####018011659#### FXUS63 KLOT 090502 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 1102 PM CST Mon Dec 8 2025 .KEY MESSAGES... - 30-60% chances of light snow mainly northeast of a Rockford to Rensselaer line tonight with a dusting of snow accumulation possible. Very low chance (<20%) for freezing drizzle late tonight into Tuesday morning, also along/north of I-80. - Period of light freezing rain late Tuesday afternoon into early Tuesday evening, mainly northwest of an Ottawa to Joliet to Chicago line, during the evening rush hour. - Possible snow squalls Wednesday morning. - Windy conditions Tuesday night into Wednesday with wind gusts to 40 mph possible. - More fast moving clipper systems could result in some additional periods of accumulating snow in our near our area late this week into the weekend. - After a brief warm-up midweek, temperatures will turn sharply colder during the latter half of the week. The deep cold may also result in some periods of dangerous wind chills to -20 this weekend. && .UPDATE... Issued at 818 PM CST Mon Dec 8 2025 The forecast appears to be in good shape. Main slight change was to increase snow chances a bit late tonight mainly near/north of I-80. An area of 10-20 dBZ returns on the DVN radar is currently virga, with cloud bases generally running above 9-10 kft and a significant dry layer present beneath. An 850-700 mb shortwave trough axis is forecast to push east of the Mississippi River late this evening and then across the local forecast area through midnight to 6 AM. During this timeframe, a slight uptick in 700 mb frontogenesis is forecast to take shape in the vicinity of the I-90 corridor. The associated increase in large scale forcing will result in a quick saturation of the aforementioned dry layer, and likely enough to support the development of at least flurries across the northeast 2/3rds of the CWA. Roughly along and northeast of a Rockford to Rensselaer line, have increased PoPs a bit given indications that this increasing ascent may allow for some steadier (but still light) snowfall as the main trough axis pivots overhead. Any accumulations look like they'll remain limited to a tenth or two or less owing to the brief nature (2 hours or less) and generally modest nature of the incoming ascent. Expecting any light snow to be pushing east of our NW Indiana locales through 5-6 AM. Finally, while the potential for a little freezing drizzle into mid-morning Tuesday remains non-zero, latest guidance continues to suggest this potential remains low. While models maintain ascent through the low-levels early Tuesday morning, forecast soundings reveal a bit of a mismatch between the arrival of lower cloud ceilings and deeper saturation/cloud depths, with the latter rapidly diminishing through mid morning on the backside of the departing trough. This results in cloud depths that remain just a bit too shallow to support impactful drizzle. Have certainly been surprised by FZDZ setups before though, so don't want to entirely rule out the threat, just that it remains low and too low for an inclusion in the gridded forecast given the latest upstream observations and latest model output. As dewpoints increase through the upper 20s and lower 30s tomorrow afternoon, some mist may develop as this higher- moisture airmass pushes across our expansive snowpack. Carlaw && .DISCUSSION... Issued at 145 PM CST Mon Dec 8 2025 Through Wednesday: There are multiple forecast concerns/challenges through Wednesday afternoon. The local area will be on the far southern end of a clipper system moving across the northern Great Lakes tonight with a chance of light snow overnight, mainly north of I-80. There may be a dusting of snow accumulation, especially closer to the IL/WI state line. There has also been the concern for some patchy freezing drizzle as this light snow potential ends in the predawn hours, which then could persist through daybreak. The moisture depth looks rather shallow for freezing drizzle and confidence remains too low to include in the forecast but trends will need to be monitored. The gradient will also tighten tonight with southwest winds gusting into the middle 20 mph range, which will diminish some on Tuesday. The next fast moving system arrives late Tuesday afternoon with some large changes to the forecast. Given how cold the ground and snow pack is, there remains quite a bit of uncertainty for how warm temps will rise on Tuesday and if they may cool as precipitation arrives late in the afternoon/early evening. As a result, still have high temps generally in the mid 30s Tuesday, but then have temps falling back into the lower 30s for a large area northwest of an Ottawa/Joliet/Chicago line. While not a classic freezing rain set-up, even if the bulk of the precipitation falling is in the form of liquid rain, less traveled surfaces, such as sidewalks, parking lots, etc, may still develop some icing and have included freezing rain in the forecast for these areas. Both from a precipitation duration and from a temperature perspective, this freezing rain potential may only last a few hours. For the rest of the area, air temps slightly above freezing, should limit freezing rain and have continued with just liquid rain in the forecast. And since this is a large change to forecast, plan to hold off on an advisory to allow trends to confirm these changes as well as where the cutoff to any possible advisory may be needed. Also of concern is any further shift south to the track of this system, which may possibly push the freezing rain potential a bit further south, but may also bring more snow to far northern IL. From this distance, confidence is too low to say where the southern edge of the swath or snow will fall as just a small change to the track of the system could have large changes to the precipitation forecast. As this system