textproduct: Detroit/Pontiac

KEY MESSAGES

- Hot and humid conditions arrive Monday with highs in the low-mid 90s and heat indices nearing 100 degrees.

- Hottest conditions expected Tuesday through Friday with potential for highs to reach 100 degrees and heat indices in excess of 105 degrees. There will be little nighttime relief with lows in the mid 70s.

- Low thunderstorm chances for most of the work week, then increasing Friday into the holiday weekend.

DTW THRESHOLD PROBABILITIES

* Low for ceiling at or below 5000 ft this morning.

PREV DISCUSSION

Issued at 254 AM EDT Sun Jun 28 2026

DISCUSSION...

High amplitude large scale upper level pattern in the early stage of evolution heading into the back half of the weekend. Satellite and upper air analysis depicting the sizable corridor of height falls ongoing throughout the western conus, with geopotential heights responding accordingly downstream with steady growth with northward extent through time. Generally benign weather conditions to finish off the weekend period, as forecast attention fixates on the looming heat wave set to grip the region next week as this pattern becomes firmly entrenched. The noted increase in mean thicknesses today as upper heights begin to climb will effectively moderate the resident thermal profile, despite a lack of more meaningful warm air advection as low level flow remains from the east/southeast. Highs in the low to mid 80s.

Ridge axis anchored off a 594 dam upper level high centered to the south will take residence starting Monday. There remains a portion of the model solution space that allows a weak mid level wave to break off the western upper trough and shear across the advancing ridge periphery and associated moisture/thermal gradient tonight into early Monday. The projected trajectory from portions of NE WI into central/northern MI will present a limited opportunity for a disorganized, lower coverage of convection to survive into the area. The forecast simply highlights a lower end mention over the far north. Otherwise, poor convective signal exists for the possibility of a diurnally enhanced window of convective development Monday as the deeper moisture plume makes progressive inroads with time. Profile likely capped just enough to preclude a greater concern. The uptick in humidity as dewpoints climb above 70 degrees will bring heat indices into the mid 90s to around 100 degrees by late in the day /highest west/. Initial heat headline decision point here with a at least a portion of the forecast area likely peaking at advisory level but not yet at warning level /105 or greater heat index/. For simplicity, will elect to defer a decision to the forecast package later today to afford an opportunity to review and potentially provide an additional watch headline decision for the mid-week period at the same time /see below/.

Peak in heat magnitude across an extended window from Tuesday through at least Thursday as the sprawling high amplitude ridge engulfs the region. The forecast continues to call for high temperatures solidly in the mid to upper 90s, with a heat index in excess of 105 degrees each day with a 70+ dewpoint in residence. Watch/warning headlines anticipated with consideration given to cumulative heat stress generated from a multi-day event and factoring in an elevated overnight low temperature that offers little relief. Little evidence at this stage to suggest convective episodes will prove more problematic in realizing projected highs, likely owing to the strength of the underlying subsidence and disconnect from the storm track held to the northwest given the ridge positioning/amplitude. This could still change and will continue to monitor.

Hot and humid conditions likely persist Friday into the upcoming holiday weekend, but with some potential for the governing upper ridge to gradually dampen with time and offer a slight downgrade in both temperature and heat index relative to earlier in the period. This also offers greater opportunity for convective activity to spill into the region from upstream and/or emerge locally as forced/free ascent potentially proves more attainable.

MARINE...

Dominate area of high pressure will hold over the region into Monday resulting in light northeasterly winds generally under 15 knots through that time. A warm front will then lift north through the region on Monday causing winds to increase and flip around to the southeast. Winds continue veering to the southwest overnight into Tuesday behind the warm front bringing very warm air into the region for next week. There will also be a chance of showers and thunderstorms for northern Lake Huron Monday as the front lifts north. Gradient will increase but question remains how much wind will reach the waters in a very stable airmass.

CLIMATE...

Daily Records for the Upcoming Week...

Detroit Record High Record Warm Minimum Mon June 29 96 (1933) 77 (1945) Tue June 30 96 (1931) 76 (2018) Wed July 1 98 (1931) 80 (1931) Thu July 2 99 (2011) 76 (2018) Fri July 3 100 (1911) 78 (1911) Sat July 4 102 (2012) 79 (1921)

Flint Record High Record Warm Minimum Mon June 29 100 (1934) 75 (1945) Tue June 30 98 (1933) 76 (2018) Wed July 1 102 (1931) 72 (2018) Thu July 2 100 (1931) 73 (2002) Fri July 3 99 (1921) 73 (1983) Sat July 4 102 (1921) 76 (1999)

Saginaw Record High Record Warm Minimum Mon June 29 100 (1971) 75 (1971) Tue June 30 99 (1964) 77 (2018) Wed July 1 103 (1931) 78 (1931) Thu July 2 100 (1931) 73 (2002) Fri July 3 99 (1966) 76 (1974) Sat July 4 97 (2012) 75 (2012)

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None.