textproduct: Central Illinois

KEY MESSAGES

- While periods of showers and thunderstorms are expected into Sunday, the Memorial Day holiday currently looks to be dry and warm.

- The highest rain chances during the work week will be Tuesday night into Wednesday, though the prospects of severe weather remain low.

DISCUSSION

Issued at 118 PM CDT Sat May 23 2026

Short Term (through Memorial Day):

The cooler weather pattern has begun to break, as dew points have climbed into the lower 60s over most of the forecast area early this afternoon. Still a fair amount of cloud cover near/south of I-70 which has kept temperatures confined to the 60s in southeast Illinois, but enough sunshine elsewhere has resulted in low-mid 70s at midday.

Water vapor imagery shows a prominent upper low near Lake Winnipeg, with a trailing trough extending into the central Plains. An associated cold front is slowly advancing across central Iowa into southwest Missouri, with scattered thunderstorms beginning to increase in coverage. As these features edge eastward, scattered showers/storms will continue to pop near the surface boundary as CAPE's reach 1500 J/kg. High-res models show a period of subsiding activity this evening with loss of diurnal heating, but the approach of the upper trough should help trigger additional showers/storms overnight. With the front close to I-57 by mid morning Sunday, most of the lingering activity will be over east central and southeast Illinois.

The upper pattern will begin a transition through the holiday weekend, with ridging developing over the Rockies Sunday night. This will result in the trailing cold front from tonight's trough getting hung up over the Ohio Valley, which should largely keep Memorial Day dry in our area. However, it will be close enough for a mostly cloudy day south of I-70, keeping temperatures closer to 80, while mid 80s are more likely in the sunnier northwest CWA. While a shortwave will be moving into the Great Lakes region in the northern upper flow, it currently appears to stay to our north.

Long Term (Tuesday through Saturday):

The upper ridge will amplify across the Plains on Tuesday, as a deep upper low digs south across the Pacific Northwest. This low should loiter over California/Nevada much of the week, as another upper low strengthens over southern Quebec. With this pattern, there remains questions as to how much of a northward push the lingering boundary can make mid week. ECMWF ensembles are in decent agreement with getting rain chances as far north as I-80 or so, while the GFS ensembles are more mixed on how much of central Illinois will see rain. NBM guidance remains on the wetter side, with enough uncertainty precluding any significant changes at the moment. More of a drier trend is likely later in the week, as the upper low strengths north of New England.

While temperatures will be several degrees above normal much of the week, it should not be unusually warm for the end of May. Temperatures look to lower some late week with the strengthening northeast wind flow.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 550 PM CDT Sat May 23 2026

A weak front will cross the area late tonight and Sunday morning, and bring around a 30% chance of -TSRA to the central IL terminals. Another round of MVFR ceilings is expected to develop over eastern IL late tonight. There is medium-high probability that this will impact KDEC-KCMI, and a lower probability it will reach as far west as KSPI-KBMI. Light southwest winds ahead of the front will veer north behind the front for Sunday afternoon.

ILX WATCHES/WARNINGS/ADVISORIES

None.