Wind chills tumble as colder air settles in

 

It has been a rather chilly November afternoon thanks to an abundance of cloud cover and gusty north wind. Afternoon temperatures have struggled to warm much above the low 40s, with wind chills remaining in the 30s.

While there was some sunshine earlier in the day, clouds took hold and will remain through at least sunset - if not a little after. We may see some of the cloud cover clear through the night but skies are likely to remain at least partly cloudy into Friday morning. The north wind will ease some after sunset, but gusts between 20-25 mph will continue.

As clouds hold on through the night overnight lows will fall into the upper 20s, to right around 30 degrees. The breezy north wind will push wind chills down to around 20 degrees, with a few locations possibly falling into the upper teens near sunrise Friday. Temperatures won't warm much Friday afternoon thanks to increasing cloud cover and a breezy north wind. Afternoon highs will once again remain in the low 40s, with wind chills holding into the low to mid 30s.

Fall's biggest chill spills in today, but no flakes for Rockford

Getting Colder Quick:

A second cold front sweeping through this morning is opening the door to an even colder air mass, one that will send high temperatures below mid-November standards for the rest of the week.  

 

 

After reaching the mid-60s on Tuesday, temperatures have taken a dramatic turn. A persistent northerly wind today, followed by a north-northwest wind on Friday, will place the coldest air of the season thus far overhead, keeping afternoon highs stuck in the 40s. That's a solid 20-plus degrees colder than where our afternoon highs were a few days ago. Bundle up because adding to the chill will be the wind, leaving values in the low 30s this afternoon. Wind chills then tumble into the teens into Friday before recovering only into the 30s during the afternoon. 

First Flakes? 

One thing we won't be seeing with this latest blast of cold air is our first flakes of the season. While a few flakes may mix in across parts of the Great Lakes, the better opportunity for any "flakage" will remain close to Lake Michigan. Areas from Chicago's south suburbs into northwest Indiana will have the greatest chance of seeing lake-enhanced rain and snow as the colder air flows southward over the relatively warm waters of the Great Lakes. 

Here in the Stateline, conditions are expected to stay relatively dry with an area of high pressure building eastward west of Lake Superior. 

It's worth noting that Rockford typically records its first trace snow around Halloween, but we've already moved well past that benchmark without seeing any snowflakes. While this cold snap certainly bring a more winter-like feel to the region, it appears "snow-lover" will need to wait a bit longer. 

Winter Weather Preparedness: Understanding Timeline for Forecasting Winter Storms

 Snow may not be in our forecast just yet, but this week is Winter Weather Preparedness week in Illinois. It's a time to not only look over your winter weather preparedness plans but also learn about different winter weather hazards that can occur and how meteorologists forecast those hazards.

Part of being prepared for winter weather is understanding the terminology that is used when winter weather threatens. Meteorologist Owen Szarley talked about that in an earlier post.

But let's talk about the science of forecasting those winter storms and why you should always be aware of any snowfall forecasts that begin to circulate, especially on social media, several days in advance. It's important to understand that the forecast can, and will, change in the days leading up to a winter storm. This is because often times those upper-level features that eventually lead to larger low-pressure systems are forming over data sparse areas. And until the atmosphere is able to be better sampled, the possible outcomes for developing low-pressure systems can be quite large. But as the atmosphere becomes better sampled meteorologists are able to get a better understanding of how those low-pressure systems will eventually develop and travel, and the impacts they will have on a region.

5-7 days out: Pattern recognition: Meteorologists begin to have a general idea of the region that could be impacted by a winter storm, usually within a 1-2 day window. Any sort of snowfall forecast is still way too early.

3-4 days out: Possible outcomes/scenarios: Meteorologists are able to identify a region, usually within a couple states, that will see impacts of an incoming winter storm within a 12-24 hour window. Exact snowfall amounts are still too early to determine but we can start to give some very broad estimates.

1-2 days out: Figuring out details: Meteorologists now are starting to get a handle of where exactly the storm will travel and start to give general impacts within a 6-12 hour window. General ranges of snowfall totals are discussed.

12-24 hours out: Meteorologists now can give a best estimate of snowfall totals within the county level, usually within a few hour window.

Adjustments to winter forecasts will always happen, even in the hours leading up to - and often times during - a winter storm. But knowing generally what to expect leading up to the storm can help you better prepare for any potential impacting snow or ice that may occur.

Pattern flip ahead: Showers first, then a November chill

Rain Chances Return:

Big changes are on the way for the Stateline's weather pattern, and it all begins with an area of low pressure diving southeast into the Midwest. This storm system will first bring the chance for a few showers, mainly during the mid to late morning hours with chances extending into the early afternoon. While widespread rainfall is not expected, a brief heavy downpour or two cannot be ruled out. Rainfall totals should remain light, landing below a tenth of an inch. 

