Hot and humid conditions will stick around today, setting the stage for multiple rounds of storms. We'll be watching an initial wave develop early this afternoon, followed by a secondary round later this evening into the early stages of tonight.
The Storm Prediction Center overnight expanded the Level 3 of 5 Enhanced risk for severe storms to now include the entire area Damaging winds will serve as the primary concern. While the overall tornado threat is lower locally, a brief, isolated tornado or two cannot be ruled out - though the better chances for that remain to our north and west across eastern Iowa and southwest Wisconsin. Skies will begin to clear a bit overnight, but breezy conditions linger. With this wind remaining warm out of the south and southwest, temperatures won't fall much, landing near the 70-degree mark by Thursday morning.
Thursday's Severe:
Moving right along into Thursday, the severe weather threat ramps up even further. The strongest impacts are expected to be centered right over the Stateline as a surface low lifts to our northwest, placing us firmly within the unstable warm sector.
This setup will support the chance for multiple rounds of strong to severe storms as the approaching cold front pushes through. All severe hazards will be on the table, including damaging winds, large hail, and even the potential for a strong tornado or two. Similar to today, the Storm Prediction Center has the area under a level 3 of 5 enhance risk, signaling that numerous severe storms are possible.
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Written By: First Warn Weather Intern Patrick Murray
After what was the second driest May on record for the Rockford Airport, we’re entering a very active stretch of weather across the Stateline region over the course of the next few days. Multiple chances of showers and thunderstorms will make their way into the area, and severe weather is expected at times.
We started this morning with mostly cloudy skies, but have since cleared out a bit allowing for our temps to soar into the 80s. With dewpoints in the upper 60s/lower 70s, it has certainly felt more like mid-August rather than early June.
This afternoon, as yet another Mesoscale Convective Vortex (MCV) spins away to our south, an isolated thunderstorm or two will be possible. These storms could contain frequent lightning, very heavy rain and perhaps a severe wind gust or two. The Storm Prediction Center (SPC) has the entire Stateline under a MARGINAL (level 1/5) risk for severe thunderstorms.
TONIGHT:
For tonight, a surface warm front is expected to push north through the area overnight tonight, and with that, it will bring a chance for isolated to widely scattered showers and thunderstorms. These likely wouldn’t be anything to worry about, just seeing mainly heavier downpours with the strongest thunderstorm.
WEDNESDAY:
Then, our attention quickly turns to tomorrow, where more widespread, potentially significant severe weather appears possible, if not likely. A broad area of low pressure has developed across the northern Plains. This storm system will begin to eject northeast, bringing multiple rounds of thunderstorms to the Stateline. The first round of storms could arrive as early as late Wednesday morning into early Wednesday afternoon. The High Resolution Rapid Refresh (HRRR) model shows a potent Mesoscale Convective System (MCS) moving through central Wisconsin early tomorrow morning. The concern with these storms is they may leave an outflow boundary or two draped across the Stateline area. These boundaries help to enhance the severe weather potential. The HRRR shows strong thunderstorms firing across far eastern Iowa by late morning and moving into northern Illinois/southern Wisconsin by early afternoon. The big takeaway is that these storms MAY fire. There is always the chance that these boundaries don’t set up where they are forecasted to and we don’t see development in the early afternoon OR storms develop somewhere outside of the Stateline.
Unfortunately, that is only round one of what could be three rounds of strong to severe weather. The “main” threat for Wednesday will be in the late afternoon into the evening hours, when a more pronounced MCS moves into the area. With this, damaging wind gusts will be the main threat. However, brief spin-up tornadoes are always possible with MCS complexes.
Regardless of if severe weather occurs or not, very heavy rainfall is expected with these thunderstorms, along with frequent cloud to ground lightning.
THURSDAY:
Unfortunately, the threat doesn’t end there. Another day of severe weather is expected Thursday across the entire Stateline. Much of the day will be spent seeing partly sunny skies. This will give the atmosphere ample time to destabilize ahead of a cold front that will be moving into the Stateline Thursday afternoon into Thursday night. The HRRR indicates yet another strong MCS moving through the Stateline late Thursday morning.
We’d need to keep a close eye on this complex for the potential for significant damaging wind gusts and again, spin-up tornadoes. These storms would likely drape outflow boundaries across the Stateline again and could work to help enhance severe potential Thursday afternoon. Again, all severe hazards will be in play on Thursday.
Things quiet down Friday as the cold front pushes through the area, bringing more mild temperatures and less humidity.
The takeaways; ensure you know your severe weather plan, keep close tabs on the forecast over the course of the next few days, and have multiple ways to receive warnings. Thursdays severe potential will depend heavily on what happens Wednesday, and Wednesday’s severe potential will depend heavily on what happens tonight elsewhere.
Cloud cover will gradually give way to a partly sunny and humid afternoon across the Stateline. Dew point temperatures will be in the upper 60s, giving the air a more noticeably humid feel.
That added moisture could be enough to spark an isolated thunderstorm or two during the peak heating hours of the day. Any storm that does manage to pop-up will be brief and spotty, though could produce gusty winds at times. Overall, today's severe potential remains low, with the Storm Prediction Center placing our area under a level 1 of 5 Marginal Risk. Chances remain isolated for tonight, with overnight lows falling to 70 degrees.
Wednesday's Severe:
Looking ahead into Wednesday, the setup becomes more concerning for severe weather. A strengthening surface low lifting into Minnesota will drag a strong cold front towards the region, providing a somewhat better focus for storm development by the afternoon and evening. This morning, the Storm Prediction Center kept most of the region under a level 3 of 5 enhanced risk for severe weather.
