503
FXUS63 KDTX 011942
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
242 PM EST Mon Dec 1 2025

.KEY MESSAGES...

- Light accumulating snow tonight. South of M-59, 1 to 3 inches of
  accumulation expected, with Monroe County seeing the highest total.
  North of M-59, just a dusting to maybe a half an inch.

- Temperatures will remain well below normal throughout the week.
The coldest conditions arrive Thursday and Friday with wind chill
values bottoming out at or below zero.

- Arctic front will bring the potential for snow showers late
Wednesday, with some minor accumulation possible.

&&

.DISCUSSION...

Extremely dry airmass in place over southeast Michigan this morning,
as 12z DTX sounding indicated a PW Value of 0.11 inches, right
around the daily min record.

Thick canopy of high clouds today, coupled with the cold start, has
resulted in temps holding around 30 degrees for the afternoon, a
good 10 degrees below normal.

Still looking a light snow developing this evening/tonight with
decent moisture advection, height falls/upper level PV advection,
and mid level frontal circulation. Top down saturation process may
take much of the evening to saturate the low levels however.
Specific humidity in the 850-700 MB layer still on track to rise to
1.3 g/kg north to 1.75 g/kg along the southern Michigan border.
Despite some of the weak forcing(9-12 hr)/moisture being used up to
saturate the low levels, snowfall accumulations of 1-3 inches are
expected south of M-59. Areas which look to reach 3 inches is Monroe
county and possibly southern Wayne county, as the flow at the sfc to
925 MB is light southeast off of Lake Erie, which should help
accelerate the moistening of the low levels and enhance the qpf a
bit. North of M-59, pronounced surface ridging holding on through
the night, and would expect accumulations a half an inch or less.

Shortwave ridging on Tuesday with the next arctic front still on
track to move through late Wednesday as a strong shortwave/spoke of
energy around the strong polar low near/over Hudson Bay rotates
through the northern Great Lakes Wednesday night. With a little
moisture flux off Lake Michigan and good low level convergence with
the front, do think a line of snow showers will develop. Low level
lapse rates steepen up and some modest cape is generated, which will
flirt with the DGZ. As such, could become a borderline scenario for
snow squalls, as there does look to be 40 knots of flow at 850 MB.
Exact timing of front and magnitude of the cold air sweeping in will
determine. Right now, 850 MB temps progged to drop into the
-15 to -20 C range over the Central Great Lakes Thursday morning,
per 12z Euro. Temps likely hold in the lower 20s during Thursday,
setting us up for mins of zero to 10 above Thursday night. Short
lived warming (but still below normal) ahead of another arctic front
on track to move through for the first half of the weekend, but
uncertainty with the southward push and how fast it washes out.

&&

.MARINE...

High pressure will continue to push off towards the east and away
from the Great Lakes this afternoon, while maintaining light winds
across the southern half of the region.  Over the northern Great
Lakes, persistent southwest flow will continue through tonight as
the broad low pressure system continues to reside over the Hudson
Bay region. A system trailing the high crosses the Ohio Valley late
this afternoon into Tuesday offering light snow chances but
otherwise brings minimal local marine impacts. Next significant
system arrives Wednesday as a strong arctic cold front drops out of
northern Ontario resulting in both strong preceding southwest winds
and trailing northwesterly winds as the coldest air of the season
thus far moves over the Great Lakes. Currently, greatest chances
(~40-50%) at seeing gusts to gales occur during the preceding
southwest aided by longer fetch over the central portions Huron.

&&

.PREV DISCUSSION...
Issued at 1240 PM EST Mon Dec 1 2025

AVIATION...

A VFR mix of mid and high clouds covers SE Mi this afternoon as weak
high pressure is nudged eastward by the next wave of low pressure
entering the Ohio valley by this evening. It brings an area of snow
that is on schedule to spread into Lower Mi this evening and then
last much of the night. The entire terminal corridor sees at least
MVFR restriction for a few hours, although coverage and intensity
will be greater south of FNT where both IFR visibility and ceiling
are expected along with a general 1 to 3 inch accumulation. A few
hours of LIFR visibility carries lower probability of occurrence
this far north but upstream observations will be monitored for later
updates. Accumulating snow ends after 12Z, however a fog component
lingers in the col region between pressure systems and ceiling is
also slow to improve during the morning.

For DTW... Sub 5000 ft VFR is nearby to the north and west and
remains there as cloud layer wind increases from the south this
afternoon. Conditions then decrease rapidly into IFR this evening
with a 02Z snow onset time on schedule and a 2 inch accumulation the
most likely number at DTW. Snow ends around 12Z Tuesday while MVFR
lingers through the morning.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 ft this afternoon, then high this
  evening through Tuesday morning.

* High for precipitation type as snow tonight.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

DISCUSSION...SF
MARINE.......KDK/SS
AVIATION.....BT


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