Expert Forecast Opinion

124
FXUS63 KDTX 082059
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
359 PM EST Mon Dec 8 2025

.KEY MESSAGES...

- Light snow begins early Tuesday morning, with accumulations ranging
from a dusting near the Ohio border to 2 inches in the Thumb.

- Areas of freezing drizzle possible mid-day Tuesday before
temperatures rise near the freezing mark in the evening.

- Snow returns Tuesday evening before transitioning to a rain-snow
mix overnight; areas along/north of M-46 could maintain all snow
leading to accumulations in excess of 4 inches by Wednesday
morning

- Colder air returns Wednesday evening with a bit of additional light
snow possible, followed by the next arctic airmass heading into the
weekend.

- Periodic lake effect snow chances exist from Thursday onward.

&&

.DISCUSSION...

Main focus of this forecast cycle is an active Tuesday-Wednesday
stretch as a series of clippers dive toward the Great Lakes/Ohio
Valley. The first of these is set to reach SE Michigan during the
Tuesday morning commute, with top-down saturation leading to the
onset of light snow between 09-12z (4a-7a). It will be a chilly
start to the day, with temperatures in the teens and wind chills in
the single digits to ensure freezing p-type through majority of the
morning hours. Maximum ascent is displaced to our north as the
height fall center tracks across nrn MI, with the southern edge of
the height fall gradient clipping the Saginaw Valley/Thumb. Areas
further south rely on deep isentropic ascent for snowfall
production, which ramps up during the morning as system-relative
winds veer ahead of the wave. Main limiting factor with this system
(as is often the case with clippers), is limited duration of deep
column moisture. Slightly longer residence time of deep saturation
is expected in closer proximity to the wave (north of I-69),
affording a better opportunity for 1-2" of dry/fluffy snow while
areas to the south (e.g. Pontiac/Detroit/Ann Arbor) are held to an
inch or less by mid-day Tuesday. Even though overall storm totals do
not reach advisory thresholds, timing of peak snowfall rates (5a-9a)
will occur during the morning commute and will create variable road
conditions and slick spots.

The short duration of deep saturation is attributed to the arrival
of a mid-level dry slot, which strips away moisture from the DGZ and
leaves a shallow ~5.0 kft cloud layer that could generate a few
hours of freezing mist/drizzle mid-day. This comes as temperatures
are warming and ice nucleation becomes less likely aloft. Precip
gradually tapers off through the early afternoon with temperatures
climbing into the upper 20s by noon. Warming temperatures afford
better mixing of the boundary layer to tap into a ~35-40 knot LLJ,
resulting in a breezy afternoon. Southwest gusts of 25-30 mph will
be possible to keep wind chills in the teens for most of the day.

Immediately behind this wave is another clipper system, although
with a more organized circulation in terms of both magnitude and
depth. This wave carves toward the Ohio Valley late Tuesday evening,
with light snow returning to SE Michigan after about 03z (10p Tue
night). With the low tracking along a more southerly path, its warm
front is able to pivot into Lower Michigan overnight and gradually
raise temperatures into the low-mid 30s by Wednesday morning. Fairly
sharp gradient in snow accumulations exists across SE Michigan as a
result, with the 32 degree isotherm generally holding right along
the M-46 corridor (coincident with the forecast track of the surface
low). This low (and the freezing line) however have both trended
south in recent forecast cycles. Main implication of this is that
forecast temperatures are trending colder, and snow totals are
increasing especially across nrn portions of the cwa. The current
forecast calls for 4-6" of wet snow north of M-46, with tapering
accumulations to below 1" near the Ohio border where temperatures
may be aoa freezing at precipitation onset. Pending any dramatic
northward shifts in the track, advisories will likely be needed
across nrn portions of the cwa. Not entirely out of the question to
reach entry level warning criteria either in the far north,
especially along/north of the surface low where banded structures
will be possible in the focused ascent regions of the frontal zone.
This outcome looks more likely over nrn Lower Mi at this time,
precluding any watch issuances with this forecast cycle.

