textproduct: Detroit/Pontiac

KEY MESSAGES

- Chance of showers with gusty northwest winds this evening.

- Turning colder tonight with low temperatures Saturday morning reaching the low to mid 30s. This will lead to some areas of frost.

- Cooler conditions exist Saturday, then turning warmer Sunday into next week. No rain expected through this time.

DISCUSSION

High amplitude longwave trough on pace to pivot across the region this evening. Strong cold front attendant to the main height fall center noted accelerating southeast across the local area this afternoon. A few pockets of showers will continue to emerge over the next several hours as the frontal slope and trailing cold air advection engage sufficient resident moisture depth. Improvement in mixing depth within the immediate wake of this front will also provide a greater window for gusts to exceed 30 mph during the evening hours, particularly across the northern thumb. A secondary brief lake effect response likely off lake Huron, as a short window for meaningful shower production occurs within a zone of convergence along the eastern thumb through at least the first half of the night before low level flow veers sufficiently to direct activity offshore. Progressive clearing trend through the back half of the night as the notably colder/drier post-frontal environment gains traction with time. Latest NBM guidance offers a general spread in projected low temperature Saturday morning ranging from sub-freezing in the Saginaw valley to mid 30s portions of metro Detroit and near the immediate shoreline locations. While a persistent low level gradient may prove more detrimental at times for frost formation, in collaboration with neighboring offices still operating within the end of the growing season, will elect to highlight appropriate frost/freeze headlines based on projected low temperature.

Seasonably cold airmass entrenched to start the weekend period, marked but sub-freezing temperatures at 850 mb. Surface ridging in control beneath prevailing mid level northwest flow affords deep layer dry and stable conditions, translating into a high degree of insolation potential. Despite this, existing thermal profile will simply support highs of lower 50s - or a solid 10 degrees below average. Light winds emerging from the southwest Saturday night as the surface ridge slips east. This may offer some limitation to radiational cooling potential, but with minimum temps Sunday morning still arriving in the mid 30s given the magnitude of the existing colder profile. This will afford some areas of frost. Ensuing warming trend starting Sunday as existing low level southwest flow establish a pattern of warm air advection beneath a building upper height field. The strength of the advective process will bring temperatures back closer to average for mid October.

A high magnitude deep layer dry and stable environment will exist through much of the upcoming work week, as conditions remain governed by low and mid level ridging. This ensures precipitation free conditions during this time. Moderating thermal profile magnified by existing upper ridging will lend to above average temperatures throughout this period. Highs mid 60s to around 70 degrees, with minimum temps in the 40s.

MARINE

Strong cold advection is ongoing this afternoon as low pressure quickly departs to the east. As the depth of cold air increases over the warm lakes, increasing instability and the strengthening northerly wind field will allow stronger gusts to reach the surface through this evening. Model guidance is still in line with max gusts on the order of 35 to 40 kt over Lake Huron, especially over the southern basin where fetch is maximized. Confidence has increased to see a period of marginal gales over Lake St. Clair as well, and the Gale Warning has been expanded to include Lake St. Clair as well as all of Lake Huron. A Small Craft Advisory remains in effect for western Lake Erie. 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 Hudson Bay to produce a strong WSW pressure gradient over the local area late Saturday into Sunday. Sunday afternoon remains a target for potential gusts to 35 kt gales over Saginaw Bay and central Lake Huron. Will allow current headlines to expire before issuing any additional headlines for this period. The high pressure then gradually expands northward to bring more tranquil marine conditions early next week.

PREV DISCUSSION

Issued at 225 PM EDT Fri Oct 16 2026

AVIATION...

Nuanced aviation forecast this afternoon given the highly variable environment as it relates to ceilings, gusts, and shower potential. During this on-going lull, winds have trended weaker with a distinct absence in gusts, but this should be temporary as the secondary cold front makes further inroads this evening. The upstream cold advection steepens temperature profiles and promotes renewed mixing, favoring gusts in excess of 25 knots, at times. Gradient winds also respond accordingly, both in increased magnitude and veered directionality, eventually becoming northerly. Could see brief heavier rainfall rates with the shower activity positioned along the front, before drier air eventually fills in behind the boundary. Lake moisture flux complicates the drying/clearing rate, but should eventually see an aggressive decrease in cloud coverage overnight to reach a SKC condition. Gusts also drop-off nocturnally as stabilization occurs in tandem with the departure of the stronger low-level wind field, while prevailing speeds appear slightly slower to respond. High pressure builds rapidly from The Plains to Appalachia on Saturday ensuring a low cloud fraction, weaker winds, and a shift back to WSW flow.

D21/DTW Convection...No thunderstorms are forecast today or tonight.

DTW THRESHOLD PROBABILITIES...

* Medium for ceilings at or below 5,000 feet today and through the first half of tonight.

* Low in crosswind thresholds being exceeded today.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Freeze Warning from 3 AM to 8 AM EDT Saturday for MIZ047-048-053- 054-060>062.

Frost Advisory from 3 AM to 8 AM EDT Saturday for MIZ049-055-063- 068>070-075-076-082-083.

Lake Huron...Gale Warning until 4 AM EDT Saturday for LHZ361>363-421-422-441>443- 462>464.

Lake St Clair...Gale Warning from 7 PM this evening to 4 AM EDT Saturday for LCZ460.

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