498
FXUS63 KDTX 291759
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1259 PM EST Sat Nov 29 2025

.KEY MESSAGES...

- A Winter Storm Warning and Winter Weather Advisory are in effect for
  widespread 5 to 8 inches of snowfall starting this afternoon and
  continuing overnight. The heaviest snowfall rates are expected this
  evening.

- Below normal temperatures continue through next week. Highs in the
  20s and overnight lows in the teens will be prevalent from Monday
  onward.

- Light accumulating snow is forecast Monday night and Tuesday
  morning with 1 to 2 inches possible for Metro Detroit and areas
  south.

&&

.AVIATION...

Light intensity snow to spread across the terminal corridor within
the 19 to 21Z window with an increase in snowfall intensity this
evening into tonight. Greatest impact window to ceilings and
visibility will be during the 23Z to 05Z window where snow rates will
be the highest. Expect ceiling heights to fall mostly in the
MVFR/IFR category with brief intervals of LIFR under the more intense
bursts of snowfall. VSBYs fall below 2SM with potential for 1/2SM
under the heavy bursts of snowfall. Predominately IFR ceilings look
to prevail by 06Z tonight and through about 12Z tomorrow morning. Lighter
snowfall expected to persist until around 15Z. Winds out of the S-SE
to around 10-15 knots into tomorrow morning with a veering wind to
the W-WNW mid morning Sunday into the afternoon with gusts picking up
to 20-25 knots.

For DTW... More impactful snow expected this evening bringing
conditions MVFR to IFR in the 23Z to 05Z window. Potential exists for
LIFR conditions and visibilities AOB 1/2 SM during the peak of the
event, most likely between 01Z and 04Z this evening.

DTW THRESHOLD PROBABILITIES...

* High for ceiling at or below 5000 ft by around 20Z and through
  tonight.

* Medium for visibility at or below 1/2 SM late this evening.

&&

.PREV DISCUSSION...
Issued at 1027 AM EST Sat Nov 29 2025

UPDATE...

No changes to the forecast or headlines are planned here at the late
morning update time. 29.12z KDTX raob captured very dry air in the
lowest 10.0 kft agl that will require time to saturate. Snowflakes
have begun to reach the ground at Kalamazoo and Ionia so a
precipitation onset time between 18-21z seems on track. Consensus of
29.12z numerical weather prediction continues to support 0.5 to 0.6
inch total liquid equivalent for much of Southeast Michigan.
Uncertainty does exist with regards to what the liquid to snow ratios
will be observed at, but a general 5 to 8 inch snowfall forecast
highlighted in the Winter Weather Message continues to be reasonable.

PREV DISCUSSION...
Issued at 422 AM EST Sat Nov 29 2025

DISCUSSION...

A Pacific wave is emerging over the Rockies this morning, digging
into the central Plains and producing widespread snow over the
Midwest. This snow will spread into the local area this afternoon
through tonight as the wave contracts and lifts into the Great
Lakes. Elevated isentropic ascent is already underway this morning,
evidenced by the high cloud moving in on IR imagery. This marks the
beginning of a top-down saturation process that should bring the
first flakes around or shortly after noon, with increasing rates
late afternoon into the evening. Temps will briefly rise toward 32F
this afternoon but will stay below freezing once steady snow begins,
so melting is not anticipated at the onset.

A number of factors contribute to synoptic and mesoscale ascent with
this system, offering high confidence in impactful snowfall and
periods of heavy rates this evening. A corridor of PVA targets Lower
MI late this afternoon and evening, while the coupled upper jet
induces a broad area of upper divergence supportive of synoptic
lift. System relative analysis indicates deep layer moist isentropic
ascent in the lower to mid levels. The forcing is shown to collapse
into mesoscale processes this evening as sharp frontal forcing
accompanies the inbound mid-level wave. This is noted in highly
unbalanced flow emerging along the 280-310 K surfaces and reflected
in a sharp fgen response that works in from the southwest between 23
and 03z. This marks the peak in the event with rates of 0.50 to
0.75"/hr, possibly approaching 1"/hr in spots, but this magnitude of
forcing should be relatively transient at any given location. Hi-res
models have been targeting areas south of I-94 with the greatest
rates during this period, and HREF snowband probability tracker
offers added confidence in this with some signs that upstream
banding may stay intact into the area.

