467
FXUS63 KDTX 221926
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
226 PM EST Wed Jan 22 2025

.KEY MESSAGES...

- Wind chills remain in the negative single digits through this
evening.

- Light snow expands over the area late this evening through
Thursday morning. Accumulations north of I-69 forecast to be between
1-2" with accumulations for areas to the south between 0.5-1".

- Cold front Thursday afternoon brings a weaker shot of arctic air
with highs Friday only around 20 with positive single digit wind
chills both Thursday and Friday nights.

- Scattered lake effect snow showers possible latter half of
Thursday into early Friday morning. Only minor accumulations
possible.

- A gradual warming trend begins this weekend into next week as
temperatures slowly climb towards near normal mid next week.

&&

.DISCUSSION...

Breezy southerly winds in place this afternoon in response to a
clipper system advancing across the northern Great Lakes. While the
Cold Weather Advisory was allowed to expire at noon, these winds
will keep apparent temps in the negative single digits through this
evening. SW 40-45kt LLJ between 925-800mb aids in both modest WAA
(850mb temps climb 5C to around -10C this evening) and moisture
advection into lower MI ahead of the low. Primary axis of moisture
transport occurs to our west and north, orientated from SW lower
towards the far northern Saginaw Valley, where specific humidity
reaches near 2g/kg. Snow initially has to overcome a very dry near-
surface layer leftover from prior arctic airmass (see surface Td`s
well below 0F across the area this afternoon). The Tri-Cities and
Thumb reach column saturation much faster than the rest of SE MI
owing to their closer proximity to the aforementioned moisture
transport axis as well as their closer relation to the low/PV
anomaly. These locales will see flurries/light snow showers through
the rest of the afternoon, though better accumulating light snow
begins this evening after 00Z. Saturation is much slower for areas
south generally confining accumulating snow potential to after
midnight. Forecast soundings south of I-94 struggle to fully
saturate tonight which would greatly limit snow chances and accums.
That said, there is signal amongst the higher res models and the
NAM12 for a sheared central Plains shortwave to reach the Toledo
area between 05-09Z tonight and support a brief few hour period for
enhanced ascent south of I-96 offsetting the weaker
moisture/saturation. Better window for accumulating snow over
Detroit and south comes Thursday morning when the cold front folds
the moisture axis southeast towards Lake Erie. For overall
accumulations by the end of Thursday afternoon, areas north of I-69
expected to see around an inch with the Tri-Cities/Thumb potentially
seeing up to 2 inches. For areas south of I-69, 0.5-1" possible with
the lower amounts of that range favored the further south you are.

Cold front crosses the region by Thursday afternoon ending synoptic
snowfall chances. Renewed CAA under NW flow and steepening low level
lapse rates support scattered lake effect snow showers into late
Thursday night. Core of the prior arctic airmass will be over
eastern Canada by this point, so while this front won`t bring a true
plunge back into the recent cold pattern, 850mb temps still fall
back to around -18C with highs Friday only in the low 20s and single
(positive) digit wind chills. Ridging expands over the state daytime
Friday shutting off any lingering lake effect snow showers as well
as setting up southwesterly return flow by the latter half of the
day. While the magnitude of this warm advection isn`t particularly
strong, it will support highs closer to normal in the upper 20s to
around 30 for Saturday.

Low pressure tracking along the southern shores of the Hudson Bay
drags a cold front through the Great Lakes late Saturday night-
Sunday briefly pausing our warming trend- highs Sunday fall back
towards the mid 20s. Some light snow showers can`t be ruled out over
the northern Tri-Cities/Thumb with with fropa however due to the
detachment from the main shortwave, overall forcing is limited
confining main snow chances north of our CWA. Upper jet pattern then
turns more zonal for the first half of next week offering moderating
trends back to around normal late January temperatures (ie lower
30s).

&&

.MARINE...

Low pressure tracking into Lake Superior this afternoon will
continue into Lake Huron by Thursday morning, dragging a cold front
and pattern of widespread light to moderate snowfall across the
central Great Lakes. Southwest winds will remain gusty ahead of this
front through this evening, around 25 to 30 knots, though some
localized brief 35 knot gales will be possible over Lake Huron.
Heavy Freezing Spray Warnings remain in effect until 10 PM. Wind
direction will shift to northwest behind the front on Thursday with
speed on the order of 15 knots. Some lake effect snow showers may
linger as the more widespread snow moves out. A ridge of high
pressure then builds in from the south on Friday, promoting lighter
winds and waves. Southwest wind ramps up again on Saturday as the
next low tracks into the northern Lakes. At this time wind speeds
look to remain below gales.

&&

.PREV DISCUSSION...
Issued at 1222 PM EST Wed Jan 22 2025

AVIATION...

Brisk southerly winds this afternoon, with gusts of 20-25 knots. Mid
clouds (6-10 KFT) will gradually lower through the day, with just
enough moisture transport and forcing ahead of a cold front to allow
for light snow to develop/reach the surface this evening and persist
through the night, with IFR/MVFR conditions. Looking at accumulations
of half an inch to two inches across the airports before activity
tapers off tomorrow morning, with highest totals over the northern
taf sites. Winds shift westerly behind the cold front late in the
morning, but not terribly strong and mostly under 10 knots.

For DTW...It will take most of the evening for low levels to moisten
up, and expecting mainly virga or flurries through midnight. Light
snow finally develops tonight, with the main light accumulating
(~0.5") window (8-13z) Thursday morning.

DTW THRESHOLD PROBABILITIES...

*  Medium for cigs aob 5000 this evening, high tonight and
   tomorrow.

*  High in precip type falling as snow.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Heavy Freezing Spray Warning until 10 PM EST this evening for
     LHZ362-363-462>464.

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

$$

DISCUSSION...KDK
MARINE.......TF
AVIATION.....SF


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