####018005986#### FXUS64 KHUN 061014 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 414 AM CST Sat Dec 6 2025 ...New NEAR TERM... .KEY MESSAGES... Updated at 1105 PM CST Fri Dec 5 2025 - Some patchy fog towards daybreak. Very brief patchy freezing fog possible in portions of southern middle Tennessee. Due to it expected patchy and brief nature, no significant impacts are expected. - Periods of light rain have a low-medium chance (20-40%) of occurring late Sunday afternoon through Monday morning. - Colder again Monday/Monday night with sub-freezing lows. Then warming again. && .NEAR TERM... (Today) Issued at 414 AM CST Sat Dec 6 2025 In the mid/upper-levels, a highly sheared trough (initially extending from the western Great Lakes to the central High Plains) will progress quickly southeastward today within the flow between a cold core vortex across southern portions of Hudson Bay and a flat subtropical ridge centered east of the Bahamas. Strengthening deep-layer ascent downstream from this feature has recently resulted in the development of a few pockets of light rain well to the north of a more dominant axis of precipitation in the vicinity of a lengthy surface trough extending from the northwest Gulf Coast into the southeastern Atlantic Coast. Based on the northeastward movement of the light rain, we will include a very low (10-20% POP) across our southeastern forecast zones through 15Z. Across the remainder of the forecast area, a layer of very low stratus clouds exists, with light westerly flow (to the east of a surface high across northern MS) keeping the boundary layer sufficiently mixed to prohibit development of mist/fog. The axis of the previously mentioned 500-mb trough is predicted to cross the region later this morning or early this afternoon, resulting in veering flow aloft and weak subsidence that should contribute to rapid drying of the mid/upper tropospheric column. However, this may not be sufficient to erode the layer of low stratus clouds in the (especially given a relaxed pressure gradient and light winds). Should this occur, currently advertised max temperatures in the u40s-l50s may be 5 degrees or so too warm, and we will nudge these down a bit to reflect this potential scenario. && .SHORT TERM... (Saturday night through Monday) Issued at 1105 PM CST Fri Dec 5 2025 Zonal to slightly SW flow aloft will be the rule of thumb Saturday night into Sunday, as a weak longwave trough axis pushes from the Central Plains into the Missouri Valley region. A frontal boundary near the surface develops with it and merges with a weak area of low pressure over the western Gulf coastal area. This surface low helps to advect enough moisture northward ahead of this front to allow for some precipitation to move into parts of Mississippi Sunday morning and afternoon. Not sure if the atmosphere will be moist enough for precipitation to reach the ground in NW Alabama until late in the afternoon hours at the earliest if not after 6 PM CST. Took our 20 pop during the morning/early afternoon hours the NBM ensemble was putting in for now. Kept a 20 pop in after 4 PM CST, with higher pop between 30 and 60 percent Sunday night. Still looks like all rain with no thunderstorm activity. The models still move the longwave trough axis ENE pretty quickly Sunday night. Most guidance has the precipitation east or northeast of the area by 12Z on Monday. This should keep any wintry precipitation out of the forecast, but may need to watch for flurries in southern middle Tennessee around and just after daybreak. For now, left them out of the forecast since even flurries would have little impact. Much drier and colder again on Monday with some cloud cover lingering into the early afternoon hours east of the I-65 corridor. Strong cold air advection should keep highs in the upper 30s to lower 40s, despite some afternoon sunshine. && .LONG TERM... (Monday night through Friday) Issued at 1105 PM CST Fri Dec 5 2025 Back to sub-freezing lows again Monday night with clear skies and high pressure building in. Lows in the mid 20s are expected. This intrusion of colder air should be brief, as warm air advection ahead of another front moving through the western Great Lakes early next week keeps things on the warmer side. Highs in the lower 50s should warm into the 55 to 60 degree range on Wednesday with lows warming as well into the lower to mid 30s. This front seems to have a hard time pushing into the southeast and hangs up over eastern Texas into the Ohio Valley. However, a weak pre-frontal trough axis looks to be close enough to produce a few showers over the area Wednesday night into Thursday. This weak pre-frontal trough axis may focus a bit more moisture and forcing over the area Thursday