textproduct: Gaylord

KEY MESSAGES

- Extended period of hot and humid conditions, hottest likely Tuesday through Thursday. - Periodic shower and thunderstorm chances throughout the week, severe storms possible with heavy rain, large hail and damaging wind.

DISCUSSION

Issued at 241 PM EDT Mon Jun 29 2026

The heat is on. A 596 dam upper high builds over the southeast CONUS early this week with anomalously warm and moist air extending northward into the Great Lakes. At the same time, height falls with an upper trough deepening across the intermountain west. The upper high will slowly drift eastward throughout the week, with a number of shortwaves riding the periphery of the ridge resulting in shower/storm chances. The convection will certainly "muddy" the temperature forecasts from day to day over northern Michigan, with cloud cover and shower/storm threats largely controlling max temperatures. Despite the uncertainty on temperatures, it will be hot and very humid as deeper moisture surges into the Great Lakes with dewpoints over 70F. I will transition the Extreme Heat Watch to a Heat Advisory for all of northern Michigan for Tuesday, with greater than triple digit heat indices likely in many areas. Even in areas that may not quite reach criteria, it will be quite hot and heat stress will be an issue. Check on those most sensitive to heat including the elderly, young children, outside workers and pets. Will handle the heat headlines day by day given the uncertainty in convective evolution.

Several convective threats throughout the week with developing southwest flow across a very moist/unstable airmass across the Great Lakes. Any minor perturbation could act as the trigger given the high instability, with leftover convective outflows/boundaries acting as focusing mechanisms for storms. On Tuesday, storms may fire over portions of northern Wisconsin and western upper Michigan within an extremely unstable corridor, then shift east for the afternoon or evening. Moderate shear and potentially extreme instability could produce a damaging wind and large hail threat, with bowing segments possible into parts of northern Michigan. Additional shortwaves over a gradually flattening ridge toward the end of the week may bring additional shower/storm chances.

The upper level pattern becomes less amplified heading into the holiday weekend but still quite warm and remaining active with shower/storm chances.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 130 PM EDT Mon Jun 29 2026

Showers with embedded thunderstorms are seen on radar slowly tracking west to east across the region. Mainly VFR conditions expected to persist, with drops in categories possible as stronger storms continue, mainly across PLN. Winds will decrease tonight with BR/FG/low stratus becoming likely in the morning hours (dropping conditions to IFR to even LIFR at times), but should burn off as we head into the afternoon, returning to VFR.

APX WATCHES/WARNINGS/ADVISORIES

MI...Heat Advisory from noon to 8 PM EDT Tuesday for MIZ016>018- 020>036-041-042-086>088-095>099. MARINE...Small Craft Advisory until 11 PM EDT this evening for LHZ345>348. Small Craft Advisory until 8 PM EDT Tuesday for LMZ323-341-342- 344>346.