024
FXUS63 KDTX 171809
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
109 PM EST Mon Nov 17 2025

.KEY MESSAGES...

- There is a chance for rain and snow on Tuesday, mainly south of
the I-69 corridor. Some wintry mix is possible near the Ohio border
Tuesday morning.

- Dry and seasonally cool conditions will prevail Wednesday.

&&

.AVIATION...

A well mixed boundary layer will support northwest winds of 10 to 20
knots this afternoon. Winds will become light and variable tonight.
A wave of low pressure will then bring light precipitation to the
region late tonight and Tuesday. A very high amount of uncertainty
exists when precipitation will begin at the taf sites because a
significant amount of dry air will be in the lower atmosphere
between 7-10 kft agl. The predominate model trend from the 17.12z
suite is to push back the start time of precipitation due to
evaporation. Maintained a Prob30 group for -SN at the southern sites
with prevailing MVFR cig/vsby restriction with a rain snow mix. Did
transition to all rain at DTW during the afternoon. Precipitation
with the elevated warm front is not expected to impact FNT and MBS.

For DTW... Northwest winds of 10 to 20 knots this afternoon. A lot
of uncertainty with start time of precipitation because of dry air
in the lowest part of the atmosphere. Prob30 for light snow between
11-14z with prevailing MVFR rain snow 14-19z. Expecting prevailing
light rain after 19z.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling 5000 feet or less late today. High after 14z
  Tuesday.

* High for ptype of snow after 11z with rain snow mix after 14z.

&&

.PREV DISCUSSION...
Issued at 301 AM EST Mon Nov 17 2025

DISCUSSION...

Persistence of the northwest flow across the Great Lakes today will
continue to sustain some lake clouds across portions of the forecast
area, mainly northeast of a Saginaw to Detroit line. Strengthening
subsidence in the mid levels will lower convective cloud depths,
making it less likely for any residual lake effect showers from
extending into the thumb region like yesterday. A colder airmass
will warrant forecast highs around 40 in the thumb. Warmer thermal
profiles combined with some sunshine will boost forecast highs to
the mid 40s across the southern/western portions of the forecast
area.

A compact mid level low now churning over nrn Utah is forecast to
emerge in the lee of the central Rockies late today and cross Iowa
Tues morning before moving across the nrn Ohio Valley Tues
aftn/evng. The ascent along/in advance of this system will drive a
respectable frontogenetical response in the mid levels. This will be
aided by the ageostrophic response within the left exit region of the
an upper jet max and increased low-mid level flow into the elevated
front, transporting specific humidities up to 4 g/kg into the elevated
front. This forcing is likely to impact the southern portions of the
forecast area as the Saginaw Valley and thumb region will be more
influenced by persistent mid level subsidence and dry air remaining
over northern and central Lower Mi. One of the main uncertainty
points continues to be the northern extent of the mid level fgen
band as several high res solutions barely bring ascent far enough
north to reach into the Ann Arbor and Monroe areas, suggesting the
frontal ascent will be more narrow and farther south. Given the full
ensemble suite and taking into consideration previous forecasts, the
morning forecast package will represent a broader/farther north
solution. This supports high chance/likely pops south of a Howell to
Detroit line and chance type pops north to Flint and the northeast
Detroit suburbs.

As the forcing advances into the southern portions of the area
overnight into early Tuesday morning, wet bulb cooling will be
supportive of snow as the main precip type. There are some solutions
which bring a little bit of an elevated warm layer into the far
south, suggestive of some potential for a little mixed precip.
Toward afternoon, warming boundary layer temps will favor more of a
rain/melting snow situation assuming the mid level fgen persist into
the afternoon/early evening. Some potential loss of ice nuclei
during the later part of the day may also result in light
rain/drizzle. Taking into consideration some of the more northerly
solutions and potential forcing during the morning, minor snow
accums (an inch or less) in the south seem justified at this time.

Broad mid level ridging and associated sfc high pressure will expand
across the region in the wake of the Tuesday system. Dry conditions
with temperatures near climatological norms will prevail Wednesday
into Thursday.

MARINE...

Influence of New England low pressure wanes throughout the day as it
lifts toward Quebec. This allows high pressure to gain traction
locally, causing winds to subside over the course of the day. Small
Craft Advisories remain in effect until this afternoon from Outer
Saginaw Bay to Harbor Beach, mainly due to the lag in wave response.
The next weather system is already over the Rockies and will quickly
eject into the Ohio Valley Tuesday, with its greatest impact being
the chance for wintry precipitation for Lake Erie and Lake St.
Clair. Light winds will take on variable directions as this system
approaches, with a deformation axis setting up over the Great Lakes.
Surface high pressure then settles in for mid-week, but the upper
level pattern remains active introducing uncertainty into the
forecast for the back half of the work week.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 4 PM EST this afternoon for LHZ421-
     441>443.

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

$$

AVIATION.....CB
DISCUSSION...SC
MARINE.......MV


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