Dangerous cold likely Saturday into Sunday

 

Over the next 24 hours cold weather headlines will be at the forefront of most weather discussions across the Central United States as a large high-pressure system from Canada is expected to bring arctic air into portions of the Midwest as well as plummeting temperatures as far south as Alabama. This has already started for portions of the Midwest as multiple states are waking up to single digit and below 0 temperatures!

Across the Stateline temperatures this morning are already in the single digits with wind chill values well into the negatives. Don't expect much to change today as we'll stay in the single digits for a majority of the day, while into the night temperatures are expected to plummet into the negatives with wind chills values of -20° or below.

Because of such bitter wind chills, a cold weather advisory has been issued for the entire region highlighting the dangerous wind chills. It will be crucial to wear multiple layers over the next 24 hours while also limiting time outdoors as frostbite can set in as quickly as 20 minutes with wind chills below -20°.

The peaks of coldest temperatures and wind chills will arrive overnight tonight at the morning hours of tomorrow as the previously mentioned high pressure system moves overhead. By tonight, temperatures will drop below 0° after 8 p.m. while at the same time wind chill values will already be below -15°. Conditions will only worsen into the morning then as even after sunrise tomorrow, wind chill values very well could be approaching -30°.

Not only dangerous cold is forecasted today but also some scattered snow showers into the afternoon. A clipper system will move in from the west today bringing snowfall mainly south of the I-80 corridor. However, on the northern fringe of the system a few scattered snow showers will make their way through the region although accumulation totals with this system will remain under 2" inches across the state line. 

 

 Although temperatures today won't be anywhere near warm, they'll still be warm compared to the forecasted high temperatures over the next few days heading into the weekend. We'll still be under average with our forecasted high of 24° but temperatures will drop nearly 30° from this at times towards Saturday and Sunday. Along with that, a few chances for light snowfall may be possible as well.

Ahead of our next high-pressure system that will move in this evening temperatures will still be rather comfortable while a breezy westerly wind may keep those temperatures from feeling like 24°. However, towards the evening tonight, cooling temperatures will favor the little amount of moisture we have in our atmosphere, so cooling temperatures into the nighttime may allow for a few scattered showers to move into the region beyond 6 p.m.

Temperatures will quickly drop then heading into tonight and early tomorrow morning as the center of the high-pressure system will be in place to our west transporting arctic air southward. Wind Chill values tomorrow morning may be pushing -20° or below so cold safety will need to be practiced while staying inside will be recommended as well into the weekend.

As temperatures plummet at the surface, a weak clipper system will move overhead tomorrow which will bring the chances for a few snow showers tomorrow afternoon. The good news with this though is that higher moisture content will be in place further to our south which will keep higher snowfall chances and accumulation totals to our south. Still though, with any moisture that pushes north a few light snow showers will be possible however accumulation totals will remain less than 2" inches.
 

Heaviest of the snow misses the Stateline Thursday evening

 

Winter Weather Advisories extend from the Plains down into central Illinois Thursday evening as heavier snow falls from Iowa into west-central and central Illinois. Most of this will miss us to the southwest as northern Illinois sits right on the northern fringe of the snow.

Still, a few flurries and/or light snow showers could come down for some through the evening with the highest chance of that occurring from parts of southern Jo Daviess County, southeast into Carroll and Whiteside Couties. There, a dusting to at most an inch will be possible. But where any snow falls the chance of it sticking is high thanks to temperatures currently in the 20s. This could lead to a few slick conditions through late evening.

Skies are expected to remain mostly cloudy through the night as temperatures fall back into the teens. Cloud cover will hold strong Friday as a cold front, the first of two, approaches northern Illinois and southern Wisconsin during the evening. A few flurries could fly throughout the day but nothing impactful is expected. Our next chance for snow returns Saturday morning and afternoon followed by a quick, but mighty, burst of Arctic air for the weekend.

"Clipper express" to keep snow chances into the weekend

Ahead of the next pair of clippers, areas from eastern Montana to western Virginia have been placed under a winter weather advisory. Currently, this does not include any of our counties. 

