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FIRST ALERT: Winter’s first sub-zero temperatures, two snow systems highlight eventful few days

Streak of 21 straight January days above normal to come to crashing halt
Published: Jan. 21, 2021 at 7:16 PM CST
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ROCKFORD, Ill. (WIFR) - Mild air’s residence here is nearly finished after an extraordinarily long stay to start 2021. Arctic air’s on the move, set to drop temperatures in a huge way later Thursday night, and promising the coldest daytime temperatures of the winter Friday. Temperatures, which soared to 40° in Rockford Thursday, are to crash into the single digits by early Friday morning.

Temperatures are to fall from Thursday's 40° high all the way down into the single digits by...
Temperatures are to fall from Thursday's 40° high all the way down into the single digits by Friday morning!(Mark Henderson, WIFR)

What’s more, gusty northwesterly winds are to add insult to injury. By the time we head out the door Friday morning, expect wind chill values to be well below zero.

Bundle up! By the time we head out the door Friday morning temperatures will be in the single...
Bundle up! By the time we head out the door Friday morning temperatures will be in the single digits and wind chills will be well below zero!(Mark Henderson, WIFR)

Despite full sunshine Friday, daytime high temperatures are not likely to head above the middle or upper teens, and wind chills may hover right around the 0° mark for most, if not all of the afternoon.

Temperatures during the daytime Friday aren't to get out of the teens, with wind chills right...
Temperatures during the daytime Friday aren't to get out of the teens, with wind chills right around 0°.(Mark Henderson, WIFR)

Winds are to subside overnight Friday, which will allow temperatures to crash more expeditiously. It’s likely that most, if not all communities will witness their first sub-zero low temperatures come early Saturday morning. Thankfully, the lighter winds will keep wind chill values in check.

Temperatures will likely fall below 0° in most spots Friday night into Saturday morning. The...
Temperatures will likely fall below 0° in most spots Friday night into Saturday morning. The silver lining? Winds won't be as gusty, so chills won't be as brutal.(Mark Henderson, WIFR)

By January standards, this isn’t by a long shot an extreme cold outbreak based on historic temperature trends at this time of year. What’s more, this cold blast’s to be brief, lasting only through Saturday, and the pattern’s to be quiet.

The next 48 hours are to be quiet, but among the coldest days of the winter thus far.
The next 48 hours are to be quiet, but among the coldest days of the winter thus far.(Mark Henderson, WIFR)

The first of two weather systems takes aim on the Stateline Saturday night into the early hours of Sunday. It appears a likely candidate to spread light snow over the entire area for a period of several hours during that time, potentially producing an inch or two of accumulation.

A weak disturbance is to bring widespread light snow our way Saturday night into Sunday...
A weak disturbance is to bring widespread light snow our way Saturday night into Sunday morning. An inch or two may come out of this system.(Mark Henderson, WIFR)

A break then follows for much of Sunday, though a second system will quickly be coming into view as the day progresses.

Temporarily, things will quiet down after snow exits early Sunday, though another system will...
Temporarily, things will quiet down after snow exits early Sunday, though another system will come into view as the day progresses.(Mark Henderson, WIFR)

The next system’s an intriguing one, as it exhibits at least a potential of producing some healthy snow in or around these parts, although there remain forecast issues regarding this system, not surprising considering the distance in time between now and its likely arrival Monday.

Signs continue to point to a stronger storm system that might impact the beginning of our next...
Signs continue to point to a stronger storm system that might impact the beginning of our next workweek.(Mark Henderson, WIFR)

There’s significant divergence in solutions advertised by a suite of computer forecast models, analyzed multiple times daily in this office. If it’s snow you’re rooting for, then the European Centre for Medium-Range Weather Forecast model would be your model of choice. It brushes most of northern Illinois with several inches of snow.

The European Model is much more bullish in producing significant snow over much of northern...
The European Model is much more bullish in producing significant snow over much of northern Illinois.(Mark Henderson, WIFR)

In stark contrast, though, the National Weather Service’s GFS model paints only a glancing snowfall in the Stateline, favoring areas south of us with the more significant snow.

The National Weather Service's GFS model suggests the bulk of the snow will bypass us to the...
The National Weather Service's GFS model suggests the bulk of the snow will bypass us to the south.(Mark Henderson, WIFR)

The reality is that at this early stage in the game, there’s simply too much uncertainty regarding this system’s evolution to hone in on specific snowfall amounts. That’s why any maps circulating on social media at this timeframe are to be taken with a grain of salt. It’d be a fool’s errand to put any serious stock in them at this distance in time.

Once the storm’s upper air features come ashore in the coming days, and is able to be sampled by a vast network of land-based weather balloons, a higher resolution view into the storm will be ingested into the forecast models, and the finer details will begin to come into clearer view. That’s still a little way off, though.

With all of this said, we’ve gone ahead and give the FIRST ALERT for Monday, as in a season short on snow systems thus far, it’s one of the more intriguing we’ve seen, and there exists a need for us to keep an eye on future developments, and that we will!

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