textproduct: Detroit/Pontiac

KEY MESSAGES

- Mostly dry Friday with a chance for showers near the Ohio border. Then a warming trend through the weekend.

- Very hot and humid conditions are likely next week as heat indices could exceed 100F, especially Tues into the late week period. Potential exists for thunderstorms during this time as well.

DTW THRESHOLD PROBABILITIES

* Low for ceiling at or below 5000 ft tonight, moderate early Friday morning.

PREV DISCUSSION

Issued at 313 PM EDT Thu Jun 25 2026

DISCUSSION...

Mid-upper troughing will be over the region today as a surface low pressure system migrates slowly across the central Great Lakes. Despite more dry air that has filtered into the region, there will be showers and thunderstorm potential for the remainder of the afternoon until about 9-10 pm this evening. The environment will become more supportive of better organization through this afternoon compared to yesterday evening and last night. Mean surface CAPE across SE MI per the HREF tops 1000 J/kg with areas across the Tri- Cities and Thumb approaching 2000 J/kg. Lapse rates have steepened to 6-7 C/km across the area as well. Morning model suite still shows some displacement of better 0-6 km bulk shear of 30 kts or greater to south of the south of M-59 associated with the stronger 850 mb flow. Low level shear over the area will be very weak and well below 20 knots for most southeast MI. Mid-level ascent atop the cold frontal zone and low pressure track will focus higher coverage of convection roughly across the Tri-Cities to Port Huron corridor and points north. Tall skinny CAPE profiles, weaker shear, with moderate instability will offer a marginal risk for severe weather as stronger isolated updrafts will be capable of producing strong to severe downburst winds. Secondary threat will be a hail if any updrafts can maintain a longer duration organized updraft along with some heavy downpours given the very slow storm motion. Limiting factor for heavy rain with the slow storm motion will be the lack of deeper moisture. SPC Day 1 Convective Outlook maintains a similar area for the Marginal Risk of severe weather laid across the Tri- Cities/Thumb and to the southeast into northern Macomb and St Clair County. The clouds have cleared across the I-94/I-96 corridors, which will pave the way for a run at 80 degrees across southern portions of the CWA through this afternoons peak heating.

The system's cold front will clear by this evening with high pressure and subsidence to follow resulting in a largely PoP free forecast for the overnight period beyond 03Z. A low amplitude will be tracking across the Ohio Valley during the day tomorrow. Most models have the northern periphery of the precipitation grazing southern Michigan areas south of I-94. The NAM is the outlier with the latest 12Z solution showing a trend to a further north intrusion of the precipitation. Guidance has such trended such with 30% PoP extending up to the M-59 corridor. Most other hi-res models keep it south, so expect that most of the area should remain dry Friday aided by the local E-NE flow.

The main storyline in the extended will be the potential for extreme heat starting Monday through mid-week and potentially into the late week as a high amplitude ridge develops and exhibits some staying power over the central and eastern US. Mean high temps on long range/AI outputs are forecasting an impressive mid-upper 90s scenario, especially during the Tues-Thurs period. This is when a 500 mb geopotential height nearing 600 dam centers of the Ohio and Mid Mississippi River Valleys. Within this heat dome will be high humidity with dewpoints exceeding 70 degrees, resulting in heat index values that should easily exceed 100 degrees for several afternoons next week in this set up and likely heat headlines. There again will be some convective potential during this time, which could affect some of the daily highs and associated heat indices. It will be monitored for both timing and locations in later forecasts.

MARINE...

A low pressure system over central lower MI this afternoon will drift across southern Lake Huron this evening. Scattered thunderstorms have developed and will continue through the evening hours under the low. Weak pressure gradient is keeping wind gusts mainly below 15 knots but could get a briefly stronger gust in the vicinity of a thunderstorm. High pressure is already building into the western lakes and will encompass most of the region by Friday morning. The high holds over most of the area through the weekend but there is a low looking to clip the southern Great Lakes Friday afternoon and evening. The rain shield would most likely impact Lakes Erie and St Clair. Once the high builds back across the region Friday night it will bring warmer and calmer weather along with it.

DTX WATCHES/WARNINGS/ADVISORIES

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