A late April freeze to start, calm weather to follow

Frigid Start:

It's a downright cold start to the morning across the Stateline with temperatures in the upper 20s. Because of that, all of northern Illinois is under a Freeze Warning through 9AM, a reminder that winter isn't quite ready to let go just yet. 

After a frigid morning, conditions improve nicely as the day progresses. High pressure building into the Great Lakes region will bring dry, sun-filled skies across northern Illinois. As that system settles in, winds will turn to the south and southwest, helping temperatures to climb into the mid 50s. Compared to late-April standards, this comes a few degrees below average for the city of Rockford. Overnight low will fall into the upper 40s under a partly to mostly cloudy sky. 

Storm Chances Tuesday:

Moving forward into Tuesday, much of the day will be dry under a partly cloudy sky. However, late in the day and into the evening, a weak disturbance moving in aloft could spark up a few thunderstorms. Coverage looks limited, hence the "non-severe" risk given by the Storm Prediction Center. Afternoon highs will be much warmer, landing in the low 70s. Highs will also peak in the 70s on Wednesday. 

Understanding supercells: LP, Classic, HP explained

Low Precipitation (LP):

Supercells are the most intense and well-organized types of storms, known for producing large hail, damaging straight-line winds, and tornadoes. But not all supercells look the same or post the same set of hazards. Differences in moisture, wind shear, and storm structure can result in very different behaviors from one supercell to the next. 

First, we have LP or low-precipitation supercell. This type of supercell is often the most striking visually as you more of a structure show given the low amount of precipitation being developed. These storms form in environments with strong wind shear but limited moisture, which keeps the rainfall production limited. Despite the lighter rainfall, LP supercells are known for their large hail production and can produce tornadoes. 

Classic (CL) Supercell:

The most common type of supercell is the "classic" supercell. These storms typically form in environments with sufficient moisture, strong wind shear, and lots of storm fuel, allowing them to maintain a well-defined rotating updraft - known as a mesocyclone - while still producing a decent amount of rainfall. Visually, classic supercells often feature a rain-free base, a visible wall cloud, and a precipitation core that is separated from the updraft. Because of this, they are capable of producing all severe hazards including large hail, wind, and tornadoes. 

High Precipitation (HP):

Now, the storms we dealt with last Friday are known as high precipitation or HP supercells. These storms form in moisture-rich environments where heavy rain wraps closely around the updraft. This is why this type of supercell is considered the most dangerous of the three because any focused area of rotation or tornado will quickly become "rain-wrapped". Again this is strikingly similar to what Lena went through as the tornado started out visible, but then became rain-wrapped as it approached town. On radar, they appear messy, but can still produce tornadoes, large hail, and damaging straight-line winds.  

Freeze Warning goes into effect for northern Illinois Sunday night

 

After a week filled with warmth and severe weather mother nature gave many across northern Illinois and southern Wisconsin a little taste of winter with patchy frost early Sunday morning, followed by a mix of rain, graupel, and a few snowflakes! Thankfully, the precipitation was nothing significant but just enough to wet the sidewalk. Most of the precipitation has now moved east of the area, leaving partly cloudy skies through sunset.

High pressure moving in from the northwest will settle across Lake Michigan Sunday night. This will allow our skies to clear through the night as temperatures fall into the low 30s, with a few locations dipping into the upper 20s. A FREEZE WARNING will go into effect for all of northern Illinois beginning at Midnight and running through Monday morning.

While a little too early to really start planting the recent rain and warmth has allowed things to 'green' up over the last few weeks. Anything that has sprouted and may be a little more susceptible to the cold could be at risk with the freezing conditions.

Winds will turn back to the southwest Monday bringing temperatures into the mid-50s.

Another round of severe storms possible Friday afternoon

Friday's Severe Potential:

It's been a very active week across the Stateline, with our weather pattern delivering multiple rounds of rain and bouts of severe weather. 

Before conditions finally settle down, we have one more opportunity for what could be significant severe weather. In their latest outlook, the Storm Prediction Center has placed nearly the entire Stateline, with the exception of a small sliver of Walworth County in Wisconsin, under a level 3 of 5 Enhanced Risk. 

The Bottom Line:

Looking at storm timing, initial development could begin as early the early afternoon, mainly across areas in eastern Iowa and southwest Wisconsin. Storms will shift east, pushing through northern Illinois and southern Wisconsin between 3PM-9PM. 