 

 

While northern Illinois could see flurries and snow showers this evening, the axis of heavier snowfall will end up well to our southwest. The system's track has everything to do with us missing out on this chance as the low's center aims to slide through Nebraska and into central Missouri. Clipper system #2 will take a very similar track, slicing through the Midwest during the day Saturday. This will also result in a few snow showers. However, the main headline by the weekend will be the push of Arctic air that occurs. 

Let's keep tabs on these next two clippers because any north to northeasterly shift in the system's track could heighten our chance for snow. Temperatures Friday night into Saturday will dip near 0°. 

Factoring in the breeze out of the northwest will place wind chill values closer to -15°. Both overnight lows and wind chill values get even lower Saturday night as an Arctic high approaches.  

Lows will end up closer to -10, with wind chill values ending up as low as -25. Cold weather alerts may be needed and if any are issued by the National Weather Service, we'll be sure to give you the latest. By Sunday, this high will push to our east, allowing winds to turn to the southwest. Overnight lows will dip below zero once again, dropping down to -5°. We can expect this warmer flow to continue to warm things up next week, placing highs in the 30s by Tuesday. 

Active pattern continues with a few more snow chances into the weekend

 

The wind-driven snow Wednesday morning was quick to move in, but also quick to move out. The quick hitting snow caused reduced visibility and poor driving conditions across most the Stateline, but conditions were able to slowly improve by mid to late morning. Northwest winds held strong and remain gusty here this evening but thankfully will continue to subside as an area of high-pressure moves a little closer to the region.

There are a few flurries and light snow showers moving into northwest Illinois, with the biggest impacts from those likely occurring southwest of the Rockford area. A few light snow showers could pass through parts of Carroll and Whiteside counties, before moving towards Lee and possibly western Ogle County later this evening. Otherwise, skies will remain mostly cloudy with temperatures slowly dropping back into the mid-teens.

It's possible we see some fog develop late tonight, especially if we're able to break from any of the cloud cover we have currently. There was quite a bit of snow melt that occurred between Tuesday and Wednesday morning which helped to add moisture into the lower levels of the atmosphere. It's a little uncertain yet if we'll be able to see those skies clear, but if we do I think fog is a good bet overnight.

Our next storm system is approaching the northwest Wednesday evening and will move into the Midwest Thursday. The track of the low has shifted a bit further to the southwest with the latest model guidance, however, there are still a few models that keep the low close by through Thursday night.

The southwest shift in the low's track would take the heaviest snowfall across west-central and central Illinois Thursday evening. We would still see some snow, but not as much as those to the southwest and south of us.

I think there is some truth to the southwest track but maybe not quite as far as some of the models are suggesting. My current thinking as of Wednesday evening is that at least a couple inches of snow could fall over northern Illinois, with totals over three inches possible further west from parts of Jo Daviess, Carroll, Whiteside and western Lee counties. Hopefully over the next 12-18 hours we'll get a better idea of just exactly where the surface low will track, giving us a better idea on overall snowfall totals.

But one thing to keep in mind is that whatever snow does come down will be lighter and fluffy with temperatures in the 20s. This could allow snowfall totals to 'fluff' up, adding to a bit more in some spots. 

We'll be keeping close tabs on the track of the low and will be sure to pass along any changes in the track, should they occur. A few light snow showers could continue Friday with the arrival of a cold front, followed by light snow Saturday.  

Light wintry mix Tuesday evening followed by wind-whipped snow showers Wednesday morning

 

9PM Update: The rain/snow line continues to lift north into southern Wisconsin Tuesday evening, pushing the freezing rain and snow threat further north. Temperatures have continued to warm above freezing which has helped to minimize the icing risk this evening. There are still some spots near 32 degrees and in those locations, there may be some icy patches for the next hour or two. But southwesterly winds will increase which will help push temperatures into the mid and upper 30s overnight.

Dew point temperatures have also come up with many spots above 32 degrees. This is another indication that our freezing rain threat continues to decrease. Southwest winds will increase tonight, gusting 35-40 mph into Wednesday morning.

A Winter Weather Advisory is now in effect for the following counties in northern Illinois and southern Wisconsin: Green, Rock, Stephenson, Jo Daviess, and Carroll. The advisory will run through Wednesday morning.