Snowfall tapers off through the day Wednesday as the system drifts
into Ontario and its cold front settles into Lower Michigan. Shift
to north-northwest flow looks to activate Lake Huron/Lake Michigan,
which may provide a window for Lake Huron bands to impact the
shoreline counties Wed night-Thu morning. As usual, this will be
highly sensitive to wind direction. High pressure briefly fills in
Friday, but the wave train remains active with signs for additional
snow and cold lingering into the weekend.

&&

.MARINE...

Light and variable winds around this afternoon as high pressure
remains over the area. However, a quick ramp up in south-southwest
winds this evening and tonight as low pressure tracks through Lake
Superior, dragging a warm front through the Central Great Lakes.
Wind gusts look to reach at least 30 knots across all marine waters,
with brief gales even possible in the 12-15z Tuesday time frame.
Small craft advisories will be issued with this forecast package,
and will be carried right through Wednesday as well. A larger and
stronger low pressure system is then on track to move through Lower
Michigan Tuesday night into Wednesday producing widespread snow and
even rain over Lake St. Clair and Lake Erie. The southwest low level
jet ahead of the looks to be very strong, and low level profiles may
not warm quick enough to stabilize the near water surface. Thus, it
is looking like a short period of gales will occur over western Lake
Erie, with even brief isolated gusts to gales over Lake St. Clair.
On the flip side, with the water temp near freezing and a downward
trend in model wind speeds at the surface, elected to hold on off on
gale watch. As usual with offshore flow nearing gales, there will be
heighten concern for low water conditions across the western basin
of Lake Erie.

Rush of cold air behind the passage of the low will then support
strong northwest winds Wednesday afternoon and early Wednesday
evening. Isolated, brief gusts to gales remain likely, but the cold
advection is exhausted quickly and the pressure gradient relaxes by
Thursday morning. With the short duration and the marginal nature of
the gales, elected not to issue gale watch and just have the small
craft advisories carry right into Wednesday night. The cold airmass
(850 MB temps in the negative lower teens/around -10 C) looks to
persist to close our the work week, supporting moderate winds and
scattered snow showers.

&&

.PREV DISCUSSION...
Issued at 1234 PM EST Mon Dec 8 2025

AVIATION...

Minimal aviation weather concerns in the near term as the region
remains under the influence of high pressure. Cloud cover through
the early evening will be generally confined to cirrus streaming in
from the west. There is a brief (couple hour) window in the process
of winds veering southerly overnight for southeasterly winds to draw
in remnant low VFR (~3kft) stratocu from Lake Erie over the southern
terminals. Coverage is still not expected to be more than SCT
however with this low cloud pushing north of the terminals late
tonight as southerly flow strengthens. Clipper system is then set to
sweep over lower MI Tuesday morning bringing widespread MVFR/IFR
light snow and breezy southwesterly winds. Main accumulating
snowfall occurs mid-morning with the southern terminals seeing an
inch or less with around an inch for FNT/MBS. As snow tapers off
late morning as mid-level dry air arrives, the still saturated low
levels offer a transition to freezing drizzle/mist through early
Tuesday afternoon. Little if any ice accums forecast. Southwest
winds gust 20-25kts most of daytime Tuesday.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 ft through late tonight. High by
Tuesday morning.

* High for initial p-type as snow Tuesday morning before
transitioning to a light freezing drizzle/mist midday Tuesday.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from 4 AM Tuesday to 4 AM EST Thursday for
LHZ421-422-441>443.

Lake St Clair...Small Craft Advisory from 7 AM Tuesday to 4 AM EST Thursday for
LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 7 AM Tuesday to 4 AM EST Thursday for
LEZ444.

&&

$$

DISCUSSION...MV
MARINE.......SF
AVIATION.....KDK


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