textproduct: St. Louis

KEY MESSAGES

- Low (15-35%) rain chances will persist through Tuesday, mainly in central Missouri, though most of the time will be dry.

- Scattered showers and perhaps a rumble of thunder are possible areawide along a potent cold front on Wednesday that will send Thursday's highs well-below normal.

SHORT TERM

(Through Late Monday Afternoon) Issued at 312 AM CDT Sun Aug 31 2025

Subtle shortwave impulses amidst northwest upper-level flow are evident on GOES East Mid-Level Water Vapor imagery, which is interacting with a more moist airmass across the central Plains to stimulate increased cloud cover and a few showers in western Missouri. Across our forecast area, dry, easterly surface flow is inhibiting any of this rain from reaching the ground. While a few observation sites across the Ozarks reported intermittent rain overnight, most of the region saw little to no rain. This trend will generally continue through the day today across the western two- thirds of Missouri, with mostly dry conditions and some intermittent showers. One item of note is the rainfall at Columbia - if little to no rain is observed, this will be the second- driest August on record. The more notable impact from these mid- level impulses will be the persistent cloud cover, which will suppress temperatures from today onward. Highs today will be a few degrees cooler than yesterday, particularly in central/northeast Missouri, which starts the first of several abnormally-cool days.

Nearly-identical conditions will exist for Labor Day: mostly dry conditions with temperatures ticking further below normal. By this point, a more organized mid-level wave will amplify over northwest Missouri and drift southwest into the Ozarks. This will gradually shift the focus for showers south and east accordingly, but most of the region will stay dry.

MRB

LONG TERM

(Monday Night through Saturday) Issued at 312 AM CDT Sun Aug 31 2025

The wave makes further progress southeast by Tuesday, shifting the rain chances across the Ozarks more concretely, but the quality of available moisture to this forcing is pretty poor. NAEFS depiction of low-level moisture is a few standard deviations below normal, which will keep shower coverage scattered at best and rain totals fairly low in an area that is increasingly dry. Temperatures remain seasonably cool with the abundant cloud cover on Tuesday, but will make a rebound back to early-September normals for Wednesday as the wave departs the region. The warmup doesn't last long, as all available guidance continues to show a very potent cold front and a very anomalous upper-level trough dive south into the Mid- Mississippi Valley Wednesday night. While scattered showers will pepper the front as it passes, rainfall totals of any consequence are very unlikely with the antecedent dry airmass in place. The bigger story will be the much colder air (as much as 15 degrees colder than Wednesday's highs) by Thursday. While short-lived, temperatures Thursday will struggle to warm more than the low 70s for most, with those in northeast Missouri enjoying the coolest air. While temperatures will gradually moderate into next weekend, dry and seasonably-cool air will stay in place amidst persistent northwest flow aloft.

MRB

AVIATION

(For the 12z TAFs through 12z Monday Morning) Issued at 602 AM CDT Sun Aug 31 2025

VFR conditions are expected to prevail through the TAF period across the region. A few brief, intermittent showers may impact the central Missouri terminals this morning, but categorical impacts are very unlikely. Winds will remain generally out of the east through the period, streaming in enough low-level dry air to keep CIGs largely unimpactful.

MRB

LSX WATCHES/WARNINGS/ADVISORIES

MO...None. IL...None.