####018005569#### FXUS63 KILX 110450 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1050 PM CST Wed Dec 10 2025 .KEY MESSAGES... - Snow will spread across much of central Illinois Thursday afternoon through Thursday night. There is a 50-80% chance for greater than 2 inches of snow along and northeast of a Macomb to Robinson line, with a 20-40% chance for greater than 4 inches of snow along I-74. - Another surge of very cold air is expected by the end of the week...resulting in sub-zero apparent temperatures Friday night through Monday morning. && .UPDATE... Issued at 629 PM CST Wed Dec 10 2025 An area of light snow showers has developed across eastern Iowa and northwest/west-central IL, beneath a 700-400mb differential (positive) vorticity advection (DPVA) maximum. This is spreading slowly towards the east-southeast, and based on radar trends may extend into portions of central/east-central IL - though it will have quite a bit of dry air to erode (per the 00z ILX raob) as it does so. Upstream visibility observations have been mostly unaffected, though a few drops into the 3-5 mile range have been reported. Most locations shouldn't see anything measurable, but locally up to a half inch seems reasonable based on output from the few CAMs which caught onto this activity. No model has done a great job of highlighting the location of this snow, so we needed to extrapolate based on radar for our increased PoPs - highest along roughly the I-74 corridor through 1am. Bumgardner && .SHORT TERM... (Tonight Through Late Thursday Night) Issued at 241 PM CST Wed Dec 10 2025 Light snow, with little to no accumulations, will linger across northern areas of the CWA this evening, mainly along and north of I- 74. Then, after a brief dry period, Thursday morning, a stronger clipper system will plunge into the area for Thursday afternoon through Thursday night. All models have trended southwest of I-74 with the axis of the heaviest snow band; however, the NAM keeps it along I-74. Blend of models also shifts the axis southwest and this trend was followed for this forecast package. Typical with many clippers, decent warm air advection ahead of the system will provide ample moisture to work with and there will be sufficient isentropic lift along and north of the low track; which should result in decent amount of snowfall across most of central IL, with the heaviest snowfall occurring Thur evening. Snow should begin in the west Thur afternoon with 1-2 inches possible by 6pm northwest of I-55. Snow will continue to the east and southeast with 2-3 inches possible during the evening hours across areas north of a Macomb to Robinson line. If the forecast track remains the same through tonights models, then a winter weather advisory is likely for tomorrow afternoon through tomorrow night. There appears to be a 50-80% chance of amounts being over 2 inches, with even a 20-40% chance of amounts exceeding 4 inches along I-74. The probabilities could increase, as long as models remain consistent the next 12 hours. P-type will primarily be snow. However, forecast soundings southwest of Springfield and south of Effingham show small possibilities of brief periods of rain or freezing rain mixing with the snow during the late afternoon or early evening. Do to the high uncertainty and low probability of the freezing rain occurring, will not have it in the forecast at this time. Temperatures will remain below freezing through tomorrow night, across all areas except for southeast IL. Auten .LONG TERM... (Friday through Next Wednesday) Issued at 241 PM CST Wed Dec 10 2025 Another clipper system will quickly push through Saturday, which could lay down another 2-3 inches of snow. However, the bigger concern will be the extremely cold temperatures for the weekend. Coldest temperatures will be Saturday night and Sunday night, with air temperatures below zero across most of the CWA. Combined with the winds and wind chills of 15 to 25 below zero will be common Sat night, with wind chills around 15 below for Sun night. Fortunately, dry weather is expected Sunday through the beginning of next week. The other good news is the bitter cold temps will be short lived as temperatures will begin to significantly warm with temps reaching above freezing on Tuesday and in the 40s for by Wednesday. Auten && .AVIATION... (For the 06z TAFs through 06z Thursday Night) Issued at 1047 PM CST Wed Dec 10 2025 MVFR ceilings will continue for most of the forecast period as cyclonic flow continues beneath an expansive upper level trough. Snow flurries will continue to shift east across BMI and toward CMI the next couple hours, but visibility impacts are not expected. Ceilings may (30% chance) break up or lift above the MVFR category briefly late tomorrow morning into the early afternoon, but this will be short-lived as another disturbance dives southeast into the area by mid afternoon - lowering ceilings and reducing visibility via snow (or a rain/snow mix for SPI). Confidence is medium-high (60-80%) in IFR conditions by the end of the forecast period, especially at the I-74 corridor terminals (i.e., PIA, BMI, and CMI). Bumgardner && .ILX WATCHES/WARNINGS/ADVISORIES... && $$ ####018008143#### FXUS63 KDMX 110451 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1051 PM CST Wed Dec 10 2025 ...Updated Forecast Discussion and 06z Aviation Discussion... .KEY MESSAGES... - Band of snow passes over northwest into central and southeastern Iowa Thursday into Thursday evening with accumulation of several inches possible. On the southwest side over portions of western and southern Iowa, light ice accumulations are possible. - Accumulating snow Saturday with very cold air Saturday into Sunday. Cold weather headlines look increasingly likely early Sunday. - Moderating temperatures and trending dry early next week. && .UPDATE... Issued at 1048 PM CST Wed Dec 10 2025 Still a fluid situation unfolding for Thursday. Precipitation still on track to arrive Thursday afternoon from NW to SE. Mixed precipitation and the freezing rain potential remains the primary forecast challenge and it still appears there may be a narrow corridor with minor ice accumulations. The transient progression of the greatest forcing from southwest to northeast as the warm advection and warm nose moves into southwest and central Iowa may lead to some forecast adjustments upcoming. That shift within a southeast moving band will