textproduct: Detroit/Pontiac

KEY MESSAGES

- Dry and pleasant weather conditions will persist into Tuesday.

- There is a chance of fog tonight and Monday morning.

- Rain chances increase during the latter half of next week.

DISCUSSION

The persistence of deep layer subsidence will hold across Lower Mi into Tuesday under a blocked long wave pattern across eastern North America. While some retrogression of the upper low over the Mid Atlantic will drive a few high clouds toward eastern Mi from time to time, ample sunshine will prevail. Forecast mixing depths on model soundings and probabilistic guidance supports daytime highs generally ranging from the upper 60s to lower 70s Sunday through at least Tuesday. There will be slight increase in the north-northeasterly gradient flow across Lake Huron tonight into Sunday as the Mid Atlantic system tightens the gradient over the lower Great Lakes. This will advect a little higher Lake Huron moisture into the boundary layer, raising the prospects for fog development both tonight and Sunday night. Recent HRRR runs are quite bullish in suggesting fog development over a large portions of the northern forecast area. Modified Richardson numbers do suggest some weak boundary layer stability despite increasing low level winds, enough to warrant a mention of fog in the north both tonight and Sun night.

The blocking pattern is forecast to break down Tues into Wed allowing a northern stream trough to slide across the northern Great Lakes. Model variability in the amplitude of this wave and the degree to which it breaks down the ridging across the eastern lakes on Wednesday raises a good deal of uncertainty as to the efficiency with which it drives moisture into Se Mi. This uncertainty warrants just chance type pops the middle of next week. It does appear the eventual breakdown of the ridge will allow a west to east oriented low to mid level baroclinic zone to settle across the Great Lakes and/or Ohio Valley. There is good agreement within the model prob space in phasing the remnant tropical system from the Pacific and a southern stream wave, which drive a tropical moisture plume into the southern and central plains by Wednesday. Although deterministic model solutions indicate a weakening of this southern stream wave as it lifts into the upper Midwest/Great Lakes toward the end of the forecast period, the tropical moisture plume intersecting the aforementioned frontal boundary draped across the Great Lakes suggest the potential for ample rainfall to parts of the region, warranting a chance of rain during the end of the work week.

MARINE

High pressure now situated over the Great Lakes will hold through Tuesday. Some periodic wind gust potential around 20 knots will be possible across southern Lake Huron today and tomorrow, but otherwise, wind gust potential to or below 15 knots is expected for most locations. Wind direction will mainly hold from the north to northeast with high pressure in place.

PREV DISCUSSION

Issued at 1257 PM EDT Sat Sep 26 2026

AVIATION...

High pressure in place today maintaining sunnier skies with cloud cover mainly confined to high cloud streaming in from Ontario. Northeast winds also stay light, 10kts or less, as a result. With clear/cool conditions overnight and earlier day modest near-surface lake moisture transport, there is signal amongst high-res models for fog development focused over the Saginaw Valley to the glacial ridge. Highest confidence is around FNT with MBS and PTK looking to reside on the edges of this potential development.

D21/DTW Convection...Thunderstorms are not forecast through the forecast period.

DTW THRESHOLD PROBABILITIES...

* None

DTX WATCHES/WARNINGS/ADVISORIES

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