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KEY MESSAGES

- Snow chances tonight/Sunday.

- Alberta Clipper brings more impacts Sunday night/Monday.

- Extended period of cold weather on tap for the upper Great Lakes starting Monday.

DISCUSSION

Issued at 320 PM EST Sat Jan 17 2026

Pattern Synopsis/Forecast: Full-latitude long wave trough encompassing the eastern two-thirds of North America to start this weekend...part of a highly amplified pattern with matching 3 sigma standardized height anomalies within a -EPO ridge along the west coast (+3) and within the trough over the Plains (-3). Several short wave troughs/PV anomalies rotating through the mean trough position...strongest wave moving through Kansas/Missouri per WV imagery. Small upper low spinning across eastern Iowa. Elongated PV anomaly along cyclonic side of the jet stretches from eastern Colorado northeast across the Dakotas and into northwest Ontario... on the other side of this feature are strong 500mb height rises (+120m/12h) over the northern High Plains/southern Saskatchewan. Low level lake aggregate thermal ridging across the Great Lakes with a plume of cold air (sub -20C 850mb temperatures) across northern Quebec/Ontario and spilling southward into the northern/central Plains/Midwest (850mb temperatures a relatively balmy -10C at APX at 12Z compared to -25C at BIS). 999mb surface low north of Georgian Bay with cyclonic flow in its wake across the upper Lakes...1040mb Arctic high over southern Saskatchewan ridging southward into the central Plains.

North American long wave trough will be reinforced over the coming days...opening the door for Arctic air to flood into the central/ eastern CONUS. Pattern configuration is not expected to change with more of a Rex block look to things over the eastern Pacific maintaining higher heights over Alaska...and subsequent downstream troughing. So we are staring down the barrel of an extended period of colder weather.

Surface low north of Georgian Bay lifts northeast into Quebec tonight...as upstream Arctic high splits around the Great Lakes as these features are wont to do. A series of short wave troughs crossing over the top of the upstream ridge will dig southeast and spin up another Alberta Clipper Sunday. This will "phase" with lingering surface troughing over the upper Lakes and result in a more consolidated surface low over northeast Ontario Monday. Stronger cyclonic flow in the wake of this low will usher in the real cold on Monday...with sub-500dam thicknesses always a strong signal for single digit daytime highs (above and below zero). Midweek period may bring something of a reprieve as the spin-up of another surface low swings boundary layer winds to a more southerly (warmer) component for Wednesday...but with a reinforcing push of colder air possible by Thursday. This same pattern may be on repeat for the end of the extended period (Friday-Saturday) but the potential magnitude of the cold air for next weekend...yikes if we get in the way of that. But more on that below...

Primary Forecast Concerns:

Snow chances tonight/Sunday: A broken area of snow continues to swirl around the Great Lakes and Midwest this afternoon...some of it tied to a short wave trough northeast of the Lakes...some of it tied to the small upper low over Iowa...some of it lake induced with shifting winds across the Lakes (northerly on Lake Superior/west- southwest on Lakes Michigan/Huron). Plenty of deep layer moisture hanging around within overall cyclonic flow/troughiness and somewhat steeper lapse rates/weaker static stability. For tonight a bit of a mesoscale mess with regard to precipitation evolution. Initially will be watching a surface trough currently dropping south from Lake Superior into Upper Michigan. Looking for a couple of things from this trough: 1) Pretty good signal for a strong band that kicks into gear over Lake Michigan...this should get more persistent snow going west of the US-131 corridor tonight with a nice thermodynamic environment (inversion heights above 700mb/-22C)...kinematic fields are a bit on the weak side so have to wonder how far inland this will extend or even the morphology (organized horizontal rolls versus more "mushy" convection). Have snow amounts that are pushing the low end of advisory criteria (2-4+ inches) from Manistee up to Charlevoix counties for tonight. Will lump all the headline discussion in the Albert Clipper impacts paragraph. 2) Next question is the northern portion of the band...how much of the Tip of the Mitt counties does it impact (probably not much??) and how far south it will propagate (maybe M-32/M-72 corridor)...though may see snow showers flare up over northern Lake Huron. Another possibility given the combination of good thermodynamics and weak kinematics is the possibility of a mesoscale vorticity center developing between the bays on Lake Michigan...which then drifts inland. We'll see how/if this pans out.

