####018007299#### FXUS63 KLSX 100356 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 956 PM CST Tue Dec 9 2025 .KEY MESSAGES... - Very windy conditions are expected behind a cold front late tonight through Wednesday morning. Sustained northwest winds of 20- 30 mph with gusts of 35-50 mph are forecast. - Gradually colder and colder temperatures are expected through the weekend, with the coldest period expected Saturday night/Sunday. && .SHORT TERM... (Through Late Wednesday Afternoon) Issued at 145 PM CST Tue Dec 9 2025 A clipper is currently across southeast North Dakota and will progress quickly into the Great Lakes overnight tonight. A cold front draped to its southwest will progress eastward across the mid- Mississippi Valley late tonight/early Wednesday morning. Behind the front, winds will swing to the northwest and increase in speed. Sustained wind speeds of 20-30 mph with gusts in the 35-50 mph range are expected. The highest winds/gusts should be between 0900 and 1800 UTC across eastern Missouri over into Illinois. The 12Z HREF shows 50-70% probabilities for 45+ mph wind gusts (advisory criteria) in this time period, and given the tight pressure gradient and near 50 knots of flow at the top of the mixed layer, went ahead and issued a wind advisory for much of eastern Missouri and our Illinois counties. The pressure gradient relaxes fairly quickly from northwest to southeast during the morning hours on Wednesday, so while it still will be a bit breezy during the afternoon, gusts should drop well below the 45 mph advisory threshold. Strong low-level cold air advection will also lead to colder temperatures on Wednesday compared to today. Temperatures should cool for most locations through much of the morning hours, before leveling off for the most part in the afternoon. Readings in the 30s to low 40s are expected from late morning through the afternoon. Given the strong northwesterly winds, it will feel quite a bit colder than that though. Gosselin && .LONG TERM... (Wednesday Night through Next Tuesday) Issued at 145 PM CST Tue Dec 9 2025 (Wednesday Night - Friday Night) Seasonably cold temperatures and dry weather is forecast Wednesday night and Thursday as a surface ridge of high pressure progresses across the Mississippi Valley. Yet another clipper is expected to move from northwest to southeast Thursday night into early Friday. This system will be further south/southwest, with the track of the low potentially across northern sections of the area. There remains some uncertainty with the track of this system, but most ensembles from the LREF argue for little/no impacts from this clipper in our area like its predecessors this December. Climatology also strongly argues for impacts (i.e., accumulating snow) to stay to our northeast more across north-central Illinois into Indiana. Temperatures will be closely tied to the track/timing of this clipper, but warmer (upper 20s - mid 30s) lows are expected Thursday night ahead of this system, with colder temperatures building back southward behind it. By Friday night, lows in the teens/twenties are expected. (Saturday - Sunday Night) Confidence is increasing in a short, but intense period of anomalous cold for this upcoming weekend. The coldest 24-36 hour period is expected between Saturday night and Sunday night. This is when lows in the single digits/teens are forecast, with highs Sunday only in the teens/twenties. These readings would be about 15-25 degrees below normal for mid December. There is still some uncertainty on exactly HOW cold, as our CWA will be more toward the southwestern edge of the most extreme portion of this air mass. The spread on the inter-quartile range for temperatures from the NBM this weekend is still almost 10 degrees. The deterministic forecast mentioned detailed above though generally sits near the 75th percentile, and I would not be surprised to see both Saturday night's lows and Sunday's highs trend at least toward the 50th percentile of the NBM. This would be potentially knock those values down about 3-5 degrees. If this occurs, we may be looking at our first extreme cold/wind chill products of the season. Probabilities on the LREF for wind chills at or below -10F are in the 30-60% range along/north of I-70 and 10-40% for -15F or colder. Dry weather is favored this weekend. The only chance of snow looks to come Saturday/Saturday night behind the main push of arctic air. Deterministic model guidance depicts some low/mid level frontogenesis combined with a midlevel shortwave trough moving across the Upper Mississippi Valley. Like a broken record, this axis of snow is very likely to setup northeast of our region. The highest probabilities for measurable snow stretch from central Iowa east/southeast across north-central Illinois into Indiana. Probabilities drop further southwest, with only a 20-40% chance for any measurable snow in northeast Missouri and west-central Illinois at this time. (Monday - Next Tuesday) Ensemble guidance is in very good agreement that a quick moderation in temperatures will occur early next week. Mid/upper level heights rise with strong low-level warm air advection commencing in the wake of the departing surface high. Temperatures are forecast to warm back closer to seasonal normals by Tuesday along with dry weather also being