005
FXUS63 KDTX 101801
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
101 PM EST Wed Dec 10 2025

.KEY MESSAGES...

- A Winter Weather Advisory remains in effect through 4 PM EST for
  areas along and north of M-59 where untreated roadways may become
  slick this afternoon and evening.

- All areas see a transition to snow this afternoon as a cold front
  drops through the area. Additional accumulations remain under an
  inch.

- Snow tapers off this evening followed by colder air leading
  temperatures down into the teens Thursday morning. The rapid drop
  in temperatures may result in slippery evening commute.

- An active pattern continues late this week into the weekend as
  arctic air digs in yet again. There is potential for sub-zero wind
  chill and additional rounds of light accumulating snow.

&&

.AVIATION...

A cold front is actively dropping across the airspace, postioned
between PTK and DTW at issuance. Behind this front, snow has picked
back up to a moderate intensity resulting in cig/vsby restrictions
and minor additional accumulations around an inch or less. Wind
gusts within the frontal zone are also pushing 30 knots with a
northwesterly direction. The front brings in much colder
temperatures to the airspace through the evening, with a rapid
freeze of any residual liquid expected. Trends overnight are drier,
although there is a signal for lake effect streamers from the Lake
Superior-Lake Michigan connection to at least maintain mixed
coverage of MVFR-low VFR and light snow showers over the Saginaw
Valley region. Northwest flow backs to the west by early Thursday
morning, with drier weather and continued MVFR-low VFR ceilings
expected to end the TAF period.

For DTW...Ongoing light rain will pick up intensity as a cold front
drops through the area between 19-21z, with a full transition to wet
snow expected. With temperatures currently in the mid-30s, snow will
melt on contact with warm ground with about a half inch of new snow
accumulation possible by 21z. Light snow tapers off this evening,
but a rapid drop in temperatures into the low 20s is expected with
any leftover liquid on surfaces expected to freeze.

DTW THRESHOLD PROBABILITIES...

* High for ceiling at or below 5000 ft through early Wednesday
  morning. Medium Wednesday morning onward.

* High for precipitation type transition from rain to snow between
  19-21z.

* Moderate for exceeding crosswind threshold from 300-330 direction
  through 00z this evening.

&&

.PREV DISCUSSION...
Issued at 900 AM EST Wed Dec 10 2025

UPDATE...

Some enhanced mid level ascent and slightly cooler temps in the
higher terrain along and just north of M 59 caused some over
achievement on snow totals in this area, with early reports
indicating 3 to 5 inches. With temps now surging into the mid 30s,
light rain and/or pockets of wet snow will prevail through the rest
of the morning. The cold front will push across this area during the
afternoon, causing temps to quickly drop below freezing. This will
lead to worsening conditions on any untreated surfaces and has thus
prompted an expansion of the winter weather advisory.

The advisory will remain in place across the north as light wet snow,
with some possible drizzle, will occur as temps plunge into the
upper 20s. With temps solidly in the mid to upper 30s from Ann Arbor
to Detroit and points south, rain has been the main precip type for
several hours. Given the expected later arrival of the cold air in
this region, no headlines seem warranted at this time.

PREV DISCUSSION...
Issued at 358 AM EST Wed Dec 10 2025

DISCUSSION...

Snow spread rapidly across southern Lower Mi since late last evening
leading to a peak burst progressing from SW to NE across the area.
The heaviest snow is now exiting the M-59 corridor and setting up
across the Tri Cities and northern Thumb at forecast issuance. An all
snow scenario remains focused there while a mix of rain and snow
reaches the I-69 corridor. Snow has or is in the process of changing
to all rain south of M-59 across metro Detroit to the Ohio border.
These observational trends reflect how effective this low pressure
system is at drawing warm air northward to ultimately limit snow
accumulation. The Advisory area is then unchanged with this forecast
update while monitoring the northern reaches of Midland, Bay, and
Huron counties where a short fused Warning upgrade remains possible.
The prospects of single digit snow ratio even that far north is the
deciding factor for holding off on the upgrade for now.

