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KEY MESSAGES

- Frost concerns tonight

- Some showers Saturday night into Sunday

- Even colder temperatures Monday night

DISCUSSION

Issued at 135 PM EDT Fri Oct 2 2026

Pattern Synopsis/Forecast:

Rather progressive northern stream flow found across the northern Conus/southern Canada early this afternoon, with embedded weak and moisture starved wave racing east across the northern Great Lakes. Just enough forcing and Lake Superior moisture contribution to kick off a few light showers across parts of eastern upper this morning. Otherwise, main feature of interest is expansive are of high pressure building into the western Great Lakes. Marginally gusty northwest winds on the front side of this high bringing a somewhat cooler airmass into the region, as evident by current temperatures mostly in the 50s (which are a few degrees below specific normal values for todays date).

High pressure will continue to work east, centering itself directly overhead tonight...exiting stage right on Saturday. Upper level flow regime remains progressive, propelling next rather well organized shortwave trough into the area Saturday night. Detachment between northern stream energy and any deep tropical moisture connection only increases with time, supporting mostly dry conditions as we head through much of next week.

Primary Forecast Concerns:

Initial focus centers on temperature trends tonight and attendant frost concerns. Secondary focus on weekend shower chances and next likely more widespread frost/freeze producing temperatures Monday night.

Details:

Any shower threat comes to an end this afternoon across eastern upper Michigan with departure of shortwave trough. As mentioned, upstream high pressure centers itself directly overhead tonight, bringing clearing skies and light/calm wind as it does so. This should set the stage for a good to excellent nocturnal temperature response. However, still have some concern that wet soils from recent rains (especially south of the big bridge) will prevent an all out temperature free-fall. Little doubt however that frost producing temperatures in the lower to middle 30s will be realized across eastern upper Michigan and away from the Great Lake collar counties of northern lower. Very possible some of our traditional colder locations along M-28 in eastern upper (looking at you Raco) and within the Au Sable River valley of northern lower dip down into the upper 20s. Appropriate frost headlines already issued by the overnight crew (many thanks to them).

Nice temperature recovery on Saturday as winds turn south ahead of the next wave. This wave will bring our next chance for showers Saturday night into Sunday morning. Juxtaposition of best forcing and limited moisture centers itself north of the bridge Saturday night, suggesting that is where best shower chances will reside...with shower chances decreasing the further south one travels. Another large area of high pressure follows this wave Sunday night, moving across the Northwoods to kick off next work week. Simple magnitude of cold air advection supports lows back down into the 30s Sunday night. Pattern recognition strongly supports even colder conditions Monday night as that chilly high centers overhead. Early progs support widespread sub-freezing lows across interior areas by early Tuesday morning. Rest of the week looks rather uneventful, although maturing return flow on backside of retreating high will likely bring a return to above normal temperatures on Wednesday. Fast moving and moisture starved waves may bring some additional late week shower chances, but definitely not seeing any evidence of widespread rains.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 135 PM EDT Fri Oct 2 2026

VFR conditions prevail at all sites as generally scattered to broken cu fields blanket the region with bases around FL031-046. Besides some light lake effect rainfall observed at CIU (prompting a PROB30 for -SHRA), fair weather is forecast through the period. Ongoing gusty northwesterly winds will diminish tonight from 10-20 kt to light and variable (5 kt or less). While some overnight FG cannot be ruled out at the typical overperformers (namely MBL and PLN), current probabilistic guidance suggests chances of MVFR or lower conditions are 20% or less, so will leave FG mention out of this TAF issuance. For the late morning to early afternoon of Saturday, expect winds to become light but mainly out of the south to southeast.

APX WATCHES/WARNINGS/ADVISORIES

MI...Frost Advisory from 10 PM this evening to 8 AM EDT Saturday for MIZ017-018-022-023-027>029-032>035-086-087-095-096. MARINE...Small Craft Advisory until 11 PM EDT this evening for LHZ346>348. Small Craft Advisory until 11 PM EDT this evening for LSZ321- 322.