textproduct: Detroit/Pontiac

KEY MESSAGES

- Seasonable highs today near 70 degrees.

- Below normal temperatures arrive Monday with highs only near 60 and lows falling into the 30s.

- Chance for frost Monday night particularly over the Saginaw Valley/Thumb.

DTW THRESHOLD PROBABILITIES

* Low for ceiling 5000 ft this afternoon and evening.

PREV DISCUSSION

Issued at 309 AM EDT Sun Oct 4 2026

DISCUSSION...

Deep potential vorticity troughing with phased upper level jet dynamics will push across Southeast Michigan early today. Forecasted height fields support negative tilting of the axis as it arrives but with the strongest 1000-500mb height falls passing to the north and east of the Upper Peninsula. A late timing of the deepening, relative to Southeast Michigan, results in an extremely narrow ribbon of moisture with shallow midlevel saturation. Forecast soundings support very dry air in the lowest 10.0 kft agl. Modestly better lapse rates above 12.0 kft agl resides over the northern cwa between 9-13z. The better potential to measure is north of the I 69 corridor with much of the area at less than 40% to exceed a 6 hourly rate of 0.05 inches of liquid. Forecasted PoPs may be a little low for the Tri Cities and Thumb but given the amount of dry air in the low levels will maintain the inherited. Gradient flow with mixing will result in a bump for surface winds this afternoon. West to northwest this afternoon of 15 to 25 mph. Highs today will be in the upper 60s to lower 70s, the true cold front not pushing through the area until this evening.

Sharp geopotential height rises over the Great Lakes region will support surface high pressure Monday and Tuesday. Much cooler weather is expected Monday with highs in the upper 50s to around 60 despite full sunshine. Heart of the anticyclone will be overhead Monday night with dewpoints forecasted to drop into the middle 30s. With a calm wind environment the likelihood is high that a Frost Advisory will be needed Tuesday morning for at least a portion of the forecast area.

The next upper level jet packet with a cyclonically curved exit region will push into the Great Lakes late Tuesday and Wednesday. Will need to monitor the southward extent to the absolute vorticity advection as it relates to the PoP forecast. The current forecast for the probability of precipitation is low for the midweek period. The forecast area looks to be perilously close to troughing which offers uncertainty for PoPs heading into next weekend. Temperatures look to be around normal next weekend.

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. This will result in a large-scale uptick in winds over the region and a window for low-end gales over northern Lake Huron Sunday night and Monday morning as cold air advection ushers in a higher potential for destabilizing the boundary layer over the open waters and mixing down stronger winds.

Further south on Lake St. Clair and the nearshore waters of Lake Erie, similar south winds to start the day will become west and eventually northwesterly by the end of the day. Winds will also increase Sunday night into Monday; however, they will not be as strong that far south and currently look to remain below small craft advisory levels. 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.

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.