Another Hot & Toasty Day, Storm Chances Arrive Early This Afternoon

What's a good hint that we're in for another hot and humid day across the region? Temperatures and dew points at 5 AM this morning were in the upper 60s-low 70s. I repeat, upper 60s-low 70s. Meteorologists like to call that "air you can wear". But I just describe it in one word, Yuck! Today is going to be a continuation of what the Stateline endured over the weekend, but it going to feel a bit more humid.

Highs for both Saturday and Sunday climbed into the upper 80s, leading to our 20th and 21st above average day during the month of June. This afternoon, high temperatures are expected climb back into the upper 80s. And when dew point temperatures near 70° are factored into the forecast, the heat index could make it feel more like the mid to upper 90s.

That is why it is important to practice heat safety, especially if you're someone who spends plenty of time outdoors. The heat can really take a toll on your body, so you definitely want to take it easy by limiting strenuous outdoor activity. Make sure to take frequent breaks in an area that has air conditioning. If air conditions is not available, find a place with plenty of shade and drink plenty of water to stay hydrated. Remember these tips, especially with the heat and humidity on the rise into the 4th of July holiday weekend.

Although skies will be partly sunny throughout the day, this summer-like heat and humidity will help develop a batch of showers and storms by the early afternoon hours. Today's chances do come with a low-end severe risk, as the Storm Prediction Center left a majority of northern Illinois and southern Wisconsin under a Marginal Risk (level 1 of 5) for severe weather. Damaging wind gusts will be the primary concern with thunderstorm that meets severe criteria. Due to the fact that these storms are going to be short-lived, they will be quick to develop to rise and quick to collapse. Once they collapse, the resulting force could lead to a few gusty winds.

Not only are these showers and storms going to be short-lived, but also they will be slow-movers. Similar to Saturday's set-up, winds aloft during the 2nd half of our Monday are going to be very weak. When you have weak wind shear ,or change of wind speed with height, storms won't have a sense of direction and will just sit there. That's a possibility with the activity we'll see today, especially with how much atmospheric moisture is available. Any activity should come to an end right around or just after sunset, giving way to partly cloudy skies for the overnight hours.

Heat and Humidity Continue to Fuel Scattered Thunderstorms

Temperatures Saturday and Sunday warmed into the mid and upper 80s, with the heat index rising into the low 90s Sunday afternoon. Most of the weekend was dry, however, there were heavy rain producing thunderstorms that occurred for some Saturday evening. The heat and humidity will be cranking up a little in the days to come with temperatures rising close to 90 degrees Monday afternoon. Unfortunately the rise in the temperature will also come with an increasing dew point temperature - amount of moisture in the atmosphere. Sunday afternoon dew points were in the upper 60s and low 70s. Monday afternoon dew points are forecast to rise into the low to mid 70s - meaning a very tropical air mass - which could push the heat index close to 100 degrees, especially if temperatures do reach the 90s. If we end up with a little more cloud cover to start the day, then the air temperature might not be quite as warm, however it'll still feel muggy.

A weak stationary boundary is expected to lift back to the north Monday morning, moving right over northern Illinois during the afternoon. Scattered showers and thunderstorms will be likely as the boundary interacts with the moisture, leading to localized heavy downpours. The severe threat is low Monday, but some of the stronger storms could have gusty winds with them. Those gusty winds and heavy rainfall will be our biggest threats with any storms that develop over the next several days.

Scattered thunderstorms will occur once again Tuesday and Wednesday as an upper level disturbance moves in from the south. By Thursday and Friday the wind direction shifts more to the east and northeast thanks to high pressure building in to the north. While this won't bring our heat down, as highs are still expected to remain in the upper 80s, it will knock the humidity down a little. Beyond Friday it does look like a strong ridge of high pressure will begin to build and slowly slide east into the fourth of July weekend. That building ridge could bring temperatures well into the 90s for Saturday and Sunday, assuming we stay rain free during that time.

Severe Weather Winding Down Across the Stateline Friday Evening

UPDATE: Severe Thunderstorm Warning for DeKalb County has been canceled.

Numerous severe thunderstorm warnings and tornado warnings were issued for northern Illinois and southern Wisconsin Friday evening, with reports of wind damage in Jo Daviess, Lee, Ogle and northern DeKalb counties. Most of the severe weather is beginning wind down, however, there remains a Severe Thunderstorm Warning for southwest DeKalb county until 7:45pm. Biggest threats will remain strong winds, frequent lightning and very heavy downpours.

Additional scattered showers and thunderstorms will continue for the next couple of hours with the biggest impacts remaining heavy downpours, but a few of the stronger storms may continue with gusty winds.

The Severe Thunderstorm Watch remains in effect for Winnebago, Boone, McHenry, DeKalb, Lee, Ogle, Carroll and Whiteside counties in northern Illinois until 9pm. The watch has been canceled for southern Wisconsin and far northwest Illinois counties.

