711
FXUS63 KDTX 132021
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
321 PM EST Mon Jan 13 2025

.KEY MESSAGES...

- Scattered to numerous snow showers Tonight through early Tuesday
afternoon. Localized accumulations of 1-3" expected along and
between the I-69 and I-94 corridors.

- Min wind chill readings of -5 to +5 F Tuesday morning, Wednesday
morning, and Thursday morning.

- Coldest airmass of the winter season expected to arrive next
Monday.

&&

.DISCUSSION...

Strong PV anomaly rotating through Northern Minnesota this afternoon
and through southern Lower Michigan tomorrow, shearing out in the
process however. This system and upper level trough will provide
upper level support to enhance lake effect snow showers, with
potential seeder-feeder mechanism but more likely just increase in
inversion depths 7+ kft. However,the airmass is so cold and dry (~
-10 F dew pts in Wisconsin tonight), tough to gauge just how strong
 the westerly band or bands in between I-69 to I-94 will be tonight
 into Tuesday morning, as the modest cape/steep low level lapse rates
 may actually end up being just above the DGZ (see nam soundings), as
 850 MB temps plummet into the negative lower 20s. On the flip side,
 if some of the cape/lift resides in the DGZ, the fluff factor will
 be extremely high, and if regional GEM solution verifies, 0.05
 inches of qpf easily becomes 2+ inches of snow. Its also unknown how
 persistent the band(s) will be and whether they will be transient
 enough to help limit amounts. Ultimately, preference is to highlight
 localized 1-3" amounts of fluffy snow along/in between the
 I-69/I-94 corridors. Even this afternoon`s activity has overachieved
 a bit, with Flint receiving 4 tenths of an inch through 18z.

Surface trough swinging south from Northern Lower Michigan in the
afternoon may tough off some additional snow shower activity, but
general subsidence kicking in and 850 MB temps warming into negative
mid teens by evening. Despite the northwest flow, can`t rule out
flurries and isolate snow showers tracking through tomorrow night,
as there is still saturation with respect to ice noted in the 1-3
kft layer. On flip side, would expect some pockets/streaks of
clearing as well, and will favor colder mins in the 10 to 15 degree,
but potential for normally colder sites to dip into the single
numbers with the fresh snow.

Short lived ridging during the day on Wednesday before another
shortwave/500 MB trough tracks through Wednesday night/Thursday
morning. Moisture axis from the Midwest tending to get pinched off,
thus just chance pops, as airmass is also not terribly cold with 850
MB temps in the negative high single numbers.

Strong warm advection pattern follows to end the work week before a
major cold blast arrives over the Weekend, as full fledged North
American trough develops and lingers into next week. 850 MB temps
aob -25 C forecasted by Euro/GFS on Monday, making this airmass the
coldest of the winter season by far.

&&

.MARINE...

Breezy conditions continue under the backdrop of cold air advection
which will maintain sustained west flow of 20 to 25 knots, with gust
potential holding just shy of 30 knots. The latest ice analysis
shows portions of the outer Saginaw Bay that remain ice free, thus
Small Craft Advisories will continue given wave height potential
nearing the four ft. threshold. Portions of the open water from Port
Austin down near Port Hope also may have some ice free zones away
from the shoreline which can see some elevated wave heights, but the
majority of the nearshore zone has some degree of ice, so the
decision was made overnight to drop the ongoing Small Craft
Advisory. Wind direction will veer to the northwest tomorrow as even
colder air drops in across the Great Lakes. This will sustain breezy
conditions through Wednesday morning, where a brief ridge of high
pressure then decreases wind intensity. Snow showers remain possible
with the continued cold.


&&

.PREV DISCUSSION...
Issued at 105 PM EST Mon Jan 13 2025

AVIATION...

Arctic airmass will maintain MVFR clouds and lake effect
flurry/light snow activity through the bulk this TAF period. Timing
and intensity of lake effect snow carries general uncertainty in
these set ups, but have highlighted a few periods where greater
intensity snowfall from lake effect bands may impact terminals.
Ongoing lake effect bands this afternoon are focused more in the
FNT/PTK corridor with flurries elsewhere. As lower level winds turn
slightly northwest this evening, this corridor of focused lake
effect showers will drift southward and potentially affect the
southern metro terminals tonight. A stronger upper wave arrives
tomorrow morning bringing another period of higher intensity snow
showers that will be focused towards the southern metro terminals.
Surface winds into tomorrow remain steady and generally out of the
west at 10-15 knots with gusts mostly in the 20-25 knot range.

For DTW... Persistent MVFR ceilings and scattered lake effect
flurries/light snow expected this afternoon and evening as lake
moisture streams across the area. Best chance to see accumulating
lake effect snow showers comes tonight into Tuesday morning.

DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 feet or less today and tonight.

* High for p-type all snow through the forecast period.


&&

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

Lake St Clair...None.
Michigan waters of Lake Erie...Low Water Advisory until 1 PM EST Tuesday for LEZ444.

&&

$$

DISCUSSION...SF
MARINE.......AM
AVIATION.....AA


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