Hot and humid through Thursday, severe storms likely at times

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.