afternoon into Thursday night, before pushing east of the area. This should pull the precipitation east with it as colder and drier air moves into the area. Highs look to drop back down into the upper 30s to lower 40s again on Saturday. && .AVIATION... (06Z TAFS) Issued at 1119 PM CST Fri Dec 5 2025 Previous thinking hasn't changed much. Still expect CIGS below 1000 feet to develop at both terminals before 06Z. Very light or calm winds are expected. The persistent cloud cover should keep any fog from forming. Models are in pretty good agreement that VFR conditions will return as low CIGS push southeast of the terminals between 18Z and 20Z. Kept slightly earlier time for that at KMSL at 19Z and after 20Z at KHSV. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...70/DD SHORT TERM...KTW LONG TERM...KTW AVIATION...KTW ####018009261#### FXUS63 KLOT 061019 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 419 AM CST Sat Dec 6 2025 .KEY MESSAGES... - A clipper system will deliver a swath of snow to the area tonight into Sunday morning. A Winter Weather Advisory has been issued for a portion of northern Illinois where snow totals in the 3-5" range are expected. A wintry mix also looks increasingly likely to be seen in locations south of I-80. - Light lake effect snow may develop into portions of northwest Indiana and northeast Illinois late Sunday through Monday morning. && .DISCUSSION... Issued at 419 AM CST Sat Dec 6 2025 Through Sunday: The main concern in the short term portion of the forecast is the likelihood of accumulating snow from a clipper system tonight into tomorrow. This system's surface low (analyzed over northeastern Wyoming at press time) will track east- southeastward today across the central Plains and into the Midwest in tandem with an upper-level shortwave, likely weakening over the course of the day as it loses better upper- level jet support. The earlier chasm between the hi-res model guidance depicting a stronger and more northerly tracking system and global guidance favoring a weaker and more southerly tracking system has shrunk considerably, with the broader suite of model guidance honing in on a happy medium solution with a more northerly track to the system, but a less-amped up or ill- defined surface low. The lingering model spread regarding the strength of this incoming system is still, however, leading to persisting finer-scale uncertainties in our snowfall and precipitation type forecasts less than 24 hours away from the onset of precipitation tonight. The larger-scale picture with this incoming system remains fairly clear, with isentropic ascent inducing a swath of precipitation that will spread over the area late this evening and into the overnight hours before a Canadian surface high filters in behind the clipper and puts and end to most of the precipitation Sunday morning (lake effect snow may persist beyond this time near Lake Michigan). Thermal profiles are, for the most part, expected to remain below 0C through most or all of the event in most locations, resulting in snow being the dominant precipitation type. However, with the more northerly track to the system now, parts of our southern CWA appear increasingly likely to be an exception to this as warming low- level and surface temperatures look to push the lowest portion of the thermal profiles there above the freezing mark for at least a brief period of time. This would result in a wintry mix or even outright rain occurring there for a good chunk of this precipitation event, especially in a scenario featuring a surface low that's still somewhat well-defined as it tracks across Illinois. The presence/strength of the surface low will also modulate the magnitude of low- to mid-level frontogenesis occurring coincident with the snow swath. Some of the more aggressive latest model solutions, such as the 00Z HRRR and RAP, actually depict fairly intense ascent within the heart of their modeled frontogenetical banding, with omega peaking within or just below the dendritic growth zone (which would feature steep lapse rates that would further enhance snowfall rates). If such an outcome were to be realized, then there could be a narrow corridor somewhere that overperforms accumulation-wise. However, these models have a tendency to run a little hot with wintry systems 24+ hours out, so there are reasons to be skeptical of their snowfall output. Regardless, the latest multi-model consensus suggests that there is a fairly good likelihood of locations north of I-80 picking up between 2 and 5 inches of snow accumulation (highest wherever the f-gen banding sets up) tonight through Sunday morning. Temperatures are expected to remain in the 20s here while snow is falling, which will allow the snow to