textproduct: Detroit/Pontiac

KEY MESSAGES

- Heat and humidity build back into the region Sunday-Monday with highs around 90 degrees and heat indices in the low to mid 90s.

- Isolated strong to severe thunderstorms Sunday evening/night, with a more organized severe weather threat arriving late Monday. Damaging winds are the primary hazard both days.

DTW THRESHOLD PROBABILITIES

* Moderate for ceiling 5000 ft or less late tonight through Sunday.

* Low for thunder Sunday afternoon and evening.

PREV DISCUSSION

Issued at 325 PM EDT Sat Jul 25 2026

DISCUSSION...

Influence of high pressure is waning this afternoon as amplifying central CONUS ridging builds across the Midwest. This mid-upper pattern shift allows a ridge running wave train to drop into the central Great Lakes through the remainder of the weekend and Monday offering multiple chances for storms locally.

Expansive coverage of stratus crossing Lake Michigan demarcates the lead edge of the first of these shortwaves which is set to cross SE MI this evening. Dry resident airmass in place (12Z KDTX RAOB showed 0.72" of PW) precludes any rain chances with the main consequence instead being the initiation of moisture advection into southern lower MI through tonight. Lower level moisture is established by Sunday morning tied to the arrival a second wave offering the chances for scattered showers and isolated thunder first over the Saginaw Valley. Chances then shift south of the course of the morning as the shortwave and the left exit region of an upper Midwestern jet streak shift southeast. Some afternoon-evening redevelopment remains possible from peak heating though better convective signal comes late evening-Sunday night when northern MI convection drops south into/near the area. Any storms that do manage to develop in the evening stand the best shot at becoming strong to severe with ~1000J/kg of MLCAPE still available and shear 35-40kts. While instability partially wanes by time of any northern MI convection reaches the area, shear holds unchanged maintaining organization and isolated severe potential. Primary hazards would be damaging wind gusts and locally heavy rainfall with hail being a lesser secondary threat. All of SE MI is under a Marginal Risk from SPC.

Model signal early Monday still muddled with mid-range solutions highly varied in the degree of lingering morning showers/storms which affects the magnitude of available instability late day. That said, confidence is still higher, relative to prior waves, for Monday evening/night in organized severe potential as a mid-level trough digs into the northern Great Lakes. In addition to the stronger synoptic kinematics, attendant surface cold front dropping through the state also provides more robust forcing mechanism resulting in good model agreement for MCS development. Its exact placement/track however is the main point of uncertainty with a wide range of outcomes currently advertised in the model suite ranging from west MI to eastern Lake Huron. Given the convective mode, severe wind gusts are the primary hazard with a low but non-zero chance for a QLCS tornado. All of SE MI remains under a Day 3 Slight Risk from SPC.

Low pressure peels east of the region by Tuesday leaving cooler, drier airmass in its place as 850mb temps fall to lower teens C with sub 60F dewpoints. Resultant midweek highs hold slightly below average in the lower 80s including some upper 70s possible Wednesday. Surface high pressure sinking out of northern Ontario promotes clearer skies supporting another period of pleasant weather.

MARINE...

Light southerly winds draw warmer air and greater instability into the central Great Lakes leading to increasing thunderstorm activity on Sunday, including the chance for a strong to severe storm Sunday night. The primary low pressure system then tracks across the northern Great Lakes during Monday. Thunderstorm activity continues to increase coverage and intensity with this system, especially along the trailing cold front that brings a chance of strong to severe thunderstorms as it moves through the region. Outside of storms, wind and waves are low until the northerly wind shift post front late Monday night into Tuesday when speeds likely reach 25 to 30 knots over southern Lake Huron. If the low deepens enough over the Eastern Great Lakes Tuesday evening, a short period of gales could even come into play. Winds slowly diminish on Wednesday as large area of high pressure over the Western Great Lakes slowly advances east, arriving on Thursday. This will assure dry conditions for those days.

HYDROLOGY...

Several rounds of showers and thunderstorms are possible Sunday into early next week. An increasingly humid and unstable airmass will lead to rainfall rates over an inch per hour in some thunderstorms. Recent dry weather and low soil saturation will help mitigate widespread flooding concerns, although localized flash flooding of low-lying, urban, and other flood-prone areas remains possible if thunderstorms repeatedly impact the same locations.

DTX WATCHES/WARNINGS/ADVISORIES

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