421
FXUS63 KDTX 062300
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
600 PM EST Sat Dec 6 2025

.KEY MESSAGES...

- Widespread light snow expected Sunday morning into early
afternoon. Snow accumulations to range between a half-inch to two
inches for most locations.

- Below normal temperatures continue this week, the coldest of which
arrive Monday and Tuesday. Wind chill temperatures drop to or below
zero Monday morning.

- Active weather pattern continues into the midweek period where
additional snow chances will be possible.

&&

.AVIATION...

Low level cold advection in the wake of a weak cold front will
facilitate low VFR to MVFR stratus tonight. A wave of low pressure
will then track out of Iowa through portions of northern Indiana and
Ohio Sunday morning. Plan view of RH progs support low level dry air
holding on across Southeast Michigan including the Detroit terminals
that will require moistening. A combination of isentropic ascent and
absolute moisture advection will bring a chance of light snow to
Southeast Michigan mainly after sunrise Sunday morning. The active
sequence of system relative isentropic ascent with this system
appears to be very brief mainly only lasting in the 10-14Z time
window. Any additional precipitation will then work off of some
absolute moisture overrunning into the state that should become more
increasingly undercut with time. The inherited time period of IFR
light snow remains good. Around an inch of snow is possible for the
southern taf sites. Lesser amounts and KFNT and KMBS. VFR skies
Sunday afternoon with northwest wind of 10 to 20 knots.

For DTW...IFR Light snow will push into Southeast Michigan Sunday
morning. The most likely time period is between 10 and 16z. Snowfall
amounts of around 1 inch possible. VFR conditions Sunday afternoon.

DTW THRESHOLD PROBABILITIES...

* High for ceiling at or below 5000 ft tonight and Sunday.

* High as precip type being all snow Sunday morning.

&&

.PREV DISCUSSION...
Issued at 244 PM EST Sat Dec 6 2025

DISCUSSION...

Weak cold frontal boundary finally pushed east of the region early
this afternoon however lake moisture trapped below the post-frontal
inversion has maintained cloudy skies across lower MI. Despite
ongoing weak cold advection through the evening, this cloud cover
keeps lows a few degrees warmer than they`d otherwise be instead
holding in the lower 20s to upper teens.

Next chances for snow quickly arrive Sunday morning as a weak
shortwave ejecting from the central Rockies reaches the southern
Great Lakes/Ohio Valley. Despite the wave track south of the state
line, areas north of M-59 actually look to start earliest, around 09-
10Z, tied to developing interaction with a northern stream mid-level
trough diving across the northern Great Lakes. Isentropic ascent
fills in across the remainder of SE MI over the morning with all
areas likely seeing light accumulating snow by 12Z. Strongest
isentropic ascent and subsequent peak snow rates trails lead
precipitation by a couple hours arriving closer to mid-morning as
the parent vorticity reaches northern IL/IN. High res models have
begun backing away from earlier hints at potential f-gen banding
keeping rates on the lighter side between 0.1-0.25"/hr (highest in
the south where wave positioning offer greater moisture/forcing). A
potential exception to this northern Thumb where continues to be a
subset of high-res guidance suggesting a convergence axis off the
Saginaw Bay/central Lake Huron enhancing rates. Ohio Valley surface
circulation rapidly weakens over the late morning-afternoon period
as the aforementioned northern stream trough takes over spurring new
surface low development over the eastern Great Lakes. Locally, this
tapers off snowfall by late afternoon. Total accumulations still
look to be on track for 0.5-2" across the CWA though should the lake
convergence axis manifest, areas from Sebewaing to Grind Stone City
could approach 3".

Arctic high pressure follows for Monday bringing a brief reprieve in
the active pattern. The promotion of clearing skies Sunday night as
the high builds in sets the stage for another very cold night with
morning lows in the single digits and wind chills nearing 0 for the
majority of the region. With the ridge axis not crossing the state
until Monday night, thermal recovery is minimal as daytime highs
Monday hold in the mid 20s and Monday night lows fall near 10.

A baroclinic zone is set to linger over lower MI through next week
following the departure of high pressure late Monday allowing a
series of clippers to track near or over the region almost everyday
into next weekend. First of these arrives daytime Tuesday as a wave
passing near the Straits offers light snow accumulations, mainly
over the northern half of the CWA. A stronger, more dynamic
shortwave is then progged to sweep out of the northern Plains and
directly over southern MI Wednesday. This current track allows a
degree of milder air to be partially advected into lower MI which
would support mixed precip (rain-snow) for at least a portion of the
area.

MARINE...

Northwest winds gusting 25-30 knots over Lake Huron this afternoon
will diminish this evening and tonight as a ridge of high pressure
builds over the Central Great Lakes, dropping winds under 15 knots
everywhere. Weakening low pressure tracking through the Ohio Valley
tomorrow will bring widespread light snow Sunday morning, trending
toward more localized snow squalls over Lake Huron late Sunday as
850 MB temps lower into the negative mid teens. Northwest winds
gusting between 25-30 knots appear likely late in the day. However,
winds then look to veer to the north-northeast fairly quickly and
weaken Sunday night as high pressure quickly builds in for Monday
morning. None-the-less, large waves of 6+ feet will build over the
southern Lake Huron. Some of these larger waves look to clip the
nearshore waters of Lake Huron as winds veer around, and have issued
another round of small craft advisories for late Sunday afternoon
into into Monday morning for Outer Saginaw Bay and the nearshore
waters of Lake Huron from Port Austin to Port Huron.

Brief southwest gales possible on Tuesday as low pressure tracks
through the northern Great Lakes. 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 changing
precipitation to rain over Lake St. Clair and Lake Erie. Rush of
cold air behind the passage of the low will support strong northwest
winds late Wednesday and Wednesday evening. Isolated, brief gusts to
gales will be possible, but the pressure gradient quickly relaxes by
Thursday morning.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from 3 PM Sunday to 10 AM EST Monday for
     LHZ421-441>443.

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

$$

AVIATION.....CB
DISCUSSION...KDK
MARINE.......SF


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