020
FXUS63 KDTX 090900
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
400 AM EST Tue Dec 9 2025

.KEY MESSAGES...

- An active mid-week stretch begins this morning with a fresh coating
  to 1.5 inches of new snowfall, locally up to 2 inches.

- Areas of light freezing rain/drizzle on top of new snow possible
  midday as temperatures rise above freezing.

- Snowfall resumes tonight, then changes over to mostly rain for the
  majority of the region early Wednesday morning.

- A Winter Weather Advisory is now in effect tonight through
  Wednesday afternoon from M-46 north where new snowfall totals of
  3-5 inches are expected.

- Colder air returns Wednesday evening.

- Daily snow chances exist from Thursday onward.

- The next arctic airmass arrives over the weekend with potential for
  sub-zero morning wind chills.

&&

.DISCUSSION...

A very complex and thermodynamically sensitive setup commences this
morning due to two multi-faceted wintry clippers affecting Southeast
Michigan during the next 36 hours.

The speed max tied to the first of clipper system is currently
digging through Wisconsin based on GOES vapor imagery (Channel 9).
Preceding adiabatic ascent-driven snowfall has quickly filled in
over Southwest Michigan early this morning. This wave of snowfall
expands across the rest of the state (from west to east) over the
next several hours, leading to minor accumulations for the forecast
area. Latest consensus model data shows consistency in a fresh
coating south of I-94 to around 1.5 inches further north by midday.
Isolated totals up to 2 inches are possible across the northern half
of the CWA (north of M-59). This upper bound is contingent on the
appropriate balance between peak moisture advection and proximity to
track of the VortMax. Hi-Res guidance differs from most global
solutions in handling the axis of maximum QPF (greater than 0.20
inches). Generally, the coarser models are more bullish across The
Thumb region, while the CAMs are more dispersive throughout the
northern half (to even two thirds) of Southeast Michigan. Most of
the event snowfall should occur along the front-end of system,
between 07Z and 17Z. The bulk of the fluffy snow accumulations will
occur during a 2-4 hour period with peak rates between 0.25 and 0.50
inches per hour.

The area of lowest expected snow totals, Washtenaw, Lenawee, and
Monroe Counties, will also be the most susceptible to a period of
light freezing rain/drizzle. Drier and warmer westerly mid-level
flow (as addressed in the last several discussions) will erode ice
nuclei and frozen hydrometeor concentrations by midday. Lower column
forcing weakens by then, therefore lingering 2-3 kft stratiform
cloud depths should only be capable of inconsequential freezing
drizzle atop fresh snowpack. FRAM data is lean on ice QPF which
justifies minimal coverage of measurable ice accretions. Assuming
the southern three counties receive even just a thing coating of new
snow this morning, they should be spared of transportation impacts,
especially once 2m temperatures climb above freezing. In the lower
likelihood scenario exhibiting a lack of accumulating snow and a
slower rise in temperatures above freezing, there could be minor
travel concerns.

Given forecast totals at/below 2 inches, and negligible icing
amounts, no headlines were issued for today`s clipper. Note that
areas of light icing (up to a thin glaze) are also be possible
northward, up to the I-69 corridor.

As for tonight into Wednesday, QPF has generally trended upward with
broader coverage of higher snow accumulations, attributed to a
second clipper system that follows in quick succession. Lots of
variability in modeled snow amounts relative to minute differences
in latitude before the system`s cold front clears through, roughly
between 15Z and 18Z. A preference toward snow as the dominant
precipitation type (compared to rain) is evident in the latest model
adjustments, revealing potential for the highest event totals over
the central portion of the forecast area. However, this setup is
highly sensitive to the track of the surface low and its
accompanying warm advection belt. Southwest flow tonight might allow
lows to hold above freezing along the Michigan/Ohio border. A
changeover to rain is then expected to bleed northward early
Wednesday morning after earlier re-saturation aloft degrades. As
this process unfolds heading into sunrise, locations that cling to
snow longer will see a drop in SLRs amidst 33-34F snowfall.

A Winter Weather Advisory has been issued for tonight through
Wednesday afternoon from M-46 north where new snowfall totals of 3-5
inches are expected. This grouping will be aided by the lowest
probability to changeover to rain, prior to the passage of the cold
front and related cold advection. Although the included counties
will be offset from the QPF bullseye, the preservation of snow
throughout the second clipper event should lead to the highest
overall snowfall totals. This assumption relies on forecast
thermodynamic profiles holding relative to the positioning of the
baroclinic zone. Short-notice adjustments to headlines may be needed
later today to expand the advisory southward should the warm sector
progression underperform. Even just an hour or two of partitioning
peak QPF to snow (instead of rain) between M-59 and M-46 could lead
to a spike in snowfall totals worth of an advisory.

Post-frontal airmass could spur a few flurries, but conditions
should largely dry out Wednesday evening with temperatures falling
back below normal into the extended forecast period. Some lake
effect snow will be possible Thursday, but low-level cyclonic flow
trajectories are not favorable for widespread lake effect for
Southeast Michigan. Still some solutions that brush a third clipper
past southern Lower on Friday, and latest NBM PoPs reflect this. The
next release of arctic air slams in Saturday with a drop-off in 850
mb temperatures and potential for sub-zero morning wind chills each
morning.

&&

.MARINE...

A warm front is lifting through the Central Great Lakes this morning
producing snow. 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.  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 over the nearshore waters and some
ice development, it may be just enough to limit mixing and keep
gusts to gales less than 3 hours. 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 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 1146 PM EST Mon Dec 8 2025

AVIATION...

Dry easterly feed around surface high pressure north of Lake Huron
will support gradual deep isentropic downglide through much of tonight.
Prevailing VFR conditions are expected through approximately 09-10z.
Clipper system will then track into Lower Michigan directing lift
and absolute moisture advection across the taf sites primarily in the
10-16z time window Tuesday. Forecast soundings support snow
throughout much of the precipitation period with heaviest LIFR
activity expected at the northern taf sites. Forecasted moisture
profiles suggest that deep moisture will strip out of the midlevels
at/after 16z which will bring a potential for freezing drizzle. Very
low confidence exists that fzdz will be observed but did maintain the
inherited prevailing group at DTW. Could very well be manifested as
a br/mist. West winds will then breezy in the afternoon and should
keep conditions locked in at MVFR before some potential for ceilings
to lower with nocturnal cooling Tuesday night.

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...Winter Weather Advisory from 10 PM this evening to 4 PM EST
     Wednesday for MIZ047>049-053>055.

Lake Huron...Small Craft Advisory until 4 AM EST Thursday for LHZ421-422-441>443.

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

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

&&

$$

DISCUSSION...KGK
MARINE.......SF
AVIATION.....CB


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