709
FXUS63 KDTX 121940
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
240 PM EST Wed Nov 12 2025

.KEY MESSAGES...

- Isolated showers/sprinkles taper off over The Thumb this evening.

- Wind gusts decrease overnight with clearing skies.

- Mainly dry Thursday and Friday with a warming trend through
  Saturday.

- Precipitation chances rise Saturday and Saturday night.

&&

.DISCUSSION...

Post-frontal light showers/sprinkles linger over The Thumb in
increasingly isolated fashion this afternoon as a lake-modified
moisture plume erodes and dislodges. Activity should wane by sunset,
giving way to drier air spilling in from the Canadian Prairies, as
evidenced in GOES imagery. 135+ knot jet streak at 300 mb continues
to lift northward out of the Ohio Valley as western CONUS longwave
ridging amplifies. A transition to mainly clear skies this evening
allows for efficient radiational cooling. A nocturnal inversion up
to 925 mb emerges by 00Z and inhibits mixing, therefore 30+ mph
gusts drop off early tonight.

The composite ridge axis is forced eastward overnight as northern
and southern stream cyclonic waves make landfall along the Pacific
coast. This facilitates a shift toward rising geopotential heights
and increasing stabilization, locally. Column thicknesses gradually
expand as the airmass slowly moderates through the rest of the week.
WNW surface flow holds on Thursday as high pressure builds out of
the lower Ohio Valley, displacing surface ridging (and cold
advection) emerging over western Ontario. High temperatures trend
back to climatological normals (upper 40s to near 50F) with plenty
of sunshine.

Sensible warming trend becomes more apparent on Friday as 850 mb
temperatures turn positive (Celsius), rising into the mid single
digit range. Gradient winds weaken as Southeast Michigan becomes
positioned within a split-flow configuration. Light winds shift SE,
responding to decaying surface high pressure as its center crosses
from eastern Ontario into western Quebec.

MaxTs rise well above average on Saturday, hearkening back to mid-
late October readings (upper 50s, perhaps lower 60s) after double
digit 850 mb temperatures advect into southern Lower, paired with
increasingly confluent southerly winds. Expect this well-defined
warm sector to encompass most of the Great Lakes, ahead of a
deepening extratropical cyclone (980 mb) tracking east toward James
Bay. This feature is tied to a progressive synoptic pattern where
the aforementioned Pacific troughs split. The southern wave becomes
cut-off near the California coast while the northern speed max
shears into the continental ridge axis, after responding to a lobe
of consolidating PV. The shortwave digs across the High Plains and
through the Upper Midwest Saturday. A secondary surface low emerges
along the occlusion (over the northern Great Lakes), with the
system`s elongated cold front extending southwest across Michigan
and into the southern Plains late Saturday into Sunday. A period of
gusty showers, and perhaps a rumble of thunder, will be possible as
the leap in ageostrophy triggers dynamic ascent into Sunday morning.
Additional showers, and perhaps some wet flakes, are possible
Sunday, although wind/fetch will be less favorable for widespread
lake-effect precipitation.

&&

.MARINE...

Current westerly winds following this morning`s cold front back
slightly to WNW or pure NW over the course of the evening as the
core of the colder airmass arrives over the central Great Lakes.
Magnitude of cold advection is not particularly impressive as winds
aloft only peak in the upper 30kts. Due to this marginal wind field,
expectation remains that gusts into early tonight only
briefly/sporadic touch gales (focused over northern Lake Huron) with
the bulk of gusts instead peaking in the lower 30kt range. Small
Craft Advisories however remain up into tonight. High pressure then
gradually begins to build over the region daytime Thursday, moving
overhead through Friday night, resulting in steady weakening of
winds allowing sub 15kt flow to take over by Thursday night. Next
low tracking over northern Ontario is set to swing a cold front
through the Great Lakes Saturday bringing rain-snow chances back to
the area. Trailing cold airmass looks to be stronger then the one
today supporting a good shot (~60-70%) at seeing NW gales Sunday.

&&

.PREV DISCUSSION...
Issued at 1208 PM EST Wed Nov 12 2025

AVIATION...

Cool and dry air advection in the wake of this morning`s cold front
is leading to steep low-level lapse rates supportive of gusty
westerly wind to 25+ kt and ceilings lifting to VFR. As the dry air
gains more traction, stratus will begin to scatter out from west to
east through the evening. The most likely location for any ceilings
to linger overnight will be across the Thumb and perhaps near MBS.
Meanwhile the loss of daytime heating will bring the reduction of
the gust component tonight, though the persistent gradient should
keep westerly wind active aob 10 kt. High pressure builds in through
Thursday with prevailing VFR and weaker westerly wind.

DTW THRESHOLD PROBABILITIES...

* Medium for ceiling 5000 feet or below early this afternoon. Low
  this evening.

* Low for exceeding crosswind threshold this afternoon.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 4 AM EST Thursday for LHZ421-422-441>443.

Lake St Clair...Small Craft Advisory until 10 PM EST this evening for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EST this evening for LEZ444.

&&

$$

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


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