textproduct: Detroit/Pontiac

KEY MESSAGES

- A Frost Advisory is in effect late tonight for the area generally south and east of a line from Howell to Sandusky. This extends to the Ohio border outside of metro Detroit.

- A warming trend begins Sunday and continues along with dry weather throughout the week.

DISCUSSION

A ridge of surface high pressure is providing an outstanding fall day across SE Mi as full sun counters slightly below normal temperatures. Afternoon highs in the mid 50s to near 60 lead into dry and clear conditions with light wind this evening.

Another round of frost is expected tonight but with the Frost Advisory focus on a target area mainly south of the Tri Cities and northern Thumb. Frost coverage is greatest toward the Ohio border and outside of metro Detroit, where the wind drops off under clear sky closer to the IN/OH surface high center. There is more of a pressure gradient placed toward the Tri Cities and northern Thumb where SW wind holds in the 5 to 15 mph range. The wind is a considerable limiting factor for frost in that area late tonight and early Sunday morning.

The SW wind toward the Tri Cities tonight strengthens across all areas during Sunday. This occurs within the increased pressure gradient between the Ohio valley surface ridge and the next cold front extending into the upper Midwest from the large low pressure system near Hudson Bay. The start of a warming trend is the primary outcome for Lower Mi reflected in guidance Max T around 60 Sunday afternoon and in the mid 60s Monday. Dry weather is ensured through the early week period as the Midwest front stalls and dissipates well to our north through Tuesday.

A split flow configuration in the larger scale mid/upper level pattern places the Great Lakes in a favorable position to build on the warming trend mid to late week. A progressive northern stream is positioned well north across Canada while a closed low dominates the CA coast into the 4 Corners. The mid level ridge scenario for the Great Lakes has higher than normal predictability for dry weather and above normal temperatures that make a run toward 70 Thursday and Friday.

MARINE

High pressure settles across the Ohio Valley tonight into Sunday, setting up a tight WSW pressure gradient over the Great Lakes as deep low pressure tracks from northern Saskatchewan toward Hudson Bay. Wind magnitude over Lake Huron quickly increases through the rest of the afternoon, with gusts on the order of 20 to 30 kt. This continues into Sunday with another slight uptick in wind speed during the day as the core of highest winds aloft passes overhead. This ushers in a milder, more stable air mass which will prevent the bulk of higher momentum from mixing to the surface. However, low probability does exist for gusts to reach 35 kt gales at times within longer fetch areas near the Straits and from Saginaw Bay into central Lake Huron. At this time, confidence is too low for a Gale Warning. Elsewhere, gusts between 15 and 25 kt will be more common. The peak in wind is expected between 8am and 4pm Sunday with a coincident uptick in wave heights. Wind then begins to subside late Sunday evening as the jet departs and high pressure builds northward into the Great Lakes. This brings about more tranquil marine conditions through early next week.

PREV DISCUSSION

Issued at 1245 PM EDT Sat Oct 17 2026

AVIATION...

Ridge of high pressure over the central Great Lakes region will continue to sink southward into the Ohio Valley through tonight and Sunday. The subsidence and dry air with this ridge will keep skies clear across most of Southeast MI through Sunday. As the ridge moves across SE MI and into the Ohio Valley, light and variable winds quickly become southwesterly this afternoon and continue into Sunday. A better gradient across the Tri Cities and Flint areas will keep a noticeably stronger wind overnight and allow for some gustiness on Sunday.

D21/DTW Convection...There will be no thunderstorms through the TAF period.

DTW THRESHOLD PROBABILITIES...

* None.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Frost Advisory from 3 AM to 8 AM EDT Sunday for MIZ055-062-063- 068>070-075-076-082-083.

Lake Huron...Small Craft Advisory until 10 PM EDT Sunday for LHZ421-422-441.

Lake St Clair...None.

Michigan waters of Lake Erie...None.