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KEY MESSAGES

- Heat and humidity continue into Tuesday, before gradually relenting.

- Chances for showers/storms return Thursday night thru the weekend.

DISCUSSION

Issued at 252 PM EDT Mon Jul 13 2026

500mb heat ridge extends w-e across the northern plains, upper MS Valley, the northern lakes. The location of this ridge will not change much to our west. However, this far east, digging shortwaves in northern Ontario will gradually suppress this ridge southward, into the southern lakes and eventually OH Valley. This will help the heat/humidity improve after Tuesday.

Surface dew points are in the upper 60s to lower 70s across northern MI, and heat indices are climbing toward and into the 90s for most. We will see differences on Tuesday. Model soundings suggest that the low-level airmass Tuesday is not as rich/deep. Strong diurnal heating should allow BL moisture to mix out somewhat in the interior of northern lower MI as we move thru the afternoon...eventually dropping to close to 60f, while more marine/coastal locales stay in the mid 60s to near 70f (though with less toasty air temps). A downsloping w to wnw surface wind will result in the warmest temps in ne lower MI. Continue to advertise max temps reaching near 100f for Rogers/APN/OSC/Tawas/Gladwin/Standish. In the 90s elsewhere. Heat indices should be near 100f in ne lower and eastern upper MI (the latter thanks to muggier air in the north), and in the 90s otherwise. This is after warm/steamy lows tonight in the low/mid 70s.

After collab with surrounding offices, a heat advisory is in effect until early Tuesday evening across all of northern MI. Heat indices look to come up shy of criteria in nw lower MI Tue, but it will be a 2nd straight hot day regardless. Folks still need to be very careful out there.

Again, with the displacement of the 500mb ridge to our south, and with northerly low-level flow becoming established, the airmass will moderate some after Tuesday. Wed/Thu highs are progged in the 80s to low/mid 90s, with the warmest readings in the far se Wed.

Little in the way of precip chances are expected into Thursday. However, with the upper ridge slowly reforming further upstream in the west, nw flow aloft will become more firmly established here. And eventually, this flow will contain some ripples. Chances for showers, perhaps a thunderstorm, arrive as soon as Thu night. Those pops persist thru the weekend, highest Friday into Saturday. Temps will also tend to slide as this happens, with weekend highs in the upper 70s to low 80s.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 145 PM EDT Mon Jul 13 2026

A bit of smoke drifting thru aloft from NW-SE this afternoon but should exit by evening; some afternoon cu popping up where it is not smoky, with bases ~2500-3500ft...but otherwise expect prevailing VFR. These should diminish this evening. Expect LLWS (NW around 30- 35kts) to increase tonight, esp across CIU/PLN/APN after 6- 8z...could get into TVC/MBL as well but may not be quite as strong. Some fog possible between 6-12z, esp MBL but could be elsewhere if winds light enough. Winds generally SW around 5kts tonight increasing to 5-15kts after 12z Tues and turning more W. Do not expect any storms to develop thru this taf period.

APX WATCHES/WARNINGS/ADVISORIES

MI...Heat Advisory until 8 PM EDT Tuesday for MIZ016>018-020>036- 041-042-086>088-095>099. MARINE...None.