929
FXUS63 KDTX 242041
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
341 PM EST Mon Nov 24 2025

.KEY MESSAGES...

- Rain shower chances turn likely tomorrow morning and early
  afternoon.

- Passage of a strong cold front is on schedule for Wednesday
  morning. Westerly wind gusts of 35-40 mph expected, with lower-end
  chances for gusts around 45 mph.

- Lake effect snow showers ramp up Wednesday night through
Thanksgiving Day and linger into Friday. Snowfall totals will be
highly variable, ranging from a half-inch to two inches.

&&

.DISCUSSION...

Shortwave ridging will continue to hold across SE MI through the day
in response to an upper-level wave that has been filling in across
the central Plains. This will continue to promote stable conditions
across the Great Lakes region along with a subtle boost in waa,
enhanced from the return flow of a departing high pressure system.
This has allowed for a nice warm up around 50 degrees this
afternoon, and will hold temperatures right around the 40 degree mark
for the overnight hours. The aforementioned shortwave will open up
and shear out through tomorrow morning as it paths into the northern
Ohio Valley and southern Great Lakes. Light rain showers will bloom
in response to the approaching wave from south to north through
tomorrow morning and afternoon, with projected qpf totals ranging
between .1"-.4" per ensemble guidance, with mean values around a
quarter of an inch of rain accumulation. In the wake of the wave,
mist/drizzle will be possible within this warmer pattern in the
evening and overnight hours as a saturated boundary layer extends
through 5kft.

Attention then turns to secondary upper-level wave now over the
continental northwest that will extend and strengthen across the
Rockies tomorrow morning. Lee cyclogenesis will aid in the
development of low pressure which will then push into the northern
Great Lakes Wednesday morning. Low pressure will strengthen over the
region as the trailing wave catches up, occluding as it pushes into
Ontario and Quebec. The initial response will be a broken line of
rain showers that will develop along a cold front, pushing over SE
MI between 09Z to 15Z Wed. Showers will have the potential to
produce isolated gusts of 35-40 mph. A strong dry slot will fill in
behind this line as the filtering in of cooler air enhances low-
level lapse rates, enhancing mixing depths while subsidence
prevails. Windy conditions develop as a result with wind gusts of 35-
40 mph likely, starting by the late morning hours and lasting
through the day. Gusts to 45 mph cannot be ruled out as mixing up to
50 knots will be possible. All locations will have the chance to
achieve 45 mph gusts, the most probable being across the Thumb,
especially along the Saginaw Bay shoreline with the sw-w flow.

Continuous advection of cooler air will see decreasing temperatures
through the afternoon and evening hour down into the low to mid 30s
by Wednesday night. Steep lapse rates under the backdrop of the
longwave troughing pattern/upper-level wave will bring the return of
rain showers by the later afternoon and evening hours, after the dry
slot has cleared. A fast transition from rain showers to snow
showers will commence in the late evening and night time hours as
temperatures near the freezing mark. SE MI will reside on the
cyclonically sheared side of a 95 knot jet core at 500mb with 0- 3km
lapse rates of 6-7 C/km and large jet field nearing 50 knots at
850mb. This setup, with the warmer waters of Lake Michigan, is very
conducive for generating some widely scattered convective-based snow
showers with potential depths extending through 10kft. This will
bring the potential to see highly localized snowfall accumulation
ranging from a half-inch to 2 inches, favored Wednesday night into
Thursday morning. The best location for any convergence/lake effect
snow banding will extending from west to east through the 696/I94
corridor, which can see some of these higher end snowfall totals.
Additionally, residual moisture on untreated roadways could freeze as
temperatures dip below freezing in spots by Thursday morning.

The pattern also gives way to renewed snow shower chances again
Thursday afternoon and evening, but the signal is not as robust for
any lake effect banding in any one particular location, outside of
the far northern Thumb. Windy conditions continue into Thursday,
where 35 to 40 mph wind gusts continue. Last, the cold air coupled
with windy conditions will have wind chills in the teens by
Thanksgiving morning, and wind chills in the low 20s by the
afternoon. Wind chills in the teens return Friday morning along with
additional lake effect snow shower chances, with snow show chances
ending later in the day Friday.

&&

.MARINE...

Milder air arrives on moderate SSW wind this afternoon that peaks
near 25 kt over the open waters of Lake Huron. This gradually
weakens to around 10 kt overnight and then backs to S and SE on
Tuesday as weak low pressure tracks into the central lakes from the
mid-Mississippi Valley. A band of light rain is likely over northern
Lake Huron overnight, then an additional swath of rain will spread
in from the south through the day tomorrow.

A low pressure system arrives from the Midwest Tuesday night,
deepening considerably as it tracks across the northern Great Lakes
Wednesday into Wednesday night. This system will be responsible for
a long duration gale event and the arrival of the coldest air of the
season so far. A cold front will sweep across the central lakes
Wednesday morning with W to WSW gales in its wake, then a secondary
cold front will shift winds to the WNW to NW by Thursday. There is
high confidence in gales during this period and a Gale Watch remains
in effect for all marine zones. The peak of the event is expected
Wednesday afternoon and evening with gusts reaching 40 to 45 kt
across southern and central Lake Huron including Saginaw Bay. Gales
may be slow to start across northern Lake Huron as the center of the
low tracks in the vicinity on Wednesday, but NW winds will increase
rapidly there Wednesday night after the low passes. 35 to 40 kt
gales will continue through Thursday.

Showers on Wednesday change over to snow with snow squalls likely on
Thursday. Gales gradually subside on Friday but wind remains gusty
out of the northwest with snow showers continuing through this
period. Winds weaken further on Saturday as narrow high pressure
works in ahead of the next system set to arrive by Sunday.

&&

.PREV DISCUSSION...
Issued at 1127 AM EST Mon Nov 24 2025

AVIATION...

South flow is developing in the wake of departing high pressure. The
gradient flow and limiting mixing depths will keep sustained winds
around 10 knots. Ample low level dry air in place will keep skies
clear below 12k feet through the afternoon. Deep layer moisture
advection will commence tonight, resulting in lowering cloud bases
during the overnight. There is reasonable model agreement in showing
a surge in low level moisture in the 12Z to 15Z time frame, resulting
in a rapid drop in ceilings to IFR (with some LIFR) in light rain.

For DTW...A rapid drop in ceilings is forecast between 12Z and 14Z
Tues morning as light rain overspreads the airspace.

DTW THRESHOLD PROBABILITIES...

* High for ceilings at or below 5000 feet Tuesday morning and
  afternoon.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Watch from Wednesday morning through Friday morning for LHZ361-
     362.

     Gale Watch from Wednesday morning through Friday morning for LHZ363-
     421-422-441>443-462>464.

Lake St Clair...Gale Watch from Wednesday morning through late Thursday night for
     LCZ460.

Michigan waters of Lake Erie...Gale Watch from Wednesday morning through late Thursday night for
     LEZ444.

&&

$$

DISCUSSION...AM
MARINE.......TF
AVIATION.....SC


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