AFTERNOON-EVENING: Clear to mostly clear skies are in place across the forecast area this morning as a warm front remains to the forecast zones north. To the west a cold front is in place, this will have an impact on our weather later on today into tonight.
Through most of the daytime hours today conditions look to remain nice with dry conditions, warm temperatures, and sunshine.
Through mid to late afternoon I won’t totally rule out a stray shower/storm. However, with the front still to the west and northwest development will be very limited.
By 7-8 PM the cold front will be moving into very west and northwestern Illinois. As it does, some rain and thunderstorms will develop along the front and move to the northeast along it.
By 12-1 AM Tuesday rain and some t’storms will be in place along the front across zone 7 and northern zone 6.
While scattered rain and storms will remain possible through the overnight, intensity will start to fade as we lose the instability from day time heating.
While a some strong to severe storms will be possible late this afternoon into the evening hours, I am not expecting a widespread severe weather event. The main threat will be across zone 7 and very northern zone 6.
This afternoon sunshine will help destabilize the environment, mainly in zone 7 and northward. CAPE forecasts of 1500-2000 J/Kg will be possible at it’s most unstable point.
Aloft, strong winds at 500 mb and lower at 850mb will be better situated across northern Illinois and southern Wisconsin, taking the main severe weather threat to the north. The other limiting factor will be cold front/storm timing. Better storm chances will not increase until near sunset this evening, so we will already be losing instability and better severe weather chances.
With any severe storm that should from the main threats will be: Damaging winds, hail, and an isolated tornado.
Lows overnight will be in the low to mid 60’s.
TUESDAY: Through Tuesday morning the front will be in place across the southern half of Illinois. By the 7-8 AM hours there will be some leftover rain showers and a few isolated storms, but most of the activity that remains will be fading by this point.
Through the morning hours some isolated to widely scattered areas of rain will remain across the front. Right now it looks like the front will stall out or greatly slow around the Springfield, IL area per models. With that being said fronts can be somewhat unpredictable on exactly where they end up, so we will have to watch that closely.
Through late afternoon/early evening on Tuesday more storms will develop in and around the frontal boundary in place. By 4 pm scattered storms will already be ongoing Tuesday afternoon.
By 7-8 PM storms will continue eastward along the front into Indiana.
Highs on Tuesday will be in the mid 70’s north to around 80 south.
While no major severe weather is anticipated across the region, I do think some strong and a few severe storms will be possible along the front. While winds aloft will be extremely weak, CAPE values of 2500-3500 J/Kg will be likely. This would be enough to create some explosive thunderstorms with gusty/damaging winds possible and some hail.
Through the evening into the overnight the main focus for storms will shift off to the east of zones 6 and 7. This should set up for a mostly quiet overnight.
Lows Tuesday night into Wednesday will be in the mid 50’s northwest to low 60’s in many locations.
WEDNESDAY: The stalled front will start to lift back to the north on Wednesday ahead of an area of low pressure. By 7-8 AM Wednesday morning more rain and perhaps a couple of storms will develop along the front as it starts to lift northward across Illinois.
Through mid-day these looks to be relatively isolated to widely scattered areas of rain and storms. However, by 1-2 PM a better concentration of rain and some storms looks to develop.
Through the evening a rain and storm chances will continue across all of the forecast area. I think by 7-9 PM the biggest part of the precipitation will be moving out of the zones as the warm front lifts farther north ahead of the low pressure system.
Highs on Wednesday will be in the upper 50’s to mid 60’s along/north of the front. With temperatures in the low to mid 70’s south of it. Winds on Wednesday will be strong at times with gusts of 30-35 mph possible.
THURSDAY – FRIDAY: The area of low pressure will be weakening Wednesday night into Thursday. This may allow more of a “wave” of low pressure to stick around at least through the morning hours on Thursday. This would allow for some scattered areas of rain and perhaps a few storms to stick around as well.
By Thursday morning some areas of heavy rain look likely across portions of Illinois. The NAM shows a widespread .75-1.10” of new rainfall with locally more.
The GFS is even more aggressive with a large area of 1.50-2” rains. I do think the heavier totals will be possible, some models are even more aggressive than this forecast. So we will watch trends closely over the next few days.
Through the afternoon hours the wave of low pressure will weaken as it continues to the east. This will allow rain chances to decrease through the afternoon hours on Thursday.
Highs on Thursday will be in the upper 60’s north to upper 70’s south.
Friday looks to be a nice day across the forecast area as we will be between the exiting low and another low pressure system developing across the Plains.
It looks like Friday will consist of a mix of clouds and sunshine. Highs will top out in the upper 60’s north to mid 70’s south.