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KEY MESSAGES

- Lake effect snow and cold tonight/Tuesday.

- More widespread mostly light snow Tuesday night/Wednesday but lake enhancement probable.

- Coldest air of the season to overspread the area starting Thursday night and continuing into Sunday.

DISCUSSION

Issued at 342 PM EST Mon Jan 19 2026

Pattern Synopsis/Forecast: We could probably put this discussion on repeat this week. Full-latitude long wave trough encompasses the eastern two-thirds of North America...getting reinforced by short wave energy coming over the top of a narrow but strong ridge along the west coast (+2 to +3 sigma 500mb height anomaly). A couple of dynamic PV anomalies in the vicinity of the Great Lakes...one is crossing southern Lower Michigan and heading to the lower Lakes...a second is over northwest Ontario with impressively cold 500mb temperatures (-45C at YPL this morning). Winds shifting to the northwest pulling colder air into the Midwest/Great Lakes with 850mb temperatures below -20C. Surface analysis shows an elongated area of low pressure from the Ontario/Quebec border west into the Straits of Mackinac...tight pressure gradient between this low and a 1035mb high over the northern/central Plains. Plenty of sub-zero cold all the way down into northeast Iowa...with the cold air wrapping around the upper Lakes and a developing lake aggregate thermal bubble across Michigan/southern Ontario.

As mentioned above this pattern is going to be on repeat this week with North American long wave trough stuck between blocking over the central Pacific and extending into Alaska (-EPO) and a high-latitude blocking ridge from Greenland to Scandinavia. Short wave disturbances will continue to move through the mean long wave trough...keeping the cold pattern in place and likely reinforcing it next weekend with a sub-498dam 500mb low passing north of the Great Lakes Friday. Surface low over the Straits today will pull away this evening...with some lake aggregate troughing left behind as short wave trough/PV anomaly over northwest Ontario rotates across the upper Lakes tonight. Next short wave trough digging in from the northwest will scoop up a lee side low over the central High Plains and pull it northeast into Lower Michigan Wednesday...a turn of the boundary layer flow to a southerly component and resultant warm advection will allow temperatures to moderate a bit for midweek. A short lived respite at that with a reinforcing push of much colder air for the latter half of the week with increasing cyclonic flow across the Great Lakes Thursday as sub-498dam 500mb low drops into Ontario. Coldest air looks to arrive Thursday night/Friday with a 1050mb Arctic high building into the Plains/Midwest with 1000-500mb thickness at or below 486dam/850mb temperatures at or below -30C Friday which is just absurdly cold.

Primary Forecast Concerns:

Lake effect snow and cold tonight/Tuesday: Transition to multi-band northwest flow lake convection has already occurred...impressive inversion heights reaching up toward 600mb. Nice two lake band enhanced by shoreline topography across central Upper extending into the Grand Traverse Bay area at early afternoon...with time anticipating that band will shift northward with backing boundary layer flow later this afternoon which should spread the snow accumulation potential out across northern Lower. Off Lake Superior decent looking band has been pushing toward Whitefish Bay...and think that is going to intensity as it drifts into the Soo region this evening enhanced by topographically forced frontogenesis as sub- zero cold over the higher terrain east of Lake Superior bumps up again lake induced thermal ridge. As mentioned in this space yesterday this should be the genesis of a three-lake band that eventually reaches Lake Ontario. Over time...expect drainage flow/density current to push the colder air across the St. Mary's River and subsequently push the band back toward Whitefish Point. Deep CBL extending up to 700mb...the only question is the colder temperatures and the DGZ getting shoved lower and lower into the cloud...resulting in more plates/columns and lower snow-to-liquid ratios as a consequence. Passing short wave trough may add in a little seeder-feeder enhancement as well which won't hurt the cause. Overall additional snow amounts of 4-8 inches across parts of western Chippewa county adjacent to Whitefish Bay...around 4 inches in the vicinity of the Soo and will all depend on how things evolve this evening.

