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  • Tim McGill

Sloppy Start To 2021

Round Two Today

Our second messy mix of the week today has prompted a winter weather advisory for most of the Chicago area until midnight tonight. We'll start with snow, freezing rain and sleet late in the morning and then transition over to snow and rain in the afternoon. Ice accumulations will be heaviest in areas south and west of the city where an ice storm warning is in effect until 6 pm Saturday.

The snowfall amounts with today's system won't be as heavy as Tuesday's system. I expect about one to four inches today. The ice with this system will be worse than our first system though with about a tenth of an inch to over a third of an inch accumulation with the hardest hit areas well south and west of the city.

We will be near freezing most of the day setting us up for a variety of precipitation. Look for highs in the lower to middle 30s.

The GFS model's precipitation meteogram for O'Hare shows a mix developing first late this morning then transitioning over to rain and snow. It also has another system with possible sticking snow late Thursday into Friday. Models are hinting at a system late Saturday night into early Sunday with more snow. The GFS model keeps it mainly south of the city so it doesn't show up on this meteogram. More on that system below.

The blue shaded counties have a winter weather advisory this morning until midnight tonight. The purple shaded counties are under an ice storm warning until 6 pm Saturday.

No Arctic Air In Sight

Today may end up being one of the coldest days we see for awhile. Average highs for early January are around freezing with average lows in the middle to upper teens. Today will be about or just above average. We will warm up then through Wednesday next week. The GFS temperature anomaly forecast for Wednesday night has us nearly 20° above average.

More Sticking Snow

The GFS model lays down about an inch of snow in the city but up to four or five inches north and west of there in total through tomorrow afternoon. It suggests only a trace of snow, if any, directly south of the city and in northern Indiana.

The meteogram for O'Hare displays several different model forecasts for snowfall. The range is from as little as around a half inch to as much as six inches of snowfall in total today into tonight. The next system to impact O'Hare is next Thursday with anywhere between another half inch to 3.5" of snow.

The European model spreads the snow out across a larger area with up to nearly four inches north and northwest of the city and an inch or more well south of the city into northern Indiana through midday Saturday.

The other difference with the European model is more additional snow with Saturday night's system. When that snowfall is added to today and tonight's snowfall the totals shoot up to nearly 6 inches just north and west of the city to nearly 5 inches in the city itself and 3 inches well south of Chicago into northern Indiana. I am favoring the GFS snowfall forecast for now but will have to watch to see if the GFS model starts to nudge this weekend system a little further north like the European model has been trending.

Icing will have a greater impact with this storm. The GFS model is spitting out anywhere between about a tenth of an inch north of the city to about two four tenths of an inch south and southwest. The heaviest snow with this scenario is north of I-88 and the worst icing is along and south of I-80.

The HRRR model suggests less ice north of the city but more south of I-80. In central Illinois it spits out nearly an inch. This will cause numerous power outages if it verifies. In either case, the models are saying this storm's impact will be worse in terms of icing than our system that hit earlier this week.

Still Strong Signal For "Mild" Pattern

Little change in the longer range temperature probabilities forecasts. This winter is now running a bit over 5° above average. The long range models continue to favor us for above average temperatures into the middle of January. The signal has gotten stronger with higher probabilities of us being relatively mild. The 6-10 day temperature probability forecast has the most of the country outlooked for average temperatures overall from January 6th through January 10th. The longer range 8-14 day forecast continues to favor us for above average temperatures overall during the period from January 8th through January 14th. Notice the highest probabilities for above average temperatures are centered around the Great Lakes.

Precip Pattern Still Looks Active

This week marked a change towards a more active precipitation period. The trend in the longer range precipitation forecasts continues this trend and favors us for above average precipitation overall. The 6-10 day forecast from January 6th through January 10th has us outlooked for above average precipitation. The 8-14 day forecast from January 8th through the 14th also has us outlooked for above average precipitation overall too. This along with the temperature probability forecasts would suggest upcoming systems might more likely feature of a mix of precipitation or even contain just rain. We are now 5.4" below average in terms of snowfall for this winter but some of that deficit will be made up with today's system.

Here is my 7 day forecast:

Winter Weather Advisory From 9 AM Friday To Midnight Tonight (most areas)

Ice Storm Warning Until 7 PM Saturday (southwest of the city)

Today: Freezing rain, sleet developing early then changing to rain and snow High: 35

Saturday: Mostly cloudy (light snow overnight) Low: 27 High: 36

Sunday: Partly to mostly cloudy Low: 25 High: 37

Monday: Partly to mostly cloudy Low: 25 High: 38

Tuesday: Partly to mostly sunny Low: 28 High: 39

Wednesday: Partly to mostly cloudy Low: 29 High: 42

Thursday: Chance of snow or rain/snow mix Low: 28 High: 38



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