textproduct: Detroit/Pontiac

KEY MESSAGES

- The potential exists for dense fog development each of the daybreak periods Friday through Monday. Any fog that will develop is expected to dissipate or lift by 10 am.

- Mild and dry through the middle of next week.

DISCUSSION

An anomalous upper level ridge advancing into central sections of far northern Canada will open the door to the rapid amplification of an Omega Block over the central Contiguous United States for the end of the work week. Upper level high pressure will then stall out and impact the forecast area through Monday of next week. Quite the structure with H3 heights reaching 588 dam over portions of the Lower Peninsula this weekend and +13C 850mb temperatures advecting well into Hudson Bay. Ideal mid Autumn conditions with high temperatures reaching the middle to upper 60s, 5 to 10 degrees above normal, and lows falling into the 40s.

The only weather of significance the next few days will be br and fog chances during the daybreak periods. A better setup for fog will be Friday morning with onshore flow advecting a marine airmass inland. The relatively warm lakes will offer higher dewpoints that combined with weak flow will provide for saturation potential. Surface condensation pressure deficits support fog beginning in the tip of the Thumb tonight before expanding southeastward through all of the area. The fog potential for Saturday morning looks to be the greatest near Lake Erie before expanding westward. Could see a scenario where the Detroit urban heat islands remain just warm enough to dissuade the fog formation. Persistent light easterly wind should bring more fog chances Sunday morning. Will likely add areas of fog in the forecast for tonight/Friday morning and maintain the patchy mention this weekend.

Models suggest the amplitude of the omega will shear off or flatten by Monday. Indications are that a weak cold front could push southward invof Southeast Michigan, however, current data suggests a dominance of anticyclonic flow trajectories that will not favor large scale synoptic ascent. Preference is for a dry forecast through next Wednesday.

MARINE

High pressure influence persists over the central Great Lakes today as a surface ridge begins to build and center over Quebec. Northerly winds veer easterly tonight with speeds generally AOB 10 knots, becoming southeasterly by Friday afternoon/evening. Winds turn southerly into the weekend with a slight uptick in speeds as the stretch of tranquil and mainly dry conditions continue into next week.

PREV DISCUSSION

Issued at 106 PM EDT Thu Oct 22 2026

AVIATION...

High pressure drifts toward Quebec tonight, causing winds to veer from north to southeast by Friday morning. This draws the pool of low level moisture currently to our north and east into the local airspace late tonight into Friday morning. A very dry airmass aloft and calm east winds at the surface affords efficient radiative cooling potential overnight with added moisture from the lakes. The greatest vsby restrictions (possibly falling below 1/4 SM) are expected across the Saginaw Valley downwind of Saginaw Bay. The favorable setup keeps fog and/or low stratus around through mid- morning before diurnal mixing leads to clearing skies by mid-day.

D21/DTW Convection... Thunderstorms are not forecast through the TAF period.

DTW THRESHOLD PROBABILITIES...

* Low for cigs/vsby to fall below 200 ft and/or 1/2SM.

DTX WATCHES/WARNINGS/ADVISORIES

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