SLRs are anticipated to be near or slightly below climo at 11 or
12:1 to start the event late this afternoon as the DGZ will be
relatively high at 10 to 15 kft AGL with much of the omega focused
below this level. Higher SLRs (~15:1) will accompany the evening
burst as deeper lift intersects with the DGZ. Afterward into the
overnight, rates will subside but the higher SLRs will persist
across most of the area as the DGZ lowers slightly and
supersaturation wrt ice increases. This should produce
larger/fluffier flakes. The exception will be the far southeast
areas from Monroe toward Mt. Clemens and Port Huron where the warm
advective wing of the inbound low will bring rising temperatures to
the lowest 10 kft which will increase riming, reduce SLRs, and cut
into accumulations. A brief changeover to rain is noted in several
solutions as sfc wet bulb temp creeps to near 33F between 09 and
12z. Otherwise, snowfall will continue through the early morning
hours before ascent begins to wane mid to late morning Sunday.
Additional lake enhanced snow may clip the northern Thumb Sunday
afternoon with up to an additional inch.

Overall, little change to the previous messaging with this system
and no changes to the headlines in place. Widespread 5 to 8"
snowfall totals are forecast across the area over a 15 to 18 hour
period. Areas west of US-23 are the most likely areas to see 7 or 8"
given longer duration of snowfall into Sunday morning and higher
SLRs overnight. Did consider expanding the Winter Storm Warning into
Monroe/Wayne/Oakland where the evening burst of snow brings
potential to exceed 5" in 6 hours for isolated locations. However
based on the latest data with the HREF 6-hr LPMM QPF trending down
from the previous run, this outcome carries low confidence and feel
more comfortable with the advisory currently in place.

Gusty NW flow follows the system on Sunday with gusts of around 30
kt expected through the afternoon. High pressure arrives on Monday
to provide calmer but colder conditions with morning lows in the
teens and highs struggling to reach 30. The next wave in this active
pattern is modeled to arrive late Monday into Tuesday, with the bulk
of the forcing displaced well to our south and east. Light
accumulating snow is still possible, particularly for Metro Detroit
and areas south, where 1 to 2 inches is in the latest forecast. The
next arctic front then brings another chance for lighter
accumulating snow Wednesday night into Thursday.

MARINE...

Light winds to start the day as the region remains under the
influence of departing high pressure. This changes by evening as the
next low ejecting out of the Midwest begins to encroach on the Great
Lakes. Winds organize out of the south-southeast with a steady
strengthening through the late evening hours as the low center
reaches lower MI. While this flow carries some warmer air north,
magnitude is not enough to set up a truly stable overlake thermal
profile allowing a portion of a 50kt low level jet to mix down to
the surface over the southern Great Lakes and southern third of Lake
Huron (roughly south of Port Austin). Gusts tonight for these waters
likely top out around 30kts with a sporadic gust to gale force not
completely out of the question particularly over St Clair/Erie. For
the rest of the central Great Lakes, winds peak closer to the 20-25kt
range. Low is forecast to track northeast directly over Lake Huron
Sunday morning and eventually into the Georgian Bay/Ontario by Sunday
afternoon. This allows a secondary arctic cold front to drop across
the Great Lakes late Sunday afternoon-evening ushering in renewed
cold air advection on NW flow. A sharp increase in northwest gusts
accompany this frontal passage supporting solid potential (60-80%)
for a 4-6hr period of 35kt gusts over northern/central Lake Huron
late day Sunday. A Gale Watch remains in effect for all open waters
north of Harbor Beach as a result. Some occasional gales are possible
over the open waters south of Harbor Beach however given the
northwesterly wind direction, confidence in 3 consecutive hours of
34kt gusts is still too low at this time to include in the watch.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Winter Storm Warning until 10 AM EST Sunday for MIZ047-048-053-060-
     068-075-082.

     Winter Weather Advisory until 10 AM EST Sunday for MIZ049-054-055-
     061>063-069-070-076-083.

Lake Huron...Gale Warning from 2 PM to 10 PM EST Sunday for LHZ362-363-441-
     462>464.

     Small Craft Advisory from 10 PM this evening to 7 AM EST Monday for
     LHZ421-442-443.

     Small Craft Advisory from 10 AM to 10 PM EST Sunday for LHZ422.

     Small Craft Advisory from 10 PM this evening to 2 PM EST Sunday for
     LHZ441.

Lake St Clair...Small Craft Advisory from 7 PM this evening to 10 PM EST Sunday for
     LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 7 PM this evening to 10 PM EST Sunday for
     LEZ444.

     Low Water Advisory from 3 AM to 10 PM EST Sunday for LEZ444.

&&

$$

AVIATION.....AA
UPDATE.......CB
DISCUSSION...TF
MARINE.......KDK


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