also have an impact on overall snowfall amounts as the area of better dendritic growth will not be static. This has also led to an overall shift northeast in the precipitation band. In addition, this will also lead to an initial period of dendritic growth but the forcing also will eventually lower into a less favorable snow microphysics process leading to the generation of more plates as opposed to dendrites. Plates are much less efficient at snow to liquid ratios. Overall, this still translates to a snow band with 1 to 3 inches possible and it may be more 1 to 2 inches with a few areas with 3. Freezing rain will be the main winter headline driver. Solar radiation passing through the clouds, latent heat release and the fact that any freezing rain occurring in the "warmer" part of the system, may lead to road temperatures AOA 32 degrees through mid afternoon. After 4 pm, icing impacts may become more likely with the loss of that solar radiation. Obviously we will continue to monitor and update as needed. && .DISCUSSION... Issued at 227 PM CST Wed Dec 10 2025 Early afternoon satellite imagery from GOES-East Day Snow Fog RGB shows widespread cloud cover over the state as the stout shortwave trough (aka clipper) departs the region. There are light snow showers passing over northeastern portions of our forecast area into east central Iowa this afternoon. Iowa DOT road cameras show little in the way of impact, but visibilities down to around 1 mile have occurred at Mason City and similar visibilities are possible downstream. While winds continue to diminish this afternoon into tonight, there are still a few wind gusts of 25 to 35 mph. The fast, northwesterly flow continues to be the main driving force behind our sensible weather into this weekend as a ridge persists over the western US. The next clipper is just moving over the British Columbia province this afternoon. This clipper will race towards our region tonight with strong theta-e advection and moderate QG convergence moving in after sunrise Thursday. As this spreads into the state, the associated upstream surface low pressure will near southwest Iowa and place much of Iowa under the precipitation shield - the exception being parts of west central into southwest Iowa. Cross sections show there is a degree of low level frontogenesis, strongest in the GFS, with saturation through the dendritic growth zone (DGZ) with moderate lift at times over central into northern Iowa. Most models show up to no higher than two to three tenths of an inch of liquid, though the GFS is the higher outlier with a narrow ribbon of a half an inch of liquid. Further, the QPF axis is shifting southwestward compared to previous forecasts. This is based on trends noted not only in past events, but also with models this time around compared to the last night's QPF axis. Many of the global and ensemble members are southwest of the overnight forecast's QPF axis whereas many of the higher resolution models are northeast of said axis. This forecast cycle trends the QPF southwestward by a few counties and centers it more from northwest Iowa across central Iowa into southeastern Iowa. Precipitation type will be tricky as cross sections and BUFKIT soundings show a warm layer trying to nose in around 850mb. This introduces the potential for a wintry mix/freezing rain potential on the southwestern edge of the precipitation shield, which could range from a glaze up to near a tenth of an inch per freezing rain accumulation model (FRAM). In the colder air where it will snow, the profile will be warming and yield snow ratios near climo of around 12:1. The QPF with these snow ratios produces a band of 2 to around 3 inches centered on a line from Estherville to Clarion to Iowa Falls that expands two or so counties either side of the band's axis. With the potential for icing and the snow amounts, a Winter Weather Advisory was considered. Uncertainty remains higher than normal for 24 hours out from event onset given the shift in track along with the how much freezing rain will occur so have held off with advisories farther into Iowa in coordination with the Sioux Falls and the Quad Cities offices. Wintry precipitation will end overnight Thursday across the area as the clipper departs and winds will remain on the lighter side as they become from the north and northwest. Friday will offer a break in wintry precipitation, but attention will turn towards Canada as a more amplified shortwave trough moving into the Great Lakes region combines with a more subtle shortwave trough scooting beneath it. Mid-level thermodynamic and kinematic forcing will be maximized over the state and yield a period of accumulating snowfall over a good portion of Iowa on Saturday. In addition, very cold air will funnel into the state with highs Saturday and Sunday in the single digits above zero over northern Iowa to the teens over far southern Iowa. As the snow ends Saturday night and clouds clear into Sunday morning with a large zone of high pressure moving in, overnight temperatures will fall to around 20 below zero over northern Iowa to the single digits below zero over southern Iowa. Wind chill values of at least 15 below zero will be common by sunrise Sunday with 30 below zero possible over northern Iowa. These values would necessitate Cold Weather Advisories and Extreme Cold Warnings (formerly Wind Chill Advisory and Warning, respectively). As the high departs Sunday, flow will become more from the southwest with ridging pushing over the central US. This would offer rebounding temperatures and perhaps some degree of confidence that temperatures may near normal for mid- December with a period of dry conditions. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1048 PM CST Wed Dec 10 2025 A wedge of VFR conditions between two areas of MVFR stratus is moving southeast into parts of central Iowa. This will bring a period of VFR conditions at times overnight at most sites. A system will arrive on Thursday and will bring increasing stratus and precipitation. Most locations will have snow in the afternoon while KDSM could have a period of FZRA mixed in at times. The precipitation will end from northwest to southeast from late afternoon through mid evening. Northwest wind will become light overnight then transition to southeasterly on Thursday. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Donavon DISCUSSION...Ansorge AVIATION...Donavon