A few non-severe thunderstorms have developed within the last couple of hours of over northern Illinois producing mainly locally heavy rainfall and frequent lightning. The threat for these storms to turn severe remains very low.
A weak little ripple, or upper-level wave, in the jet stream is currently moving across the Midwest and has provided just enough force in the atmosphere to allow some of these storms to develop. But with the atmosphere remaining 'capped' the threat for the storms to grow to severe limits remains very low.
These widely scattered thunderstorms will continue through this evening, roughly through 8pm or 9pm. Overnight there does remain an isolated chance for a couple storms, but we may see a better chance for more storm coverage late Tuesday into Wednesday.
Temperatures have warmed into the mid and upper 80s, with the heat index pushing the mid-90s in a few spots. But expect temperatures to briefly drop as the rain moves through. Unfortunately, it won't clear some of the humidity we are experiencing this afternoon.
We haven't used the phrase "Ring of Fire" in quite some time, but itmakes a return as we round out the month of August and start September. What does this mean? Expect temperatures to climb close to the 90-degree mark through the first half of the week. Since we're positioned along the northern edge of the ridge, we'll also need to keep tabs on storm potential. Weak systems ridging around the ridge may occasionally trigger showers and marginally-severe storms.
Current Heat Alerts:
As of this morning, no counties across the Stateline are under any heat-related alerts. However, the heat is becoming more intense farther to our south and west where Heat Advisories are in place. Again, pending storm chances, we may see that expand into northern Illinois but for now, we have no alerts.
Today's Heat:
For today, expect mostly cloudy skies to gradually become partly cloudy as the day goes on. A weak system arriving late in the afternoon and evening could be enough to spark up an isolated shower or storm after 3-4PM. Now, with the ridge anchored to our south, a large reservoir of warm air is spreading into the low levels of the atmosphere.
That warm air acts like a cap, limiting thunderstorm potential for much of the day and keeping any storm chances isolated and confined to the late afternoon and evening hours. Temperatures will climb into the upper 80s, and with humidity continuing to increase, it will feel more like the low 90s. Overnight, storm chances will lower after midnight, allowing skies to turn partly cloudy with lows in the low 70s.
Tomorrow's Heat:
Tuesday will bring another hot and somewhat humid day to the Stateline. Like today, high pressure and the cap will keep daytime storm chances at bay for the most part, allowing temperatures to climb close to the 90-degree mark. With dew point values sitting in the low 70s, heat indices could end up in the mid to upper 90s at times Tuesday afternoon. Forecast models do show a disturbance pushing through late in the day towards the evening. This could again be enough for us to see an isolated chance for a shower or thunderstorm.Wednesday may end up being the hottest day of this upcoming stretch as highs may end up a degree or two past the 90-degree mark.
Showers have been a little more widespread this afternoon than I was expecting, limiting temperatures to the mid/upper 70s like yesterday. Many locations in the Stateline picked up between a quarter inch and an inch of rainfall from late Saturday night through Sunday evening, with light showers continuing for some as of 5:30PM.
We will keep the light showers with pockets of heavy rain into the evening and night, but likely in lesser coverage than the daytime. Temperatures will hold steady through the night, only falling into the low 70s.
Increasing humidity will bring a noticeable summer-like feeling this week, with isolated thunderstorm chances to boot. The heat and humidity will be characterized by a rise in dew points, pushing into the 70s at times. With a very warm air mass just above the surface, temperatures will rise near 90 degrees some days, pending thunderstorm development. As for storm chances, the daytimes will be mainly capped and dry each of Sunday, Monday, and Tuesday. The evening and overnight periods may bring slightly better coverage of rain. Whenever they develop, the strongest storms may be strong to severe.
But the storm development is far from a guarantee. This is because of that very warm air above the surface mentioned above, otherwise known as a "cap". This effectively acts as a lid on the atmosphere which can work to prevent thunderstorms from developing. If we were to be capped during the day, the temperature would likely be able to reach its maximum, pushing near or above 90 degrees. Conversely, if the cap is weaker or breaks, thunderstorms may be able to develop. This would promote slightly cooler afternoons with highs in the middle or upper 80s, but likely still rather humid.
Because of the small-scale nature of this cap, models will likely change a lot each day, promoting wildly different rain chances even within the same day. In short, we may see isolated thunderstorm development anytime starting Saturday night through Monday evening. But much of that time will be dry.
The first wave may arrive early Sunday morning in the form of some scattered showers and a few embedded storms. Depending on how long this lingers into the afternoon, temperatures may not quite reach as high.
Chances drop off for the evening a bit, but higher coverage may return overnight and Monday morning. Another chance looks to develop Tuesday morning. Similar to Sunday, the afternoon temperature depends on how quickly the clouds and rain thin out, and if the cap holds for the afternoon. If we remain dry, temperatures will likely push near 90 degrees Monday and Tuesday afternoons.
