textproduct: Detroit/Pontiac

KEY MESSAGES

- Increasingly hot and humid conditions develop today, with peak afternoon heat indices reaching the mid to upper 90s.

- Extreme Heat Watch in effect Tuesday to Thursday with highs reaching the mid-upper 90s to 100 degrees and heat indices in excess of 105 degrees each day. There will be little nighttime relief with lows in the mid 70s each night.

- Hot and humid conditions extend into Friday and the holiday weekend with potential for showers and thunderstorms.

DTW THRESHOLD PROBABILITIES

* Low for ceilings at or below 5000 feet this morning.

PREV DISCUSSION

Issued at 307 AM EDT Mon Jun 29 2026

DISCUSSION...

Prolonged high magnitude heat episode set to grip the region throughout the upcoming work week. Early morning surface analysis shows a northeastward propagating warm frontal boundary draped across the northern Ohio valley, marking the lead edge of a deeper moisture plume projected to steadily advect into lower Michigan over the next 24 hours. This upward adjustment in low level moisture quality occurs within the backdrop of substantial growth in the upper height field with time, as the northern expanse of an expanding 594 dam upper level high pressure system dominates across the eastern/southern conus. Likelihood for some degree of higher based cloud to exist at times today, as decaying areas of convection originating from northeast Wi drift southeast along the advancing theta-e gradient. Generally weak, ill-defined ascent exists locally, but the advective process may prove sufficient to generate/sustain a lower coverage of garden variety convection. Confidence in occurrence remains quite low, with general model consensus offering chances at less than 20 percent through this evening. With this said, some disruption to the diurnal heating process remains possible. A notable step up in both temperature and humidity expected with time today, bringing highs into the 90 to 94 degree range. NBM projection of dewpoint appears a touch aggressive for the daylight hours, considering low level flow still features greater influence from the southeast until this evening. Slight downward revision in expected heat index as a result, but with readings still solidly peaking briefly in the mid to upper 90s most locations /highest west of I-75/.

The multi-day heat wave will see a peak in intensity across the Tuesday through Thursday window, as the sprawling, anomalous subtropical ridge centers just south of the region and effectively maintains a core of 850 mb temperatures within the 23 to 25C range. Widespread ambient highs in the mid to upper 90s are expected, with some locations making a run at 100 degrees. The oppressive humidity as dewpoints remain in the low to mid 70s will drive peak afternoon heat index values to between 105 and 110 degrees. Minimal overnight cooling is forecast. Lows will struggle to drop below the mid to upper 70s, with some areas within the metro urban heat island near 80 degrees overnight. Extremely low convective potential during this period, owing to strong mid-level capping and robust subsidence within the influence of upper ridging, with a storm track still favored to hold just to the north and west. An extreme heat watch remains in effect for this time.

Heat will remain elevated Friday and into the upcoming weekend. Magnitude of the warmth becomes less certain as upper ridging influence relaxes as upper heights gradually dampen with time, while convective potential increases as prospective shortwaves begin to work across the northern periphery of the suppressing heat dome. Medium-range ensemble guidance indicates the upper-level ridge axis will anchor itself over the southern US/Ohio Valley, keeping Lower Michigan warmer and more humid than average heading into the second week of July.

MARINE...

A strong low over the northern Plains will pull a warm front up through the region on Monday. Winds will veer more out of the southeast by morning. This will hold through today as gusts reach 20 knots across Lake Huron. There is a chance of showers and thunderstorms this morning into the afternoon along the front especially across the north half of Lake Huron. By Tuesday morning, winds will have become southwesterly while again topping out around 20 knots. Though the gradient increases, stability also increases under a very warm airmass which will limit gust potential.

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...Extreme Heat Watch from Tuesday afternoon through Thursday evening for MIZ047>049-053>055-060>063-068>070-075-076-082-083.

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