949
FXUS63 KDTX 101821
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
221 PM EDT Fri Oct 10 2025

.KEY MESSAGES...

- Scattered light showers this evening across the Tri-Cities and
  Thumb, with coverage more isolated toward Metro Detroit. Additional
  isolated light showers are possible on Saturday.

- Milder conditions through this weekend into early next week.

&&

.AVIATION...

Deep-layer low pressure system spins southeastward across the state
today and tomorrow. This promotes an influx of atmospheric moisture
with a band of thickening clouds and eventually some showers well
ahead of the system`s cold front, which is currently still west of
Lake Michigan. Stubborn resident dry air supported by Mid-Atlantic
high pressure helps keep rainfall rates in-check, therefore no
visibility restrictions were included this TAF cycle. Main forecast
consideration is how low ceilings get late this evening and into
Saturday morning. The bulk of the model data suggests high-end MVFR
to low-end VFR ceilings fill in with the passage of the front
Saturday morning before lifting and scattering out midday Saturday.
Winds flip from SSW to NNW behind the front.

For DTW/D21 Convection...Thunderstorms are unlikely tonight or
Saturday.

DTW THRESHOLD PROBABILITIES...

* Moderate for ceilings at or below 5000 feet tonight and Saturday
  morning.

* Low for thunder tonight.

&&

.PREV DISCUSSION...
Issued at 410 AM EDT Fri Oct 10 2025

DISCUSSION...

High pressure over the St. Lawrence Valley dominates local
conditions this morning with mostly clear skies leading to a chilly
start. High clouds moving in are the first indication of changing
conditions today with the arrival of a potent upper vort max. This
system is currently evident on water vapor imagery just north of
Lake Superior, and is progged to drop across the eastern UP today
before tracking over Lake Huron tonight. Latest guidance offers much
higher confidence in a farther east track vs. several older
solutions that advertised a track over SE MI.

The inbound system gradually dislodges the resident ridging with a
tongue of higher theta-e that arrives later in the day. Conditions
are expected to stay dry through the daytime for most of the area as
the moisture transport remains elevated and dry air holds within the
lowest 7000 ft or so. The exception will be the Saginaw Valley and
Thumb where there will be a chance for some scattered showers along
a warm frontal feature before sunset. Breezy southwest wind will
boost temps into the mid to upper 60s for a high today.

The system`s farther east trajectory over Lake Huron tonight keeps
the bulk of unbalanced upper flow and ascent well to the northeast.
Still, the cold front and plume of moisture along the system`s
southern flank will track southeast across the area bringing a
chance for showers late this evening. Highest PoPs (~60%) are placed
across the north tied to the corridor of height falls/PVA and system
relative isentropic ascent. Moisture depth remains fairly shallow
which will keep showers light in nature. Farther south, occurrence
of showers remains more of a question as ascent will be weaker. The
NBM has trended much drier there over the past 24 hours with the 01z
run now advertising a 10% PoP at the MI/OH border. With the clouds
and southwest gradient wind tonight, frost will not be a concern
with lows in the 40s.

Upstream ridging builds in quickly on Saturday, with the closed
upper low stalling over the eastern Great Lakes and weakening
through Sunday before merging with a coastal low on Monday. Latest
guidance supports a downward revision in PoPs on Saturday, but
maintained a 20-30% chance east of I-75 as additional shallow
moisture pivots around the backside of the low. A 850mb thermal
trough and easterly flow hold over the region, bringing a dip in
high temps to the lower to mid 60s. The downstream merger of lows
should hold a mainly subsident pattern overhead, offering a dry
outlook into early next week with a slight warming trend. The next
window for possible rain arrives midweek along the next cold front,
but current solutions are lean on moisture.

MARINE...

South-southwest winds strengthen through the morning between
departing high pressure and low pressure pushing into the northern
Great Lakes. Strongest winds, gusting 25-30kts, occur over central
Lake Huron and Saginaw Bay this afternoon/early evening with the
southern portions of the area expected to hold closer to 15-20kts. A
Small Craft Advisory is in effect for Saginaw Bay and around the tip
of the Thumb. Low weakens as it drops south near or directly over
Lake Huron late today-Saturday which aids in keeping winds under
30kts. Scattered showers can be expected for this timeframe as will
waterspout chances as the cooler airmass is reinforced. A weak area
of ridging, induced by low pressure systems over the northern Plains
and Atlantic seaboard, then expands over the local area Sunday-
Monday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422-
     441.

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

$$

AVIATION.....KGK
DISCUSSION...TF
MARINE.......KDK/TF


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