Union, IL Weather

Key messages

- Above average temperatures to persist through the upcoming weekend, though today looks the warmest.

- While not a wash out, there will be some periodic chances for showers and perhaps isolated thunderstorms at times late tonight through the upcoming weekend.

Discussion

Issued at 257 AM CDT Wed Oct 28 2026

Today is shaping up to be an unseasonably mild day area-wide. High temperatures are forecast in the low to mid-70s with breezy southwesterly winds gusting up to 25 mph this afternoon.

While quiet weather is expected locally today, focus remains on a shortwave impulse tracking eastward into southern Manitoba early this morning. This feature will stay well north of our region today and tonight. However, an associated surface low will push a cold front southward into our area on Thursday. Although the strongest forcing will pass well to the north, unseasonably high low-level moisture (dew points in the mid-to- upper 50s) beneath steepening mid-level lapse rates along the boundary will bring isolated to widely scattered showers late tonight into Thursday.

Shower chances (and possibly a few non-severe thunderstorms) are forecast to increase to 20-40% across northwestern IL for a period after midnight tonight. While some of this activity may work its way eastward into parts of the Chicago metro into the predawn hours of Thursday, it appears the coverage will be at a diurnal minimum as it moves ahead of the primary frontal boundary still to the northwest of the area. However, renewed widely scattered development looks favorable along the front as it shifts into the I-80 corridor and points southward Thursday afternoon.

Although there is not a big push of colder air in the wake of this front, temperatures will be turning cooler (dropping into the 50s by sunset) in its wake Thursday afternoon and evening. Cooler (more seasonable) weather is then expected to persist Friday into the weekend as onshore easterly flow and extensive cloud cover (and even rain at times) persists. Highs are generally forecast to be in the 60s. However, temperatures could end up struggling to climb out of the 50s, particularly across northern IL on Saturday.

Ensemble guidance suggests a series of impulses will track from Mexico east-northeastward into the Lower Great Lakes region during the weekend, followed by a stronger system moving slowly across the central U.S. next week. This will bring periodic rain chances from Friday night through next week. However, dry stretches are still expected between systems. Currently, the highest rain chances appear to be Friday night into Saturday, and again early to mid-next week. This may allow for a dry window late Saturday, just in time for outdoor Halloween activities.

KJB

Aviation

Issued at 634 AM CDT Wed Oct 28 2026

Key messages for the 12Z TAF period:

* A potential LLWS shear set up tonight

* Light rain possible overnight into Thursday morning with MVFR potential after daybreak

Light S to SSW winds early this morning will go 10 to 15 kt out of the SSW for the late morning and afternoon. A relative lull is expected during the late afternoon and early evening before 10 to 15 kt returns for the late evening and overnight. A nocturnal low level jet will bring as many as 45 kt of SW flow down to 2 kft AGL overnight. With breezy winds anticipated at the surface, left an explicit mention out of the TAFs for this cycle.

A system of widely scattered, light rain showers will move across the area overnight into Thursday with a consistent signal for a period of MVFR cigs after mid-morning. Potential is largely low enough to omit mentioning in the TAFs for now. However, a PROB30 was introduced at the Chicago sites after 14Z mostly to highlight the MVFR potential.

Doom

Watches, warnings and advisories

IL: None. IN: None. LM: None.