####018006915#### FXUS63 KLSX 090256 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 856 PM CST Mon Dec 8 2025 .KEY MESSAGES... - Up and down temperatures are expected this week with highs in the 40s/50s Tuesday transitioning to potentially dangerous cold this weekend. && .SHORT TERM... (Through Late Tuesday Afternoon) Issued at 208 PM CST Mon Dec 8 2025 A surface ridge of high pressure will continue to slide southeastward into the lower Mississippi/Appalachian Mountains overnight tonight. Winds will turn out of the south/southeast in its wake, with speeds gradually increasing overnight as the pressure gradient tightens. This increase in winds along with some mid/high level clouds streaming in from the northwest should actually yield some rising temperatures overnight. Lows in the mid 20s to near 30 degrees are forecast from northeast to southwest, but these lows likely will be reached in many areas around/before the midnight hour. Winds are expected to veer more to the southwest on Tuesday ahead of an approaching cold front. At least partial sunshine and low-level warm air advection are expected to yield the warmest day for most locations in over 2 weeks. Highs in the mid 40s to mid 50s are expected across the bi-state area. Coldest locations are forecast to be across northeast Missouri and west-central Illinois. This is where there is still a snow pack on the ground. Warmest locations are expected to be across portions of central/east central Missouri. south of the snow pack and in a region that will see winds favorable for downslope off of the Ozark Plateau. Gosselin && .LONG TERM... (Tuesday Night through Next Monday) Issued at 208 PM CST Mon Dec 8 2025 (Tuesday Night - Thursday Night) Topsy-turvy temperatures are expected for midweek as multiple cold fronts pass through the region. The first is expected to come late Tuesday night. Temperatures ahead of this boundary will be quite mild, with lows only dropping back into the low to mid 40s. The exceptions are in northwest sections of the area, where lows in the low to mid 30s are forecast due to the timing of the frontal passage. Any threat for precipitation should stay to our northeast. Like most clippers, a vast majority falls as snow along/northeast of the track of the surface low. This low is forecast to track close to the climatologically favored zone across the Upper Midwest/Great Lakes. Strong low-level cold air advection is forecast on Wednesday. Not surprisingly, steady or slowly falling temperatures are expected during the day. For most areas, readings will be in the mid 30s to low 40s from north to south during the afternoon. In addition to the cooler temperatures, it certainly looks windy. Sustained northwest winds of 15-25 mph are forecast with gusts of 30-40 mph. The strongest gusts are likely to be Wednesday morning as diurnal mixing commences. A brief 1-2 hour period of near-advisory gusts (45+ mph) are possible 12-15Z in far northern areas as winds atop the mixed layer approach 50 knots. Seasonably cold conditions are forecast Wednesday night through Thursday night along with mostly dry weather. We will have to keep a loose eye on the Thursday/Thursday night time period for the potential for some precipitation. Model guidance suggests some increasing low-level moisture convergence across a tight northwest- southeast baroclinic zone across the region during this time period. Chances for measurable precipitation range from 20-60% on the LREF from southwest to northeast, but drop quickly into the 10-25% range for at least 0.10" of liquid equivalent. Precipitation type isn't guaranteed to be snow either, with marginal or too warm temperatures the further southwest you travel. (Friday - Next Monday) The focus heading into the weekend continues to be on the incoming arctic air mass. While confidence in cold coming with below-normal temperatures is very high, exactly how cold is still a question mark. Ensemble guidance has backed off quite a bit with the brunt of the cold, focusing it more across the Great Lakes/Ohio Valley/northeast. However, these arctic air masses are very difficult to stop from bleeding south and east with time, particularly without strong mid/upper level ridging across the southeast CONUS (which largely looks absent). Both the EPS and GEFS forecast 850-hPa temperature anomalies of -20 to -25C along the lee of the Canadian Rockies later this week. This air mass should come southeast behind any northwest flow disturbance. Once it does, the abnormally expansive snowpack to our north will help prevent too much in the way of modification as it heads southeast. Long story short, all signs point to a (short) period of anomalous cold centered on this weekend. At this time, the coldest period is expected between Friday night and