textproduct: Detroit/Pontiac

KEY MESSAGES

- An Extreme Heat Warning remains in effect through Thursday, with high temperatures reaching the mid 90s-to-upper 90s and heat indices at or above 105 degrees each day.

- Marginal risk of severe thunderstorms this afternoon north of I-69. - Friday will also be hot, with high temperatures exceeding 90 degrees, but scattered to numerous showers and thunderstorms are likely to develop in the afternoon.

- A good chance for showers and thunderstorms will continue at times over the weekend, with temperatures gradually cooling down.

DTW THRESHOLD PROBABILITIES

* None

PREV DISCUSSION

Issued at 246 AM EDT Wed Jul 1 2026

DISCUSSION...

Very hot and humid conditions will persist over the next couple of days, but convection chances ramp up as we head into the weekend.

The upper level ridge center (597 DAM at 500 MB) over Kentucky will hold nearly stationary or drift east into the Mid-Appalachians through Friday. However, the extension of the ridge axis into the Central Great Lakes folds over into the Eastern Great Lakes today. This allows for some modest heights falls over Lower Michigan. Particularly across northern Lower Michigan, there is heightened concern for severe storms, where 0-6 KM bulk shear values in excess of 40 knots will reside. Warm (12 C at 700 MB) and dry mid levels over much or all of southeast Michigan are expected to provide a cap, but some activity could clip areas along/north of I-69 (See ARW/FV3). Mlcapes in excess of 2000 J/kg support a marginal risk with the southern edge of the stronger wind fields. Damaging winds being the main hazard.

Yesterday's high temperatures reached into the low to mid 90s, despite considerable cloud cover for a good portion of the day. The 00z DTX sounding indicated an 850 MB temps of 21 C. Today, the southwest pressure gradient will be a bit better, allowing for slightly better mixing and warmer 850 MB temp of 22 C. We are expecting highs in the 94-98 degree range for most areas, as moist low levels (surface dew pts in low to mid 70s) will make it difficult to reach 100 degrees. None-the-less, should see heat indices of 105+ degrees, and no changes are being made to the extreme heat warning through Thursday since the airmass remains similar.

However, multiple shortwaves riding the northern edge of the ridge will gradually erode the cap as the main moisture axis (PW values of 1.75-2 inches) sinks south. There is a slight concern for convection to get going as early as Thursday afternoon (marginal risk of severe if storms do in fact develop), with a much higher chance for likely activity Friday afternoon. This makes heat headline decisions for Friday difficult, as temps should still quickly reach and exceed 90 degrees with heat indices of 100+ degrees.

The very moist airmass holds into the first half of the Weekend, and there looks to be multiple shortwaves coming out of the Rockies to trigger showers and thunderstorms at times over the weekend. There is concern for heavy rainfall with 700 MB dew pts of 2+ C, as wind fields look to diminish on Saturday, leading to slower storm movement. However, confidenceremains low regarding the exact location and amount of instability around.

MARINE...

A hot and humid air mass resides over the region today and through the rest of the week. Prevailing wind will be from the southwest at 10 to 15 kt with gusts generally capped around or below 20 kt due to higher stability over the relatively cooler water. The heat dome will maintain very low chances for precipitation for most of the area, but northern and central Lake Huron will reside near the edge of the cap which offers potential for multiple rounds of thunderstorms today and tomorrow. Severe thunderstorms will be possible, capable of producing wind gusts in excess of 50 kt and large hail. The cap migrates farther south by late week which brings higher chances for storms to the rest of the region by Thursday and Friday.

CLIMATE...

Daily Records for the Upcoming Week...

Detroit Record High Record Warm Minimum 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 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 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 Warning until 8 PM EDT Thursday 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.