The system has a very dynamic presentation in satellite and radar
imagery making it no wonder that so much warm air is being drawn
northward as it tracks roughly along the I-69 corridor during the
morning. The rain/snow line set up immediately on the south end of
Lake Mi before midnight and has since moved northward/eastward over
AZO/BTL to near LAN and PTK at forecast issuance. This matches up
well with the surface low track combined with model 1000-850 mb
partial thickness that suggest the rain/snow line grazes the I-69
corridor with single digit snow ratio all the way up to M-46. REFS
mean soundings show a substantial rain/snow mix up to FNT with
support from HREF mean precip type while SREF mean soundings are
closer to all snow. At minimum, this supports a sharper single digit
snow ratio gradient north of M-46 into about 10:1 ratio toward the
northern fringe of the QPF axis across northern Midland, Bay, and
Huron counties. The peak snow intensity is definitely Advisory
worthy as strong theta-e advection occurs in a steep lapse rate
environment to focus high rate snow ahead of the low track where
accumulation up to around 6 inches is on target. Totals drop off
into the 2 to 4 inch range south of I-69 toward the M-59 corridor
where mid level instability is promoting a more cellular character
in the pattern leading to a rain/snow shower mix, or just rain
showers south of the M-59 corridor after leaving about a 1-2 inch
accumulation across metro Detroit since midnight.

Strong SW low level jet forced isentropic ascent supports both the
leading pattern of snow while also leading to gusty surface wind
driving mild air into region. Surface temperatures surge into the
upper 30s on SW gusts in the 30 mph range south of the surface low
track to support the full change over to rain. System forcing then
transitions to a deformation zone trailing the 500 mb trough and
along the cold front this afternoon. This transition has a pivot
point just north of Saginaw Bay during the morning and then slides
NW to SE across southern Lower Mi. It is aligned along and behind
the surface cold front both of which bring a switch back to all snow
and about an additional 1 inch of accumulation before exiting into
Ontario mid to late this afternoon.

Colder air rushes back into the Great Lakes tonight through
Thursday, although with a limited lake effect response still
reflected in model data. NW flow around the west flank of the larger
mid level trough is shown to generally carry dry air through the mid
levels for muted convective depth across the Great Lakes. The colder
temperatures end up as the weather highlight as readings drop into
the teens by Thursday morning and only recover into the 20s
representing the next round of arctic air the just deepens during
the late week into the weekend.

MARINE...

Wide spread snow and some rain to the south is ongoing as low
pressure tracks across southern Lower Michigan today. The
southwest low level jet ahead of the low looks to be very strong
(40+ at 925 MB/50+ knots at 850 MB) toward the southern Michigan
border. Still a very difficult call on the near lake surface
stability over over the nearshore waters of western Lake Erie, as
peak south-southwest winds look to be around 12z Wednesday. With the
water temp near freezing over the nearshore waters and surface dew
pts rising into the low to mid 30s, anticipate just enough limited
mixing to keep gusts to gales less than 3 hours, as winds also look
to be more southwest/offshore. 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 in the afternoon
will then support strong northerly winds Wednesday afternoon and
early Wednesday evening. A gale warming remains in effect,
as model data continues to support frequent gusts to marginal gales
over most of southern Lake Huron. 850 MB temps lowering
to -16 C over northern Lake Huron will promote deep mixing and lake
induced troughing, which should keep gusts to gales going over the
open waters of Lake Huron, at least through midnight, before winds
gradually diminish through the rest of the night into Thursday
morning. However, a 500 MB low tracking south along the
Ontario/Quebec border will re-enforce the cold air, and should
maintain sufficient mixing/gradient over Lake Huron to support gusts
in the 25 to 30 knot range out of the northwest during Thursday.
Surface ridge building in for Thursday evening/night will lead to
much lighter winds, which should linger into Friday as a wave of low
pressure track through the Ohio Valley. None-the-less, an
Arctic front is on track to move through Friday night, with
sporadic gusts to gales possible over Lake Huron during the weekend
as 850 MB temps plummet to -20 C, supporting snow squalls and
freezing spray as well.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 4 PM EST this afternoon for
     MIZ047>049-053>055-060>063-068>070.

Lake Huron...Small Craft Advisory until 4 AM EST Thursday for LHZ422.

     Gale Warning until 3 AM EST Thursday for LHZ363-462>464.

     Gale Warning until 11 PM EST this evening for LHZ421-441>443.

Lake St Clair...Small Craft Advisory until 4 AM EST Thursday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 4 AM EST Thursday for LEZ444.

&&

$$

AVIATION.....MV
UPDATE.......SC
DISCUSSION...BT
MARINE.......SF


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