Storm mode will be a key factor to monitor as these strong storms roll in from the west. If storms remain isolated in nature, they would be capable of producing a higher tornado risk given stronger, most focused and healthy rotation. However, if storms this afternoon quickly line up and turn linear, the primary severe threat would shift towards damaging straight-line winds. Also in that scenario would be the risk for quick-hitting Q.L.C.S (quasi-linear convective system) tornadoes. These tend to develop rather quickly, producing damage in the EF-0 to EF-2 range. 

Mystateline+ App: 

Again, it's important to have multiple days to receive severe alerts on days like today. Cell phone, NOAA weather radios are great sources. But now you can download the Mystateline + app for the latest when it comes to First Warn severe coverage! 

Throughout the afternoon both Meteorologist Candice King and Meteorologist Jordan Wolfe will be providing in-studio updates. Both myself and Meteorologist Owen Szarley will be out in the field keeping an eye on the skies. Review your severe storm safety plan at home, or if you're going to be out - know where to go should a warning be issued. But know that myself, Meteorologist Candice King, Meteorologist Jordan Wolfe and Meteorologist Owen Szarley will have you covered!   

Areas of dense fog possible Thursday night

 

We have had a much-deserved break from the active thunderstorms from the last few days, but unfortunately that break is going to be short-lived. More on that coming up in the next post.

It was a bit of a cloudy and damp start to the morning Thursday but with the push of some dry air by the afternoon skies were able to turn partly cloudy as temperatures warmed back into the low 70s. Skies will remain mostly clear through sunset but fog moving in from the east, off of Lake Michigan, will slowly push west through the late evening and overnight hours. This will eventually lead to some fog in the local viewing area, with dense fog possible east of I-39.

Be aware of the possibility of quickly changing visibility during the morning commute Friday, especially if you're traveling east. The fog shouldn't last too long after sunrise as southerly winds start to increase by mid-morning.

Sunshine and calm conditions Thursday, severe storms return Friday

 

Not only was it an active day across the state line with severe weather but this whole week we've certainly experienced our fair share of severe weather! Although our chances for severe weather were not as high as Tuesday, we still seen our fair share of reports. The most prominent of these reports being multiple funnel clouds from multiple storms as a few were able to weakly rotate, thankfully though none of these reached the ground.

As we turn the page to today this will be the first time in almost 4 days that we won't be under any sort of threat for severe weather! Not only that but it'll be a gorgeous day overall with temperatures in the upper 60's and low 70's with sunshine peeking out later this afternoon.

We are right in the heart of spring after all, so you know dry days don't come around too much this time of year. Unfortunately, tomorrow the chances of storms as well as severe storms will return tomorrow as our next system approaches. As of now, the Storm Prediction Center has outlined areas west of I-39 in an Enhanced (Level 3/5) risk with areas east under as Slight (Level 2/5) risk for the possibility of severe thunderstorms. Very similarly to Tuesday, thunderstorms are expected to our west in Iowa and will move through the state line into the late afternoon and early evening.

As of now, chances for storms may move in slightly earlier than Tuesday closer to 3-7 p.m. We'll have to watch how storms evolve over time as depending on how clustered they become it will affect our overall severe threat. As of now, damaging winds and large hail look to be our main threats, however an isolated tornado or two cannot be ruled out as well.

 

Severe threat ending across northern Illinois, Scattered showers and thunderstorms will continue

 

The viewing area is currently severe thunderstorm and tornado warning free as the severe threat has decreased quite a bit locally. However, FLASH FLOOD WARNINGS remain in effect for Stephenson, Winnebago, Boone, Jo Daviess, Carroll, Green and Rock counties until either late Wednesday night or early Thursday morning. This is following not only the heavy rainfall many experienced Tuesday night, but the additional rainfall we received tonight.

Thankfully, the thunderstorms tonight are a little more progressive than the storms Tuesday but steady to heavy rain will continue for the next couple of hours, impacting areas that have already experienced a significant amount of rainfall.

Scattered showers will continue through early Thursday before drying out by mid to late morning. We get a break from the active weather Thursday, but it is set to return Friday afternoon and evening ahead of an even stronger cold front that'll finally bring an end to our very rainy and stormy pattern.