Storms Once Again Possible Later Today, Some Strong to Severe

Many across the Stateline may have been woken up to the sound of thunder on this Friday morning. The region was greeted to a round of showers and thunderstorms that sparked up along a lifting warm front, tracking eastward through the mid-morning hours. There hasn't been any severe weather with the activity we've seen so far this morning. However, these thunderstorms have been capable of producing heavy downpours, and even small sized hail with the stronger updrafts. The chances for scattered thunderstorms will stick around into late morning hours, so it wouldn't be a bad idea to grab the umbrellas and rain gear before heading out.

After the morning activity comes to a close, another round of thunderstorms is set to arrive by this afternoon, bringing a higher chance for severe potential. The environment over northern Illinois and southern Wisconsin will be better primed for stronger storms later today with effective wind shear aloft and better forcing thanks to an approaching cold front.  Overnight, the Storm Prediction Center did upgrade the entire Stateline area from a Slight Risk to an Enhanced Risk (level 3 of 5). Storm mode ahead of an approaching cold front will quickly turn linear, leading to the development of a strong line of storms, or a system we call an M.C.S or a Mesoscale Convective System. Typically, this type of storm system is known for producing very gusty winds, and torrential downpours.

This complex of storms of storms will begin to form in northeast Iowa, tracking southeastward as the evening progresses. The main time frame for severe weather continues to be between 4PM to 10PM. The main threats will include damaging wind gusts heavy rainfall, and large hail. The SPC's discussion also includes the chance for a few brief tornadoes, which can happen with a line of strong storms. Typically, you will have to keep an eye out for any kinks in the line with rotation. That, if the rotation is tight enough, could lead to quick spin-ups. This is why it is very important to make sure you, and your family are weather ready later on today. Severe weather is possible at any point in the year, so have multiple ways to receive watches and warnings from the National Weather Service. Whether that's from a weather radio, from us here at the First Warn Weather Center, or the First Warn Weather App.

As for the rest of the weekend, thunderstorms from today should come to a close before midnight. The rest of our night will feature mostly cloudy skies and muggy conditions, with low temperatures by tomorrow morning in the low 70s. The cold front responsible for the severe potnetial for this evening will glide through the region shortly after sunrise, maybe even into the mid-morning hours. Following this frontal boundary, cloud cover will gradually decrease leading to some sunshine for our Saturday afternoon. An isolated t-storm or two remains possible for the second half of the day, with a bigger thunderstorm threat residing to the south in central Illinois. Sunday also features many dry hours, with highs climbing back into the upper 80s. Along with the summer-like heat is an uptick in humidity. It's going to feel humid not only through the weekend but also into next week.

Severe Weather Possible Friday

After a gorgeous Thursday in the Stateline, stronger, possibly severe, thunderstorms are possible late Friday.

On Thursday, temperatures warmed to the daily normal again in Rockford for the first time since Sunday and dewpoints in the middle 50’s made conditions all the more comfortable. However, a storm system centered in the far northern plains as of Thursday evening will propagate southeastward through the night on Thursday. The system is dragging along with it a warm front and a cold front, both of which will present a chance for thunderstorms on Friday. Cloud cover will increase through the night and into the predawn hours of Friday as dewpoint temperatures climb ahead of the warm front. The warm front is expected to pass over the Stateline early Friday morning which will likely lead to a line of morning showers and thunderstorms. While in the storm’s warm sector, the area in between the warm and cold fronts, from the late morning through the afternoon, sporadic showers and thunderstorms can be expected here in the Stateline.

As the day progresses, the dynamics for severe weather build up over the Stateline. Dewpoints in the warm sector could approach the middle 70’s at the surface with sufficient moisture present through the mid-levels of our atmosphere. With temperatures expected to reach the upper 80’s, plenty of instability is expected over the area with as many as 3500 J/kg of CAPE building by the evening. A good directional shear profile could provide some additional low level vorticity but a lack of speed shear will likely keep the tornado chances low. A lifting condensation level above 1km above ground level with a level of free convection near 3km above ground level should keep any organized convection from forming prior to the arrival of the cold front. However, the cold front should provide more than enough lift to pull the warm, moist air down near the surface into the highly unstable airmass which sits just under 3km above ground level. This front should arrive in the Stateline in the early evening which is when the severe threat begins. Storms will propagate from north to south and the severe chances should exit the Stateline by around 10:00PM.

As of Thursday evening, the Storm Prediction Center has a slight risk (category 2 of 5) for severe weather over the Stateline with an enhanced risk (category 3 of 5) positioned just to our northeast and includes far northeast Walworth County in Wisconsin. The primary concerns with these storms are gusty winds and sizeable hail while the tornado threat remains relatively low. Torrential downpours are also possible which could result in flash flooding.