If you woke up Monday morning thinking it was a little on the cooler side, you'd be correct! Temperatures area wide fell into the low 50s, with a couple spots even dipping down into the upper 40s! But with the late August sunshine we warmed nicely during the afternoon reaching a high of 79 degrees in Rockford.
Rockford's low fell to 50 degrees, our coolest overnight low since the middle of June. Before Monday morning, our coolest August low temperature was 55 degrees reached on the 20th and 23rd. The average overnight low for late August should be around 61 degrees.
We've actually been running a bit on the 'lower' end with our overnight lows for the last week as a flip from above average lows to below average lows took place on the 17th. In fact, every night since the 17th has had a below average low temperature. Monday night will be cool once again, but not quite as cool as Monday morning. Temperatures will fall into the mid-50s early Tuesday. Low temperatures will slowly begin their climb as a southerly wind takes us through the middle to end of the week. This will also help bring in a little more moisture which will slowly cause the humidity to rise into the upcoming weekend.
Three years ago, late August was delivering some of the most dangerous heat of the summer across the Stateline region. Highs soared into the upper 90s, and when combined with tropical humidity, heat index values climbed into the 115 to 120 degree range. Fast forward to this year, and the weather headlines couldn't be more difference. Instead of extreme heat, we're looking at a much more comfortable stretch with afternoon highs in the upper 70s.
Those upper 70s will come with plenty of sunshine as a weak high pressure system continues to keep a firm grip on our weather pattern. With sinking air limiting cloud development and thunderstorm chances, expect there to be partly cloudy skies. Winds will also be lighter than they were on Sunday, further adding to the day's comfortable feel. As we head into tonight, skies will remain mostly clear thanks to that lingering area of high pressure. That will make for another cool start to the day with mid 50s for most.
Hit or Miss Chances:
Tuesday remains dry across the Stateline, though we will see signs of our next weather maker by the time we get into the evening. Forecast guidance shows a pocket of upper-level energy or spin tracking into the western Great Lakes by Wednesday afternoon. Ahead of it, we do see moisture spill inas the associated cold front approaches. This may result in the chance for rain after midnight while also fueling the chance for a few thunderstorms on Wednesday.
Because of that setup, the Storm Prediction Center has much of northern Illinois and southern Wisconsin under a level 1 Marginal Risk. It's still a few days away, but it's a setup we'll be keeping a close eye on as details continue to come in focus.
A typical summertime heat dome will set up across portions of the country next week, but the Stateline will be spared from the worst of the heat and humidity. The continued feed of weather systems across the Great Lakes and Northeast will keep the most oppressive heat away from the area.
Even so, we will still reach the upper 70s to low 80s each day this week. That's not very far from the typical highs this time of year! A bit of a humid feel returns Wednesday and Thursday with isolated or scattered rain chances, but we will stay dry through at least Tuesday evening.
An EF-0 tornado touched down Southern Lee County, IL during Friday evening's storms, the National Weather Service confirmed during a recent storm survey. The tornado touched down near Henkel, or about halfway between Sublette and Mendota, just before 6PM. It was spotted by storm chasers and reported to the National Weather Service but lifted shortly after and did not touch down again.
The Henkel tornado was only on the ground for 0.7 miles, producing estimated peak winds of 70 miles per hour. The tornado's maximum width was estimated to be 200 yards. Thankfully there was minimal damage and no injuries reported. There was a severe thunderstorm warning for Lee County at the time of this tornado.
[9PM] The last of our storms are pushing across Eastern Lee County and Southern DeKalb County this evening. There are still some pockets of heavy rain and lightning, but storms will remain sub-severe now that the sun has set.
[8:20PM] A severe thunderstorm warning is in effect for Southwestern Whiteside County until 9PM. This storm is capable of producing 60 mph wind gusts and quarter sized hail as it moves East at 25 mph.
[7:20PM] The Severe Thunderstorm Warning remains in effect for southwest Carroll and Whiteside counties until 8pm. Over the last few minutes, the storm has weakened some but still may produce some gusty winds and small hail.
[6:50PM] Storms are still producing a bit of lightning as they track Southeast at around 30 mph. Highest concentration of lightning will be with the cell in Carroll County, but a few strikes of lightning remain possible within any cell.
[6:30PM] Our lone severe thunderstorm is moving Southeast across Southern Jo Daviess County and is currently capable of producing 60 mph wind gusts and quarter sized hail. The warning is out for portions of Jo Daviess, Stephenson, and Carroll Counties until 7:15PM.
[5:50PM] Two active severe thunderstorms at this time. One for portions of Lee and DeKalb Counties until 6:30PM and the other for Jo Daviess County until 6:15PM. Both storms may be able to produce 60 mph wind gusts and quarter sized hail as they move Southeast at 20-30 mph.
