Aviston, IL Weather

Key Messages

- Warm and dry weather will extend through this weekend.

Short Term

Issued at 300 AM CDT Thu Oct 22 2026

A mid-level longwave trough is currently swirling off the coast of Southern California as seen in water vapor imagery. The trough will make landfall today, and a shortwave on its poleward side will begin to phase into the northern stream. What does that mean for us? For now, nothing notable. Ridging in the mid and low levels will still dominate our sensible weather despite being pushed eastward by the western trough, and our copy-and-paste regime will continue. Insolation will again push high temperatures a few degrees warmer today than yesterday with most locations expected to peak in the upper 70s this afternoon. Tomorrow, low-level winds will shift to southeasterly as the ridge slides east, and weak cold air advection will be introduced to the region. The effects of this will be stronger with eastern extent. Mid-Missouri will likely experience a very similar day to today, whereas south-central Illinois is forecast to be a few degrees cooler. Expect morning lows to fall into the 40s and low 50s in the interim.

Long Term

Issued at 300 AM CDT Thu Oct 22 2026

A cold front will drape across the Upper Midwest this weekend in response to the aforementioned northern stream shortwave trough zipping into south-central Canada. It and all of its associated cold air and rain are forecast to stay north of the Mid-Mississippi Valley, so our warm streak will continue through the weekend. High clouds blowing off from showers to our north and west may stunt warming Saturday and Sunday afternoons, but highs are still expected to climb well into the 70s each day.

The mid-level ridge centered over the eastern 2/3rds of the CONUS will deamplify early next week as a longwave trough over the Desert Southwest finally pushes into the Plains and weakens into a shortwave. Its progression is expected to shove the cold front into the Mid-Mississippi Valley sometime around Tuesday, but the variability in guidance is too high to pinpoint an exact time. This stems from differences in the phasing, amplitude, track, and timing of the shortwave. For instance, the ENS shows a stronger shortwave that swings more poleward than the other ensembles. As a result, the front barely clears Chicago, and the majority of our CWA has a 40- 80% chance of reaching 70 degrees by 1pm Tuesday. The GEPS, on the other hand, shows a very weak and much more southerly shortwave. In this solution, the front clears St. Louis and the CWA has a 20-50% chance of reaching 70 degrees by 1pm Tuesday. Then there is the question of whether the front actually passes and we cool down, or if it lifts northward as a warm front and the unseasonable warmth continues further. This is a question that can't be answered right now given the reliability of the data, but it is what we'll be watching for the next several days.

Aviation

Issued at 1211 PM CDT Thu Oct 22 2026

Dry and VFR flight conditions will persist through the TAF period with the exception of river valley fog again Friday morning. KSUS and KCPS are most favored for a short period of impacts from fog around sunrise Friday. Winds will remain light and eventually become more southeasterly to southerly on Friday.