Detroit/Pontiac forecast discussion

Key Messages

decreasing temperatures through the day.

- Frost/freeze conditions are likely Saturday morning for portions of SE MI.

- Dry with above normal temperatures next week.

Aviation

Westerly wind gusts will top 20 knots this morning under post frontal cold air advection. A secondary cold frontal passage this afternoon will veer winds toward the NNW while deepening mixing depths supports 25 to 30 knot wind gusts to the surface this afternoon into the evening. Residual low level moisture will sustain MVFR based clouds well into the afternoon. Deepening convective cloud depths this afternoon along the with passage of an upper short wave will result in scattered to numerous showers, shallow enough to refrain from thunderstorm mention. Growing depth of the cold layer will trend ceilings toward VFR this evening. Deep layer dry air advection under more northerly winds will support a clearing trend at the terminals overnight into early Saturday morning.

D21/DTW Convection...Thunderstorms are not forecast today.

Dtw Threshold Probabilities

* High for ceilings at or below 5,000 feet today into the overnight.

* Low in crosswind thresholds being exceeded today.

Prev Discussion

Issued at 343 AM EDT Fri Oct 16 2026

DISCUSSION...

An cold front is in the process of clearing SE MI and will bring about breezy conditions, steadily falling temperatures, and periodic rain showers for today. The departure of low pressure from Michigan into Ontario and Quebec will have cold air advection ramp up through the day as low level flow backs from west to north-northwest. The advection of cooler air will greatly dampen or nullify the typical diurnal peak in temperatures this afternoon as they fall from the 50s-60s this morning into the 40s by the evening. This will be reinforced from a secondary cold front that will progress across SE MI late this morning into the early afternoon hours. Passage of this secondary frontal boundary will further increase mixing depths, producing breezy conditions with gusts ranging between 30-35 mph. Some isolated potential to 40 mph will be possible after the passage of the secondary cold front, but the absence of appreciable stronger wind speeds within the mixed layer lowers confidence for higher frequency gusts to 40+ mph. The exception will be within the Thumb given reduced surface friction along the lake as flow backs to the NNW.

Retainment of appreciable low-level moisture wrapped in cyclonic flow coupled with shallow instability within the mixed layer will support drizzle and rain shower chances through the afternoon and evening hours. Coverage of rain showers will start to decrease in the evening hours for most locations as flow backs to the north, which cuts off the additive moisture advection derived from Lake Michigan. Consequently, coverage will likely increase around the Lake Huron shoreline once wind direction orients more favorably off of Lake Huron. The enhanced pocket of shallow instability coming off the lake will supplement moisture advection onshore. Notably stronger lapse rates extending through 700mb and positive buoyancy extending through the -10C isotherm could support more vigorous convective shower development and/or isolated thunderstorms, capable of producing small hail.

Strong high pressure will rapidly build in from west to east overnight which will scour and advect out low-level stratus as dry air works in. Clear skies coupled with the early day cold air advection will bring chilly overnight lows. Efficient radiational cooling drop temperatures into the low to mid 30s, bringing high potential for patchy to widespread frost. The coldest temperatures will be found across the interior of SE MI through the Tri-Cities where temperatures in the upper 20s to low 30s are possible. Below normal temperatures hold tomorrow afternoon with highs capped in the low to mid 50s.

High pressure then sets up and expands over the Midwest and Great Lakes next week which will bring an extended period of dry weather. Temperatures rebound back to above normal values in the mid to upper 60s, possibly low 70s, by the late week period. This will bring a period of idyllic fall weather under mostly clear skies for a greater portion of next week.

MARINE...

Deepening low pressure tracks across central/southern Lake Huron this morning before quickly departing east today. The system sends a strong cold front southward across the region with wind shifting to N/NNW in its wake. Cold advection over the lakes brings increasing instability through the day with lake effect showers and gusty northerly flow ensuing. The strongest core of winds aloft arrives late afternoon and this evening with gusts to gales up to 40 kt on Lake Huron, especially across the southern basin where fetch is maximized. A Gale Warning remains in effect for all of Lake Huron. Farther south to Lakes St. Clair and Erie, brief gusts to 35 kt will be possible late this evening but expectation is for most gusts to hold near or below 30 kt given shorter fetch.

Wind magnitude begins to subside after midnight and continues to weaken through Saturday morning as a ridge of high pressure extends in from the Midwest. The ridge then quickly shifts into the Ohio Valley, pairing with a deep low over northern Ontario to produce a strong WSW pressure gradient over the local area late Saturday into Sunday. Sunday afternoon remains a target for potential gusts to gales over Saginaw Bay and central Lake Huron. The high pressure then gradually expands northward to bring more tranquil marine conditions early next week.

Dtx Watches/Warnings/Advisories

MI...None. Lake Huron...Gale Warning from 1 PM this afternoon to 4 AM EDT Saturday for LHZ361>363-421-422-441>443-462>464.

Lake St Clair...Small Craft Advisory until 10 AM EDT Saturday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 AM EDT Saturday for LEZ444.

AVIATION.....SC DISCUSSION...AM MARINE.......TF

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