Before clipper system #1 arrives, we will see a cold front move in overnight into Saturday. Ahead of it will be the opportunity for snow, possibly a scattered rain/snow mix this evening into tonight. The best time frame will be an hour or two after sunset, with chances lingering into midnight.
This stint of Arctic air is on its way out, though it couldn't leave without bringing breaking news to the temperature department.
Shortly before midnight, the thermometer at the Rockford Airport fell to -4° which ties the record low for December 4th set back in 1991.
In comparison to the last 4 meteorological winter seasons, this is the earliest Rockford has observed a sub-zero low temperature. The next closest was the 2022-2023 season where the airport fell to -10 on the December 22nd. That Arctic stint would linger into the Christmas holiday.
Despite the bright sunshine of Thursday, temperatures were only able to reach the teens including 14 degrees in Rockford. Quickly as the sun set, temperatures shot down into the single digits and below zero. Wind chills were as low as -15 degrees for the second night in a row. But as arctic high pressure pulls out of the area, we will see an increase in "warmer" Southwest winds. This will aid to bring temperatures back to the teens by 8-9AM and mid-20s for the afternoon high.
Next chance for some flurries or light mix will arrive Friday evening-night, with the bulk of precipitation remaining North of the Stateline. We will only see influence from a weaker cold front here, keeping precipitation on the lighter side. Better chances for snow will arrive Saturday night with a potential for a couple inches of accumulation.
As previously mentioned, afternoon highs will barely make it out of the single-digits. On the flip side, high pressure overhead will make for less cloud cover and more sunshine. Again, the main priority weather-wise will be getting prepared for this Arctic chill.
Following a strong arctic cold front Wednesday afternoon, temperatures are set to plummet as clouds will thin out. Overnight lows will drop down toward zero, while wind chill values will make it feel closer to -10 or -15 by early Thursday morning!
While the afternoon high temperature Thursday will return back to the low teens above zero, wind chills may remain closer to zero even under a very light breeze. Temperatures again drop toward zero Thursday night, with wind chills down around -10.
The overnight low temperatures below zero the next two nights would be the earliest in the season we have seen subzero temperatures since 1991! Forecast lows will return to the teens by Friday night with our next weather system passing overhead.
The Stateline will be toeing the line of much colder air to the North and milder air to the South. This will funnel several "clipper" systems our direction over the next week, with each of them featuring a slim chance for snow or mixed precipitation. The most favorable windows for wintry precipitation in the near term appear to be Friday into Saturday, then Saturday into Sunday.
This will cause some patchy slick spots through the morning commute, likely through 8am to 9am as this is when the winds will be at its strongest. Take it slow if you encounter any snow on the road. As a cold front comes through mid-day winds will turn to the northwest. We'll likely see wind gusts back around 20-25 mph which will keep the threat for blowing and drifting snow through the evening.
Wind chills will sit between -15 and -20 degrees. Highs on Thursday will only warm to the low teens, dropping briefly back below zero Thursday evening before warming above zero Friday morning.
This combined with cloudy skies will help keep temperatures on the milder side, with most locations staying in the low 20s. In fact, we could even see temperatures rise through sunrise Wednesday. But with the breeze wind chills will remain in the mid and upper teens, so it'll still feel cold when you head out the door.
Overnight lows will fall below zero for the first time this season, with wind chills as low as -15 degrees Thursday morning. Sunshine should return for the afternoon Thursday, but it won't do much to warm us up as highs are expected to stay in the low teens.
Similar to Monday, the day is beginning with a round of dense freezing fog. Visibility for a few, such as Janesville and Sterling, are registering at a mile or less so please, travel with caution.
Our next item of concern will be the potential for the development of fog early Tuesday morning, especially if we see any sort of clearing during that time. We should see skies turn mostly cloudy by the afternoon and evening ahead of our next cold front that'll move through Wednesday.
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6:30pm Update: While there have been some improvements in visibility over the last hour the light snow continues to fall. We'll see another round of steadier snow move in from the southwest, now currently over Carroll and Whiteside counties along with some steadier snow in Lee and southern DeKalb counties. The Rockford Airport has already picked up 0.7 inches, with some spots in our southern counties measuring just a little over an inch. This snow isn't fast to accumulate but will
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5pm Update: The light snow continues to fall, but there have been some improvements in visibility where the steady snow has lightened up just a bit. We'll continue to see the light snow fall through late evening, with only a few flurries around through Midnight.
