088
FXUS63 KDTX 212333
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
733 PM EDT Mon Sep 21 2026

.KEY MESSAGES...

- Extended stretch of seasonably cool conditions will exist into the
  middle of the week.

- Aside from a low chance of rain early this week near the Ohio
  border, dry conditions are expected throughout the week.

&&

.AVIATION...

Deep layer of mid-level subsidence continues to sit atop a moist
boundary layer augmented by Lake Huron moisture. While MVFR cloud
trends observed earlier today have since lifted, there continues to
be the potential for MVFR/low VFR cigs to mix in overnight and into
Tuesday. This is particularly likely beginning early Tuesday morning
as winds veer slightly more easterly which would redirect the Lake
Erie moisture plume toward DTW/YIP/DET. Meanwhile, ENE winds stay
elevated in the 10-15 knot range through the TAF period with gusts
of 20-25 knots returning by mid-day Tuesday.

D21/DTW Convection...Thunderstorms are not forecast today through
Tuesday.

.DTW THRESHOLD PROBABILITIES...

* Medium for ceiling at or below 5000 feet tonight. High Tuesday.

&&

.PREV DISCUSSION...
Issued at 320 PM EDT Mon Sep 21 2026

DISCUSSION...

Broad surface high spread across most of the Great Lakes, Ontario
and Quebec will keep a cool easterly flow across the region through
the bulk of the week. Mid level split flow pattern will help keep
the current conditions stagnate through the week as well. 850mb
temps will hover in the mid-upper single digits setting the stage
for highs in the 60s all week with low dipping into the 40s. The
cool air flowing over the relatively warm waters will open the door
for some cloud cover which would largely affect locations west of
Lake Erie. With clearer skies across Mid MI, could see a gradient in
temps from the low 60s across the south under the blanket of clouds
and upper 60s northward with the additional sun.

A mid level low will ride along the southern stream of the split
flow through Ohio Tuesday night into Wednesday. This will bring
deeper moisture depths back north into southern MI with model
soundings showing saturation layers from 2-10kft with some mid level
deformation just north of the low with low level convergence south
of I94 as well. This is the only period in the week which will
support a chance of precip as once the low passes Wednesday, heights
begin to rise and surface high pressure settle back southward.

Weak troughing over the east coast will strengthen mid week in part
because a mid level wave tracking across northern Ohio phases with
it. Moreso the deepening will occur because the overall longwave
pattern amplifies in response to the next trough coming ashore the
Pacific NW later in the week. This causes the Plains ridge to
amplify and shift over the Great Lakes and stalls the downstream
upper low over the East Coast. This will all result in a gradual
warm up across the region this weekend back into the low 70s with
dry conditions continuing.

MARINE...

Modest northeasterly gradient wind field persists over the central
Great Lakes through mid week as an expansive 30.40 inHg high
pressure system makes little forward progress between Ontario and
Quebec. This translates to elevated wave action for most of the
waterways, therefore, a Small Craft Advisory remains in effect for
all nearshore waters. Afternoon/diurnal contribution to elevated
gusts will be most prevalent over Saginaw Bay, briefly exceeding 30
knots late this afternoon and Tuesday afternoon. Additionally, upper
level energy intersecting a stalled elevated frontal boundary could
offer some sporadic light shower chances over the far southern
waterways (i.e. Lake St. Clair and western Erie) this evening and/or
Tuesday night. A weak low pressure system should emerge over the
northern portion of the Ohio Valley on Wednesday, altering the
pressure and moisture fields. This could lead to slightly broader
coverage of showers for the south-central Great Lakes on Wednesday
while wind speeds gradually start to decline for the latter half of
the week. An extension to the Small Craft Advisories may still be
needed for a subset of the nearshores.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EDT Wednesday for LHZ421-422-
     441>443.

Lake St Clair...Small Craft Advisory until 10 PM EDT Wednesday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT Wednesday for LEZ444.

&&

$$

AVIATION.....MV
DISCUSSION...DRK
MARINE.......KGK


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