While the warmth over the last week has not come with much humidity, that is about to change in the coming days. While Saturday will remain somewhat comfortable with clouds and slim chances for rain, the humidity really builds in after Sunday.
Sunday will begin the first of several hot and humid days, with temperatures pushing into the mid-80s. The heat index will make it feel a bit warmer, possibly near 90. Monday through Wednesday will be even hotter, with near 90-degree highs possible each day. The peak heat index will likely be well into the 90s, and possibly close to 100 degrees at times.
Normally when you have excessive heat and humidity like this, you will see storm chances not far away. The Stateline will be right on the edge of the more active jet stream aloft. This acts like the highway for storms to form and maintain themselves on. South of us, the atmosphere will likely remain capped each day, preventing storm activity. With the active jet centered mostly around Central and Southern Wisconsin, the Stateline itself will have a chance for rain each day, but the highest concentration of storms may remain just to the North. If this jet stream were to shift South even a bit, storm chances will increase each day with slightly lower concerns about the heat.
A line of decaying storms will approach the Stateline by mid-day Saturday, bringing the potential for at least some light showers mainly between 11AM and 5PM. The threat for thunder will be near zero, but a few pockets of rain may bring a brief steady shower. Outside of that, light sprinkles will be the primary form of precipitation. Any rain we do see will begin to clear by 5-7PM. The bigger impact the rain will have is on the temperature. We may not quite reach the 80s with the clouds in place during the peak heating hours of the day.
The rain that does fall will not amount to much, with most seeing under a tenth of an inch. Better chances for 0.1-0.2" of rain will be primarily Northwest of Freeport. Some locations in the Stateline may not even see any measurable rain at all. Higher chances for rain and storms may be possible toward the end of next week, following increased heat and humidity.
Mother nature really delivered this week, treating the Stateline to several comfortable days with afternoon highs settling in the low to mid 80s. We'll wrap up the workweek on a similar note, with skies remaining dry and partly cloudy and temperatures climbing into the low 80s, right around 83 degrees.
Even better, Friday evening/night plans look weather-friendly. Unlike last week, there are no thunderstorms or rain in the forecast, meaninghigh school football games across the area should kick off and finish without interruption. The dry and pleasant conditions are also great news for anyone heading downtown for City Market, with comfortable temperatures lingering into the early overnight hours.
Weekend Outlook:
This quiet weather pattern won't disappear entirely over the weekend, but most of us will stay dry. Our next disturbance arrives around or just after midday Saturday, bringing the chance for an isolated shower or two during the afternoon.
Even so, the better rain chances and moisture will stay north of the Stateline, focused across central and southern Wisconsin. As a result, many location across northern Illinois may end up seeing a few clouds and a sprinkle. Sunday brings a similar setup, though temperatures will be a touch warmer as a ridge of high pressure aloft pushes east across the midsection of the lower 48. This will allow highs to climb into the upper 80s. A pop-up shower or isolated thunderstorm cannot be ruled out, but rain isn't expected to be widespread. If you have outdoor plans, keep an eye on the heat but also the radar.
Meteorological Fall:
As we turn the calendar from meteorological summer to meteorological fall on September 1st, the weather certainly won't be following suit. In fact, the average high for early September hovers around the 80-degree mark, but temperatures will run well above that mark as an upper-level ridge settles across the Tennessee Valley and the Deep South States.
That ridge will allow summer-like heat to build into the Stateline at the start of next week, sending highs back near the 90-degree mark.
Despite a cold front sliding through during the late morning hours yesterday, temperatures still managed to climb into the mid 80s. The front itself wasn't particularly strong, but it came through early enough to where the severe potential was shoved to our south and east, leaving us dry and warm.
Today will feature a much more comfortable setup as high pressure settles into the region. Dry conditions are expected from start to finish, with a mix of clouds and sun present for our afternoon. The drier air will keep the area's humidity in check, while afternoon highs will top out in the low 80s.
August's Full Moon:
Tonight, high pressure will also keep us dry, giving us a great view of August's full moon. Also known as the "Sturgeon Moon", this full moon earned its name from Native American tribes, as late summer was traditionally one of the best times of the year catch Sturgeon in lakes and rivers. With only a few passing clouds and calm winds in the forecast tonight, we should be in for a show when peak illumination occurs at 12:18AM Friday morning.
Partial Lunar Eclipse:
Tonight's full moon is extra special as it coincides with a partial lunar eclipse. A lunar eclipse occurs when the Earth passes between the Sunand the moon, causing the Earth's shadow to fall across part ofthe moon's surface. The partial eclipse will begin at 9:33PM, reaching its maximum eclipse at 11:12PM, then ending at 12:51AM Friday.
