242
FXUS63 KDTX 180344
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1144 PM EDT Mon Aug 17 2026

.KEY MESSAGES...

- Dry and seasonable conditions persist through Tuesday.

- A low chance of showers and thunderstorms starting late afternoon
Tuesday across the Saginaw valley and thumb, with a greater
potential for showers with isolated thunderstorms for all of
southeast Michigan Tuesday night.

- A few lingering showers possible early Wednesday, then turning
drier again with temperatures slightly below normal for the end of
the week.

&&

.AVIATION...

Horizontal convective rolls combined with lake breeze boundary
convergence has led to a higher based BKN cumulus deck at the
Detroit terminals late this afternoon. Cloud coverage will wane
quickly with the loss of daytime heating. A relatively dry low level
easterly flow will persist throughout the taf period underneath
subsidence and very dry air between 6.0 and 18.0 kft agl. Just
looking at a possible broken cumulus deck at 5.0 kft agl Tuesday
afternoon.

D21/DTW Convection...No thunderstorms are anticipated throughout the
taf period.

.DTW THRESHOLD PROBABILITIES...

* Moderate for ceiling at or below 5000 feet Tuesday afternoon.

&&

.PREV DISCUSSION...
Issued at 223 PM EDT Mon Aug 17 2026

DISCUSSION...

Drier and slightly cooler post-frontal environment will continue to
settle across Southeast Michigan through the overnight period as a
diffuse bubble of high pressure builds under weak zonal flow aloft.
Any lingering lower stratus will rapidly scour out during the
evening hours as greater drying takes hold. With lighter northerly
to variable winds at the surface and clearing skies, efficient
radiational cooling will allow overnight lows to drop into the upper
50s across the northern Thumb and rural corridors, while urban areas
around Metro Detroit hover in the lower 60s. Shallow patchy fog
cannot be ruled out in localized low-lying areas, though low surface
dewpoint depressions should limit widespread visibility impacts.

Tuesday starts off with dry conditions and ample sunshine as high
pressure lingers over the Great Lakes. Light surface winds will turn
southerly to southwesterly around 10 to 15 mph by afternoon,
initiating weak return flow moisture advection. High temperatures
will reach seasonable averages in the lower to mid-80s. Dew points
will gradually creep back up into the lower 60s ahead of the next
incoming disturbance. An upper-level wave traversing northern
Ontario will drag a mid-level trough and accompanying surface cold
front into Northern Lower Michigan late in the day, expanding across
Southeast Michigan toward 00z. As forcing increases along the
frontal boundary, scattered showers and embedded thunderstorms will
push in from the northwest through the overnight period. Modest
elevated instability will build ahead of the front. While severe
organized convection is not favored due to marginal thermodynamic
support, isolated stronger storms with brief downpours and gusty
winds remain possible. Overall coverage diminishes from north to
south late Tuesday night into Wednesday morning. A smaller window
may emerge Wednesday afternoon for shower production, mainly in the
thumb, as a secondary front slides through as more notable height
falls commence late in the day.

Broader mid level troughing to govern conditions to finish the work
week. This occurs atop another sprawling area of high pressure. This
ensures dry and stable conditions both Thursday and Friday. Resident
thermal profile marked by 850 mb temperatures of 10-12C. This will
keep boundary layer temperatures seasonable to slightly below late-
August normals. Stronger mid level wave digging into the mean trough
will offer the next opportunity for unsettled conditions Friday
night into the upcoming weekend.

MARINE...

Diffuse region of high pressure now established over the Great Lakes
will support light winds for the remainder of the day. As this high
pressure system washes out east of the region, this will allow
southwest flow to become established for most locations tomorrow.
Winds generally remain light with this transition to southwest flow,
but localized stronger gusts around 20 knots will be possible
through the Saginaw Bay given the more favorable fetch.

More active weather returns tomorrow afternoon through tomorrow
evening with the passage of a cold front. Showers and thunderstorms
will be likely with the passage of the front as winds veer from
southwest to northwest in the wake of the front. A slight uptick
in winds are expected along and behind the front as cooler
conditions filter in. Wind gust of 20 to 25 knots will be likely
with the frontal passage.

&&

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

$$

AVIATION.....CB
DISCUSSION...MR
MARINE.......AM


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