Chesterfield, MO Weather

Key Messages

- Dry and seasonably warm conditions will persist through the end of the week.

Short Term

Issued at 227 AM CDT Tue Oct 20 2026

The forecast for the next several days can be summed up in one phrase - status quo. With an omega block in place in the mid-levels and high pressure stationed over the eastern CONUS at the surface, there is no reason for our sensible weather to change. The small increases in temperature we expect over the week can be attributed to persistent insolation rather than any sort of advection or dynamical reasoning. High clouds blowing into the region from the southern Plains may enter Mid-Missouri slightly before peak heating, which would prevent that area from gaining that degree or two of warmth this afternoon - a negligible difference on human skin. In all, the forecast today calls for highs around 70 degrees with very little wind and plenty of sun. Add a degree and we have the forecast for Wednesday as well. The high clouds and warmer afternoon will support higher low temperatures tonight for our Missouri counties. To the east where skies will be clearer for longer, radiational cooling is expected to create similar conditions to this morning.

Long Term

Issued at 227 AM CDT Tue Oct 20 2026

The forecast from Wednesday night through the end of the week is the same as that of today and tomorrow. Widespread 70s increase a degree or two each day unless warming is perturbed by high clouds. Late in the week mid-level ridging will be shoved eastward and flattened as a longwave trough strengthens over the Four Corners region. This system is forecast to drive a cold front into the Midwest late Saturday into Sunday, but latest model guidance indicates the front will pivot into a more west-east orientation before it reaches Missouri/central Illinois. This would keep accompanying rain and cold air to our north and lengthen the duration of our warm streak. Ensembles, aside from the GEFS, appear to support this solution. 850 mb temperatures Sunday into Monday are still forecast to be about 10C - the same as today - so a drastic cooldown within that period is not likely if the models are correct. Beyond that guidance diverges, and that's reliant on if the cold front does push through the CWA or not Monday into Tuesday. The NBM high temperature IQRs reflect the uncertainty quite well, with KSTL jumping from a 4 degree split on Sunday to a 12 degree split by Tuesday.

Aviation

Issued at 1032 PM CDT Mon Oct 19 2026

High pressure continues to bring very light winds to the area and persistent VFR conditions. The only possible exception is for valley fog in the morning. Mid and high level cloud cover will be the dominant factor determining whether valley fog forms. Early this evening, temperatures in favored valleys like SUS and CPS dropped 20 degrees in 2-3 hours. However, as clouds have thickened those temperatures have leveled off or even risen a bit. Thus the clouds are having their anticipated effect, preventing the strong surface cooling needed for fog formation. However, there is a back edge to these clouds, and if the clouds do disperse before sunrise then a brief period of valley fog is possible mainly after 09Z.