While much of the region has enjoyed some cooler days and refreshing nights as of late, a more summer-like pattern featuring heat and humidity will return starting this weekend. The upper levels of the atmosphere have been favorable for cooler, more comfortable weather as of late, with a Northwest direction to the flow aloft. This has kept a lot of the typical summertime heat and humidity away from us across the Western United States.
But as that ridge begins to shift East, it will bring a lot of the heat with it. As the jet stream flows North of the Stateline, summertime heat and humidity will build up across the Plains and into the Midwest. This will push temperatures into the upper 80s and near 90 some days next week, beginning Sunday and Monday. Isolated to scattered thunderstorms will be possible each day, with higher confidence on storms along the higher concentration of jet stream winds across the Northern Plains and Upper Great Lakes.
It does appear this pattern will stick with us a bit longer, as the Climate Prediction Center is giving us a 70-80% chance we will see above average temperatures to start the month of September. Average highs for this time of year are closer to the low 80s and upper 70s, so it appears likely we will see more mid to upper 80s if not a couple 90s thrown in there.
8pm Update: Just a few very isolated showers moving across the region as the last few pieces of energy rotate around the upper-level low over the Great Lakes. Skies will clear this evening with a little patchy fog possible early Thursday morning.
A line of thunderstorms continues to develop from Michigan down through east-central Illinois Wednesday afternoon, ahead of a cold front that moved across northern Illinois during the morning. Precipitation chances remain limited locally with the front well to our east, but with still a little moisture around and some instability it isn't completely out of the question that an isolated shower or two may still occur through sunset.
Temperatures have warmed into the low 80s with just a touch of humidity as dew points have reached the low to mid-60s this afternoon. Skies should begin to clear with high pressure settling back in Thursday. Temperatures Wednesday night will sit right around 60 degrees with highs on Thursday warming into the low 80s. Thursday night should be good sleeping weather with lows dipping back into the upper 50s. Friday will remain mostly dry with high pressure still over the Great Lakes, but a return to southerly winds Friday night into Saturday will slowly begin to set the stage for the return of not only a rise in temperatures, but also a climb in humidity and thunderstorm chances across the Midwest through early next week.
Temperatures are running a bit warmer than they were at this time yesterday. This is largely thanks to a blanket of cloud cover overhead but also a light but warm wind out of the south. Most Stateline locales are waking up roughly 10 to 15 degrees warmer, in the mid to upper 60s. There has also been a slight increase in humidity levels since yesterday as dew point are now sitting in the low 60s.
With the early arrival of our next cold front, there will be a chance for an isolated shower or thunderstorm from now up until about 9-10AM.
Once the cold front passes, winds at the surface will shift out of the northwest and gradually increase, helping to usher in slightly drier air for the rest of our "hump day". Expect partly cloudy with afternoon highs reaching the low 80s. Occasionally, wind gusts could top out around 20 mph.
Severe Potential Very Low:
It is also because of the cold front's early arrival that the severe weather threat today is expected to stay well to our south and east, even beyond the Chicago metro area. The Storm Prediction Center has placed portions of eastern Illinois, northern Indiana, and the southernmost areas of Michigan under a level 2 of 5 SlightRisk for scattered strong storms.
Once again, the atmosphere is setting upfavorably for some patchy fog to develop. Winds remain calm, the moon is shining overhead (meaning mostly clear skies) and temperatures are within 1 or 2 degrees of the dew point, allowing moisture to condense near the ground. The good news is that conditions don't appear to be supportive for widespread dense fog.
Once any patchy fog lets up, another pleasant late-summer day is in store across the Stateline. The same area of high pressure that brought spectacular weather Sunday and Monday will be parked to our east over the Ohio Valley, keeping conditions quiet with partly cloudy skies. Afternoon temperatures, thanks to a south to southwest wind, will end up a little warmer, pushing into the low 80s. Thankfully, it won't feel humidly warm as dew points should remain around the 60-degree mark. Great weather for Food Truck Tuesday over by the Conservatory.
Midweek Storm Chances:
At the same time, thunderstorms are expected to develop across northern Wisconsin and portions of northern Minnesota this afternoon. While that activity will be well to the Stateline's northwest initially, forecast models suggest some of those showers and storms could drift southeastward overnight. As a result, we could see a chance for a shower or storm after midnight, with the possibility of a few lingering into the Wednesday's morning commute.
Thunderstorm chances during the day all depend on the timing of our next cold front. It does seem the front pushes through without any worry, pushing the better environment for thunderstorm development to the south and east of the Stateline. For now, I've kept a chance for a few thunderstorms during the midday and afternoon hours. But again, it wouldn't surprise me if much of the day remained dry. Expect afternoon highs to land in the low 80s.
In their latest round of severe outlooks, the Storm Prediction Center has left the entire Stateline under a non-severe risk with the higher potential along the cold front being south and east of Chicago.
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.
