209 FXUS63 KLSX 020425 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1025 PM CST Mon Dec 1 2025 .KEY MESSAGES... - Light to moderate snow is expected this evening, before exiting from northwest to southeast. Additional snow amounts of 1-2" are expected. - Seasonably cold temperatures will continue through the weekend, with another Arctic blast expected late Wednesday through Thursday. && .SHORT TERM... (Through Late Tuesday Afternoon) Issued at 227 PM CST Mon Dec 1 2025 Moderate, to occasionally heavy, snow has moved east/northeast over into west central and south-central Illinois and should exit over the next 1-2 hours. There should be a 4-6 hour window with lighter, spottier snow across much of the area this afternoon/early evening. The exception is parts of northeast Missouri and west-central Illinois where light to moderate snow should be more continuous. Another round of light to moderate snow should move northwest to southeast this evening across the entire area. This snow will be aided by moderately strong low/mid level frontogenesis and the main midlevel shortwave trough moving through the region. Snowfall rates should be more modest than the earlier round, generally in the 0.25-0.50"/hr range. By the time the snow ends, a max band of 3-4+" is expected across parts of central Missouri east/northeast into south-central Illinois just north of the I-70 corridor. The snow amounts taper down sharply once you head southeast of the I-70 corridor, as these areas saw much lighter snow amounts this afternoon than neighbors further north. For this evening's round, additional snow of 1.0-1.5" should be common for most of the area, with some totals as high as about 2". The concern for Tuesday shifts to low-level clouds and temperatures. Guidance is showing low stratus clouds to hang on well into the day on Tuesday, particularly for parts of eastern Missouri over into west central and south-central Illinois. Given that these locations also have some fresh snow cover, temperatures should really struggle to rise that much. Highs in the mid to upper 20s are forecast for these areas. Further southwest, highs in the low to mid 30s are expected in central and southeast Missouri. Parts of central Missouri will have a snow pack, which could lead to slightly lower high temperatures than forecast. There is more confidence in southeast Missouri. This part of the CWA should not have as much snow cover and should see some sunshine. Gosselin && .LONG TERM... (Tuesday Night through Next Monday) Issued at 227 PM CST Mon Dec 1 2025 (Tuesday Night - Wednesday) Moderating temperatures are forecast heading into midweek as low- level winds turn out of the southwest ahead of an approaching cold front. Lows Tuesday night will still be cold however as a surface ridge of high pressure works eastward into the Ohio Valley. Lows in the mid teens to low twenties are forecast. Areas with still (relatively) fresh snow cover though into south-central Illinois still may not be cold enough. Winds shouldn't pick up until after 0600 UTC, so we could see some single digits potentially. Highs on Wednesday are expected to range from the mid 30s to mid 40s from north to south ahead of the front. There is a bit more uncertainty with highs in our far northwestern counties as the front should move through there during the early afternoon. A slightly earlier (later) passage could yield highs a few degrees colder (warmer) than forecast. (Wednesday Night - Thursday Night) The arctic cold front will move through most of the CWA Wednesday evening. Behind that front, a brief but strong push of unseasonably cold air is expected. We also will have to watch for some light snow to occur due to low/mid level frontogenesis behind the front. LREF probabilities for measurable snowfall are in the 20-50% range across the area. From past experience, these arctic fronts are efficient at squeezing out some light snow. Any snow that does fall though would likely be efficient (high SLR) and accumulate as temperatures rapidly fall through the 20s. PoPs may need to be adjusted upwards and expanded if this signal remains or increases in the next 24 hours. Wednesday night's lows will vary sharply from northwest to southeast. Parts of northeast Missouri are expected to go below zero, whereas lows in southeast Missouri and southwest Illinois are forecast to be in the upper teens. Thursday is expected to be the coldest day of the young winter season so far with highs ranging from the mid teens to near 30 degrees from north to south. Timing of the surface high does not look ideal at this point for radiational cooling Thursday night as it quickly scoots out into the Ohio Valley. This should keep lows in the single digits/teens across the region. (Friday - Next Monday) Broad northwest flow aloft is expected this weekend into early next week. Deterministic guidance shows multiple midlevel shortwaves coming across the Mississippi Valley. These look like hybrid clippers, with accumulating snow along/poleward of their tracks. This far out, it is difficult to say when/where they will occur, but climatology heavily favors these systems mostly impacting areas to our north. Temperature wise, largely below normal readings are forecast through the period. The uncertainty comes with the individual clippers themselves as they can yield higher temperatures than forecast ahead of the, with colder temperatures in their wake. The latest NBM shows the uncertainty well, with inter-quartile ranges for highs around 10 degrees. Gosselin && .AVIATION... (For the 06z TAFs through 06z Tuesday Night) Issued at 1018 PM CST Mon Dec 1 2025 Bands of snow continue to push east through east-central/southeast MO and southern IL tonight. Within these bands, expect IFR to LIFR visibilities. Snow is on track to exit the area completely between 09z and 12z. Low MVFR to IFR ceilings will persist well behind the front, not clearing until Tuesday afternoon. In the meantime, a growing number of terminals across Missouri have begun to report freezing fog with one report of freezing drizzle. Reports have been few and isolated, and we expect it to remain this way. We will continue to monitor and amend as needed. Jaja && .LSX WATCHES/WARNINGS/ADVISORIES... MO...Winter Weather Advisory until midnight CST tonight for Crawford MO-Franklin MO-Jefferson MO-Lincoln MO-Saint Charles MO- Saint Louis City MO-Saint Louis MO-Warren MO-Washington MO. Winter Weather Advisory until 3 AM CST Tuesday for Iron MO- Madison MO-Reynolds MO-Saint Francois MO-Sainte Genevieve MO. IL...Winter Weather Advisory until midnight CST tonight for Bond IL- Calhoun IL-Fayette IL-Greene IL-Jersey IL-Macoupin IL- Madison IL-Monroe IL-Montgomery IL-Saint Clair IL. Winter Weather Advisory until 3 AM CST Tuesday for Clinton IL- Marion IL-Randolph IL-Washington IL. && $$ WFO LSX