857
FXUS63 KDTX 182336
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
636 PM EST Tue Nov 18 2025

.KEY MESSAGES...

- Rain or snow chances will end by the early evening hours.

- Dry conditions with highs mainly in the 40s are forecast Wednesday
and Thursday.

- A low chance for rain or drizzle Thursday night along and behind a
cold front.

- High pressure will move into the region for the beginning of the
weekend.

&&

.AVIATION...

Waning window for light precipitation production over the next
couple of hours as supportive mid level forcing fades. Observational
trends still suggest limited consequence outside of a brief
disruption of visibility should a few pockets of light melting snow
yet materialize mainly from PTK northward. Otherwise, some degree of
low cloud expansion into MVFR/low VFR will occur early tonight
targeting PTK and the Detroit corridor as the governing system pulls
east. Prevailing northeast flow will draw in drier air with time,
but with the trajectory maintaining potential for some degree of
downstream moisture flux off lake Huron. Forecast will outlook a
more prolonged opportunity for lower cloud to persist again mainly
from PTK southward through mid morning. Greater clearing potential
would then occur after sunrise as greater diurnal mixing takes hold
and eradicates any linger shallow moisture. Winds remain light from
the northeast through the period.

DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 feet or less tonight. Low Wednesday morning.

* High for precipitation type of rain this evening.

&&

.PREV DISCUSSION...
Issued at 347 PM EST Tue Nov 18 2025

DISCUSSION...

NWP highlights, corroborated by satellite, that weak 850-700mb
deformation will linger over Southeast Michigan from Grand Rapids to
Detroit this afternoon and into the evening. Models support one last
gasp of some midlevel fgen (850-700mb, 700-500mb) that will release
across the forecast area late this afternoon. This forcing appears to
be timed with the increase in radar returns that is now occurring
over western Lower Michigan. Large scale forcing is generally weak (a
very weak brushing of absolute vorticity advection, no upper level
jet forcing here locally) so it`s difficult to imagine a big increase
in precipitation coverage. Preference was for chance PoPs to slight
chance PoPs. With some upstream presentation suggesting a cellular
structure and organization, rates may be intermittently heavy enough
to still produce some snowflakes. Temperatures will be warm enough
the next 6 hours with a precipitation duration short enough to limit
any impacts.

Midlevel system relative flow trajectories will quickly transition
to anticyclonic after 00Z this evening. This change in flow
direction will cause downward vertical motion and active subsidence
after 04z tonight. Very apparent in the forecast soundings the
strength of the static stability between 4.0 and 10.0 kft agl.
Expecting an aggressive clearing trend before some Lake Huron
cloud/moisture pushes inland from the northeast. There is a solution
or two that suggests some light lake effect precipitation will be
possible in the Thumb Wednesday morning. Decided against any mention
with extremely shallow moisture/lapse rate structure below 2.0 kft
agl. Could be some non-measuring drizzle or freezing drizzle.

Strong 1000-500mb geopotential height rises under confluence aloft
will allow for dominant surface anticyclone over the state Wednesday
and Thursday. Early day Wednesday sunshine will give way to
increasing mid-upper clouds as general midlevel thetae returns from
the southwest. Highs Wednesday are expected to be in the lower 40s
with upper 40s expected Thursday.

An upper level low pressure system over northern portions of Canada
is forecasted to drive a cold front through Lower Michigan Thursday
night. Suppression of thetae by this anticyclone Wednesday and the
subsequent arrival of the cold front is expected to limit deep
moisture return well south of Southeast Michigan ahead of the
Thursday system. Latest model data suite generally agrees with lower
moisture and saturation in the lowest 6.0 kft agl. This lack of
moisture also brings question to the potential for ice nucleation.
Chance PoPs over the land areas for light rain will suffice late
Thursday night.

Differential height rises with Southeast Michigan sandwiched
between split flow brings a good prospect for high pressure and
quiet weather at least the first half of the weekend. Temperatures
this weekend look at or just below normal.

MARINE...

A light rain-snow mix persists through the evening, generally
holding south of Port Huron. Current east flow observations
gradually take on a northerly component overnight as high pressure
fills in. The high then drifts across central Michigan through the
day Wednesday, maintaining light wind speeds and dry weather. Winds
Wednesday night-Thursday organize out of the southwest ahead of the
next cold front which impacts the region during the late week
period. Modest tightening of the gradient in this case brings
sustained winds toward 15-20 knots Thursday-Friday, but overall wind
and wave trends are expected to hold below headline thresholds into
the weekend.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....MR
DISCUSSION...CB
MARINE.......MV

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