Boundary layer flow will back to the southwest early Sunday...but will actually be cold advection in the low levels so the thermodynamic environment will not relent...with the snow focus on the Leelanau Peninsula early then shifting north toward Emmet/ Mackinac counties. Add in a synoptic component to this by late in the day (more on that in the next paragraph) will likely need additional snow headlines for these zones Sunday/Sunday night (already carrying 2-5+ inches for the Emmet/western Mackinac zones just for Sunday).

Alberta Clipper brings more impacts Sunday night/Monday: More snow will overspread northern Michigan probably starting late afternoon Sunday but especially Sunday evening with consolidating surface low over Michigan. As of now strongest dynamic forcing is expected south of the forecast area...though organizing circulation will like result in some wraparound/deformation snow Monday. Southwest flow lake enhancement will be an issue off Lake Michigan...with the evolution impacted by multiple convergence zones along the Arctic cold front as well as a surface trough that spins across the area Monday (and the cold and wind will follow). Snow will transition to northwest flow lake effect in the wake of the trough passage Monday as 850mb temperatures drop below -20C...though that will being to wreak havoc with snowflake growth processes with more plates/needles and more of a talcum powder consistency to the snow (lower SLR than what the guidance will suggest). Will certainly blow around readily but the accumulation efficiency will be compromised (the wind won't help in that regard either). Winds are expected to gust 20-30+mph Monday...with gusts 30-40mph along the northwest Lower shoreline south of Little Traverse Bay. And lest we forget falling temperatures on Monday (though that is a separate headline issue which will be discussed more below).

So what to do with all of that from tonight through Monday from a headline perspective? Will put up a Winter Weather Advisory through 1200Z Sunday for the Lake Michigan shoreline counties from Charlevoix down to Manistee including Grand Traverse Bay to cover expected lake effect mesoscale banding. For Sunday night/Monday current snowfall totals are definitely in the high end advisory/low end warning amounts along and west of the US-131 corridor...and throw in the wind/blowing snow potential for Monday is expected to make for a rather nasty late morning/afternoon. That alone might tip the balance in eventual favor of a warning...so will start with a Winter Storm Watch for all of the northwest Lower shoreline counties plus Grand Traverse/Kalkaska/Wexford (a watch transitioning to a high end advisory is perfectly acceptable...these aren't pre- warnings). Will run the watch time from 2100Z Sunday through 0000Z Tuesday except for Emmet county where given the potential for heavier southwest flow banding early in the day Sunday will start the watch there at 1800Z.

Extended period of cold weather on tap for the upper Great Lakes starting Monday: Shifting winds and cold advection in the wake of Monday morning's clipper passage expected to send temperatures on a downward trajectory...falling into the single digits during the afternoon most locations. Tuesday morning lows in the single digits above and below zero...with wind chills expected to be in the vicinity of Cold Weather Advisory criteria (-15 to -25F northern Lower...-20 to -30F eastern Upper). Single digits highs likely across eastern Upper Tuesday as well as across interior northern Lower. Temperatures expected to moderate Wednesday with highs back into the upper teens-20s...and the drop again back into the teens Thursday/Friday...and next weekend could potentially be the coldest portion of this week.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1240 PM EST Sat Jan 17 2026

CIG's will remain mostly MVFR through the forecast period as ceiling heights remain BKN and OVC between 015 and 025. Periodic -SN and SHSN will continue at all TAF sites tonight through Sunday, with the lowest VISBY's expected at KTVC and KMBL dropping less than 2SM between 0000Z and 0500Z tonight. Other sites will have temporary VISBY drops, but should mainly remain above 3-4SM.

APX WATCHES/WARNINGS/ADVISORIES

MI...Winter Storm Watch from Sunday afternoon through Monday evening for MIZ016. Winter Weather Advisory from 7 PM this evening to 7 AM EST Sunday for MIZ020-021-025-026-031-099. Winter Storm Watch from Sunday afternoon through Monday evening for MIZ020-021-025>027-031-032-099. MARINE...Gale Watch from Monday morning through Monday evening for LMZ323-342-344>346.