AVIATION

Dense fog and low stratus developed in the MI/OH/IN border area during the late night and continues to expand westward leading up to sunrise. High pressure centered from central Lower Mi into eastern Canada is helping nudge this main area of fog/stratus away from the SE Mi terminal corridor with light easterly wind just above the ground. Brief and borderline IFR/MVFR in patchy fog and stratus does however remain possible at all locations as the last bit of nocturnal cooling occurs followed quickly by daytime improvement.
This afternoon, Carolina low pressure moves away from the Great Lakes while supplying just enough low level moisture into remaining easterly flow for a return of scattered cumulus into this evening.
The sky clears tonight with a repeat performance of at least shallow MVFR fog likely toward sunrise Thursday.

For DTW/D21 Convection...No thunderstorms are forecast through this week.

DTW THRESHOLD PROBABILITIES...

* None.

PREV DISCUSSION
Issued at 346 AM EDT Wed Sep 18 2024

DISCUSSION...

Deep layer ridging over the Great Lakes is responsible for continued dry, stable, and warm conditions today through the end of the week.
Remnants of a tropical system and the parent cut off upper low will remain stalled across the Carolinas today with the bulk of its moisture holding well to our south. The main impact will be more boundary layer cumulus that develops today as a tongue of sub-800mb moisture spreads in from the southeast. Otherwise mostly sunny skies will send high temps back to the lower 80s this afternoon. Mainly clear skies follow for tonight, setting us up for another night of favorable radiating conditions and patchy fog around daybreak Thursday.

A pseudo omega block sets up Thursday into Friday as the cut off low and a second deep upper low over the northern Plains maintain an amplified 500mb shortwave ridge directly over the Great Lakes. This favors a persistence forecast with little prospect for air mass advection in this setup. Highs in the lower to mid 80s and lows in the mid 50s to lower 60s will continue to be the norm. Mostly sunny skies likely Thursday but Friday shows signal for higher cloud cover as the northern Plains low sends an elevated front over the region.
This will be largely detached from the surface front that will lag behind until Friday night or into Saturday morning. The parent low will be far displaced over Hudson Bay so the front will be steadily weakening as it moves in and encounters the resident ridge and dry air mass. Still, this front presents our next opportunity for a few light showers Friday night into Saturday.

A pattern shift is looking possible by early to mid next week with the past few runs of medium range guidance advertising the ridge giving way to a 4 Corners low and/or a Pacific trough. Still plenty of details to work out regarding the interaction of these systems but the pattern does support our first appreciable chances for rain in over two weeks. Not surprising at this stage that there is a good amount of spread in temperatures among ensemble members, but the general trend does suggest a trend toward more seasonable temps will be possible.

MARINE...

Persistent surface high pressure situated beneath a split-flow configuration aloft maintains benign marine conditions across the central Great Lakes through Friday, if not Saturday. Light east- southeast winds (generally AOB 10 knots) veer more easterly today as the surface ridge recenters over southern Ontario. Upstream surface low pressure then tracks northeast across central Canada and into Hudson Bay by Friday as its cold front extends well south of the circulation offering low-end potential for showers/storms. Current thinking favors dissipation of activity before anything reaches the local waterways as the boundary is forecast to quickly wash out. The next system emerges over the High Plains Saturday and translates eastward through Monday offering an opportunity for slightly more energetic winds and a non-zero chance for precipitation to close out the weekend. Regardless, no marine headlines are expected through the next seven days.

DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.