textproduct: Detroit/Pontiac

KEY MESSAGES

- Showers and thunderstorms return late Saturday into Saturday night. Heavy rainfall leading to localized flooding is possible, particularly along and south of the I-94 corridor.

- Additional showers and thunderstorms likely on Sunday before dry weather returns early next week.

DTW THRESHOLD PROBABILITIES

* High for ceiling 5000 feet or less early this morning, low by late morning.

* Low for visibility restrictions of 1/2sm or less or ceilings at less than 300 ft.

PREV DISCUSSION

Issued at 301 AM EDT Fri Aug 14 2026

DISCUSSION...

A tropical airmass is in place across the Midwest, as the 00z KDVN RAOB reported an extreme 700 MB dew pt of 11 C. Southeasterly trajectories beneath an upper-level ridge axis over the northern Mississippi River Valley will keep the deep moisture south of the Michigan border today. A strong upper-level wave coming out of eastern Colorado early this morning will pool another round of deep moisture (PW values 2.25 to 2.5 inches), which will make a run toward- and at least impact locations near-the southern Michigan border by Saturday evening. Several hi-res model solutions hold the instability gradient just south of the Michigan border. However, The notable exceptions are the NAM and Canadian models, which are stronger and farther north with the shortwave/MCV. This would present a heavy rain threat with MUcapes over 1000 J/kg. 700 MB dew pts are seen rising to around 10 C, which is near record high from a climatological prospective. However, with the warm and most airmass in the mid-levels, mid-level lapse rates are weak. Local probabilistic guidance suggests NAM is an outlier with the amount of instability and excessive rainfall. Most solutions indicating rainfall amounts generally under 1 inch, except perhaps right near the southern Michigan border. 18z Euro ensemble members suggest a 10- 20 percent chance for 24-hour qpf to reach or exceed 1 inch across all of southeast Michigan. However, the 00z UKMET is also bullish on heavy rainfall, indicating a swath of 2+ inches of rain across the south half of the CWA/Detroit Metro area. The SPC day 2 outlook has highlighted a marginal risk of severe for Lenawee and parts of Washtenaw/Monroe counties. If a stronger circulation and corresponding enhanced 0-6 KM bulk shear verify, then damaging winds and even a tornado would be possible. Obviously, a good deal of uncertainty exists this far out.

Assuming low clouds and/or any fog this morning dissipate by mid- morning and a canopy of higher clouds from storms over the Ohio Valley is not too impactful, highs in the mid 80s seem reasonable today. Similar temperatures are expected for Saturday as clouds thicken up during the day and potential showers arrive by day's end with light southeasterly flow at the surface.

Modest height falls for the second half of the weekend into early next week will bring modest troughing over the Great Lakes region extending east into New England. It looks like a cold front tracking through Sunday into Sunday evening will be support numerous showers and strong thunderstorms before dry weather returns for Monday and Tuesday as large high pressure over the Western Ohio Valley extends into southeast Michigan.

MARINE...

High pressure is building across the Great Lakes and Ontario leading to generally quiet conditions across the region. The high will be slowly shifting eastward eventually reaching the eastern lakes by Saturday morning. The stalled frontal boundary is still lingering to the south but convection also should remain to the south of the area today. Once the high pushes off to the east Saturday, the next low will be developing to the west and should pass through the area in the evening and overnight. Light and variable winds will become northeasterly today and increasing to 10 to 20 knots across southern Lake Huron. Winds then turn southerly late Saturday and increase to around 20 knots ahead of a cold front Saturday night. Winds then shift to the northwest on Sunday behind the front.

HYDROLOGY...

Deep tropical moisture characterized by precipitable water values rising to between 2.0 and 2.5 inches will pool along and near the Michigan/Ohio border Saturday afternoon into Saturday night. This anomalously moist airmass will support high rainfall efficiency, with heavy rain rates of 1-2 inches per hour in any robust convection. While the model consensus keeps the primary axis of heaviest rainfall just south of the state line, a few models have trended farther north. Thus, concern for heavy rainfall leading to localized flooding, particularly along and south of the I-94 corridor. However, confidence is not high enough for a Flood Watch at this time.

DTX WATCHES/WARNINGS/ADVISORIES

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