approaches Tuesday evening, southwest winds will steadily increase and then turn more westerly early Wednesday morning. Wind gusts during this time period may reach 40 mph, possibly higher, which then could lead for the need for a possible wind advisory. By Wednesday morning, the true cold front will moving across the area and this looks like a good setup for possible snow squalls, which the HRRR and Namnest are showing well, with locally higher wind gusts and significantly reduced visibilities. The overall trend in the models is colder and faster and while there is still a chance of rain Wednesday morning across the southeast cwa, its possible that precipitation ends late Tuesday night, early Wednesday morning and then there are snow squalls in the morning with lingering flurries snow showers in the afternoon. With these trends in mind, have lowered temps a few degrees both Tuesday night and on Wednesday. Northwest winds will remain gusty Wednesday afternoon, but should be slowly diminishing. The northwest winds will then likely keep lake effect snow showers going across at least Porter County in northwest IN Wednesday afternoon, with some minor snow accumulation possible. cms Wednesday Night through Monday: An active belt of strong northwesterly upper-level flow is anticipated to persist from the northern Plains southeastward across the lower Great Lakes through much of the period. This will steer at least 2 to 3 additional clipper type impulses southeastward across our general region Thursday and into the weekend, with each one coming with chances of accumulating snowfall in our very near our area. With that being said, there still continues to be little consistency in ensemble guidance regarding the exact tracks, timing, and strength of each of these weather impulses. Accordingly, while the chance of more snow near the area remains elevated (above 50%), confidence remains low with the finer-scale details of the forecast (such as the exact timing and which exact areas are the most favored) later this week through the weekend. Confidence remains high that temperatures will turn sharply colder for the weekend as another arctic airmass engulfs much of the Midwest and Great Lakes region. The ensemble signal for this remains strong, and current indications continue to generally support upper single digit to teens high temperatures and overnight lows at or below zero in most locations for the weekend. Most concerning at this point is the potential for a period of blustery northwesterly winds to accompany this deep cold over the weekend, which could result in some periods of dangerous wind chills nearing -20F. KJB && .AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 1102 PM CST Mon Dec 8 2025 Mid-level VFR stratus currently shifting eastward across northern Illinois will gradually lower into low-end MVFR levels by sunrise. A narrow but prominent N/S axis of ascent within the lowering stratus is producing a developing ribbon of SN over northern Illinois, with each site likely observing a brief 1-2 hour period of IFR or low-end MVFR visibility through 10Z. A quickly lowering inversion will greatly decrease cloud depths and likely end precip in the pre-dawn hours. However, cannot fully rule out a brief period of FZDZ in the 10-12Z window before cloud depths decrease further. It is expected that low-end MVFR to high-end IFR stratus will persist through the day under the lowering and strengthening inversion. Ceilings may lower solidly into IFR levels through the day as low-level moisture advection counters diurnal processes. LIFR ceilings may also reach as far southeast as RFD during the afternoon. With that said, the expected shallow nature of the status also means it will be prone to mixing out from southwest to northeast, with FEW/SCT clouds possible at most sites later in the day. An impressive surge of low-level moisture advection with a 50-60 knot low-level jet this evening will promote a band of precip across all terminals through the evening hours. While RA is favored through this period, evaporative cooling of the overall warming environment may yield a 1-2 hour period of PL and/or SN at the onset of precip. Strong cold-air advection late tonight will lift ceilings into VFR levels, but also generate isolated snow showers or flurries prior to sunrise. Expect SW/SSW winds around 10 knots to increase with gusts over 20 knots through the early morning hours, with LLWS whenever gusts are not present. Gusts over 20 knots will be common through the day, followed by gusts over 25 knots in response to the strong low-level jet this evening. Winds will then veer WSW/W with gusts to 35 knots behind the cold front late tonight. Kluber && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory until noon CST Tuesday for Winthrop Harbor IL to Gary IN. Gale Watch from Tuesday evening through Wednesday afternoon for the IL and IN nearshore waters. Small Craft Advisory until 3 PM CST Tuesday for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN. && $$ Visit us at weather.gov/chicago ####018007111#### FXUS63 KGLD 090503 AFDGLD Area Forecast Discussion National Weather Service Goodland KS 1003 PM MST Mon Dec 8 2025 .KEY MESSAGES... - Unseasonably warm and breezy Tuesday; gusts should remain below 40 MPH over the northwest part of the forecast area, with even lower speeds elsewhere. - Slight northward shift in the jet stream has led to warmer temperatures being forecast for the week, and shifting the precipitation north of the forecast area. - Confidence is less than 50% models have an accurate depiction of the jet stream location (which will impact temperatures and precipitation chances) given the many minor disturbances moving through. && .SHORT TERM /THROUGH TUESDAY NIGHT/... Issued at 1255 PM MST Mon Dec 8 2025 Latest upper air analysis shows a ridge over the West