favored. Gosselin && .AVIATION... (For the 06z TAFs through 06z Wednesday Night) Issued at 955 PM CST Tue Dec 9 2025 The forecast remains on track this evening with VFR flight conditions expected until Wednesday morning behind the cold front. Southwest flow is increasing ahead of the front, and there have been some intermittent gusts up to around 25kts. However the gusts are infrequent enough that I'm still concerned about low level wind shear. Short range forecast soundings continue to show little mixing so will continue LLWS mention in the terminal forecasts unless more frequent gusts materialize. LLWS conditions will diminish after the front moves through. Still expecting gusts of 35-40kts in the wake of the front on Wednesday morning. MVFR ceilings, mostly above 2000ft are still expected to move over most of the region Wednesday morning and will likely prevail for much of the day and even linger after 00Z along and east of the Mississippi River. Carney && .LSX WATCHES/WARNINGS/ADVISORIES... MO...Wind Advisory from 3 AM to noon CST Wednesday for Franklin MO- Jefferson MO-Knox MO-Lewis MO-Lincoln MO-Marion MO-Monroe MO-Pike MO-Ralls MO-Saint Charles MO-Saint Louis City MO- Saint Louis MO-Shelby MO-Warren MO. IL...Wind Advisory from 3 AM to noon CST Wednesday for Adams IL-Bond IL-Brown IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL- Jersey IL-Macoupin IL-Madison IL-Monroe IL-Montgomery IL- Pike IL-Saint Clair IL. && $$ WFO LSX ####018004152#### FXUS63 KTOP 100356 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 956 PM CST Tue Dec 9 2025 .KEY MESSAGES... -Strong northwest winds develop behind a cold front tonight. Gusts to near 45 mph are possible in far northeast KS. -Temperatures fluctuate from above normal to below normal and back again through the end of the week. -The weekend looks much colder, but snow stays north of the area. && .UPDATE... Issued at 927 PM CST Tue Dec 9 2025 Decided to issue a Wind Advisory for Brown and Nemaha Counties for the overnight hours into early Wednesday, joining with our neighboring offices to the north and east. The HREF (as well and the RAP and HRRR) continue to be most aggressive and suggest advisory-level wind gusts could be more widespread than this. However, it is spotty and appears to be on the extremely high end of guidance. Overall, far northeast KS has the most consistent signal and has been highlighted in the 90th percentile, so opted to include those two counties for now. && .DISCUSSION... Issued at 216 PM CST Tue Dec 9 2025 Today, a clipper system is moving across the northern high plains while northwest flow persists aloft. Temperatures have warmed well into the 50s and low 60s across the area this afternoon with breezy southwest winds and WAA. Tonight, a cold front associated with the low to our north will quickly work through northeast KS. Northwest winds behind the boundary will increase to near wind advisory criteria (gusts of 40 to 45 mph), especially in far northeast KS. There has not been great agreement between HREF, LREF and NBM in meeting/exceeding criteria. HREF is the more confident solution in exceeding 45 mph gusts, and have noticed that the 90th percentile of NBM has increased slightly. But for now, have held off issuing an advisory with confidence not quiet high enough. Later shifts will re- evaluate and may need to consider at least adding far northeast KS to the advisory issued by neighboring offices. A few of the high resolution models also show light QPF near the front this evening and tonight. However, forecast soundings show a 5kft layer of dry air beneath the cloud deck, so any precip is likely to evaporate before reaching the ground. Surface high pressure builds in tomorrow so temperatures will be closer to normal in the mid 40s for highs. Gusty winds will decrease during the afternoon as the low moves further east, away from the region. The forecast remains dry through the rest of the workweek with another in a series of clipper systems staying north and east of the CWA on Thursday. Southerly winds return on Thursday, allowing temperatures to warm back into the mid 50s and low 60s. The next cold front moves through with that second clipper system Thursday night. High pressure will control our conditions through the weekend, keeping temps cooler than average, especially by Sunday when a reinforcing round of cold weather moves in. Lows Sunday morning could be in the single digits with highs Sunday afternoon only in the 20s. Another batch of snow again stays north of the area this weekend. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 956 PM CST Tue Dec 9 2025 Winds continue to be the main aviation concern with VFR forecast otherwise. A cold front is on its way from southern Nebraska and will shift winds to the NW early in the period. LLWS remains a possibility for the first few hours with a 45-50 kt LLJ overhead. The stronger push of gusty winds should arrive overnight with 25-35 kt gusts remaining persistent through the morning hours. There should be a gradual decrease through the afternoon, eventually falling below 10 kts in the late afternoon and becoming light and variable by the end of the period. && .TOP WATCHES/WARNINGS/ADVISORIES... Wind Advisory from 3 AM to 9 AM CST Wednesday for KSZ011- KSZ012. && $$ UPDATE...Picha DISCUSSION...Teefey AVIATION...Picha