Models present a very challenging forecast today as they struggle to get an accurate grasp on what is really occurring within a very warm, humid, and active air mass.
Through the day we aren’t going to see much change in the way of cloud cover with partly sunny to mostly cloudy conditions. However, more isolated to widely scattered pockets of rain and a few storms will continue to develop across Illinois. By 12-1 PM a larger area of rain will be moving in from the west. While the HRRR model is pretty aggressive with coverage, I would tend to think rainfall would be a bit more scattered.
Through the afternoon scattered areas of rain and storms will continue moving across Illinois, especially from I-70 southward. By 5-6 PM the initial round of rain will be moving off to the east.
Through the evening into the overnight storms will move out of the forecast area. There will be some weak upper-level impulses swinging across Illinois tonight. These will be enough to get at least some isolated areas of rain and a couple storms going. However, a lot of the activity will be norther of zones 6 and 7.
Lows tonight will be in the mid 60’s to near 70.
THURSDAY: As you wake up to head to work tomorrow I won’t rule out a few lingering showers or isolated storms. However, overall coverage does not look that great by 7-8 AM Thursday morning.
Through the morning into the mid-day hours on Thursday some isolated to scattered rain and storms will remain possible. However, some model consensus between the NAM 4km and NMM model suggest by 12-1 PM a line or cluster of storms will be developing across zone 6 and westward into Missouri.
Through the afternoon this line looks to continue developing in an unstable environment. CAPE values from the NAM shows areas of 3000-4000 J/Kg will be possible. With such an unstable environment and high levels of moisture, strong to possibly some severe storms will not be out of the question with strong winds, hail, and heavy downpours possible.
Through the afternoon the line will continue moving to the south and southeast. By 5-6 PM Thursday evening the line will be in very southern zone 6. As it moves into southern zone 6 it does look to be weakening as well.
Highs on Thursday will be in the upper 70’s to low 80’s.
Through the evening the storms to the south will completely exit the forecast region. While a few lingering areas of rain and a couple of storms may be ongoing early into the overnight, I think the afternoon storms should leave behind a relatively stable environment. The stable environment would hinder any new storm development.
Lows Thursday night will be in the mid 60’s to near 70.
FRIDAY: As a strong upper-level wave and attendant vorticity max move into Illinois Friday, rain and storm coverage will increase ahead of it.
While NAM and EURO models do start Friday off mostly dry, rain and storms do develop quickly. The EURO is a bit quicker with development showing rain and storms getting going by 7-8 AM. However, the NAM wait until closer to 9-10 AM. Regardless, rain/storms chances will start early on Friday.
Through the morning into the afternoon on Friday areas of rain and storms will be ongoing. By 1-2 PM the NAM shows the scattered areas of rain and storms that will be ongoing.
Through the evening on Friday the upper-level energy will be moving out of the forecast region. By 6-7 PM only isolated to widely scattered precipitation will remain.
Regarding strong to severe t’storms on Friday the main question will be cloud/rain coverage and how it will relate to instability. A strong low-level jet will push into the region through the afternoon and evening with winds of 40-50 mph. However, with the higher amounts of clouds/rain, instability may struggle to develop. Overall the threat will have to be worked out in the next 24-36 hours as more small-scale details become available.
Highs on Friday will be in the mid 70’s to low 80’s.
Friday night into Saturday scattered areas of rain and some storms will remain possible within the warm, moist environment. These will be hit and miss, so many places will remain dry.
WEEKEND: Another push of moisture and precipitation looks to move in through the day on Saturday. While not everyone will get wet, scattered rain and storms will remain in the forecast.
Through the afternoon on Saturday scattered areas of rain and storms will remain possible across both zones 6 and 7.
With low-level jet winds of 30-40 mph in place still along with as much as 2000 J/Kg of CAPE in areas strong to severe storms will remain possible Saturday. Again, the big question will be how much rain/cloud coverage will there be and how much will it limit instability. However, if we do see better levels of instability severe weather will definitely be possible.
Highs on Saturday will be warm once again with temperatures in the upper 70’s to mid 80’s.
Sunday looks to be the nicest day of the weekend. Little rain or storms will be in place to start the day.
Through the afternoon isolated to widely scattered areas of rain and storms will develop within the warm, moist environment.
Highs on Sunday will be in the low to mid 80’s.
New rainfall totals through the end of the weekend will be around .90-1.20” across the Illinois. However, places that get under the strong storms could see up to 4” locally.
I want to emphasize that models are struggling with even short-term forecasts. So changes will likely be made to timing, threats, and overall coverage in later outlooks. If you do have questions feel free to reach out to us by phone, text, or email. Thanks!