textproduct: St. Louis

KEY MESSAGES

- A warming trend is expected this week, with near average values Monday followed by temperatures around 10 degrees above average Tuesday through Friday.

- Mostly dry conditions are expected this week, aside from potentially a brief round of showers and a rumble of thunder or two Thursday night through Friday morning.

SHORT TERM

(Through Late Monday Night) Issued at 1251 PM CST Sun Nov 2 2025

Largely benign weather is in store for the region for the remainder of the evening tonight and through the day tomorrow, thanks to expanding high pressure across the lower Mississippi Valley.

While widespread dense fog occurred early this morning, including throughout the St. Louis metro area where dense fog is rare compared to the surrounding area, we do not expect a repeat performance overnight tonight. Southerly surface winds, slightly warmer temperatures, and limited moisture will likely keep this in check, with the possible exception of main stem river valleys that can remain sheltered from the wind. Meanwhile, forecast temperatures suggest that the vast majority of the area will remain above freezing tonight, although some Ozark valleys may see a bit of patchy frost. After last night's widespread freeze, though, we don't expect noteworthy impacts from frost.

Overnight tonight through mid-late morning, a low pressure system across the northern CONUS and southern Canada will drive a weak cold front into the area, but this is not expected to amount to much more than a wind shift to the northwest. In fact, tomorrow will kick off a steady warmup, with temperatures likely to reach into the low to mid 60s area-wide underneath mostly clear skies.

BRC

LONG TERM

(Tuesday through Next Sunday) Issued at 1251 PM CST Sun Nov 2 2025

The main story for most of the workweek continues to be the persistence of warm and dry conditions, although confidence is growing that we will see a brief round of showers and possibly a rumble of thunder or two sometime late Thursday or Friday.

By Tuesday, synoptic-scale zonal flow aloft will develop across the CONUS, with periodic shortwaves moving through it. The next of these waves is likely to move across the northern Plains and upper Mississippi Valley between Tuesday and Wednesday, driving modest surface pressure falls and breezy south to southwest winds across our area Tuesday. This will produce another significant boost to temperatures, likely bringing our afternoon readings into the upper 60s to low 70s area-wide. We will also need to keep an eye on humidity projections from a fire weather-perspective, although current RH projections remain a bit too high to warrant serious concern at this time.

While another weak cold front is likely to follow shortly behind, once again this front is not likely to impact temperatures much, if at all, and as a result, similarly warm temperatures are very likely Wednesday through Friday. Seasonal average high temperatures are generally in the upper 50s to low 60s this time of year, putting our current forecast approximately 10 degrees above average each day Tuesday through Friday. Forecast ensemble spreads are also relatively narrow throughout this period, which bolstered our confidence in these values.

Between Thursday and Friday, models continue to suggest that a deeper, more substantial trough will dig into the central Plains, driving more substantial surface pressure falls and southerly return flow as a result. While this will help to transport a more humid airmass northward Thursday and Thursday night, the progressive nature of this trough and an advancing cold front will shorten the window for moisture return, thus putting a ceiling on the potential for meaningful rainfall and stronger showers and thunderstorms. On the other hand, precipitation probabilities along the front have trended upwards in recent runs in spite of the modest moisture return and also significant timing variance in the progression of the trough and front. Likewise, while our confidence in a brief round of showers has increased sometime between Thursday night and Friday, exactly when this will occur is less certain. Meanwhile, meager instability projections and the potential for a nocturnal or early morning frontal passage are not ideal for strong/severe thunderstorms, although a rumble of thunder or two can't be ruled out. We will need to continue to watch this potential considering the dynamic nature of the trough, but as of now the potential for stronger storms appears limited.

From Friday onward, a cooling trend appears likely behind this cold front, although we also note much increasing ensemble spread in during this timeframe. Precipitation chances also appear to be limited over the weekend and beyond, although again there is considerable spread Saturday onward and a minority of ensemble members do produce a smattering of light precipitation amounts over the weekend.

BRC

AVIATION

(For the 00z TAFs through 00z Monday Evening) Issued at 445 PM CST Sun Nov 2 2025

Dry and VFR flight conditions will continue through the end of the TAF period under the influence of a surface high. LLWS is expected overnight ahead of and along a cold front that will push through the region overnight. Speed shear will be upwards of 40 kts, and at the onset the directional shear will be near 40 degrees, though shear will become unidirectional over the evening. LLWS is more likely at KUIN, KSUS, and KJEF where the low-level support will be better.

Winds will be calm or light from the south ahead of the front, becoming northwesterly behind the front. The front will pass the area dry with winds less than 10 kts.

Delia

LSX WATCHES/WARNINGS/ADVISORIES

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