Coast with a closed low over Southeast Canada. Northwest flow continues over the Plains. A subtle short wave trough was moving over the forecast area today. Dry air has cause very little cloud cover to accompany the trough passage. At the surface a trough was moving through the forecast area. Behind it winds turned to the northwest. Tonight west winds will continue. Temperatures will be a few degrees warmer than last night due to the northwest winds and dew points being a few degrees higher than last night. Tuesday stronger low level winds will move over the forecast area ahead of an incoming cold front. Model blend data indicates the high end wind gusts will be up to 50 MPH, primarily for Yuma County area. However the more likely speeds would be in the 40-45 MPH range. The winds decrease to the east and southeast. The continued warm air advection will cause unseasonably warm temperatures. Warmed temperatures slightly further toward the higher end of the data spectrum due to the forecast highs warming over the past couple of days. Sounds show a potential for lower dew points to mix down during the late morning and first half of the afternoon. As such, lowered the dew points toward the 10th percentile of the data spectrum. This yields relative humidity values in the 20-25% range. Tuesday night a cold front will move through. Winds will turn from the west to the north as the front moves through. Model data indicates a pressure change rate that is fast but not rapid enough to be concerned about strong winds at this point with the frontal passage. Model ensemble data shows the maximum gusts would be around 40 MPH, with the highest gusts over the northwest part of the forecast area. A complicating factor in determining if the gusts will materialize is if there will be a strong enough inversion to prevent the stronger winds from reaching the ground, or if the cold air advection will erode the inversion and allow the stronger winds to reach the ground. Based on the model ensemble data, confidence is around 30% that winds greater than 40 MPH will occur with the frontal passage. The strongest winds should occur before midnight, then gradually decline through the night as the surface high pressure moves in. Am not expecting any precipitation due to large dew point depressions with the frontal passage, and the associated upper level short wave trough being to the east over the Missouri River Valley. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Issued at 1255 PM MST Mon Dec 8 2025 Slight north shift in the jet stream have led to warmer temperatures overall and moving the precipitation northward. However a small shift back south can have the opposite effect. Difficult for the models to determine the specific track of the jet stream at this time range with so many subtle short wave troughs moving through. Wednesday the cold air advection will end during the afternoon, as south winds behind the surface high pressure begin to bring in warmer air. Laminar flow and a dry environment will move over the forecast area behind the cold front. Warm air advection will continue during the night, leading to lows that will be rather warm for this time of year. Thursday warm air advection continues. Models have slightly shifted the jet stream to the north, but also move a cold front through sooner. This has increased the warm air advection occurring ahead of the cold front. Models have narrowed the temperature spread in the data for this day from last night's data. A cold front rolls through during the night. With a slightly northward shift in the jet stream the precipitation chances have also shifted to the north out of the forecast area. As such, the frontal passage is forecast to be dry. Friday temperatures will either be steady through the day after sunrise, or fall due to continued cold air advection. With the jet stream slightly further north, the cold air advection will not be as strong over the forecast area as was shown yesterday. This has allowed highs to be warmer than what was shown earlier. However, the upper level pattern is in a very favorable setup to bring cold air from Canada into the forecast area. All that is needed is a slight shift back south for that cold air to not miss the area to the east. Saturday a broad upper level short wave trough moves through the Plains. A cold front will precede the trough through the forecast area. Most of the dynamics of the trough will be over the upper Midwest. As such the forecast will continue to be dry despite the frontal passage. There is a 10 degree spread in possible high temperatures for the day. As such, confidence is low we will see above normal temperatures for highs in the west half of the forecast area on this day given the passage of a cold front. Sunday and Monday have a short wave ridge moving through as the main ridge axis briefly shifts onto the Plains. Following it will be a short wave trough, mainly over the Northern Plains. The upper level feature may bring a cold front through the forecast area. Any front looks to be weak at this point. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 953 PM MST Mon Dec 8 2025 VFR conditions remain forecast for this TAF period. LLWS is again forecast for MCK until mid morning when the nocturnal inversion wanes and winds increase. LLWS is a bit more marginal for GLD but will watch closely and issue an AMD if warranted. Wind gusts for each terminal are forecast to range from 25-35 knots with the higher end more likely at MCK. A cold front is forecast to move through during the late afternoon/early evening bringing a period of very strong LLWS and finally gusty to strong winds potentially gusting up to 40 knots again mainly favoring MCK. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...None. CO...None. NE...None. && $$ SHORT TERM...JTL LONG TERM...JTL AVIATION...Trigg