textproduct: St. Louis

KEY MESSAGES

- Up and down temperatures are expected today through Sunday, but the big story for this week will be anomalous warmth. In fact, all of our local climate sites have a reasonable potential (20-50%) to reach or exceed daily record highs on Christmas Day, when peak warmth is expected.

SHORT TERM

(Through Late Friday Afternoon) Issued at 150 AM CST Fri Dec 19 2025

Now that yesterday's round of widespread rainfall in the rear-view mirror, attention turns to temperatures over the next several days (and beyond). Temperatures are expected to fluctuate considerably between today, tomorrow, and Sunday thanks to yet another cold front, but for the most part this will feature little in the way of additional precipitation.

While winds remain somewhat gusty across the area late this evening, speeds are very gradually winding down in the wake of yesterday's double-feature cold front. While we may still see a few gusts in the 25 to 35 mph range overnight through early morning, by mid-day speeds should be rather light area-wide as surface high pressure moves overhead. Winds may even become southerly by late in the afternoon, but not quick enough to counter this temporary surge of cold air. As such, highs today are only expected to reach the 30s and 40s in spite of an abundance of sun, perhaps only barely climbing above freezing in the coldest parts of central Illinois where some stratus may linger a bit longer.

Our up and down temperature trend will resume Saturday and Sunday as another cold front approaches and moves through the area, with increasing low-level flow and strong warm advection early in the day Saturday. This will drive another rapid and temporary warm-up, with temperatures likely to climb back into the upper 40s to upper 50s in most areas, perhaps even getting close to 60 in the warmest parts of the Ozarks. As quickly as this warmup arrives, though, another surge of cold air will spill into the area Saturday night, resulting in Sunday temperatures dipping back into the 20s in the morning, and only rising into the upper 30s/upper 40s during the afternoon. It will be quite a swing in daily temperatures, and all with near- zero precipitation chances as well.

BRC

LONG TERM

(Friday Night through Wednesday) Issued at 150 AM CST Fri Dec 19 2025

After this weekend's temperature volatility, things get a bit simpler, albeit climatologically unusual from Monday through Thursday. This is because a steady warming trend will bring well above average temperatures to the area leading up to Christmas Day, with a reasonable potential to break daily record highs on the holiday itself.

The primary driver of weather across the central U.S. will be a slowly building upper ridge, which is expected to reach 99th+ percentile 500mb heights by Thursday. Meanwhile, south to southwest flow will also drive persistent warm air advection, particularly Wednesday and Thursday. Ensemble mean 850 mb temperatures reach very close to climatological maximums in all of the major ensemble suites by Thursday, and this is translating to NBM maximum temperature forecasts in the upper 60s to even low 70s by Christmas Eve and Christmas Day. Ensemble temperature spreads are also relatively narrow for this time range, and the most recent run of the NBM suggests a 50 to 70% chance for temperatures to reach above 70 degrees in most areas south of I-70. You'd have to go all the way to central Florida to find average highs in a similar range for this time of year, and we will be well within range of daily records on Christmas Day as a result.

Meanwhile, the chance for meaningful precipitation remains low for the next week, although there are some hints of some very light rain from a subtle shortwave early Monday, followed by very light warm- advection driven rain or drizzle between late Monday and early Wednesday. The latter would be most likely across the Ozarks and and southwest Illinois, although for most areas this pattern is more likely to produce low clouds rather than measurable rain. Even if the more bullish ensembles are closer to reality, precipitation amounts would be very light...on the order of a few hundredths of an inch.

From Friday onward, long-range ensembles suggest that temperatures are likely to begin a cooling trend, although forecast spreads do increase considerably beyond Thursday, leading to much lower confidence in the day-to-day values. In spite of this, Thursday (Christmas Day) appears to be the warmest day of the week, and it is also very likely (80%) that temperatures will remain above average through at least Saturday.

BRC

AVIATION

(For the 12z TAFs through 12z Saturday Morning) Issued at 321 AM CST Fri Dec 19 2025

While some patches of low clouds may linger near local terminals at the start of the period, VFR conditions are expected throughout the 12Z cycle. Breezy west winds will steadily weaken and shift to southerly through the day, with the lightest winds expected mid to late afternoon. Surface winds will increase slightly in the evening and overnight, but much more significantly just above the surface. There will also be some slight turning with height, and the combination of speed and directional sheer is likely to result in some low level wind shear that will persist through mid morning (and after 12Z tomorrow).

BRC

CLIMATE

Issued at 200 AM CST Thu Dec 19 2025

Well above normal temperatures are forecast around Christmas, with record temperatures within reach. Records for our three climate sites and the years that they occurred are listed below.

KLSX KCOU KUIN 12/2473(2021)74(2021)69(2021) 12/2571(1889)74(1889)66(2019)

LSX WATCHES/WARNINGS/ADVISORIES

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