676
FXUS63 KDTX 071149
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
649 AM EST Fri Nov 7 2025

.KEY MESSAGES...

- Rain showers move across the area late tonight through Friday
morning, with perhaps a rumble of thunder.

- Becoming drier and breezier through rest of the day on Friday.

- Turning much colder over the weekend with a chance for
accumulating snow late Saturday night through Sunday.

- Large differences in snowfall are possible between the northern
and southern areas of Southeast Michigan, with periods of initial
rain and melting snow affecting snow accumulations.

- High temperatures drop into the 30s by Monday with scattered lake
effect snow showers at times through Tuesday.

&&

.AVIATION...

A SW to NE line of rain showers is progressing across southeast
Michigan this morning bringing with it predominately lower VFR
ceilings/MVFR and scattered southerly gusts of 20-25 knots along and
just ahead of the line. Greater coverage of MVFR/IFR ceilings reside
across central and northern lower Michigan with MBS possibly having
a brief period of IFR ceilings early in this TAF period. The rain
will push east of the southern terminals by 15-16Z while lingering
moisture into this afternoon will be support maintenance of the low
VFR/MVFR ceilings through the afternoon with ceilings looking to
settle to predominately low VFR for the evening. W-SW winds will be
elevated this afternoon supported by increasing mixing depths and the
strong lower level wind field. Gusts by mid morning should increase
solidly into the 20-25 knot range through the afternoon before easing
this evening and tonight.

For DTW/D21 Convection... There is a low chance for an embedded
thunderstorm within the rain pattern through 16Z this morning.

DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less this morning and afternoon.
  Moderate tonight.

* Low for thunderstorms this morning.

&&

.PREV DISCUSSION...
Issued at 336 AM EST Fri Nov 7 2025

DISCUSSION...

An occluded low pressure system now over the northern Great Lakes
will progress east into Ontario and Quebec today. The associated
cold/occluded front will move over SE MI through the morning,
bringing a line of widespread rain showers. Thunderstorms are
generally not expected, with closest observed lightning found over
northern Illinois. Mid-level lapse rates near 6 C/km could still
produce an isolated rumble of thunder, favored around the Metro
region and locations south. QPF amounts will range between .2"-.4"
after passage of the front. Upstream observations have been tame with
the elevated nature of the showers, but very low-end chances for
gust potential around 40-45 mph will be possible, noting the strong
50 knot llj tangent to the line of showers. The weaker baroclinic
environment in the wake of the front will preclude any meaningful
drops in temperatures today. Temperatures warm up into the 50s.
Otherwise, breezy with gusts ranging between 30 to 35 mph. Zonal mid-
level flow and lack of synoptic forcing bring dry conditions for the
first half of Saturday. SE MI will be better entrenched within the
lagged caa which will hold highs in the 40s.

The arrival of a shortwave across the Pacific Northwest will induce
lee cyclogenesis across the middle Rockies which will aid in the
production of a low pressure system, set to track through the
central Plains before rounding back into the northern Ohio River
Valley. Low pressure will gradually strengthen as it arrives into
the Ohio Valley with a trailing shortwave feature also arriving over
the region, clipping southern Michigan. This brings high confidence
to see the development of a broad precipitation footprint that will
impact portions of SE MI Saturday night into Sunday. The low will be
entering a region of high baroclinicity which includes the surface
to low-level 0C isotherm, bringing increasingly likely chance for
some snow accumulation for portions of SE MI.

The 00Z EPS cyclone ensemble centers range anywhere from southeast
Indiana to central Lake Erie by 12Z Sunday, with the greatest
concentration of members clustered over northwest Ohio, giving
credence that precipitation will expand into southern Michigan.
However, the snow footprint will be highly contingent on the exact
track of the low pressure system given the extreme sensitivity to
the placement of the low-level thermal gradient and associated rain-
snow transition zone, and subsequently the degree of frontogenetical
forcing.

An example of this is found with the RAP/NAM/GFS model runs which
display strong degrees of frontogenetical forcing around of between
the I-94 to I-69 corridor. This would force a strong ageostrophic
response would quickly erode static stability, pushing saturated EPV
values down towards zero or negative values right above and north of
the fgen. These solutions produce eye catching exorbant snowfall
amounts with raw model snow output, but do not account for lower snow
ratios, mixed precip, and melting from early November warm ground
temperatures and thus should be viewed with caution. ECMWF/EPS/GFS
graphcast are in alignment and show max accumulation along and south
of I-94. The caveat with the bulk of these solutions will again snow
production takes places around the 0C isotherm, which would favor
either initial rain to rain/snow mix or melting/wet snow. Thus the
current deterministic/ensemble envelope does support accumulating (1+
inches) snow potential for portions of SE MI, but predictability is
very low at present time given the above.

Of much higher confidence... Passage of this low pressure system and
impinging shortwave off of a parent low over the James Bay into the
Great Lakes will amplify the longwave trough structure across the
Midwest and will pull down anomalously cold air. 500MB temperatures
drop to or below -36C through the Ohio River Valley, which if
verified would fall outside of all climatological values. The large
delta t off the warmer lakes will greatly boost over lake instability
while advecting lake moisture inland. Lake effect snow showers will
be increasingly likely Sunday afternoon and evening across the cwa.
The backing of flow to the northwest brings potential for enhance
convergence along the Lake Huron shoreline which will be an area of
interest for any stronger lake effect snow showers leading into
Monday. This strong thermal trough brings in much colder temperature
highs. Expect highs in the 30s Sunday - Tuesday, with lows in the
20s.

MARINE...

Low pressure deepens as it tracks across the northern Great Lakes
today, its center passing near the Soo Locks around midday. Gusty
south wind will persist through the morning at around 25 to 30 kt,
with isolated gusts to low-end gales across central/southern Lake
Huron for a brief period this morning. A band of showers advances
across the region this morning before drier air arrives behind a cold
front. Winds veer to southwest behind the front and stay gusty to
around 20 to 30 kt through the rest of the day. Wind shifts to
northwest behind a secondary cold front this evening, and the arrival
of colder air will keep wind gusty into tonight. Northern Lake Huron
will likely see gusts around 25 to 30 kt this evening before wind
begins to subside overnight.

The next low pressure system will track through the southern Great
Lakes Saturday night into Sunday. This system will produce gusty
northerly winds and snowfall on Sunday, then pull a much colder air
mass across the region for the early week. Most solutions currently
hold gusts below gale strength on Sunday, but will continue to
monitor southern Lake Huron for headline considerations. Gusty
northwest wind is expected to persist through Monday with additional
snow showers at times.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 AM EST Saturday for LHZ421-441-442.

     Small Craft Advisory until 4 AM EST Saturday for LHZ422-443.

Lake St Clair...Small Craft Advisory until 4 PM EST this afternoon for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 4 PM EST this afternoon for LEZ444.

&&

$$

AVIATION.....AA
DISCUSSION...AM
MARINE.......TF


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