340
FXUS63 KDTX 092251
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
551 PM EST Sun Nov 9 2025

.KEY MESSAGES...

- A Winter Weather Advisory has been issued for St. Clair and Macomb
County through Monday morning. This is in addition to the existing
advisory for Bay, Saginaw, and Tuscola Counties that continues
through this evening.

- An additional 1 to 4 inches will be possible in the advisory
areas, with a narrow axis of higher amounts possible. Elsewhere,
additional accumulations range from a dusting to 2 inches.

- Snow tapers off early Monday morning with a chilly start to the
day expected as wind chills drop into the teens.

&&

.AVIATION...

During the remainder of the evening, the north-northeast flow will
back toward the north. The deep layer moisture will also exit
southward. This will transition conditions to a more purely lake
effect situation by late evening with the greater snow shower
coverage likely occurring east of the terminals. Until then, some
higher intensity snow will occasionally drop visibilities below 2
miles in wet snow at the terminals. As for MBS, the wind field now
appears to suggest the Saginaw Bay snow band has finally shifted
south of the airport. While some residual snow showers may filter
off Saginaw Bay and into FNT and PTK overnight, confidence is not
high enough at this time to include in the TAFs. The depth of the
cold air advancing into Se Mi will hold ceilings VFR based outside
of any lingering snow showers. Some partial clearing late tonight
into the terminals given the north flow trajectories off northern
Lower Mi.

For DTW...The ongoing steady light snow will gradually dissipate
during the first couple hours of the TAF period under deep layer dry
air advection from the north. Lake enhanced snow showers will become
focused east of metro airport tonight.

 DTW THRESHOLD PROBABILITIES...

* High in ceilings aob 5000 feet this evening. Moderate overnight.
  Low Monday.

* High for precipitation type as snow tonight.

&&

.PREV DISCUSSION...
Issued at 416 PM EST Sun Nov 9 2025

DISCUSSION...

Broad area of light snow has persisted across SE Michigan for most
of the day, with minor accumulations noted at the DTX office and
around the CWA. Warm ground and air temperatures hovering between 32-
35 degrees have confined majority of accumulations to
elevated/grassy surfaces, although as temperatures begin to fall
with sunset some slick spots could develop on roadways where
residual moisture exists.

At issuance, the most impressive radar echoes are observed
downstream of Saginaw Bay where a few pixels of 35-40 dbz
reflectivity have been sampled. This is also where we have received
several 3" reports already, which in combination with additional
accumulations will put us at storm totals of at least 3 to 6 inches
by this evening. Should see this band begin to shift east over the
next several hours as a surface trough sinks south through the CWA,
shifting winds to the north and stripping away deep layer moisture.
Most locations downwind of Saginaw Bay will see an additional 1 to 3
inches of snow, although locations right within the convergence axis
may see locally higher amounts in excess of 3 inches by the time the
advisory expires.

Other important forecast update to note is the Winter Weather
Advisory issued for St. Clair and Macomb Counties. Hi-res signal has
been consistent in directing an organized, linear snowband into this
region once the flow shifts to the north late this evening and
overnight. Already starting to see the surface convergence axis take
shape in the advisory area, so it will just be a matter of
redirecting the moisture flux into this area for snowfall rates to
pick up. Decoupling of the boundary layer should further help
organize bands to more of a linear nature through the evening-
overnight hours. Advisory advertises a swath of 2 to 4 inches of
snow accumulation, but there is inherent geographic uncertainty to
these types of lake effect situations. Adjustments to snow
amounts/headlines are possible in both advisory areas as
observational trends are monitored.

Snow will gradually taper off in coverage overnight , followed by a
chilly start to Monday morning with lows in the low 20s and wind
chills in the teens. Any residual moisture on roadways or ongoing
snow showers will have potential to create slick spots during the
morning commute. Column moisture then starts to erode during the
daylight hours as the surface low pulls away from the Ohio Valley
and the upper low drifts into Ontario, leaving a saturated boundary
layer beneath the drying subsidence layer aloft. Precipitation
chances thus become reliant on the lake effect response over Lake
Huron, with PoPs generally hugging the Lake Huron shoreline
propagated by northerly flow trajectories. Impact of drier air and
backing trend to the winds will gradually push the lake response
offshore, transitioning to Lake Michigan moisture flux instead.
Daytime highs Monday expected to be some 15-20 degrees below average
for early November standards, in the low to mid 30s.

Quieter conditions then expected Tuesday as low amplitude ridging
moves overhead the first half of the day. This will quickly be
followed by an equally low amplitude wave embedded within the larger
scale troughing pattern. Strong warm advection precedes the wave,
accompanied by a strong low level jet (50+ knots). Breezy southwest
flow thus develops Tuesday afternoon, with gusts in excess of 30 mph
possible especially toward the Thumb. With WAA mainly occurring in
the latter half of the diurnal cycle, just expecting a moderate
boost to daytime highs (mid to upper 30s) compared to Monday. That
said, 850mb temperatures climb about 5-10 degrees C by Tuesday
evening. The wave tracks across the Great Lakes with little fanfare
as low level moisture quality will be quite poor.

Rest of the week will be characterized by a transition from the
broad troughing pattern to upper level ridging. Temperatures
gradually moderate back toward normal, with highs comfortably
breaking 40 degrees Wednesday onward. A few embedded shortwaves may
engage moisture flux from the open lakes, but overall synoptic
moisture will be lean with these waves to prevent widespread
precipitation chances.

MARINE...

Gusty northeast wind continues through the afternoon while gradually
backing more northerly this evening as low pressure tracks south of
Lake Ontario. Gusts on the order of 25 to 30 kt will be focused
across southern Lake Huron, driving a high wave field with
significant wave heights of 6 to 10 feet through tonight. Small
Craft Advisories remain in effect for the nearshore waters. A few
gusts to 35 kt gales have been reported in the vicinity but have
been isolated and brief thus far. Will continue to monitor the need
for a short fused Gale Warning through this evening. Scattered to
numerous rain and snow showers will continue across the area through
tonight.

Arctic air works in as the system departs the eastern Great Lakes
tonight into Monday. Gusty north wind of 20 to 25 kt gradually backs
to northwest through Monday afternoon with continued lake effect
snow showers. Small Craft Advisories will continue through this
period. A warm front passes through on Tuesday, shifting flow from
the southwest. Increasing stability over the water will keep the
higher magnitude wind aloft from reaching the surface, but there
will be potential for gusts in excess of 30 knots late in the day
Tuesday. Probabilities for gales remain too low for a Gale Watch at
this time. Another cold front moves through on Wednesday, continuing
the active westerly flow pattern with additional chances for showers
into the late week. A period of gales will be possible across Lake
Huron on Wednesday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 10 PM EST this evening for MIZ048-053-
     054.

     Winter Weather Advisory until 4 AM EST Monday for MIZ063-070.

Lake Huron...Small Craft Advisory until 4 PM EST Monday for LHZ422.

     Small Craft Advisory until 10 AM EST Tuesday for LHZ421-441>443.

Lake St Clair...Small Craft Advisory until 4 PM EST Monday for LCZ460.

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

$$

AVIATION.....SC
DISCUSSION...MV
MARINE.......TF


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