Off Lake Michigan...will be losing the longer effective two-lake fetch. Like over Lake Superior there may be some seeder-feeder enhancement during the first half of the night...but the shorter fetch combined with synoptic subsidence overnight will result in a lowering of the CBL depth. Radar snowfall estimates through 1900Z suggest a swatch of 1-3 inches since 1200Z across parts of Leelanau/ Grand Traverse/Missaukee/Kalkaska/Antrim counties today... heaviest additional snowfall for tonight will be 2-3 inches for an area bounded by M-33 to the east...and M-68/M-32 to the north and south. Amounts less than 2 inches outside of that zone.

Winds will remain gusty tonight except along the St. Mary's River overnight...should trend down from during the day today but still gusting over 20mph with some higher gusts along the northwest Lower shoreline counties. So some blowing/drifting snow will still occur overnight. Overall no changes to the ongoing snow headlines. As for temperatures...single digits above zero (mostly) for northern Lower...and below zero across eastern Upper with coldest readings along the St. Mary's river where temperatures may bottom out around -10F. Will expand the Cold Weather Advisory to cover all zones...it will be close enough most areas with some double digit below zero wind chills already this afternoon (PLN/CIU/ANJ)...and it limits the complaints.

More widespread mostly light snow Tuesday night/Wednesday but lake enhancement probable: Warm advection ahead of advancing surface low and some dynamic short wave trough forcing will spread more widespread snow across the forecast area starting later Tuesday evening. Lake convection during the day Tuesday will be swinging around to the southwest as winds back...and looks like a pretty good signal for a strong southwest snow band to set up along the northwest Lower shoreline during the early morning hours of Wednesday where several more inches of snow are possible (and can envision needing another advisory type headline). Snow chances will linger through Wednesday as initial short wave trough departs and a second one swings through Wednesday night.

Coldest air of the season to overspread the area starting Thursday night and continuing into Sunday: Forecast trends are pushing the next reinforcing shot of colder air into the upper Lakes starting Thursday night...with Friday (in particular) and Saturday looking very cold. Probability for sub-zero highs remain above 60% across eastern Upper for Friday...and 40-50 percent for Saturday. Certainly looking at a good bet for more cold weather headlines Friday and Saturday with minimum wind chills both days in the -15F to -30F range (coldest above the bridge).

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 640 PM EST Mon Jan 19 2026

WNW winds remain 10-15kts thru tonight with gusts to 25-35kts, though some areas may see less gusts and more LLWS, around 1500ft, esp away from lake effect areas (i.e., APN). Winds to back to W and SW after 10-12z and stay SW, esp after 18z. MVFR to VFR cigs outside of lake effect snow bands; inside snow bands, high chance of IFR, medium chance LIFR, and expect sites to continue to bounce around between VFR/IFR. If more intense band off Whitefish Bay is able to nick CIU tonight, LIFR cigs/visbys could occur..but think this will stay mostly toward ANJ. WNW flow bands tonight back to W and SW Tuesday afternoon which should keep most impacts near Lake MI shore again. BLSN to remain a problem and could drop visbys to IFR or less at times, even outside of bands.

APX WATCHES/WARNINGS/ADVISORIES

MI...Winter Storm Warning until 7 AM EST Tuesday for MIZ016-020>022- 025>027-031>033-086-099. Cold Weather Advisory from 10 PM this evening to 11 AM EST Tuesday for MIZ016>018-020>036-041-042-086>088-095>099. Winter Weather Advisory until 7 AM EST Tuesday for MIZ017-018- 023-028-029-034-035-041-087-088-095-096. MARINE...Small Craft Advisory until 5 AM EST Tuesday for LHZ345. Small Craft Advisory until 5 PM EST Tuesday for LHZ346>349. Small Craft Advisory until 5 PM EST Tuesday for LMZ341. Gale Warning until midnight EST tonight for LMZ323-342-344>346. Small Craft Advisory until 5 AM EST Wednesday for LSZ321. Small Craft Advisory until midnight EST tonight for LSZ322.