591
FXUS63 KDTX 162001
AFDDTX

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

.KEY MESSAGES...

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

- A strong low pressure system is forecasted to track across the
Great Lakes late Saturday to Sunday. It remains highly uncertain
what the duration of heavy rainfall activity will be for any one
location across Southeast Michigan. Low confidence exists in the
forecasted rainfall amounts for this system across all of Southeast
Michigan. There is a potential for rainfall amounts to exceed 2.0
inches.

&&

.DISCUSSION...

Strong H5 ridge amplification will occur over the central Great
Lakes region during the next 24 hours with 580dam heights briefly
brushing up against Southeast Michigan. Feature of interest late
tonight/early Friday period is a strengthening warm front aloft with
an active upright 850-500mb frontogenetic circulation tucked under
right entrance region dynamics. Best time window for forcing is 12-
15Z from Midland and Bay counties eastward to Huron County. Low
confidence exists in footprint of measurable precipitation with
significant amount of dry air in the lowest 6.0 kft agl. Messaging
is good with 40-65% chance PoPs after 12Z. Warm air aloft will lead
to low mixing heights, highs Friday in the 60s some 5 degrees above
normal.

First part of Saturday will be influenced by the heart of the upper
level ridge and warm sector. The first question for Saturday will be
the race between warming daytime temperatures versus the amount and
arrival of high cloud to limit any insolation. Current forecast has
a respectable temperature gradient forecast across the area with
near 70 north to near 80 degrees Detroit southward.

High confidence exists that a dynamic Autumn storm system will
impact the region, including Southeast Michigan late Saturday
through Sunday. Latest deterministic global solutions and ensemble
systems support a +140 knot upper level jet and full latitude trough
resulting in a powerful cyclogenesis event in proximity of Southeast
Michigan. Will state outright that exact sensible weather impacts
will be difficult to pinpoint leading up to the event as exact storm
track and timing relative to daytime/nocturnal instability
environments highly matter. With regards to this particular system,
a high amount of uncertainty persists with a large variance amongst
the model suite with the phasing, or lack thereof of severe
potential vorticity anomalies. For instance, the GFS/ECMWF solutions
suggest a two piece double barrel low Saturday and Sunday, whereas
the EC-AIFS/GEM solutions suggests one primary surface cyclone
lifting invof Detroit Sunday.

The potential sensible weather impacts to monitor for this system
include: 1. Potential for a line of showers and weak thunderstorms
late Saturday afternoon and evening (questionable with the NAM one
of the only solutions bullish) with an environment of 500 J/kg
MLCAPE and an inverted V sounding. 2. Potential for a long duration,
very heavy rainfall axis on a shearing deformation axis Saturday
night/Sunday. Cluster analysis with the separate QPF EOFs suggests
an overwhelming amount of spread explained by the positioning of the
heavy rainfall over Lower Michigan. Some difference continue to
exists, primarily with the GFS type solution that ejects two
separate pieces of energy/two distinct low solutions. The d(prog)/dt
of the ECMWF has been trending away from the more northern/GFS
solution towards a more primary low/CMC solution. Regardless, given
the magnitude of dynamical support and potential longer duration
need to highlight the tails of the ensemble distribution. Current
90th percentiles of the EPS has 2.50 inches of rainfall at all 3
sites, KMBS/KFNT/and KDTW. Monitor future forecasts for expected
rainfall amounts. 3. Potential for high winds with this storm
system. Too much uncertainty exists in track and character of the
low ejection to suggest any precision. Will say based on the EPS
data that a period of breezy conditions of 25 mph and greater is
expected. Really not seeing much ensemble signal for potential
duration of 45 mph greater for the land areas.

&&

.MARINE...

A high pressure system now situated over the Great Lakes will wash
out across the western Atlantic through the end of the week as a low
pressure system moves from the northern Plains into western Ontario.
This will strengthen and maintain a moderate pressure gradient over
the Great Lakes late tonight into Friday, accelerating the passage
of a warm front. The passage of this front will veer wind direction
to south-southwest with wind speeds and gust potential picking up
shortly thereafter. Sustained winds in excess of 20 knots are
expected tomorrow across Lake Huron, with gust potential ranging
between 25 to 30 knots. Small Craft Advisories may be needed for
portions of the Saginaw Bay and the Lake Huron shoreline. Some
showers with embedded thunderstorms will also be possible across
Lake Huron Friday morning and afternoon.

A second low pressure system is then expected to move over Michigan
through Sunday morning and afternoon. There is still uncertainty
regarding the exact track of the low pressure which will have big
implications on both wind direction and wind speed and gust
potential through the day on Sunday.

At present time there is somewhat of a bimodal solution space, with
solution one favoring a track that moves over northern lower
Michigan. This would bring a period of stronger southwest flow
across portions of Lake Huron with potential to reach gales, before
veering wind direction to the northwest, where gale potential will
again be possible. The second solution favors a more southern track
into lower Michigan and the Ohio Valley. This will preclude any
stronger southwest flow on Sunday morning, but still brings high
chances for gales later in the day with the flip to northwest flow.
Forecast adjustments are expected leading into the event.

&&

.PREV DISCUSSION...
Issued at 126 PM EDT Thu Oct 16 2025

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.


&&

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

$$

DISCUSSION...CB
MARINE.......AM
AVIATION.....KDK


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