Mon-Tue, Jan 25-26th Major Winter Storm Update #4

(11:45AM - 1/24/20) A major winter storm is expected to impact the state and region, Monday and Tuesday. This winter storm is expected to bring significant snowfall accumulation, as well as some ice and sleet accumulation, to portions of the state.

Summary...
A major winter storm is expected to impact the state and region on Monday and Tuesday, and is expected to bring significant snowfall accumulation, as well as some ice and sleet accumulation, to portions of the state. The storm system will eject out into the Plains tonight and Monday, then moving eastward and eventually into the Great Lakes on Tuesday as it slowly shears out and weakens...as it encounters blocking to the northeast. Model guidance has been showing the potential for this winter storm for days. There was at first significant disagreement, which has waned over time...However, there is still some disagreement that continues at this time. Additionally, there has been a slight drying trend on model guidance over the past 12 hours, which would suggest slightly lower snow/ice totals than previously expected. Because of this, we have slightly cut back on totals in some areas given this continued trend.

Forecast...
Northern Illinois: 
Snow is expected to spread across Northern Illinois Monday afternoon. Snow of varying intensity will then continue through Tuesday evening, except in Northeast Illinois where periods of lake effect snow will continue into Tuesday night. The most significant period of snow will be from late Monday afternoon through early Tuesday morning. During this time periods of heavy snow will be possible, with high snowfall rates in excess of 1" an hour possible at times. In addition to the snow, wind gusts of 30-40MPH will be possible, Monday afternoon through Tuesday morning. The combination of the snow and wind will lead to near blizzard conditions at times, especially out towards the Quad Cities and the IL/IA border area.

As hinted at in the above paragraph, lake effect snow was mentioned for Northeast Illinois. It is likely that that lake enhanced snow will be seen during the storm, from Monday afternoon through Tuesday evening...After which time periods of pure lake effect will be possible from Tuesday afternoon into Tuesday night or Wednesday morning.

Central Illinois...
Precipitation will spread across Central Illinois Monday morning, then continuing into Tuesday. South of I-72 will generally see rain for the duration of the storm, though a mix is possible at times. Along and north of I-72 will see a mix of snow/sleet/freezing rain/rain, though freezing rain is expected to dominate in a corridor across Central Illinois.

Southern Illinois...
Rain will spread into Southern Illinois later tonight, and will then continue in periods through Tuesday morning. Isolated t'storms will be possible at times. Rainfall totals in excess of 1.00" are expected across Southern Illinois.

​What's expected...
A swath of heavy snowfall totals of 6-12" is expected across Northern Illinois, with higher amounts possible near the IL/IA and further west. There will be a sharp gradient where snowfall totals rapidly taper across across Western Illinois and along I-80 in Northern Illinois. Ice accumulation upwards of 0.10-0.25" is expected in an axis across Central Illinois.

​Below are the snow and ice forecasts for this event.

JP