AVIATION

A moisture plume off Lake Erie under SSE low level flow over the last couple hours has caused an area of advective fog across metro airport and up into PTK. Given the depth of the fog layer per recent satellite imagery, the fog and low cloud deck should lift between 13 and 14Z. Following the erosion of the morning fog/low cloud deck, only a few mid and high based clouds are expected through the rest of the day. This will be due to the very dry air just above the shallow nocturnal stable layer. The broad sfc high centered over the Mid Atlantic today will maintain a weak gradient across the Great Lakes, supportive of just light south winds during peak afternoon heating.

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

DTW THRESHOLD PROBABILITIES...

* Moderate in ceilings/visibilities aob 200 feet and/or 1/2 SM for the first couple hours of the TAF period this morning.

PREV DISCUSSION
Issued at 511 AM EDT Wed Sep 11 2024

DISCUSSION...

Expansion of shallow, ground based fog is likely through daybreak this morning with Southeast Michigan influenced by calm winds and mainly clear conditions. Through 3am, fog has been reported in the usual, rural sites with satellite imagery showing most prevalent development over the eastern Thumb downwind of Lake St Clair. Will issue a Dense Fog Advisory for those counties impacted here early this morning. Will update the forecast as needed.

Poorly organized shortwave energy associated with the convergence of a modest 30 knot southwesterly low level jet will remain progressive and track through the northern Great Lakes today. Plan view of isentropic surfaces show little in the way of an upright frontal surface across Lower Michigan. The best support for light shower activity appears limited to direct moisture advection in the 650- 500mb layer for areas north of the forecast area. In vicinity of Saginaw Bay and southward, latest forecast information keeps very dry air in the lowest 10.0 kft agl and very strong static stability between 2.5-8.0 kft agl. Will maintain a dry forecast for today with some coverage of high cloud particularly in the northern cwa. Highs in the lower to mid 80s.

Very deep upper level ridging will build over the central and eastern Great Lakes Thursday through this upcoming weekend. Latest indications are that a ridge centroid of H5 heights at 588-591dam will center over northern Lake Michigan Thu/Friday before flanking and accentuating as a dipole to tropical remnants from Francine.
High confidence in a blocking ridge and very pleasant late Summer/early Autumn conditions. Warm daytime temperatures in the lower to middle 80s and lows dropping to around 60 degrees right through next Tuesday.

MARINE...

High pressure drifts from the eastern Great Lakes into New England today where it will remain stalled through the rest of the week. A weak trough passing over the northern Great Lakes this morning brings a slight increase in southerly winds to around 15 knots today as well as a slight chance for light showers in the north.
Otherwise, dry conditions will be maintained through the week as a ridge extends west from the New England high and encompasses the Great Lakes. This offers favorable marine conditions with winds predominantly out of the south at 10 knots or below. More of an easterly wind component is then likely by Friday and Saturday as the remnants of Tropical System Francine reach the lower Ohio Valley.
This system currently looks to stall well to the south, with the ridge holding locally through the weekend.

DTX WATCHES/WARNINGS/ADVISORIES
MI...Dense Fog Advisory until 9 AM EDT this morning for MIZ049-055-062- 063-068>070-075-076.

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