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KEY MESSAGES

- Cold Tonight, esp near and south of M-72

- Warm, breezy, dry Saturday; most likely warm/dry Sunday, too

DISCUSSION

Issued at 257 PM EDT Thu Oct 8 2026

120kt NW upper jet from Western Canada down into the Midwest and around into New England, circling around a 531dm 500mb upper low (and attendant 994mb surface low) in the vicinity of James Bay. Confluence zone aloft over the Mid-Atlantic...with Hurricane "Isaias" spinning over the Gulf, where the bulk of the deep moisture is focused attm; across the Southern Plains, some semblance of upper troughing. Upper jet is drawing some Pacific moisture across Western Canada into the Northern Plains; return flow over the central Plains helping to enhance convergence along western edge of a low-level baroclinic zone there, which stretches through the OH Valley into New England, around the base of the trough aloft. Some drier air sneaking into the Upper Great Lakes attm, though we do have some low- level moisture around (plus the warm waters of the Great Lakes...still around 14-16C attm). Cool air to our north...0C at 850mb over Lake Superior at 15z, with some -8C air well north over Hudson Bay attm. Temps here are just warm enough to generate some overlake instability, esp from approximately M-32 and northward; aided by some PV maxima tracking through the flow, a few showers over parts of the EUP and even into NE Lower this morning, which should hold on into at least part of the afternoon.

Subtle bit of energy crosses the area region Friday, but ridging builds in going into Friday night...as troughing digs into the western US...and Isaias tracks northward out of the Gulf. Looking at development of a stronger surface cyclone in the Northern Plains by Friday night into Saturday, resulting in strong warm advection through the Upper Midwest to start the weekend...which aside from summer-like temperatures could bring us a few showers Friday night into early Saturday. Currently, it appears troughing wants to cut off over the western US...with northern stream energy looking more progressive over Canada this weekend as Isaias tracks northward toward the OH Valley. Still some questions about how these features interact...but appears the baroclinic zone from the northern stream will stretch out to our north, and we may remain in a bit of a no- man's-land between this and what is left of the tropical system for the first couple days of next week. Increasing uncertainty for the remainder of the period into the middle of next week...depending on how quickly ridging builds into the Midwest (likely depending on how strong the troughing out west ends up) and how the northern stream pattern evolves (this may again depend on how the troughing out west evolves...but there is some potential for the ridge to build quick a bit northward over the Midwest by midweek next week). The downside to this, as energy tries to eject from said trough...is that this pattern could certainly leave the Midwest open to a period of more active weather with a more active SW-NE storm track across the CONUS...though nothing is set in stone yet, by any means.

FORECAST DETAILS...

Cold Tonight...High pressure to our west expected to build in through the day into the night tonight, which should tamp down winds with time. Cool air mass in place suggests another frosty/freeze-y night for the area. Think the best shot of temps falling into the lower 30s or colder will be near and south of M-72, especially away from the lake...though not impossible it could get colder than forecast closer to Manistee/Beulah if the pressure gradient drops off fast enough tonight. Do wonder if upstream mid/high clouds on the nose of the jet max over southern Canada will be able to limit radiational cooling. Also wonder if we will end up with some fog tonight, given some recent rainfall, though we should mix down some drier air this afternoon. Not sure the widespread cold is a sure bet, given that we should still have some overlake instability and those aforementioned mid/high clouds, particularly near and north of M-72/M-32...and current temp forecast reflects this idea. If we clear out and calm down quicker across the Tip of the Mitt/EUP, temps would fall much more dramatically than currently forecast. Given Monday night's cold (widespread temperatures below 32F for northern Lower), will consider the growing season effectively ended (i.e., no more frost/freeze headlines for this season)...though suppose some areas near the Lake MI coast will remain more sensitive with a traditionally longer growing season.

Warmth This Weekend...Warm front should move through during the first half of Saturday and result in much warmer conditions going into the afternoon than to start (plus we will likely have some clouds/rain around early Saturday morning along/ahead of the front). Much warmer air mass aloft will support temperatures rising into the mid and upper 70s; would not be surprised if some areas across NE Lower in particular (and perhaps TVC) touched or exceeded 80, given south/southwest flow should enhance downsloping. These areas would also be most likely to see dry conditions develop, with RHs dropping to 30 percent or less...again, thanks primarily to downsloping, though the antecedent dry air mass should take a bite out of the incoming moisture with the return flow. Have opted to trend dewpoints and subsequently, RHs, down for Saturday...and with breezy conditions (S/SW winds 10-15kts with potential for gusts as high as 25-35kts, esp late in the day)...think fire weather concerns are a possibility. Particularly noting it will be a warm, sunny fall day, otherwise perfect for lawn clean-up...just not the burning kind of clean-up.

Sunday...Expectations are for the remnants of Isaias to track somewhere in the vicinity of KY/TN Sunday. There are some signals for a band of deformation rainfall on the northern edge of Isaias' influence...and it isn't out of the question this could yet sneak into our Saginaw Bay region/M-55 on Sunday...but still a lot of uncertainty regarding timing/placement of this feature, and most signals keep this to our south, closer to the Thumb/central Lower MI attm. Subsidence and warmth appear to overtake most of northern Michigan otherwise, though think the strongest winds and warmest temps could remain to our west/northwest closer to the tighter pressure gradient, as we could remain in that no-man's-land between systems. Next chance for rain could hold off till later Monday night into Tuesday as the upstream baroclinic zone starts to trend eastward.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 134 PM EDT Thu Oct 8 2026

VFR conditions for all terminals with VCSH near KCIU/KPLN/KAPN lasting through 22z. A brief MVFR cig is possible around this activity. W/NW winds of 9 to 15kts with G15 to 25kts will weaken by 00z. VCSH possible near KCIU after 04z, and couple result in a quick MVFR cig or two. Chances for impactful BR/FG near KCIU after 08z. Lighter winds and VFR conditions for all terminals after 12z through the end of the period.

APX WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...Small Craft Advisory until midnight EDT tonight for LHZ345>349. Small Craft Advisory until 8 PM EDT this evening for LMZ323- 341-342. Small Craft Advisory until midnight EDT tonight for LSZ321-322.