024
FXUS63 KDTX 222020
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
320 PM EST Sat Nov 22 2025

.KEY MESSAGES...

- Mainly dry conditions this weekend, aside from a low chance for a
  shower late tonight.

- Breezy conditions develop Sunday with northwest winds gusting 25 to
  30 mph.

- Periods of rainfall possible late Monday through Wednesday with
  above normal temperatures.

- Colder air and lake effect snow showers ensue late Wednesday
  through Thursday, and possibly into the weekend.

&&

.DISCUSSION...

1019 mb surface high pressure extension exits southern Lower
Michigan this evening, resulting in a return flow configuration. The
departure eventually shifts winds southwesterly as upstream low
pressure works southeast across central Ontario, strengthening the
local surface pressure gradient. A mid-level speed max accelerates
across the Upper Midwest tonight, driving the system`s cold front
through the region. FROPA timing remains focused between 06Z and 12Z
Sunday, then surface winds veer zonally. 12Z/18Z NWP consensus
maintains a predominantly dry passage, in spite of low-level pre-
frontal ThetaE advection. A few solutions indicate potential stripes
of measurable QPF, generally over The Thumb and along the I-94
corridor. This conditional activity would be coincident with the
realized moisture transport maxima, limited by the degree of
subsidence drying within the column, particularly through the mid-
levels. Given the variability in possible coverage of sparse light
rainfall, opted to withhold any PoPs for rain or sprinkles late
tonight.

Geopotential height rises ensue Sunday as southern stream ridging
begins to mesh with a longer wavelength ridge axis over the upper
Mississippi basin. Despite the post-frontal airmass and northwest
flow, the 0C 850 mb isotherm bisecting Southeast Michigan lifts
northeastward into Lake Huron throughout the day. This helps boost
high temperatures several degrees above climatological averages,
into the upper 40s to lower 50s. Meanwhile, a 125+ knot jet streak
(at 300 mb) slides over Lower Michigan as a shallow mixed-layer
develops within the surface to 2 kft layer. Forecast soundings
depict a favorable environment (steep lapse rates) leading to a
period of 25-30 mph afternoon gusts. Lower column anticyclone rolls
through the Ohio Valley Sunday night backing surface flow southerly.

Mild conditions persist into Monday as confluent southwesterly sub-
800 mb flow trajectories moderate thermodynamic profiles. Similar
temperature trends to Sunday, perhaps a degree or two warmer.
Looking west to an occluded low currently rotating toward the Baja
Peninsula, the system ejects and tries to open up across The Rockies
Sunday and into Monday. Instead, the wave becomes much sharper with
a jump in ageostrophy as it deepens toward the lee side. Benign
conditions for the forecast area expected during the daylight hours
while top-down saturation gets underway. The closed low finally
opens up late Monday night as it releases, responding to a
progressive northern stream Pacific trough digging into the High
Plains. CVA should accordingly move into Lower Michigan late Monday
night, providing the basis for an initial period of scattered (rain)
showers.

More substantial moisture advection occurs with system-relative
isentropic ascent Tuesday morning, helping showers fill in more
broadly across the CWA. Climatologically mild conditions linger on
Tuesday with MaxTs in the low (perhaps mid) 50s. The northern stream
surface reflection undergoes rapid intensification Tuesday night,
emerging as a 995 mb surface low over Lake Superior by Wednesday
morning. Although the system`s precipitation shield should largely
be confined to northern Michigan, its cold front eventually works
through southern Michigan with a stark change in readings on
Wednesday. Thermal troughing then takes residence over the Great
Lakes for the latter half of the week. This activates Lake Michigan
where the bulk of surface temperatures reside in the lower 50s.
Periods of lake effect showers are likely late Wednesday and into
the weekend. One interesting indicator with this setup is that prior
to settling into WNW-NW flow on Thursday, models indicate lake
effect band persistence into Southeast Michigan in the midst of
zonal low-level flow.

&&

.MARINE...

&&

.PREV DISCUSSION...
Issued at 1241 PM EST Sat Nov 22 2025

AVIATION...

Wind direction will become westerly this afternoon and continue to
back towards the south this evening in response to the departing
high and increasing influence of the Ontario low pressure. Wind
speeds during this time should still hold below 10 knots through the
evening while coverage of mid and high clouds increases. The arrival
of a warm front will quickly be followed by a cold front and lead to
a period of MVFR ceilings spreading across the terminals from NW to
southeast toward early tomorrow morning. Post frontal winds will
veer winds back towards the W-WNW early tomorrow morning with gusts
expected to increase to 20 knots or greater within a couple hours
after sunrise and continue into the afternoon. Ceilings improvements
expected by late tomorrow morning and afternoon as clouds start to
scatter out.

DTW THRESHOLD PROBABILITIES...

*  Moderate for ceiling 5000 ft or less late tonight and tomorrow
   morning.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Warning from 7 AM to 4 PM EST Sunday for LHZ361-362.

     Small Craft Advisory from 1 AM to 4 PM EST Sunday for LHZ421-441.

     Small Craft Advisory from 7 AM to 4 PM EST Sunday for LHZ422-442-
     443.

Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

DISCUSSION...KGK
MARINE.......SF
AVIATION.....AA


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