Tornado potential looks to be greatest north and west of the area, especially across northeast Iowa, southeast Minnesota, and southwest Wisconsin - where storms have a higher chance of being discrete. Closer to home in northern Illinois and southern Wisconsin, the main threats will shift toward damaging winds along with the possibility for a few tornadoes as storms roll in Wednesday evening into Wednesday night. The evolution of today's weather will be important to watch, as it could significantly influence Wednesday's severe threat.
Thursday's Severe:
Thursday also could be a significant day across the region as the strong cold front pushes through. Again, what happens the day before will play a huge role into what happens later in the day.
There's been a mention - though confidence remains low for now, of an M.C.S, or a strong line of storms, moving through Thursday morning. That's something we'll be watching closely. However, IF that scenario does not materialize, the atmosphere could become primed for more significant severe weather later in the day, with all hazards on the table, including the potential for strong tornadoes. As always, continue to monitor the forecast, but also take time to review your severe weather plan. Make sure you have multiple ways to receive severe weather alerts and know exactly where you would go if threatening weather develops.
4:15pm Update: Widely scattered thunderstorms continue to move across northern Illinois and southern Wisconsin late Monday afternoon, all ahead of a little low-pressure system - known as an M.C.V (mesoscale convective vortex) leftover from the showers and thunderstorms Monday morning. The overall severe threat has remained pretty low with the storms so far this afternoon, but copious amounts of moisture over the region has led to heavy downpours with any thunderstorms that have developed.
The line of storms will continue to lift north into southern Wisconsin over the next 30-45 minutes, with isolated activity lasting through sunset. The humidity will remain high and temperatures warm through the night, only dropping to around 70 degrees. Light winds and plenty of moisture, combined with a stalled boundary near the state line, will lead to areas of fog and drizzle Tuesday morning.
It was a noisy start for some of us this morning as showers and a few thunderstorms pushed through the Stateline early this morning. These early morning thunderstorms included a display of cloud-to-ground lightning and, at times, loud thunder.
Additional showers and embedded thunderstorms are moving across the Stateline now, with heavy rain and more lightning/thunder. We expect at least widely scattered showers and thunderstorms to persist throughout the day today as a weak area of low pressure associated with storms from yesterday move through the region.
This area of low pressure is also known as a mesoscale convective vortex (MCV). An M.C.V forms when storms develop and form their own small area of low pressure. Severe weather is not expected today, though, with the M.C.V present, we will want to keep an eye on changing weather conditions just in case. More significant and potentially widespread severe weather is expected Wednesday evening and then again Thursday afternoon.
An upper-level low lifting in from the south will bring a bit more active weather to the Stateline, helping bring scattered shower and thunderstorm chances as we begin the new work week. With plenty of moisture in place, some of these storms could produce heavy rain, though severe weather will not be on the table. Despite the clouds and occasional rain, temperatures will still climb into the low 80s.
Tuesday's Severe:
Looking ahead, we'll begin to see a low-end severe weather threat develop Tuesday. Storm Chances will be isolated, but for some, may present the potential for damaging winds and large hail.Areas south and west of Freeportand Rochelle have been placed under a level 1 of 5 Marginal Risk. The strongest potential Tuesday will actually be up in the Upper Great Plains, focused in North and South Dakota.
Wednesday's Severe:
The severe potential ramps up noticeably as we head into the middle of the work week. A surface low lifting into Minnesota will drag a cold front closer to the region, setting the stage for storms to develop along that boundary. These storms are expected to push east into the Stateline Wednesday evening into Wednesday night, posing a risk for all severe hazards including damaging winds and isolated tornadoes. For now, the Storm Prediction Center has much of northwest Illinois and southern Wisconsin under a level 3 of 5 enhanced risk for severe weather.
Active Stretch Continues:
Please make sure to keep an eye on the forecast for not only Wednesday, but also Thursday as the surface low will likely contribute to potentially another round of significant severe weather.In their latest round of severe outlooks, the Storm Prediction Center has put the region under a 30% risk, which is equivalent to a level 3 of 5 enhanced risk.
Like Wednesday, a very moist and unstable airmass will allow all severe weather hazards to be on the table. So again, today, tomorrow, and even Wednesday morning will be a good opportunity to review your severe weather safety plan and make sure you are prepared ahead of time. With the potential for strong to severe storms increasing by midweek, having multiple ways to receive warnings and knowing where you would go pending severe weather makes all the difference.
Several pockets of heavy rain were realized Sunday afternoon with the isolated storms that developed late morning through early afternoon. Most did not see more than a few tenths of an inch of rain, but a couple locations across Ogle, Lee, and Jo Daviess County saw more than an inch of rainfall!
Similarly heavy rain may be possible in another isolated to scattered fashion Monday afternoon. This time around, rainfall should be a bit more widespread for more of the area compared to the little coverage from Sunday. Strongest storms will still be capable of producing strong downpours and some gusty winds, but the severe weather threat is limited.
The reason behind the limited severe weather risk has been a lack of better organization in the storms. So far, many of the storms have shown pulse-like, popcorn behavior. That is good for producing very heavy rainfall, but severe storms need more of a driving force in the upper levels to sustain them.
Such a pattern may develop toward the middle of the week as an upper-level trough slides overhead. This interaction between the extremely humid air mass ahead of it and the increased dynamics will allow for a few more chances for organized and possibly severe storms to develop later this week.
Much of our daytime hours Tuesday and Wednesday may end up dry, but isolated to scattered storms may pose a risk for severe weather late Tuesday evening, then again on Wednesday and Thursday. Each wave timing will depend heavily on the one before, but the ingredients are there for a mentionable risk for severe weather both Wednesday and Thursday in particular. For now, keep tuned to the forecast as we will be sure to bring you the latest!