Sunday, with lows in the single digits (above zero) each night and highs on Saturday in the teens/twenties (and Sunday possibly as well). These readings would be about 15-25 degrees below normal for mid December. The spread is still high though, with inter-quartile ranges from the NBM of about 10 degrees. Given what was described above and the propensity for shallow arctic air masses to sag southward, I would not be surprised to see forecast lows/highs trend a bit colder over the next day or two, and closer at least to the 50th percentile of the NBM. Dry weather is forecast through the weekend. Anything that does fall behind the arctic front would fall as snow, but we are not seeing any signs at this point for measurable snowfall. Probabilities on the LREF over any 24-hour period don't really top 25%. The "best" chance likely would be with some low/mid level frontogenesis behind the arctic front itself sometime between Friday night and Saturday night, but at this point in time there is no consensus on if this will happen at all, and if so, where. Gosselin && .AVIATION... (For the 06z TAFs through 06z Tuesday Night) Issued at 850 PM CST Mon Dec 8 2025 Little change in thinking since previous update. VFR flight conditions are expected to continue through the period. Winds will increase from the south and southwest through Tuesday. Low level wind shear potential over central Missouri may be a bit lower than earlier forecast as forecast soundings show a bit less directional shear. However the 40+ kt jet remains, so will keep LLWS in central MO TAFs for the 06Z update. Carney && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX ####018008404#### FXUS63 KGRB 090258 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 858 PM CST Mon Dec 8 2025 New Information added to update section .UPDATE... Issued at 834 PM CST Mon Dec 8 2025 Took a closer look at tonight's system, as well as the stronger system for Tuesday night. Tonight's system appears to be on track to produce 1-3 inches of snow. The main change was to add a bit more areal coverage of freezing drizzle as the snow ends and moisture shallows out in central and east central WI late tonight into Tuesday morning. Don't think the freezing drizzle will result in additional travel concerns, as any very light ice accumulations will be falling on snow covered roads. Tuesday night's system continues to be a problem, as surface low tracks range from southern WI (ECMWF/GFS) to northern WI (latest RAP/HRRR), with most other models taking the low through central WI. This leads to significant differences in the position of the axis of max snowfall, and opens the possibility for warmer air and a mix with rain in central and east central WI (with the northern solutions). There is also the issue of whether or not we'll see heavy snow, as earlier probabilistic forecasts were only showing a 30-50 percent chance of 6+ inches. So, with so many question marks, the plan is to leave the current watch in place and let the midnight crew digest the full 00z model suite and make any necessary headline adjustments. The only changes made to the Winter Storm Watch earlier were back off on blowing snow wording in eastern WI due to an expected wetter/denser snow, and adding a mention of possible sporadic tree damage and power outages. && .KEY MESSAGES... - A clipper system is expected to bring a swath of 1 to 3 inches of snow across the area tonight. Highest amounts across far northern Wisconsin. - A more potent clipper system is expected to bring another round of snow to the area late Tuesday afternoon into Wednesday morning. This system is expected to produce 3-5 inches of snow over much of the forecast area, with a narrow band of higher amounts closer to 6 to 7 inches. A Winter Storm Watch is in effect for the southern two-thirds of the forecast area. - Much colder temperatures arrive for the end of the week. Wind chills of -10 to -30 are possible Friday night into early Saturday and again Saturday night into Sunday morning. && .DISCUSSION... Issued at 349 PM CST Mon Dec 8 2025 Short Term...Tonight and Tuesday Ahead of an approaching clipper system, low-level moisture moved into the area bringing low-level clouds and flurries to central and north-central WI this afternoon. Southerly winds have also allowed for low-level moisture/clouds to move inland from Lake MI resulting in scattered flurries across eastern WI this afternoon. These conditions are expected to continue until the aforementioned clipper system moves into the area this evening and overnight. While not very strong, this clipper system will spread snow across the region from west to east from late this evening and taper off/end by early Tuesday morning. By Tuesday morning, snowfall amounts of 1 to 3 inches are expected across the