991
FXUS63 KDTX 281733
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1233 PM EST Fri Nov 28 2025

.KEY MESSAGES...

- Cold weather will persist through the weekend and into next week.
Wind chills will be in the teens each morning and 20s during the day.

- Widespread accumulating snow is forecast Saturday afternoon into
Sunday morning, with the peak of the event during Saturday evening.
Forecast totals are in the 4 to 7 inch range with the higher end of
the range most likely west of US-23.

- Additional light snow is possible Monday night.

&&

.AVIATION...

Gusty west-northwest winds and diurnal cloud cover have increased
right on cue. Ceilings through the afternoon will be high-based and
above 3kft. Given the deeper mixing and pocket of cooler air aloft,
could see some flurries associated with afternoon diurnal cloud
cover as these ceilings are embedded within the dendritic growth
zone with a small pocket of instability to work with. Later this
evening and through the overnight hours a surface ridge moves
overhead and brings lighter winds to the region. Attention then
focuses on the arrival of winter weather for the latter half of
Saturday. All terminals will see snow late Saturday into Sunday
morning. For now, have introduced mentions of light snow at DTW
around 21Z on Saturday.

DTW THRESHOLD PROBABILITIES...

* High for ceilings at or below 5000 feet through 0300Z this
  evening.

* High for ceilings at or below 5000 feet by/around 2100Z Saturday.

* Low for crosswind threshold exceedence Today.

&&

.PREV DISCUSSION...
Issued at 334 AM EST Fri Nov 28 2025

DISCUSSION...

Cold cyclonic flow remains pervasive across the area today as broad
low pressure slowly treks across Quebec toward the Canadian
Maritimes. Continued WNW wind trajectories will favor advection of
lake cloud and occasional flurries through the first half of the
day. Deep layer subsidence then gains a boost as the upper jet left
entrance region passes overhead, which should promote a clearing
trend later into the afternoon/evening. The thermal trough will be
positioned right over Lower MI with 850mb temp at -13C, supportive
of highs right around freezing. With the persistent 20 to 30 mph
wind, wind chill will top out in the 20s.

A Pacific wave tracking across the PNW this morning will be
responsible for our next bout of winter weather this weekend. This
wave will emerge over the Rockies early on Saturday, producing a sfc
low that tracks from the central Plains northeast across the Great
Lakes Saturday night into Sunday. Synoptically, this is a good set-
up for widespread accumulating snow as the wave drives an area of
PVA directly across the area. Coupled upper jet structure provides
broad upper divergence, while isentropic analysis indicates deep
layer moist system relative ascent from 925 to 550mb as the nose of
the theta-e ridge works in from the south. This ascent will begin to
ramp up Saturday afternoon then peaks during the evening as fgen
contributes an uptick in forcing along the mid-level baroclinic
zone. Precip production will then wind down Sunday morning as the
ascent passes east and drier air begins to work in aloft.

Temperatures Saturday will be rising from around 20 at sunrise to
the lower 30s by the time the precip moves in. Meanwhile the dry
boundary layer will still have dew points in the 20s, favoring all
snow at onset Saturday afternoon. The DGZ will be positioned mainly
between 10 and 15 kft AGL, with the bulk of omega in model soundings
targeting just below this level. This all favors SLRs near or
slightly below climo at around 11 or 12:1 through Saturday evening.
This will be locally higher where any fgen flare-ups occur.
Meanwhile the interquartile range of ensemble QPF is predominantly
between 0.30 and 0.50", but with a small handful of ensemble members
advertising 0.70"+. NBM statistical processes appear to be over
inflating the higher-end QPF probabilities based on a look at the
raw ensemble output. The higher amounts seem anomalous given strong
agreement among guidance of 850-700mb specific humidity peaking
around 2 to 2.5 g/kg and lack of stronger dynamics with this system.
That being said, QPF has trended up slightly the past few model
cycles, so will need to see if this trend continues.

00z ensemble and deterministic guidance are in very good agreement
with the low taking a SW-NE track across Lower MI but some timing
and strength differences do exist, which would affect northward
moisture transport and organization and persistence of the
deformation/fgen response Saturday evening. Adjustments to the
forecast are expected today and tonight. Additionally, the low track
across SE MI does present a possible shorter window for accumulating
snow for far southeastern areas where a changeover to melting
snow/rain is possible by early Sunday morning. At this time there is
high confidence in widespread advisory-level snowfall across the
area, and <50% confidence for >7" totals that would warrant a Winter
Storm Watch with this package. This morning`s forecast will
highlight storm totals of 4 to 7" across most of the area. Higher
totals in excess of 8" cannot be ruled out, particularly west of US-
23, but this outcome carries low confidence given some of the
moisture concerns noted above. Wind will not be a major concern with
this system as the gradient will remain relatively weak as the low
pressure center works in.

Gustier conditions ensue daytime Sunday as cold advection follows in
the wake of the departing system, with gusts topping out around 25
to 30 mph. Lighter snow showers will likely continue across parts of
the area but additional accumulation past noon will be relatively
light. High pressure building into the southern Great Lakes brings
nearly calm conditions Sunday night into early Monday. This paired
with fresh snow cover favors a very cold night with lows dipping
into the teens. 850mb temp progs hover near the 10th climatological
percentile into the early week, favoring continued cold conditions
with highs in the 20s and lows in the teens. Medium range guidance
highlights the next trough working across the Midwest Monday night,
presenting another opportunity for lighter snowfall as low pressure
tracks well to the south and east. There is also fair agreement
among guidance for a lobe of arctic air to surge southward out of
central Canada during the Wednesday/Thursday period, perpetuating
the ongoing cold and active pattern.

MARINE...

Influence of low pressure begins to slowly, but steadily wane
through the morning as the northern edge of Ohio Valley high
pressure begins expanding into the Great Lakes. Gales over the open
waters of Lake Huron taper off by mid-morning with NW flow falling
below 30kts by late afternoon/evening. Region then holds under said
high into the first half of Saturday supporting a brief period of
light wind. Active pattern quickly returns the second half of
Saturday as low pressure coming out of the Midwest is set to track
directly over the central Great Lakes Saturday night-Sunday bringing
widespread snow. In advance, winds organize out of the south-
southeast late day Saturday with peak gusts falling around 20-25kts.
Low reaches the Georgian Bay Sunday afternoon ushering in renewed NW
flow as another surge of arctic air is drawn over the Great Lakes.
Overall window for potential NW gales remains fairly narrow, a 3-6hr
period, Sunday evening/early night due to the weaker low (relative
to Wednesday`s system) as well as a fast progression into
northeastern Canada. Local probabilistic guidance is still holding
with a 30-40% chance to see gusts reach 35kts across the
northern/central waters of Lake Huron.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 4 AM EST Saturday for LHZ421-441.

     Small Craft Advisory until 10 PM EST this evening for LHZ422-442-
     443.

Lake St Clair...Small Craft Advisory until 4 PM EST this afternoon for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 4 PM EST this afternoon for LEZ444.

&&

$$

AVIATION.....JA
DISCUSSION...TF
MARINE.......KDK


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