The first half of Thursday will be dry. Come the late-afternoon hours, the surface low will lift into eastern Iowa. This will allow the chance for rain, potentially steady and heavy, to overspread the area. Highs will end up unseasonably warm, peaking in the upper 40s. Scattered showers will continue into Thursday night, drying out by Friday morning.
We'll have to monitor conditions as the morning progresses as the National Weather Service hints that a Dense Fog Advisory may be needed. If traveling, be prepared for changes in visibility. Travel slower and increase following distance from other vehicles, especially on busier roadways. Fog may stick around into the mid to late morning hours before giving way to some clearing this afternoon.
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7AM UPDATE: Green and Rock Counties up in southern Wisconsin as well as Jo-Daviess, Stephenson, Carroll, and Whiteside Counties in northern Illinois have been placed under a DENSE FOG ADVISORY. This will run until 11AM.
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With zonal flow in place across the lower 48, we saw a system track in overnight. This brought a better shot for a wintry mix to the north, leaving us with a chance for drizzle and patchy dense fog.
As of 4:30AM, visibility values are at their lowest up in southern and southeastern Wisconsin. Travel with caution if you wind up in lower visibility.
Thursday starts on a dry note, though cloud cover will increase quickly as system #1 of 2 approaches from the southern plains. Plenty of moisture will build out ahead of the incoming low, resulting in precipitation chances by the late-afternoon Thursday. Temperatures will be warm enough to where the main precipitation with this system will fall steadily as rain. Chances will likely carry on into Thursday night and may even linger into the first half of Friday.
Behind the departing low, dry conditions settle in for Friday afternoon as we wait for system #2. As we mentioned in yesterday's morning update, changes with the forecast for system #2 are likely as we're still a few days out. What has changed? Forecast models this morning came in weaker with the surface low and shifted the overall track to the southeast.
This would favor a rain/snow mix late Friday into the early stages of Saturday morning, with a transition to snow on the table once cold air wraps around the low. Snow showers could very well carry on into the early-afternoon hours. With that being said, nothing is set in stone just yet so tune in to Eyewitness News as well as keep tabs on the First Warn Weather App for updates! Once system #2 departs, the cold air that spills in behind it will make for a cold end to the weekend, leaving highs in the upper 20s and low 30s.
Low-pressure centered over the Plains will quickly move through the Midwest and into the western Great Lakes Tuesday morning, taking a trek nearly right across the Stateline. As this occurs, we could see some fog develop area wide late Monday evening ahead of a little drizzle and light rain. Most of this is expected to move in after Midnight, lasting through Tuesday morning.
Locally, temperatures will remain centered around 34-35 degrees overnight, rising back into the low 40s Tuesday afternoon. But unlike Monday, Tuesday won't see much sunshine. Low-pressure will be sliding to our east by late morning as winds turn back around to the northwest. After a little fog and drizzle during the morning we'll hang on to mostly cloudy skies for much of the afternoon. Another quick moving system late Tuesday evening could bring us a brief shower or two, with mostly cloudy skies expected Tuesday night.
This will happen under a mostly cloudy sky. A weak system pushing in overnight will bring the potential for patchy fog as well as drizzle. Temperatures will once again end up mild in the low 30s.
Less cloud cover will be in place Wednesday. This should allow highs to climb well-above early-January standards, in the upper 40s. We can expect upper 40s to stick around into Thursday, though cloud cover will be on the increase late in the day.
Right now, both global models bring in said low into north central Illinois Thursday evening. Given how warm temperatures will be during the Thursday evening and Thursday night time frame, precipitation should fall as mostly rain. Again, we'll keep an eye on things as the weekend approaches. It's what happens with the second low pressure system that will help determine how impactful the weather will be into the weekend.
The slightest change in the low's track may change that to a rain/snow mix or entirely rain. Precipitation chances may stretch into Saturday as colder air wraps into the departing surface low, allowing for lingering scattered flurries and snow showers. Once the cold air is in place, afternoon highs will fall from the 40s to the 30s for Saturday, then possibly upper 20s Sunday. For now, know that nothing is set in stone and many uncertainties exist with our late-week precipitation chances. It would be best to keep an eye on the forecast.
While trends will be turning milder for January standards, some of that warmth will be muted by abundant cloud cover overhead. This will be most prevalent Monday, as our afternoon high would likely soar well into the 40s under a sunny sky given the warmer air mass that will be flowing overhead. But with the clouds in place, a few spots may even struggle to reach 40°.
On the positive side, low clouds will prevent much downward trends in temperatures at night, as we will only drop within a few degrees of 32 each of the next several nights. We will see a slim chance for some patches of fog Monday morning, but a better chance arrives Monday night with the potential for drizzle as well. Some fog Tuesday morning could be locally dense along with the patches of drizzle. Surface temperatures will be near freezing, so a few slick spots could develop. Afternoon high temperatures will be held in the low 40s Tuesday, but some sunshine should push us to the mid-40s by Wednesday.
There's been some chatter about a weather system that could bring a chance for rain and snow toward the later part of the week. This system is still several days out, so there are a LOT of different scenarios that could play into our forecast. In short, a North and West track would keep things warmer here and leave us with mostly rain. A South and East track would place us on the cooler side and give us a higher potential for a wintry mix or snow.
One thing we can do to narrow the possibilities of this low pressure's track is look at ensemble models in addition to the typical deterministic EURO or GFS you may sometimes hear about. Ensembles compare many different solutions based on subtle changes in the math or physics equations going into the model data. Some of the more commonly accessible ensemble models show 20 different member solutions with these various subtle changes.
Below are the latest ensemble runs from the American model through the end of the week, courtesy of weather.cod.edu. You can see the wide range of possibilities when it comes to precipitation type Friday evening (top) and as a result, total snowfall through Saturday (bottom). Notice all of the solutions have the general track of the low pressure nearby, which means even small shifts in as little as 100 miles could flip our precipitation type from rain to snow or vice versa.
Until we get more consensus between these various ensemble members, any snowfall "forecast" you see will just be a shot in the dark. For now, I think the *best* chance for any accumulating snow is centered mainly Northwest of the Stateline region, but that is subject to change as we get closer to Thursday and get a better grasp of how this system will evolve. A general rule of thumb is not to trust any snow totals more than 2-3 days out from a system. Keep tuned to the forecast and we will be sure to bring you the latest!
