textproduct: Central Illinois

KEY MESSAGES

- A benign pattern is forecast through the end of May, with no severe thunderstorms or heat impacts expected. Temperatures will be slightly above normal, with highs in the low to mid 80s.

DISCUSSION

Issued at 158 PM CDT Mon May 25 2026

Pleasant conditions are in place across the region this afternoon as an expansive sfc high pressure is centered near Lake Ontario. An upper low was positioned over eastern TX, with the associated baroclinic leaf extending from the Gulf Coast to the Ohio Valley. Visible satellite imagery shows a broken cirrus shield extending almost as far north as the IL River Valley (as of 130pm/1830z). A very gradual increase in cirrus coverage and thickness can be expected over the next 24-36 hours. Otherwise, sfc temps are right around 80F as of this writing, and will likely warm a few more degrees through the early evening.

For the rest of this week, the synoptic forecast is largely on track, with the aforementioned upper low expected to slowly lift into the TN Valley. Meanwhile, an Omega block develops with an upper ridge building over the eastern Plains/Midwest, a cut- off low over the western US, and a trough digging into New England. The biggest change is that guidance is less aggressive in the northward extent of precip Tues night-Wed, and an early look at CAMs show uninspiring precip coverage. Given these trends, PoPs have decreased a bit from previous forecasts, still peaking at around 70% south of a Taylorville to Paris line during the day Wed, but quickly falling off to less than 30% north of I-72. Marginal instability and minimal shear preclude a severe storm threat with this disturbance. While some locally heavy rain still can't be ruled out due to weak cloud layer winds, guidance also exhibited a trend towards lower PWAT values, reducing the risk of excessive rainfall.

The timing and strength of the late week trough over New England, and a sfc high pressure to its west, continue to come into better focus. This sfc high pressure is expected to be located over the Great Lakes by Thurs, with persistent northeasterly low-level flow locally. This will largely shunt any additional precip chances to the southwest and advect drier dewpoints in for the end of the week. The latest blended guidance seems to be catching up to this trend, with forecast dewpoints for Thurs-Fri now in the mid 50s to low 60s, as opposed to mid 60s (which is what yesterday's model blend delivered). Ultimately, this sfc high should offer another stretch of benign, pleasant weather.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1217 PM CDT Mon May 25 2026

VFR conditions should prevail through the period, along with winds less than 10 kts. Winds will have a southeasterly component this afternoon, then become light/variable overnight into Tues AM. A few diurnal Cu are possible around 4 kft this afternoon, otherwise, increasing cirrus will overspread the terminals from south to north during the period.

ILX WATCHES/WARNINGS/ADVISORIES

None.