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KEY MESSAGES

- Lingering showers (rain/snow) over the EUP, especially tonight.

- A few showers Saturday, with milder weather ahead.

- Watching potential for colder and unsettled weather for mid to late week next week.

SHORT TERM /THROUGH TONIGHT/

Issued at 310 AM EST Fri Nov 21 2025

PATTERN SYNOPSIS/FORECAST:

Split flow across the western US...with 140+kt upper jet punching into the PacNW; some of this energy sinking southward along the coast of California, resulting in broad troughing across the southwestern US, including a lobe lifting through the southern Plains ....while additional energy tracks northward overtop a subtle ridge over the Intermountain West. Potent upper low over Manitoba/western Ontario with a lobe swinging through the Upper Midwest/Upper Great Lakes attm with quite a cold punch of air aloft (500mb temps in the - 30s C to our north). Surface cold front stretches from James Bay back into Iowa...with a secondary front draped across the Canadian Prairies at 01z/21. Broad upper ridge remains firm over the southeastern US...with quite a bit of warmth and moisture over the southern half of the US. Confluence zone aloft stretches from west to east across the Midwest into Michigan...as these two features battle for dominance...though attm...cooler, drier air from the trough is winning...as moisture struggles to make it further northward than the Mid MS Valley per IR satellite.

Expect lobe to continue to sweep through...with attendant cold front exiting early this morning. Broader upper low to swirl by to our northeast today...though an additional lobe of PV should spiral down toward the area this afternoon into tonight, with another uptick in lake effect likely across the area, particularly the further north you go. Highs today perhaps a touch cooler than yesterday's with the cold advection...in the 40s for the most part (warmest near Saginaw Bay)...which is near normal.

Primary Forecast Concerns through tonight:

Lingering rain/snow chances today...Primary focus for precipitation today will be the EUP, perhaps into the Tip of the Mitt, closer to the better forcing and cold advection...as well as colder air aloft for better overlake instability on NW flow. Still watching some signals for an fgen band to develop across the EUP late this afternoon/tonight after dusk, particularly as winds should diminish and could allow for drainage flow out of Ontario. Think this will largely be in the form of snow, especially after dark...with a few tenths or so at best...but cloud top temps should be flirting with about -10C or so, suggesting a lower chance we could lack ice nuclei and remain drizzle or a mix.

Outside chance of some stronger gusts at times today if we can mix deeply enough...though the question is, will we get there? Primarily expecting 20-25kts or less, and this is what probabilistic guidance based on bufkit soundings suggest. However...there is a 30-40+kt jet around 700mb at the inversion...and some deterministic soundings suggest we could tap into this, particularly in favored NW flow areas (EUP to northern Lake Huron). Not confident enough attm to put this in the forecast, but may need to keep a eye on this idea today just in case.

LONG TERM /SATURDAY THROUGH THURSDAY/

Issued at 310 AM EST Fri Nov 21 2025

Days 2-3 (Saturday-Sunday)...

Subtle ridging slips in Saturday...ahead of our next niblet of energy crossing the Plains...bringing a round of warm advection activity to the region, perhaps with a bit of SW flow lake enhancement, particularly in the afternoon into Saturday night. While the front should be on its way out Sunday morning...think we may need to keep an eye on some lingering clouds/lake effect, particularly across the eastern UP where temps aloft will be most favorable for overlake instability.

Days 4-7 (Monday-Thanksgiving Day)...

Northern and southern stream not quite in phase to start Thanksgiving week Monday...with remnants of an upper low over the central Plains...and a potent punch of PV digging into the PacNW. Overall expectation for next week is for troughing to settle into the Upper Midwest mid to late week, with a storm system (possibly two?) crossing the central/eastern US...with brisk northwesterly flow expected to develop at some point over the Midwest. Think we will be milder for the first part of the week, with rain a more likely scenario until the cold air wraps in and the lake effect machine kicks on...with potential for some strong/gusty winds, pending the position/evolution of the surface low.

Still quite a bit of disparity in guidance on the evolution of the midweek trough...noting deterministic guidance has flip-flopped a bit from last night's runs. Still think there are a couple scenarios in play -- a) upper wave closes off over the Upper MS Valley, resulting in a longer period of nebulous flow/low pressure in the vicinity which could throw a wrench in pinning down lake effect details (timing and position of bands...transition to snow...and potentially accumulations, with enough shifting of winds). b) The more progressive solution, a more open wave, zips through...bringing the colder air in a day or so quicker...perhaps even spinning up the surface low to our northeast a bit quicker as well, which could crank up the lake machine quicker, too.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1139 PM EST Thu Nov 20 2025

IFR or MVFR conditions in stratus/fog expected tonight across the northern Michigan terminals as a weak system crosses the area. This system will be accompanied by drizzle or light rain showers which will wane once the cold front associated with the system passes through tonight. Can't rule out some light lake effect precipitation in the shallow unstable layer behind the front, but this should be a minimal threat. Drier air will raise CIGs at most terminals to VFR during the day Friday. South to southwest winds ahead of the front this evening will trend west- northwest behind the front, becoming gusty at times especially after daybreak.

APX WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...Small Craft Advisory until 9 PM EST this evening for LSZ321.