Vandalia, MO Weather

Key Messages

- High pressure remains in place allowing for our dry and warm weather continues well into next week.

Short Term

Issued at 148 PM CDT Fri Oct 23 2026

An upper-level ridge will remain positioned over the Mid-Mississippi River Valley through Sunday, stagnated by the configuration of the wave pattern into an Omega Block. This pattern will result in very little change in sensible weather from day to day with seasonably warm temperatures and dry conditions. The only change through the weekend will be the very slow departure of a surface high pressure center and upper-level clouds of varying thickness streaming overhead by Saturday through Sunday. The most pronounced nocturnal radiational cooling during the period will be across southeastern MO/southwestern IL and/or river valleys with low temperatures in the 40s F and patchy morning fog, mainly low temperatures in the 50s F elsewhere. High temperatures will continue to be in the 70s F, near 80 F on Sunday depending on the thickness of cloud cover.

Long Term

Issued at 148 PM CDT Fri Oct 23 2026

Global model guidance is coming into better agreement on the ejection of an upper-level trough into the Central/Northern Plains and Upper Midwest Monday through Tuesday as the Omega Block breaks down. With this track of the trough, it is increasingly likely that the associated cold front does not reach the CWA, favoring similar, seasonably warm temperatures continuing along with dry conditions.

It is not until late next week now, that there are any signs for our sensible weather to change with varying signals for an upper-level trough to propagate into the north-central CONUS. However, the track and amplitude of the trough is uncertain which will influence its ability to force an associated cold front east/southeastward. If the front reaches the CWA, it would be accompanied by an opportunity for rain and temperatures cooling closer to average late next week. If the front fails to reach the CWA, there would be no clear catalyst for seasonably warm temperatures and dry conditions to end. Ensemble model guidance cluster analysis depicts these scenarios all being valid possible outcomes at this point. Taking all scenarios into consideration, probabilities of measurable rainfall range from 20 to 50 percent Thursday, onward, along with NBM interquartile ranges increasing to between 10 and 20 F.

Aviation

Issued at 543 PM CDT Fri Oct 23 2026

Dry and mainly VFR conditions are expected through the period. There will be some fog late tonight into early Friday in low lying areas with MVFR and possible IFR visibilities including at SUS and CPS. Otherwise winds are expected to remain light.