Most of our Tuesday was dry, but cloudy. A few peeks of sunshine earlier in the day allowed temperatures to warm above freezing for some, but the increase in cloud cover held most in the upper 20s and low 30s. Through the night those numbers will rise, but for a few hours Tuesday evening the risk for light freezing rain will be possible for some. Surface temperatures will be key in determining who sees what type of precipitation, and for how long. So, let's break it down:

Rest of tonight:

Temperatures across northern Illinois and southern Wisconsin are currently in the low to mid-30s, with numbers just a bit further above freezing in our southern counties. Visibility has fallen over the last couple of hours as light drizzle and even some light rain showers are beginning to develop. The risk for light freezing rain will occur where air temperatures are right at, or slightly below, freezing this evening. This places areas along and north of Highway 64 at a slightly higher potential than those to the south. Now, that doesn't mean that there can't be some light freezing rain - especially on some of the back and county/country roads and untreated surfaces - in those locations, too. So, it's important to take it slow if you're out and about this evening. Where we do see freezing rain occur a thin glaze of ice will be possible which will make it slick before temperatures warm above freezing later tonight. This means bridges and overpasses, along with parking lots and sidewalks could be a little icy through the evening.

Most of the precipitation should come to an end after Midnight as drier air wraps in behind the surface low. Winds will increase, gusting from the southwest initially before turning to the west early Wednesday. Gusts could approach 35 mph.

Wednesday:

Wind-driven snow showers can be expected Wednesday morning as colder air settles in from the north. This will cause temperatures to drop through the afternoon after starting out in the 30s. The combination of the incoming snow and gusty northwest winds will cause visibility to drop where the heavier snow showers develop. This will have an impact on the morning commute. The snow will move in early Wednesday morning between 4am and 5am and continue through mid-morning. Visibility will become an issue under the heavier snow bands and minor accumulations could also occur. If the snow is heavy enough there could be some accumulations on some of the roads.

Scattered snow showers will continue into the afternoon Wednesday as temperatures drop back through the mid-20s. Winds will ease some as skies slowly begin to clear Wednesday night.

Winter weather alerts issued for some ahead of next clipper system

ALERTS: Clipper system #1 dragged a warm front through the region overnight. Ahead of it was a batch of light snow that was enough to produce a dusting. Winter weather alerts are being posted this morning for clipper system #2 which is expected to sweep in this evening into Wednesday morning. Right around 3:30 this morning, the National Weather Service placed Stephenson, Jo-Daviess, and Carroll Counties under a WINTER WEATHER ADVISORY. This will run from 6PM this evening until midnight. 

TIMING: Ahead of this next clipper system, a breezy west to southwest wind will draw in both warmth and moisture, but the warmth won't be felt right away. Temperatures will climb but likely fall short of their full potential due to the deep snowpack. This means temperatures may only rise to, or just hover around the 32-degree mark. 

This will be warm enough for any precipitation at the beginning of the event to fall as a freezing rain/wintry mix. Significant ice accumulations are not expected, but it doesn't really take much ice to cause problems, and we could see some icy travel for at least the late-day commutes. Be mindful of sidewalks as well as a light glaze may cause further issues. 

With the low tracking across southern Wisconsin, this would leave us on the warmer side overnight into Wednesday morning. In fact, forecast models keep the rain/snow mix (32 degree) line close by, in between highway 20 and highway 11. Precipitation will likely remain a rain/snow mix across northern Illinois, with temperatures being cool enough for mostly snow up in our southern Wisconsin counties. 

  

By Wednesday morning, a strong cold front will pass through, allowing another dose of frigidly cold air to spill in for the second half of the week. Temperatures will drop as the Wednesday progresses, falling into the mid 20s by the evening. This is why we will see a quick transition to scattered snow during the morning commute hours. Similar to this evening, travel with extra caution as the the snow and wind could reduce visibility but also allow slick spots to form. 

ACCUMULATIONS: Unlike the past few clipper systems, the highest potential for accumulating snow with this one will be to our north. I do think most will wind up with a dusting to 1" with the higher totals being in southern Wisconsin. Highs will stay in the 20s for Thursday and Friday before dipping into the single digits this weekend.