textproduct: Detroit/Pontiac

KEY MESSAGES

- Peak heat expected today with highs in the upper 90s and heat indices near or above 100 degrees. A Heat Advisory is in effect for all of Southeast Michigan between Noon and 8pm.

- Hot conditions will exist again on Wednesday with heat indices approaching 100 degrees. The warmest of conditions is expected south of I 69. A Heat Advisory may again be needed for portions of the area Wednesday.

- Potential for showers and thunderstorms exists late in the week into next weekend.

DTW THRESHOLD PROBABILITIES

* Low for thunderstorms Wednesday evening.

PREV DISCUSSION

Issued at 258 AM EDT Tue Jul 14 2026

DISCUSSION...

Clean mid to upper level ridging in place across all of the Great Lakes region with nary a reflectivity return from surrounding radars. The combination of high static stability in the lowest 10.0 kft agl and relative humidity at less than 10% at the base of the steeper lapse rates aloft has resulted in little cloud outside of some patches of cirrus. Modeled vorticity fields and height charts show the centroid of the ridge elongating and pivoting directly through Southeast Michigan today. Outstanding absolute anticyclonic vorticity dipole set to move through indicative of strong active subsidence. Model soundings show significant additional warming between 3.0 to 9.0 kft agl this morning with a lowering of the capping inversion this afternoon. All dynamical processes support the hottest day this week with highs today making a run at 100 degrees. Humidity in a relative sense will be lower, but it is important to stress that surface dewpoints will still be in the 60s. A Heat Advisory is in effect today between noon and 8pm and any duration of heat indices reaching 105 degrees is expected to be at less than 3 hours.

Forecast data supports temperatures settling into the lower to middle 70s tonight. As a result will allow the Heat Advisory to fall off this evening and make additional decisions on a day to day basis. Broad long wavelength troughing is expected to evolve over northeastern North America by the daylight hours on Wednesday with some semblances that upper level jet axis will push into northern portions of the Lake Huron basin. This change in curvature in trajectories is usually adequate in inducing a backdoor front off the Great Lakes. Thetae fields show the sharp low column baroclinic zone pushing in and stalling over northern portions of the forecast area between 15-18z. Notable item for Wednesday is that with the frontal zone in proximity, NBM guidance has surface dewpoints rising into the lower 70s for the southern cwa, the same areas that are still eclipsed by the compressed heat dome/ava signal. Anticipating additional heat headlines south of I 69 Wednesday. Nocturnal release of the marine layer should help usher in lower dewpoints for areas south of Detroit Wednesday night.

Very warm conditions are expected to persist through the end of the week with daytime temperatures ranging in the 80s in the Thumb to the lower 90s across the southwest forecast area. Current thought is that heat indices for the warmest locations should hold below 100 degrees Thursday and Friday.

Upper level northwest flow will carve out a deeper atmospheric frontal axis in vicinity of Southeast Michigan and the Great Lakes this weekend. Jet entrance region dynamics sliding into the upper Great Lakes should lead to synoptic scale lift and precipitation chances beginning this weekend. Difficult to time onset and duration of precipitation periods with details highly dependent on thunderstorm complex tracking.

MARINE...

A hot airmass (850 mb temps in the mid-twenties) will be in place today over the Central Great Lakes, leading to stable low level profiles. This should hold the max westerly winds in the 20 to 25 knot range, with the highest winds across northern third of Lake Huron due to the channeling through the straits. A mainly dry backdoor cold front dropping south Tuesday night into Wednesday will allow winds to veer to the northwest behind the front, but still only topping out around 20 knots Wednesday evening over the north half of Lake Huron. Northwest winds at or below 20 knots holds on Thursday. The forecast on Friday and Saturday unravels due to conflicting model guidance regarding the location and magnitude of a surface low moving through the Great Lakes region. This has significant impact not only on wind speeds, but also on wind direction, along with bringing chances of showers and thunderstorms.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Heat Advisory until 8 PM EDT Wednesday 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.