270
FXUS63 KDTX 072346
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
646 PM EST Fri Feb 7 2025

.KEY MESSAGES...

- Accumulating snow moves in Saturday afternoon and evening with the
highest potential to exceed 3 inches in the northern Tri Cities and
northern Thumb.

- A mid-winter pattern will hold high temps mainly in the upper 20s
to low 30s and low temps in the teens through early next week.

- Additional chances for snow Tuesday and Thursday.

&&

.AVIATION...

Dry and stable low level conditions held within lingering high
pressure maintain VFR with cloud base above 10 kft tonight. Emerging
easterly low level flow will support VFR conditions through the
morning period ahead of an encroaching mid level wave from the west
and low pressure tracking across the Ohio valley. Potential does
exists for a lead narrow wing of isentropic ascent to align invof
MBS during the morning hours, affording an initial opportunity for
light snow development and accompanying reduction of visibility.
Snow probability increases area-wide Saturday aftenoon and evening,
although with lower confidence yet in possible magnitude and
duration as the heavier and more prolonged activity may split the
region. Forecast outlooks the most likely period for IFR conditions
in accumulating light snow.

For DTW...Main window for accumulating snow centered 19z-00z late
Saturday. The potential does exist for some higher intensity snow
showers during this time. The probability for brief freezing
rain/drizzle remains very low.

DTW THRESHOLD PROBABILITIES...

* Moderate in snow Saturday afternoon/evening.

* Moderate in ceilings aob 5000 feet Saturday afternoon/evening.

&&

.PREV DISCUSSION...
Issued at 345 PM EST Fri Feb 7 2025

DISCUSSION...

For the remainder of the day... High pressure supports mostly clear
skies this afternoon and evening. Temperatures drop in the teens to
low 20s overnight. An active winter weather pattern will then spread
across Michigan tomorrow afternoon and evening, bringing widespread
wintry precipitation to a greater majority of SE MI. While confidence
is high regarding active winter weather, uncertainty also remains
higher than normal regarding snowfall amounts for portions of the
cwa, despite being about 24 hours from onset precipitation. This is
due to a combination of possible constructive or deconstructive
processes along with sensitivity to moisture quality within the dgz,
discussed below.

First of higher confidence... A pacific mid-level wave has now
arrived onshore across the coastal west and will progress through the
northern Plains, arriving over the Great Lakes by tomorrow evening.
Concurrently, the jet stream will extend and strengthen across the
central Plains, with the left exit of the jet core pushing into the
southern Great Lakes tomorrow afternoon before the 160 knot core
extends over the cwa. As a result, a strong frontogenetic response
will likely be observed at and around h700 through the afternoon and
evening hours. The combination of the unbalanced flow along the exit
region of the jet and strong forcing of the fgen will bring initial
snow production along or north of I-69 by the early afternoon. While
there is high confidence regarding development of this snowfall,
higher-end snowfall totals will be very sensitive to the placement of
the fgen, which in consecutive model runs have trended farther
north. As of right now, if fgen sets up over the cwa, the highest
likelihood to achieve 3-4+ inches of snowfall would fall over
northern portions of Bay, Midland, and Huron County. Huron county
also has a window for lake enhancement lake tomorrow night which may
bring some locally enhanced 4+ totals. This scenario would get us
close to Winter Weather Advisory criteria, but will defer to
subsequent shifts to give time for better sampling of the
aforementioned Pacific wave and another round of hi-res output.

Winter weather, mainly comprised of snow, will fill in for the
remainder of SE MI through the afternoon and early evening, tied to
an area of low pressure that fills in across the Ohio Valley. System
relative flow within the lower levels becomes conducive for a round
of light snow, which is expected to hold below an inch for areas
around and south of M59. There are two caveats to this -- The first
being a window for some elevated instability to glide above the low-
level fgen which has the capability to produce a quick but narrow
corridor of 1-2" snow accumulation somewhere around I-94 south. This
signal is subtly noted in some hi-res and ensemble output, but the
majority of solutions hold this outcome south of the border, so at
this time there is about a 10% chance of this developing over the
cwa. The second caveat comes to moisture quality within the dgz.
Moisture depths are already shallow within the southern half of the
cwa, but convective processes firing south of the border could hamper
moisture farther north, which would then call into question ice
nucleation for precipitation around to south of I-94. This scenario
brings the chance to see periods of freezing drizzle outright, or
mixed in with the snowfall, leading to a light glaze of ice
accumulation by the late evening.

The locations not mentioned above (~north of I-94 to around or north
of I-69) reside in an area that still has broad, lighter forcing
from both the incoming jet and lagging shortwave, but lack of any
deformation processes should limit snowfall production to an inch or
less. With the better moisture depth within the layer leading into
the dgz, snow is the likely p-type.

High pressure builds in behind the departing wave on Sunday and
fills in through early Tuesday which will bring dry weather coupled
with highs in the upper 20s to low 30s and lows in the teens. The
next chance for light snow enters on Tuesday, along a cold front.

MARINE...

High pressure drifts directly over the southern Great Lakes this
evening maintaining weakening wind trends going into tonight. High
pressure vacates the region by Saturday morning in advance of a low
lifting through the Ohio Valley. This next system brings widespread
snow shower chances and a steady wind shift from SE Saturday
afternoon to NE by evening and eventually NW by late Saturday night.
With a weaker central pressure, relative to this past Thursday`s
low, and a track over western West Virginia, local gradient isn`t
expected to tighten enough to support wind gusts much above 20kts
Saturday night into daytime Sunday. A broad area of Plains high
pressure then expands over the central Great Lakes late Sunday
through late Monday bringing another period of lighter flow and
quiet weather.

&&

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

$$

AVIATION.....MR
DISCUSSION...AM
MARINE.......KDK

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