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KEY MESSAGES

- Impactful snow tonight with passing short wave trough/warm advection.

- Additional precipitation chances with quick moving disturbances Tuesday/Wednesday.

- Mid/late week warming trend.

- More weekend storm potential? Trends are leaning that way...

DISCUSSION

Issued at 305 PM EST Sun Jan 4 2026

Pattern Synopsis/Forecast: Large scale pattern features high- latitude -NAO blocking from eastern Canada into Europe; long wave trough axis associated with the western portion of the block stretches down the east coast into the Gulf. Broad long wave ridge lies across the nation's midsection/Canadian prairie provinces... with a -PNA trough just off the west coast of North America. Cold polar air increasingly confined to eastern Canada/New England with more Pacific-origin air spreading across the western/central CONUS. Water vapor imagery shows a short wave trough/height falls emerging from the northern Rockies into the mean ridge position...with rising heights ahead of it across the Midwest/Great Lakes (+80m/12h 500mb height change on 1200Z APX sounding). Still deep layer northwest flow across Michigan initially (and still -14C at 850mb at APX this morning)...though strong low/mid level warm advection underway across the Midwest/northern and central Plains. At the surface a narrow/elongated high pressure ridge extends from northern Manitoba...through the upper Great Lakes and into the Mississippi Valley. A bit of a lake aggregate trough lingering over the Great Lakes...with cold air horseshoeing around the upper Lakes. Elongated lee side troughing downwind of the northern/central Rockies. Pattern across the CONUS turns a bit more zonal for the first part of the week as west coast trough splits...leaving some energy behind off Baja California. Initial short wave trough moving through the central North America long wave ridge position will cross the Great Lakes during the first half of Monday. Another piece of energy will get kicked out of the southern branch portion of the west coast trough...along with perhaps a northern branch counterpart. These waves will move through the Great Lakes/Ohio Valley in the Tuesday/Wednesday time frame. Pattern then becomes more amplified during the latter half of the week with long wave troughing developing over central North America. Questions on how this trough evolves regarding flow "allocation" between northern and southern branches will have impacts on sensible weather for next weekend...at the very least it does look unsettled.

Lead short wave trough coming through early Monday won't have much of a surface reflection with it as upper level feature quickly outruns a weak attempt at lee cyclogenesis. Southern branch wave for Tuesday expected to have a little better surface reflection... with a lee side low that develops over Kansas and eventually propagates across southern Lower. By Friday looking at another lee side cyclone emerging from the central/southern Plains that may evolve into a stronger cyclone that impacts the Great Lakes for the weekend.

Primary Forecast Concerns:

Impactful snow tonight with passing short wave trough/warm advection: Some lingering snow showers off Lake Superior this afternoon mainly around Whitefish Bay...and flurries off Lake Michigan with lingering shallow instability. Tonight's snow event getting better organized with increasing radar returns across northwest Ontario/Minnesota... with a number of factors coming together to drive this event including isentropic ascent...low/mid level frontogenesis and short wave trough providing dynamic support. All of this ahead of steeper mid level lapse rates which will help provide a better upward motion response to the given forcing. Column saturation should come from the top down as is occurring upstream so initial precipitation will go into that but looks like better snow should moving into western portions of the forecast area around 0200Z (will not change headline start times to account for this). After around 0700Z or so mid level moisture will begin to strip out...leaving behind a saturated layer below 700mb but at temperatures warmer than -10C which suggests possible issues with ice nucleation and precip tapering to some combination of freezing drizzle/very light freezing rain (given the depth of the moisture left behind)/or light snow/flurries from southwest to northeast through daybreak Monday (snow at least across eastern Upper likely to persist through then). Made some small adjustments to the liquid precip forecast but still looking at a nice quick hitting event...as mentioned in this space yesterday snow consistency should be a bit more dense/lower SLR due to the thermal profile...but the DGZ while relatively narrow due to the lapse rates could offer some stronger vertical motion through the layer given the weaker stability profile. Overall have a southwest-northeast oriented SLR gradient ranging from around 10:1 to 16:1...resulting in 12h snowfall totals (0000-1200Z) of 4-8 inches roughly north of a Leland-Kalkaska- Tawas City line...and from 2 to 4 inches south of there with a lower SLR and an earlier switch to freezing drizzle/ flurries.

Only change to headlines will be geographic...adding in Manistee due to the freezing drizzle potential. Expect some locales to push warning criteria snowfall especially east of I-75/north of M- 55 where warning criteria for snowfall is lower (7"/24h versus 8"/24h in the lake snowbelts). Also why southern Schoolcraft has been upgraded to a warning since their criteria is only 6" versus 8" for Mackinac county (before you ask). Not anticipating blowing/ drifting snow to be a big factor...but with snowfall rates in the 1+"/hr range visibilities below 1/2 mile are likely north of M-72 just from falling snow. Snow will probably linger into the daylight hours Monday for eastern Upper/northeast Lower as last bit of forcing/deeper moisture associated with the short wave trough moves through. Threat for freezing drizzle/drizzle likely ends from west to east during the afternoon.

Additional precipitation chances with quick moving disturbances Tuesday/Wednesday: Another slightly stronger short wave trough and attendant surface low will move through Lower Michigan during the day Tuesday...bringing another round of precipitation. Definitely a wintry mix look to the event with questions regarding the thermal profile...probability space suggests a rain/freezing rain to snow/wintry mix transition. So will have to account for this in afternoon messaging.

Mid/late week warming trend: Zonal flow becoming more amplified during the latter half of the week will keep the cold air at bay... with above normal temperatures even by Tuesday. Highs in the 40s appear in the cards especially on Thursday; record highs for Thursday include 41 ANJ/45 PLN/47 GLR/49 TVC/50 APN/52 HTL but those look safe based on current forecast trends.

More weekend storm potential? Trends are leaning that way...: As mentioned above the weekend is looking unsettled with forecast trends honing in on another strong system across the Great Lakes region...and track will ultimately depend on whether this is an all snow event or do we get to play around with precipitation types? But another system that bears watching in a winter that seems sort of relentless at this point.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 637 PM EST Sun Jan 4 2026

IFR conditions develop early tonight, as a swath of snow pushes into and across the area. This will be a relatively heavy/wet snow compared to recent events, snow/liquid ratios in the lower teens to near 10:1. Low cigs (and perhaps fzdz/dz) will linger into Monday after the snow exits (MVFR to IFR). Southerly winds increase tonight at the more southern TAF sites (MBL/TVC), otherwise winds are on the light side.

APX WATCHES/WARNINGS/ADVISORIES

MI...Winter Weather Advisory until 10 AM EST Monday for MIZ016-017- 020>022-025>028-031>034-086>088-095>099. Winter Weather Advisory until 10 AM EST Monday for MIZ018-023- 024-029-030-035-036-041-042. MARINE...Small Craft Advisory from 10 PM this evening to 10 AM EST Monday for LMZ345-346.