599
FXUS63 KDTX 161726
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
126 PM EDT Thu Oct 16 2025

.KEY MESSAGES...

- Warmer air arrives Friday and Saturday with scattered rain showers
mainly north of Metro Detroit on Friday.

- Increasing confidence for a strong low pressure system to track
across the Great Lakes late Saturday to Sunday bringing widespread
rain, embedded thunderstorms, windy conditions, and cooler
temperatures.

&&

.AVIATION...

High pressure remains in place over lower MI today promoting VFR
skies and light winds. Drier airmass and active subsidence keep any
diurnal cu to a minimum with clouds generally confined to transient
cirrus. Mid/high cloud fills in late this evening ahead of an
approaching elevated warm front. Said front then lifts through the
region Friday morning offering a period of `lower` cloud (6-8kft).
While some elevated showers are expected with the front, with drier
air still in place near-surface, most of these are expected to
become virga or only a sprinkle. For now have only added a Prob30
shower mention to MBS which is closest to the main moisture pool.

For DTW/D21 Convection... Thunderstorms are not in the forecast for
today or tonight.

DTW THRESHOLD PROBABILITIES...

*  None.

&&

.PREV DISCUSSION...
Issued at 401 AM EDT Thu Oct 16 2025

DISCUSSION...

Rising geopotential heights commence this morning as an amplified
mid-level ridge builds in from the west. This supports deep layer
subsidence and allows surface high pressure to pass directly across
the region. Tranquil weather with plenty of sun through the day and
temperatures typical of mid October, peaking in the lower to mid
60s. The high departs to the east tonight with an embedded shortwave
rounding the crest of the mid-level ridge. This ushers in an
elevated warm front late, accompanied by a swath of moisture in the
800-500mb layer. The bulk of deeper moisture will be directed across
northern MI along the nose of a LLJ, but flow veering with height
will spread some of this southward toward SE MI. Clouds are expected
to fill in from northwest to southeast. Current guidance gives about
a 30 to 40% chance for this moisture and elevated fgen to bring some
light rain overnight to the Saginaw Valley, but with greater
coverage impeded by the still dry lower levels.

Rain coverage expands across the Thumb early in the day Friday as
the elevated warm front continues passing through. Remnant ridging
influence and lack of deeper moisture look to hold mostly cloudy but
mainly dry conditions in the south. A strong warm advective pattern
ensues into Friday night with 850mb temp rising to 13-15 C by
Saturday. This warmth will not be fully realized on Friday as
boundary layer mixing will be weak beneath the cloud cover and
strong stable layer setting up, so highs in the mid to upper 60s can
be expected.

By Saturday, mixing deepens into the warm layer aloft and boosts
temps well into the 70s. Some lower 80 readings near the Ohio border
are not out of the question late in the day. Southwest flow picks up
within the warm sector with 850mb winds increasing to 25-30 kt, so
gusts to around 25 mph will be likely. These could be locally higher
to 30+ mph in Monroe and Lenawee County where the deepest mixing is
expected. Showers arrive over Mid MI in the morning with a tendency
to spread east across the forecast area as moisture transport eases
in along the baroclinic zone/height fall corridor arriving from the
west. Weak instability offers potential for a few embedded
thunderstorms. However, organized severe weather is not currently
anticipated.

Aloft, troughing upstream becomes amplified as an energetic Pacific
jet streak digs in across the intermountain west. Guidance continues
to depict the potent shortwave at the nose of this jet phasing with
a southern stream wave, resulting in a dynamic system that forms
over the mid-Mississippi Valley and tracks across the Great Lakes on
Sunday. This system will induce substantial poleward moisture
transport characterized by integrated water vapor transport near the
98th percentile per ECWMF reforecast climatology, sending PWAT to
near 1.25" and supporting categorical PoP Saturday night into
Sunday.

There is high confidence for the low to track over Lower MI
on Sunday, but still plenty of variability within each ensemble
suite with regard to timing and strength. At 12z Sunday the
GEFS/ECMWF/CMC ensembles each have members placing the center of the
low anywhere from Chicagoland to Georgian Bay. These details will be
important for placement of mesoscale precip enhancements via
fgen/deformation, as well as favored corridor for any stronger wind
response behind the departing low. Ensemble mean QPF through 12z
Monday ranges between 0.75 and 1.50" with some solutions producing
over 2.00" over relatively broad areas. Additional rain is becoming
increasingly likely by Tuesday as the next trough dives into the
Great Lakes.

MARINE...

A high pressure system will settle over the Great Lakes this morning
which will sustain light winds and dry weather today. High pressure
will then wash out across New England tomorrow while a low pressure
system strengthens and moves over western Ontario. This will
strengthen the pressure gradient over the Great Lakes behind the
passage of a warm front, which will veer wind direction to the south-
southwest with wind speeds increasing shortly thereafter.

Sustained winds of 20 knots with gust potential around 25 knots will
be likely after the passage of the front starting tomorrow evening.
There will also be a chance for showers with embedded thunderstorms
with the frontal passage. A second low pressure system is then
expected to develop and move over the Great Lakes late Saturday into
Sunday, bringing continued rain and thunderstorm chances. Sunday
bears monitoring for stronger winds depending on the strength and
track of this system.

&&

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

$$

AVIATION.....KDK
DISCUSSION...TF
MARINE.......AM


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