(3:00PM - 2/1/21) A brief recap regarding the Sat-Sun, January 30-31st winter storm that affected portions of the state with significant snowfall and some ice accumulation.
A winter storm impacted the state and region Saturday through Sunday (Jan 30-31st), and brought a significant snowfall to Northern and Eastern Illinois. The storm system ejected out into the Plains Friday night into Saturday morning. The storm system then moved eastward through the Mid-Mississippi Valley on Saturday, and eventually through the Ohio Valley on Sunday as it weakened. Model guidance was in remarkable agreement regarding this storm, even up to 5 days out, making the forecast for this storm one of the easiest in years.
Precipitation spread into Northern Illinois this Saturday afternoon. While portions of Northwest and North-Central Illinois started as a period of freezing rain/sleet/snow, precipitation steadily changed over to snow as dynamic and evaporative cooling processes occurred Saturday evening. Across Northeast Illinois, precipitation was all snow from the onset. Precipitation of varying intensity then continued through Sunday evening. The most significant period of snow occurred from late Saturday afternoon through early Sunday morning. During this time periods of heavy snow occurred, with high snowfall rates of 1-2" an hour having occurred. In addition to the snow, wind gusts of 25-40MPH occurred, late Saturday afternoon through Sunday morning, which caused significant blowing and drifting of snow.
Additionally, lake enhancement occurred across Northeast Illinois during the event from Saturday evening through Sunday afternoon, which enhanced snowfall totals near the lake.
Precipitation spread into Central Illinois late Saturday morning into Saturday afternoon. Precipitation then continued through Sunday evening. Across Central Illinois for areas south of I-74, much of the precipitation was generally rain from the onset through Saturday night. Beyond this time, areas of snow and snow showers then occurred from Saturday morning through Sunday evening. Across Central Illinois for areas along and north of I-74, this event was mostly mixed precipitation.
Area of rain spread into Southern Illinois this Saturday morning. Periods of rain then continued through Sunday morning. A period of mostly dry conditions occurred for a time Sunday morning, before colder air wrapped in and snow showers occurred late Sunday morning through early Sunday night.
A swath of snowfall totals of 6-12" occurred across much of Northern and Eastern Illinois, with locally higher. A sharp gradient set up across Central Illinois, where snowfall amounts quickly tapered. Additionally, minor ice accumulation of a glaze occurred across portions of Northern and Central Illinois.
Below are map representations of final forecasts an observed snowfall and ice totals across the state and adjacent areas.