TONIGHT: Fresh snowpack and strong arctic high-pressure systems typically result in VERY quickly falling temperatures. The wrench in that forecast tonight is cloud cover. High clouds have been moving overhead from the West, and it is still to be seen how much of an impact that will have on our temperatures tonight. As of 7PM, a few spots were down into the low 20s. Several locations may end up well into the single digits overnight, but this kind of a forecast has very high boom/bust potential with the clouds. We could end up seeing 10° temperature differences across relatively short areas, depending on how clouds and snow influence the temperature trends tonight. Regardless of how far temperatures fall, melted spots from earlier this afternoon will likely freeze back over, so be very cautious of slick surfaces through tomorrow!
MONDAY: Temperatures will return into the 20s for Monday afternoon, but our next weather system will slide in from the West, bringing another round of some accumulating snow. Snowfall may begin as early as 12PM in some of our Southwestern counties before spreading over the whole area by mid-afternoon. Snow will only last into the late evening of Monday and likely wrap up entirely by midnight.
This will NOT be nearly as impactful as the weekend winter storm, but most locations will see between 1-3" of fresh powder on top of the current snowpack in place. With surface temperatures already cold, anything that falls will stick and likely onto roadways once again.
The good news is this snow will be a much lighter and fluffier snow, with snow ratios closer to 15-20:1, rather than the 11-12:1 we saw Saturday. That means the snow will not have as much liquid contained in it. A winter weather advisory was issued for Whiteside County that will run from 12pm Monday to 12am Tuesday. There is a potential for a narrow band to set up with 3"+ totals near and South of I-88, so Lee and possibly DeKalb County *may* get added onto this advisory.
TUESDAY-ON: We have some ups and downs in the forecast ahead, but Wednesday night through Friday morning will be downright frigid with temperatures likely not getting above the mid-teens Thursday and pushing zero overnight. Any chances for precipitation beyond Monday evening look very slim in nature, but there is a small chance for some light snow or freezing drizzle Wednesday, then another chance for snow Saturday night. Once we get closer to those, we will have more information on how those systems will track.
12AM UPDATE: Steady snow still ongoing for much of the Stateline, but the end is in sight across Eastern Iowa. After 2AM, snow will begin to taper off, but wind will be picking up from the Northwest (20-30 mph gusts). Blowing and drifting snow will remain a concern into midday Sunday, especially on open and rural roads. Road conditions should improve greatly by morning as plows are able to keep up with the lighter rates of snow.
9:15PM UPDATE: North of I-88 will likely continue to see steady snow persist beyond midnight. But snow will become more scattered throughout the night as winds pick back up from the Northwest. Blowing and drifting snow will remain a concern into Sunday.
7:15PM UPDATE: Steady to heavy snow continues to push across the Stateline with snow rates near 1"/hour at times. Visibility will remain limited below a mile while the snow is coming down. Some roads are "impassable" in Boone County according to the sheriff's office, so avoid travel if at all possible!
5:40PM UPDATE: Real heavy burst of snow developing along the Stateline in Green/Jo Daviess/Stephenson Counties, moving ENE. Significantly reduced visibility and faster accumulation likely in that pocket over the next hour or two as it moves along the IL/WI state line.
4:20PM UPDATE: Radar is showing a bit of a lull moving into parts of Whiteside and Lee Counties. Additional heavy snow is still expected to move in from the West, so we are not done yet. Snowfall rates up to 1" per hour remain possible through about 7-8PM.
2PM UPDATE: The heaviest snow is moving into Northern Illinois this afternoon, with snowfall rates approaching 1" per hour at times. While snow will not come down this heavy the entire time, the heaviest bands of snow will accumulate much quicker and result in very poor to dangerous travel this afternoon and evening.
Road conditions, per the Illinois and Wisconsin departments of transportation, are reporting "completely snow covered" roads across nearly the entire area. Plows are out and working, but the snow is coming down faster than roads can be cleared. Travel is not advised Saturday afternoon or evening.
Visibility is significantly limited with the falling snow and not helped any by the strong Southeast winds. Visibility is down near a half mile for most in the Stateline, and some down to a quarter mile.
Heaviest snow will persist through about 8PM this evening, with snowfall rates up to 1" per hour. Snow will ease up some after 8PM, but blowing and drifting will remain a concern through the evening and into the night. Snowfall tapers off by 6AM Sunday morning. Winds will flip to come from the Northwest Sunday morning, which will continue the threat for blowing and drifting even after the winter storm warnings expire at 6AM.
