textproduct: Detroit/Pontiac

KEY MESSAGES

- Dry and pleasant weather conditions will persist into Wednesday.

- Areas of dense fog are forecast Monday and Tuesday mornings.

- Rain chances increase during the latter half of next week with cooler temperatures expected.

DISCUSSION

Deep layer subsidence across Lower Mi will persist through Tuesday as a broad ridge hold in place. The departure of the upper low over the Mid Atlantic across New England on Tuesday and height falls across the Upper Midwest will actually amplify the mid level ridge across Lower Mi, which will only strengthen the subsidence. Forecast mixing depths on model soundings and probabilistic temperature data suggest a continuation of afternoon high temperatures in the low to mid 70s Monday and Tuesday, while the large scale subsidence will support abundant afternoon sunshine. Late night and morning fog will be the primary forecast concerns the next few mornings. NNE flow off Lake Huron will persist through tonight. Given the response off the lake this morning and considering dewpoints across the region are a few degrees higher than yesterday, another stratus/fog plume off Lake Huron and Saginaw Bay is forecast to develop tonight/Monday morning. A little stronger winds atop the nocturnal inversion and slight backing of the winds toward the north may advect the stratus/fog layer farther south into Metro Detroit. The low level wind fields will be much weaker Mon night/Tuesday morning as high pressure settles overhead, reducing the risk of advective fog. However, residual moisture in the nocturnal boundary layer capped by ideal radiative cooling potential will raise the risk of pure radiation fog development.

Phasing of a southern stream long wave trough with the remnants of Hurricane Polo will transport a tropical moisture plume into the southern and central high plains Tuesday and will increase moisture advection into a low to mid level frontal boundary forecast to progress across the Upper Midwest and Great Lakes region in the Thursday to Friday time frame. The front will be driven across the region in response to the northern stream wave tracking across nrn Ontario. Differences in amplitude and timing of this wave leads to large spread among the model ensembles in timing the frontal system across Lower Mi. Trends in the latest probabilistic guidance are supporting a later timing, leading to higher chances of an all out dry and warm day Wednesday. The potential for good frontal dynamics within the high theta e axis along the front will support a good chance for rain. Within the latest probability space, that is expected sometime in the Thursday to Friday time frame. High spread in ensemble 24 hour forecast QFP values (ranging anywhere from a quarter inch to 2 inches) is a result of the variation in ensemble members as to how progressive this front will be across the southern lakes.

MARINE

High pressure now situated over the Great Lakes will hold through Tuesday. Some periodic wind gust potential around 20 knots will be possible across southern Lake Huron this evening. Otherwise, wind gust potential to or below 15 knots is expected for most locations. Wind direction will mainly hold from the north to northeast with high pressure in place. A warm front will then move through on Tuesday which will shift wind direction from the south to southwest. This will also bring the next chance for some rain showers or thunderstorms Wednesday and Thursday.

PREV DISCUSSION

Issued at 1259 PM EDT Sun Sep 27 2026

AVIATION...

Fog potential late tonight into Monday morning remains the main aviation concern; otherwise clear to mostly clear skies will be the rule. Dense morning fog at FNT and PTK finally dissipated late in the morning/around noon. However, surface dew pts remain elevated in the 50s (2-5 degrees higher compared to 24 hours ago). Low level northeast flow off Lake Huron will persist through tonight. However, the actual flow at the surface looks to become a bit more north- northwest, which adds uncertainty on the areal extent of the expected fog, as it may be more confined to the Thumb region. With support from LAMP guidance, confidence in dense fog is highest at FNT once again, with some potential at both MBS/PTK. Confidence in fog developing over the southern tafs remains low, so mention has been left out.

D21/DTW Convection...No thunderstorms forecast through the TAF period.

DTW THRESHOLD PROBABILITIES...

* None

DTX WATCHES/WARNINGS/ADVISORIES

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