768
FXUS63 KDTX 170729
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
329 AM EDT Mon Aug 17 2026

.KEY MESSAGES...

- Dry, seasonably average conditions for the early week period.

- Some scattered showers/thunderstorms are possible Tuesday late
afternoon-evening in Saginaw Valley and Thumb. Wider spread showers
cross Tuesday night with the arrival of the next cold front.

-Slightly below normal temperatures from midweek into next weekend.

&&

.DISCUSSION...

Cold front currently residing near Detroit at time of discussion
finishes clearing south of the area early this morning with
satellite obs showing developing stratus over the northern CWA.
Ongoing weak cold advection supports the expansion of this low cloud
across the bulk of the region by mid-morning before diurnal heating
and improving mixing heights gradually scatter it this afternoon.
Cooler airmass (850mb temps 11-12C) in combination with the healthy
coverage of AM cloud cover hold highs right around average in the
low 80s. Similar day in store for Tuesday albeit a few degrees
warmer with sunnier skies to start the day before clouds return late
day marking the arrival of another cold frontal boundary sagging
through the Great Lakes.

Prefrontal trough centered over northern lower MI looks to slide
across northern Lake Huron Tuesday late afternoon-evening with the
Saginaw Valley/Thumb sitting near its southern edge. Favorable
timing within the diurnal window offers several hundred J/kg of
MLCAPE to be in place over the northern portions of the CWA
supporting chances for scattered showers/thunderstorms. Wider spread
rain chances arrive Tuesday night with the frontal boundary itself.
Showers are predominate with isolated thunder given only a few
hundred J/kg of elevated instability available. Bulk of activity
pushes out of SE MI by the daylight hours Wednesday morning though
some lingering pockets of light showers/drizzle are possible through
the morning as the elevated portions of the frontal slope are slow
to vacate.

Cold frontal passage brings a reinforcing push of cooler air as
850mb temps fall to around 10C. As such, slightly below normal
temperatures are favored from Wednesday on with highs in 70s to low
80s and overnight lows in the 50s. Arrival of a respectable mid-
level shortwave from the Canadian Prairie amplifies the upper trough
over the Great Lakes next weekend maintaining slightly below normal
temps as well as offering additional rain chances.

&&

.MARINE...

High pressure is building into the region in the wake of Sunday`s
cold front. The winds have become northwesterly while increasing to
15 to 20 knots with gusts to 25 knots across Lake Huron. The
increased northwesterly winds will reach Lake St Clair and Lake Erie
by morning but gusts should only top out in the 15 to 20 knot range.
The winds increase will cause waves to increase to 3 to 5 feet in
the nearshore zones of Lake Huron thus a Small Craft Advisory has
been issued through this morning. The area of high pressure will
persist through most of Tuesday keeping the northerly flow around
but at tempered speeds. Next chance of thunderstorms comes late
Tuesday with the next cold front.

&&

.PREV DISCUSSION...
Issued at 1149 PM EDT Sun Aug 16 2026

AVIATION...

925mb cold front is poised to push southward through Southeast
Michigan between 06-12z this morning. Low level cold advection will
help steepen near surface lapse rates and lead to MVFR stratus over
all of the area. Given trends this evening did push the onset of the
MVFR cigs back a couple of hours. Cloud is expected to hold into the
day on Monday before rising mixing heights cause ceilings to lift
low VFR .

D21/DTW Convection...No thunderstorms are anticipated at this time.

DTW THRESHOLD PROBABILITIES...

* High for ceiling below 5000 feet tonight and Monday.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until noon EDT today for LHZ421-441>443.

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

$$

DISCUSSION...KDK
MARINE.......DRK
AVIATION.....CB


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.