textproduct: Detroit/Pontiac

KEY MESSAGES

- Below normal temperatures arrive Monday with highs only near 60 and lows falling into the 30s. Chance for frost is possible Monday night particularly over the Saginaw Valley/Thumb.

- More seasonably average temperatures return for the midweek period with little to no rain chances.

DISCUSSION

Surface cold front finishes crossing lower MI this evening with only a low chance for an isolated brief shower as primary moisture axis has shifted over the eastern Great Lakes. Post-frontal cold advection in place through the night into Monday as upper troughing settles over the eastern half of the Great Lakes. Core of the coolest air arrives Monday keeping tonight's lows in the upper 30- lower 40 range precluding a risk of frost. Local 850mb temps fall towards 0C by midday Monday capping high temps around 60 despite building high pressure promoting mostly sunny skies. Said high drifts directly overhead by Monday night leading to calm or near calm winds under clear skies allowing temperatures outside of the urban centers to fall into the 30s. Coldest temps expected across the Saginaw Valley and Thumb where mid 30s are likely offering potential for areas of frost to develop by Tuesday morning.

High pressure departs for the mid-Atlantic daytime Tuesday as broad low pressure dives southeast across northern Ontario setting up south-southwest return flow across southern lower MI. Low pressure looks to track far enough north that SE MI stays dry save for perhaps a stray shower towards the tip of the Thumb Tuesday night. With the area currently favored to reside on the southernmost fringe of the James Bay upper low, temperatures throughout the midweek period would hold around the seasonal average, in the mid-upper 60s, with Wednesday making a run towards 70.

MARINE

Surface flow will turn to northwest this evening in the wake of a weak cold front. Across Lake Superior, gusts have increased to occasional low-end gales at the end of fetch. Given the parent storm system track is well to the north, the best forcing of lengthy low gale potential will be across Lake Superior, with lower chances across the north arm of Lake Huron. As the cooler air deepens through the Straits out onto the main body of northern Lake Huron, wind gusts will increase and approach entry level gales - with the greatest potential tied to the more aggressive cloud growth formations. Current forecast package will continue with the Gale Watch, offering some opportunity for stronger gusts to present themselves upstream.

High pressure builds into the region on Monday into Tuesday - flattening out the wind field for a day or so. Southwest winds will increase later Tuesday with the approach of the next system across the northern lakes region. Small craft conditions are likely across Saginaw Bay and possible down the southern Huron shoreline.

PREV DISCUSSION

Issued at 1248 PM EDT Sun Oct 4 2026

AVIATION...

Full sun and breezy/mild SW wind precedes a cold front on its way through Lower Mi this afternoon and early evening. The front is too moisture starved for shower production but is supporting borderline MVFR/VFR ceiling along and behind a modest NW wind shift. After an initial cloud decrease this evening, the air is cold enough to activate the Great Lakes for additional cloud production late tonight. Coverage tends to be areas of low end VFR with stray patches of MVFR this far south away from the Lake Superior/Michigan connection. NW surface to cloud layer flow persists late tonight through Monday morning.

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

DTW THRESHOLD PROBABILITIES...

* Low for ceiling 5000 ft this afternoon and evening.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Gale Watch from 8 PM EDT this evening through Monday morning for LHZ361-362.

Small Craft Advisory until 8 AM EDT Monday for LHZ421.

Small Craft Advisory until 2 PM EDT Monday for LHZ441.

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