sleet/snow will push into portions of Southwest Illinois early this afternoon. This activity will quickly turn to snow, as precip spreads across much of Central and Southern Illinois during the evening. Snow will then continue right on through Saturday night across Central and Southern Illinois, before becoming scattered and diminishing Sunday morning and afternoon. One area to point out will be far Southern Illinois, from the Carbondale and Marion areas on south to around Paducah. This area may start as a mix, turn to accumulating snow, turn to rain or a mix, before turning back to accumulating snow once again. Model guidance is disagreement on where exactly this gradient will set up, but it will be somewhere within that aforementioned area of far Southern Illinois. This gradient will be fine tuned in our forecast on later updates as model guidance continues to come in and the storm is ongoing.
Further north, snow will also push into portions of Northern Illinois tonight and Saturday morning. This activity will continue into Saturday night, before becoming scattered and diminishing Sunday morning. Northern Illinois is another area to point out, where there will be a sharp gradient in snowfall totals, quickly ranging from only a trace of snow to a couple inches in a relativity short distance. Dry air advecting in from the northeast will help create this sharp gradient. Model guidance is also in disagreement with where this gradient sets up as well, with some guidance having the gradient up into Southern Wisconsin, and other guidance with the gradient across I-88 in Northern Illinois. This gradient will be fine tuned in our forecast on later updates as model guidance continues to come in and the storm is ongoing.
Snow will be moderate to heavy at times across the state during the weekend, especially across Central and Southern Illinois tonight into Saturday night. One good bit of news is that winds will remain relativity light during this event, which will help limit blowing and drifting.
With all of that said, final snowfall totals over a good portion of Central and Southern Illinois will be in the 6-12" range. Across a portion of Eastern Missouri on east close to the Illinois/Missouri border, amounts of 12-15" are possible. Amounts taper across far Southern Illinois and across Northern Illinois, and remember the gradient will likely be much sharper that currently shown across these areas.