Cold Air Plunges South:

Changes in the temperature department will follow closely behind the departure of today's storm system and the passage of a second cold front. 

 

  

Afternoon highs today will still manage to climb into the low 50s, but much colder air will spill into the Midwest and the Great Lakes behind the front. Because of that, temperatures will take another step down Thursday and Friday, with afternoon highs struggling to reach the low 40s. A lingering shower cannot be ruled out early in the day Thursday as the front pushes through. Anything this far west will fall as rain. However, areas east of I-39 may get cold enough for a flake or two to fly.  

Temperatures plunge, but fall's remarkable warmth isn't done yet

Fall Warmth By The Numbers:

If you're thinking to yourself, "Wow, it's been a warm fall so far," or even, "Are we actually in fall?", you're certainly not alone. This fall has been one for the record books. Since September 1, we've recorded 64 days with highs at or above 60°, setting a new record for most up until November 9th.  The previous record was 63 days back in 1963 and 1956. There's a great chance we'll add one more day to this impressive total before our next shot of cold air arrives. 

Mild Tuesday:

Today will be a copy-and-paste of yesterday's nice weather. With high pressure briefly building in behind today's frontal passage, expect abundant sunshine and highs in the low 60s. The main difference is the wind which will be out of the northwest and noticeably lighter as the cold front pulls away.  

 

Temperatures Plunge:

Tomorrow's clipper-like storm system will bring the chance for scattered sprinkles and showers starting around the morning commute, continuing into the early to mid afternoon hours. On the backside of the system, much colder air will wrap in and spill across the Great Lakes, setting the stage for a massive drop in daily highs and lows. Highs Wednesday will still manage to reach the low 50s, but will then tumble for both Thursday and Friday.  

Long-Range Warmth:

As we've seen throughout much of this fall, any shots of colder air have been short-lived, with temperatures quickly rebounding to above-average levels. That trend appears likely to continue. The latest outlooks from the Climate Prediction Center continue to favor a higher probability of above-average temperatures in the days leading to Thanksgiving. 

Rain chances return Wednesday to northern Illinois

Our dry skies will briefly come to an end mid-week as a quick moving low-pressure system is set to move across Illinois Wednesday, bringing a few showers and isolated thunderstorms for some.

For the rest of Monday night skies will remain mostly clear, although we will see a few clouds move in with the arrival of a cold front late in the evening. A light southerly breeze will limit how fast temperatures fall before the front arrives, which means our evening will remain in the low 40s. The cold front will come through dry, just shifting winds to the northwest Tuesday morning. Temperatures right before/around sunrise will likely fall back into the 30s thanks to some drier air moving in behind the front. Look for some patchy fog and frost early in the morning. With little air mass change behind the front temperatures on Tuesday will warm back into the upper 50s and low 60s, with a forecast high temperature of 61 degrees for Rockford. We should see a good amount of sunshine for the afternoon as well.

Cloud cover will move back in Tuesday night, though, ahead of an incoming low-pressure that'll move across central Illinois Wednesday afternoon. Ahead of the low moisture will spread north bringing scattered showers across northern Illinois. While there is a little bit of instability associated with the low, any big threat for thunder will remain to our south. Moisture with the low isn't significantly high but will be enough to bring some accumulating rainfall to the Stateline, but totals are expected to remain below a quarter of an inch.

The low will be quick to move out Wednesday evening, pulling in behind it an unseasonably cold air mass. This will push afternoon highs Thursday through at least Saturday into the 40s and overnight lows down into the 20s. While not too far from the average high (upper 40s), it'll be our coolest stretch of weather so far this fall season. But just like every cool snap it won't last. Temperatures are expected to warm back up into next week.

Enjoy the 60s while you can: Colder air arrives this week

Staying Mild:

If you loved the weather this past weekend, you'll enjoy the start of the new week as well. High pressure settling overhead will keep conditions quiet through much of the day, allowing for periods of sunshine and mild November temperatures. After a chilly start, we can expect temperatures to steadily climb to similar levels to Sunday, leaving us in the low 60s.

High pressure will remain parked nearby tomorrow, helping sunshine and pleasant conditions to stick around for another day across the area. 

Much like today and Sunday, we'll start off on the chilly side during the early morning hours before temperatures rebound nicely. Despite winds being out of the northwest, afternoon highs are expected to reach the low 60s once again.  

Midweek Storm System:

Changes arrive in the weather pattern on Wednesday as a clipper-like system dives southeast into the Great Lakes region. While this system will bring the chance for scattered showers during the day, especially for those along and south of I-88, the bigger story will be the colder air that follows in its wake.

 

Temperature Trend:

A reinforcing shot of chilly Canadian air will spill in for the latter half of the week, knocking temperatures back below-average. Highs are expected to reach the low 50s on Wednesday, then drop into the low 40s for Thursday and Friday. Compared to mid-November standards, this is 5° to 10° below average. Overnight lows will end up in the upper 20s.