407
FXUS63 KDTX 180800
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
300 AM EST Tue Nov 18 2025

.KEY MESSAGES...

- Snow and sleet, changing to rain and melting snow is forecast
today, mainly southwest of a Saginaw to Mount Clemens line. Some
patchy freezing rain is possible around Adrian, Onsted and Chelsea.

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

&&

.DISCUSSION...

A compact mid level low rotating into Iowa this morning will track
across the nrn Ohio Valley late this afternoon/evening and weaken
into an open wave. A swath of rain is ongoing upstream as the mid
level height falls in advance of the approaching low interact with a
lower to mid tropospheric frontal boundary. As this wave progresses
east, the mid level fgen region will advance into the southern
portions of the forecast area during the morning. Of note is the
area of convection along the nose of the low level jet over south-
central IL/ern MO. The strongest low-mid level theta e advection
will progress across the Ohio Valley today along the nose of the
better low level inflow, which will also sustain a good deal of
elevated instability in this region. This will likely force a more
active response along the lower portions of frontal boundary,
generally south of the forecast area. This suggests some degree of
weakening of the response farther up the frontal slope over srn
Lower Mi, mainly this afternoon. These factors suggest precip
expanding into the southern portions of the area this morning, with
an overall weakening trend during the course of the afternoon.

The 00Z DTX sounding showed a formidable mid level dry layer.
Overnight temps across Se Mi are in the 20s, with sfc dewpoints
around 20. While the precip upstream is in the form of rain,
substantial wet bulb cooling will result in precip change over to
snow as it expands across far srn Lower Mi this morning. Model
soundings remain supportive of some slight warming of the column which
suggest some snow pellets and/or sleet. Any freezing rain signal
looks limited, with a little more probability in nrn/cntl
Lenawee/wrn Washtenaw counties. Sfc temps are forecast to rise above
freezing toward late morning. This combined with forecast low QPF
amounts will limit any snow accums to grassy surfaces, primarily
south of a Flint-Owosso to Detroit line. Residual mid level frontal
forcing, albeit weak, will warrant lingering chances for rain and/or
wet/melting snow across the south this afternoon. There are several
high res solutions which show a secondary mid level fgen response
along/south of the I-69 corridor this evening as the mid level wave
tracks into Ohio. This will be worthy of a chance of rain/snow.

Mid level negative vorticity advection and associated sfc high
pressure will expand across Lower Mi from the northwest on
Wednesday. A notable drying trend is forecast overnight into
Wednesday morning. This may even limit the extent of any strato cu
on Wednesday. Despite shallow mixing depths, the expectation for
some sun will push afternoon highs into the low to mid 40s
Wednesday. An upper low forecast to move into northern Ontario from
north central Canada will force a sfc cold front across Lower Mi
Thursday night. A strong confluence in the mid/upper level flow
across the southern Great Lakes is forecast to suppress the deep
moisture pool across the Ohio Valley, limiting the available
moisture along the cold front as it works across Se Mi. The last
several model cycles have trended drier with this front, which is
now being better reflected in the model blends. So only a low chance
for rain is now forecast along the front. Prefrontal warm air
advection on Thursday will allow temps to make a run at 50 degrees.

&&

.MARINE...

Low pressure slides across the Ohio Valley today, with the northern
edge of its precipitation shield lifting as far north as Port Huron
by this afternoon. A wintry mix is possible this morning before
changing to rain during the daylight hours. The resident northwest
flow regime will be dislodged toward more of a north-northeast flow
pattern by tonight as the low departs in favor of a northern stream
high pressure center. This high will gradually drift over the Great
Lakes through mid-week, reinforcing light winds and calm waves.
Winds flip to the southwest Wednesday night as the high moves into
eastern Ontario, with a cold front projected to impact the Great
Lakes to end the work week. This brings the next chance for elevated
wind/wave action and precipitation chances.

&&

.PREV DISCUSSION...
Issued at 1157 PM EST Mon Nov 17 2025

AVIATION...

High clouds increase coverage and lower to mid levels during the
late night on departure of surface high pressure and ahead of the
Plains to mid MS valley low pressure system. The system only reaches
the lower OH valley by morning but extends mid to upper level
moisture well north into the Great Lakes. Dry air below 700 mb
remains a formidable obstacle for precip advancement and supports
mid morning onset timing along the DTW corridor and a struggle to
reach PTK. Later timing means a better chance of above freezing
temperatures for a light snow to rain/snow mix and then a transition
to all rain by early to mid afternoon. Both ceiling and visibility
drop into the MVFR range during the most favored time window for
SN/RA while stopping short of FNT on the northward fringe of the
system. Rain showers then linger along the DTW corridor late in the
day and this keeps ceiling at low end of MVFR while the low pressure
system settles into the TN valley and mid Atlantic Tuesday night.

For DTW... Dry air remains a factor in slower onset timing of snow
or rain/snow mix in the morning. Mid to late morning onset improves
the chance of above freezing temperatures in light easterly wind and
a transition to all rain early in the afternoon.

DTW THRESHOLD PROBABILITIES...

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

* High for precipitation type of snow after 11z with rain snow mix
  after 14z, and then all rain in the afternoon into Tuesday
  evening.


&&

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

$$

DISCUSSION...SC
MARINE.......MV
AVIATION.....BT


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