entire forecast area. The higher snowfall amounts are anticipated across far northern WI where the better forcing will be located. While there may be minor travel impacts to the Tuesday morning commute on untreated/secondary roads, there is also potential for a brief period of freezing drizzle Tuesday morning, as forecast soundings indicate the loss of ice crystals aloft as the snow is ending. Therefore, a few spots may become slick Tuesday morning following the departure of the snow. Additionally, gusty southerly winds will accompany the clipper system with gusts to 20 to 25 mph, which will cause reduced visibility at times while the snow is falling. There will be a lull in precipitation and winds late Tuesday morning through the late afternoon before the next clipper system arrives. During this time, a few breaks in the clouds are possible as high temperatures climb into the mid 20s to low 30s. The next clipper system will arrive from the west late Tuesday afternoon into the evening, bringing the chance for several inches of snow. For more details, see the long term discussion. Long Term...Tuesday Night Through Monday The main focus for the extended will be a passing clipper system Tuesday night into Wednesday followed by much colder air temperatures around the end of the week. Snow Tuesday into Wednesday... A strong clipper system is expected to cross into Wisconsin Tuesday, bringing accumulating snowfall late Tuesday afternoon and Tuesday evening. The timing/location for the heaviest snowfall will likely be Tuesday evening in an area just north and east of the upper low Tuesday evening, but this will likely be a relatively narrow band compared to the overall snowfall. As a result a widespread 3-4 inches seems likely with a narrower band getting closer to 5-7 inches. As model certainty remains low on the location of this higher band, maintained the watch over the region this forecast issuance. Would expect the current Winter Storm Watch covers more counties than will ultimately see a warning, given the above info. On the backside of this system Wednesday, expect strong cold air advection to continue snowfall into Wednesday morning and stronger winds by the late morning to afternoon period. Wind gusts up to 20 to 30 mph at times will allow for some drifting snow in open areas during the day Wednesday. Drier air will ultimately bring an end to the snow for most Wednesday afternoon. Cold... Much colder air moves in behind this system, starting Wednesday night through the early weekend. Overnight low temperatures will see a downward trend from a few degrees above zero Wednesday night to below zero across the whole area Friday and Saturday night. Saturday high temperatures are expected to only be a few degrees above zero for much of the area. Wind chills in the coldest parts of the weekend may also reach as low as -10F to -30F at times. && .AVIATION...for 00Z TAF Issuance Issued at 538 PM CST Mon Dec 8 2025 MVFR flight conditions were observed over NC/C WI at issuance time, with VFR conditions in the east. Patchy flurries were reported in many areas. Regional radar showed a large area of light to occasionally moderate snow approaching from Minnesota, in association with a clipper low pressure system. The quick-moving clipper system will bring accumulating snowfall, reduced vsbys, and widespread IFR conditions to the area from west to east late this evening into the early overnight hours. General arrival times at CWA/AUW/RHI should be around 04z-05z/Tue, and around 06z-07z/Tue at the east central WI TAF sites. By early Tuesday morning, 1-3 inches of snow is forecast over the area, with the highest amounts expected along and north of Hwy 29. As the snow ends late tonight/early Tuesday, a period of light freezing drizzle and IFR conditions may occur for several hours in central and east central WI. A gradual improvement in flight conditions is expected during the late morning and afternoon, though light snow is poised to return to central WI (including AUW/CWA) toward the end of the TAF period. Widespread significant snow will overspread the area Tuesday evening as a strong low pressure system arrives. Southerly winds will increase this evening with gusts to 15 to 20 kts. A period of LLWS is expected at AUW/CWA/GRB/ATW later this evening into the overnight hours, as southwest winds increase to 35 to 40 kts just above the surface. Surface winds will turn westerly late tonight into early Tuesday. && .GRB WATCHES/WARNINGS/ADVISORIES... Winter Storm Watch from Tuesday afternoon through late Tuesday night for WIZ018>021-030-031-035>037-045. Winter Storm Watch from Tuesday evening through Wednesday morning for WIZ022-038>040-048>050-074. && $$ UPDATE.........Kieckbusch DISCUSSION.....Kruk/Uhlmann AVIATION.......Kieckbusch