[5PM] A severe thunderstorm warning has been issued for Eastern Ogle and Lee Counties, along with a portion of Central DeKalb County until 6PM. This storm is now capable of producing half dollar sized hail and 60 mph wind gusts. Storm movement is to the East-Southeast at around 20 mph.
[4:15PM] Our lone severe storm stretches across portions of Whiteside and Lee Counties, just North of Sterling. This storm is capable of producing 60 mph wind gusts and quarter sized hail as it moves Southeast at around 15-20 mph. This storm will pass over Dixon soon. Take shelter if you are ahead of this storm!
[3:45PM] A new severe thunderstorm warning has been issued for Winnebago and Boone Counties until 4:45PM. This storm is capable of producing 60 mph wind gusts and quarter sized hail as it moves to the East at 25 mph. There is frequent lightning on the West side of this cell, too. Take shelter if you are near this storm!
[3PM] With the main wave of storms still developing to our Northwest along a cold front, a severe thunderstorm watch has been issued for the entire Stateline until 10PM. Strongest storms will be capable of damaging wind gusts, large hail, and frequent lightning. An isolated tornado may also be possible. Main timing of storms is still expected between 5-9PM for local Stateline Counties.
[2:20PM] A severe thunderstorm warning has been issued for portions of Boone, McHenry, and DeKalb Counties until 3PM. This storm is capable of producing 60 mph wind gusts and ping pong ball sized hail as it moves to the Southeast at 25 mph. Heavy rainfall and frequent lightning is also possible.
For those heading out tonight for the first week of high school football, be prepared for some lightning delays and scattered storms. The wave of storms moving through this afternoon (radar as of 2PM) is sub-severe but may be producing 40 mph winds and small hail over Southern Boone County.
The main wave is Northwest along a cold front and will arrive after 5PM. Our main window of storms is 5-9PM. The primary concerns within strongest storms will be lightning, damaging wind gusts, and heavy rainfall.
Pockets of large hail and an isolated tornado cannot be ruled out, either. Once storms clear to the Southeast after 9PM, we will be drying out for the night. Temperatures will drop from the mid-70s by the time games are scheduled to start to around 70 by 9PM.
Overnight, the Storm Prediction Center upgraded the entire Stateline to a level 2 of 5 Slight Risk for severe weather this afternoon and evening.
Today is one of those days where what happens later will largely depend on how the atmosphere responds to the early round of rain and storms. The first batch is expected to arrive around or shortly after the midday in the form of scattered showers and storms. After that pushes on through, the second wave will enter the western Great Lakes, giving us a another opportunity for not only thunderstorms, but strong to sever storms. Again, the placement and intensity of this round is a bit more uncertain.
IF enough instability can rebuild, additional storms may develop along an approaching and slow-moving cold front over southern Wisconsin before tracking south and southeast into northern Illinois between 4PM and 5PM. Any storms that become severe will be able to produce damaging winds and large hail, with even the possibility of a tornado or two due to the turning in the atmosphere. I know it's a busy day with fairs, football games, and outdoor plans, but make sure you have multiple ways to get severe alerts should severe storms develop.
Winnebago County Fair:
Speaking of the Winnebago County Fair, the weather for the rest of the weekend is looking solid. Saturday should remain dry, with a light northwest wind and afternoon highs in the low 80s. While a stray shower or storm can't be completely ruled out, most locations will stay rain-free. Sunday looks even better, with plenty of sun and highs in the upper 70s.
After a little bit of a humid Wednesday, Thursday has turned into a spectacular afternoon! After a very comfortable start and temperatures falling into the mid-50s afternoon highs reached the upper 70s, to right around 80 degrees. We are beginning to see a few upper-level clouds move in as showers develop well to our northwest. Over time, the cloud cover will increase which will turn our skies mostly cloudy by Friday morning. Until then, temperatures are expected to remain very comfortable Thursday evening and there should be no issues with the weather if you have any outdoor plans.
But if you're plans take you outdoors Friday, you'll want to keep tabs on the forecast as a few showers and isolated thunderstorms could roll through during the afternoon and evening. The morning will start off with a bit of cloud cover followed by a few showers mid-morning. These will be left over from a weakening storm complex from the Upper Midwest Thursday night. Conditions will then clear out early afternoon but with dew points rising into the upper 60s it'll feel a little more humid. An incoming cold front late in the day may be enough to trigger a few thunderstorms during the late afternoon and evening, beginning across northwest Illinois and moving east through sunset.
Widespread rain and thunderstorms are not expected but isolated thunderstorms after 4pm or 5pm could be enough to interrupt some evening plans, including night one of the high school football games. While not a washout, you'll want to remain updated on the forecast and radar through the evening. The threat for thunderstorms should decrease after sunset.
There remains a marginal risk, level 1 out of 5, for isolated severe storms during the afternoon and evening. Biggest threats with any storms that do reach severe limits would be damaging winds and large hail. But an isolated tornado threat can't be entirely ruled out.
