947
FXUS63 KDTX 071649
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1149 AM EST Sun Dec 7 2025

.KEY MESSAGES...

- Below normal temperatures continue this week, with the coldest air
expected Monday morning when wind chills drop to or below zero.

- Active weather pattern returns Tuesday with additional
opportunities for accumulating snow, and even some rain (Tuesday
night).

- Abnormally cold conditions settle back in by Thursday with lake
effect snow chances through the end of the week.

&&

.AVIATION...

The region of light snow will exit southeast of the area by 18Z.
Colder and drier air will then advect across Se Mi during the
afternoon within NNW winds of 8 to 15 knots. Model guidance suggests
some lingering and/or redevelopment of MVFR strato cu in the wake of
the region of light snow due to some remnant moisture under the low
level inversion. As cold air deepens during the afternoon/evening,
lifting inversion heights will trend ceilings to VFR. North flow and
continued low level cold and dry air advection is likely to support
partial to full clearing this evening into the overnight.

For DTW...Ongoing radar trends are showing a rapid degrease in snow
coverage and intensity. Nothing more than a few flurries is expected
after 18Z.

DTW THRESHOLD PROBABILITIES...

* High for ceiling at or below 5000 ft today. Low tonight. Moderate
  Monday.

&&

.PREV DISCUSSION...
Issued at 359 AM EST Sun Dec 7 2025

DISCUSSION...

Initial wave of light snow along preceding isentropic upsloping is
starting to work in from the west early this morning. The adjacent
low pressure system and inverted trough axis should hold well to the
southwest, over northern Indiana, and track east across the Ohio
Valley. This setup will lead to minor accumulations by midday.
Snowfall rates are not expected to be overly impressive given
deficiencies in column saturation (lack of sustained supersaturation
WRT ice through the DGZ) and weak dynamic ascent (gradual height
falls). Still, isolated areas of brief moderate snowfall rates,
capable of up to a third of an inch per hour cannot be ruled out,
particularly between 10Z and 14Z this morning. Depth of the
marginally saturated DGZ per forecast soundings (roughly 6-10 kft
AGL) suggests sufficient nucleation and hydrometeor growth aloft to
broadly produce SLRs above climatological averages, likely into the
13:1 to 15:1 range.

Model spread in QPF has decreased significantly as the event horizon
approaches. Deterministic and ensemble agreement is shown for most
areas receiving 0.05-0.15 inches of SWE. The NSSL/GSL CAMs were much
more bullish (up to a half inch of liquid) have fallen into line.
NBM (V4.3) 50th percentile has shown a decrease from most prior runs
over the last 24 hours, now in the 0.5 to 1.5 inch range by 00Z this
evening (90th percentile shows a range of 2 to 4 inches). The higher
totals are mainly expected for the western portion of CWA
(along/west of US-23), but portions of The Thumb could approach 2
inches once the reinforcing shot of cold air (upon a shift to NW
flow) arrives later in the day. Period of shore-parallel winds poses
the best chance for additional accumulations along the southern
Huron coastline. Decreasing cloud cover and stronger anticyclonic
flow from 1032 mb high pressure moving into the Upper Midwest leads
to a chilly night. Lows in the mid single digits to lower teens
(Metro Detroit), modified (warmer) by mild over-lake water
temperatures (Superior/Michigan).

The arctic airmass combined with the last bit of gradient flow will
cause early morning wind chills to approach 0F, possibly slightly
below for areas west (clouds cleared out sooner). The lower
tropospheric ridge passes over Lower Michigan on Monday leading to
subsidence, but mid and upper clouds will be present as shortwave
troughing aloft passes overhead. Highs will be capped in the 20s for
most areas, some 10-15 degrees below seasonal normals.

Active pattern returns midweek with the next quick-hitting system
arriving late Monday night. Model progs reveal a negatively tilted
compact speed-max rolling into the Upper Midwest along a western
CONUS longwave ridge. This VortMax digs into the state amidst
reorientation of the sub-700 mb height field, southwesterly. This
helps advect a plume of moisture into southern Lower heading into
Tuesday morning. Precipitation type concerns have decreased given a
cold onset, therefore snow is favored, even while temperatures lift
above freezing Tuesday afternoon. Most of the snowfall should occur
during the morning hours with the better accumulation potential
further north, closer to the surface reflection. Latest guidance has
a gradient of over an inch north of M-46 to perhaps a coating south
of I-94 where temperatures have a higher chance of lifting several
degrees above freezing by Tuesday afternoon.

The next Pacific wave arrives in quick succession Tuesday night into
Wednesday with a warmer airmass. Temperatures could hold steady near
the freezing mark overnight as the next round of precipitation gets
underway. Latest sounding data shows higher confidence in snow at
onset, switching over to primarily rain late Tuesday night into
Wednesday morning once mid-level dry air strips out DGZ layer
moisture during ensuing zonal flow. While most of the lower column
will be saturated and sub-freezing, a lack of ice nuclei will be the
main factor in the nocturnal change-over. The surface low pivots
across northern Lower Wednesday morning with a trailing cold front
which results in winds veering northwesterly. Some lake effect snow
is possible Wednesday night.

Colder post-frontal airmass and occasionally favorable trajectories
maintain lake effect snow chances through the end of the workweek.
The next release of arctic air is set to arrive Friday night into
Saturday, marked by 850 mb temperatures in the minus teens (Celsius).

MARINE...

Light winds around this morning as a ridge of high pressure has
arrived over the Central Great Lakes. Weakening low pressure
tracking through the Ohio Valley will bring widespread light snow
this morning, trending toward more localized snow squalls over Lake
Huron late in the day 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 will clip the nearshore waters of Lake Huron as winds
veer around, and small craft advisories are in effect late this
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 this afternoon to 10 AM EST Monday
     for LHZ421-441>443.

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

$$

AVIATION.....SC
DISCUSSION...KGK
MARINE.......SF


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.