accumulate on roadways and make for a messy drive for anyone who is planning to head out early Sunday morning. Have issued a Winter Weather Advisory for our Illinois counties north of I-80 to highlight this. Snow totals farther to the south and eastward into northwest Indiana are less certain due to the expectation that the system will be weakening and the potential for warming temperatures to cut into snow totals and reduce the overall magnitude of the impacts that the snow may cause there. That said, it's possible that a southward expansion of the advisory may eventually be warranted if the system wiggles a little farther south from its presently favored track or if the likelihood of freezing rain icing up roadways north of the I-74 corridor increases. Ogorek Sunday night through Friday: A period of lake effect snow may develop in the wake of the weekend winter system late Sunday into early Monday morning as surface high pressure moves into the region. This will lead to a period of north northeast winds which would be favorable for the development of a lake effect snow band oriented into the Chicago metro counties of northeast Illinois and northwest Indiana. The combination of cooler lake temperatures, overall lower inversion heights (barely touching the DGZ around 5-6kft) and a shallower cloud layer, suggests that snow ratios will lean lower and limit accumulations overall. Have opted to maintain a roughly 20-40% chance of lake effect snow showers from Sunday evening through Monday morning but have kept QPF under 0.1" which results in additional snowfall accumulations of a dusting to locally up to around 1". The advertised active clipper pattern continues with the next disturbance moving across Wisconsin Monday night into Tuesday morning, which may graze far northern Illinois with some light snow. Current indications are that accumulations may be mainly limited to a dusting toward the WI/IL state line. A stronger system (sub 1000mb low) then arrives right on its heels Tuesday night into Wednesday. The warm advective regime that sets up ahead of it will support temperatures warming into the 30s and likely above freezing here locally if the current forecast track holds. Before this occurs a wintry mix of precipitation would be possible before switching over to mainly rain for most if not the entire area. Temperatures then quickly drop back below freezing Wednesday morning in the wake of the Tuesday night system with a continued signal for gusty snow showers possible mid morning into early afternoon Wednesday. Something to keep an eye on over the coming days. Periodic snow chances then continue through the end of the week (20-30%) as the active clipper wave train continues. Temperatures trend cooler for the latter half of the week with forecast highs in the teens and 20s and lows in the single digits to lower teens. Petr && .AVIATION /06Z TAFS THROUGH 12Z SUNDAY/... Issued at 1145 PM CST Fri Dec 5 2025 Key messages for the 06Z TAF period: * MVFR cigs expected overnight through early Saturday afternoon (IFR possible at RFD). * Accumulating snow expected Saturday night into Sunday morning with associated MVFR to IFR vsbys. A cold front is moving into northern Illinois as of this writing. Out ahead of it, scattered flurries and light snow showers moved across Chicagoland earlier this evening. While the bonafide snow shower potential appears to have wrapped up, a few flurries can't be ruled out overnight. MVFR cigs will gradually expand in coverage overnight across the area with a period of IFR possible at RFD. Have maintained a return to VFR for mid-late afternoon with this update though guidance is beginning to trend toward the possibility that MVFR stratus could persist through the day. Widespread accumulating snow will move in from the west late Saturday evening and impact all TAF sites into Sunday morning. Light snow/flurries may begin at RFD around 03Z and Chicagoland closer to 05-06Z, with steadier snowfall and associated MVFR to IFR cigs and vsbys expected within a couple of hours thereafter through the end of the TAF period. Southwest winds late this evening will veer WNW overnight. Expect WNW winds to then continue through the first half of the day on Saturday, then becoming light and variable late afternoon ahead of the snow. Winds then settle into a prevailing SE direction after snow begins. Doom/Petr && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Winter Weather Advisory from 9 PM this evening to 6 AM CST Sunday for ILZ003-ILZ004-ILZ008-ILZ010-ILZ011-ILZ019. Winter Weather Advisory from midnight tonight to 9 AM CST Sunday for ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ103- ILZ104-ILZ105-ILZ106. IN...None. LM...None. && $$ Visit us at weather.gov/chicago