textproduct: Detroit/Pontiac

KEY MESSAGES

- Cool tonight with lows in the lower 40s to upper 30s. Narrow band of light showers possible late tonight into Sunday morning mainly north of I-69.

- Seasonable highs Sunday near 70 degrees.

- 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.

DISCUSSION

High pressure centered over northern lower MI has maintained a pleasant fall day across SE MI. East-northeast winds have wrapped enough lake moisture around the periphery of core subsidence to support a healthy coverage of diurnal cumulus over the southern/eastern portions of the area with sunny skies holding over the western/northern portions. Clouds fade early this evening with sunset leading to another cool night with lows falling into the lower 40s.

A shortwave trough currently working across the upper Midwest tracks into the north-central Great Lakes late tonight as high pressure is shunted east. Moisture transport isn't particularly strong due to weak lower level winds (sub 40kts below 700mb), however is enough to draw in ribbon of modest theta-e from the Midwest along the lead edge of the mid-level wave/PV anomaly. Isentropic ascent is also confined along this lead edge resulting in a narrow band of potential showers sliding across between ~09-13Z. Owing to closer proximity to the shortwave and cold pool, said shower chances essentially confined north of I-69. Surface cold front lags, not crossing until Sunday evening, with minimal fanfare outside a low chance for an isolated shower/drizzle.

Some of the coolest air of the season thus far follows as 850mb temps fall to 1-2C by Sunday night dropping lows to the low 40s- upper 30s. Thermal troughing holds over the central Great Lakes through Monday as 850mb temps nudge down further to around 0C limiting diurnal recovery to highs near 60. Building surface high pressure late day Monday promotes clearing skies and near calm winds by Monday night supporting SE MI's first shot at frost, particularly across the Saginaw Valley/Thumb, as lows approach the mid 30s. More seasonably average temperatures return for the midweek period as Hudson Bay upper troughing shifts towards Labrador.

MARINE

High pressure over the central and eastern Great Lakes region will gradually move over the Northeast through the end of the weekend as low pressure tracks east across southern Ontario, remaining north of Lake Superior. While this low is progged to remain well north of the area, it is expected to intensify as it moves east towards the James Bay area, resulting in a large-scale uptick in winds over the region. A cold front extending south from the low pressure system will also usher in a wind shift on Sunday. Tonight into Sunday morning, south winds prevail across Lake Huron. Winds then become westerly mid-day Sunday and gradually will shift and come out of the northwest Sunday afternoon and evening. Generally speaking Sunday through Monday, winds of 25 to 30 knots are expected over Lake Huron, with the strongest winds expected across the northern third. Sunday evening through Monday morning will see the best window of potential for winds around or in excess of 30 knots over the open waters of Lake Huron. This is especially so up across the far northern third of the lake. Will continue to monitor trends in the forecast and probabilistic data on low-end gale potential for Sunday night into Monday morning. Right now probability fields are around 20% for seeing low-end gales around 34 knots across far northern Lake Huron.

Further south on Lake St. Clair and the nearshore waters of Lake Erie, similar wind directions and wind shifts will be observed, but they will be delayed in time compared to over Lake Huron. Winds will also increase Sunday night into Monday; however, they will not be as strong that far south.

Winds gradually weaken late Monday into Tuesday as a transient area of high pressure briefly moves through the region. We then see another system track north of the area, but will bring another uptick in winds for mid-week.

PREV DISCUSSION

Issued at 1252 PM EDT Sat Oct 3 2026

AVIATION...

The center of surface high pressure extends from Lower Mi into southern Ontario and is in full control of weather conditions this afternoon. A shallow scattered to broken cumulus field within the high pressure air mass is boosted by an easterly wind component off the Lakes and building daytime instability through the afternoon.

The high moves into the New England states this evening followed quickly by the next low pressure system tracking from the upper Midwest into the northern Great Lakes. Warmer air and elevated moisture transport already have a substantial field of mid and high clouds spread out over WI along with a few pockets of light rain. The leading edge of these clouds is subject to erosion while moving through Lower Mi this evening but eventually solidifies into a VFR mid level ceiling late tonight through Sunday morning. D21/DTW Convection... Thunderstorms are not forecast this period.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling 5000 ft or less today.

DTX WATCHES/WARNINGS/ADVISORIES

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