539
FXUS63 KDTX 081953
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
253 PM EST Wed Jan 8 2025

.KEY MESSAGES...

- Scattered to numerous snow showers expanding late this afternoon
  into evening south of I-94, with a dusting to 1 inch expected.
  Mainly flurries/light snow showers elsewhere.

- Temperatures to start the day Thursday will be very cold, zero to
  10 degrees for most locations.

- Widespread light snow producing an inch or two of accumulation
  likely Friday afternoon and evening.

&&

.DISCUSSION...

Lake effect plume streaming southeastward off of Lake Michigan today
is still expected to release into part of the far southern forecast
area late this afternoon into early this evening as a shortwave in
the arctic flow pivots through the area. Inversion heights deepen a
thousand or two additional feet from current profiles as this system
passes which should bring better moisture depth into portions of the
DGZ and assist snow shower production. This activity still looks to
focus mainly west of the area, but with decent snow shower coverage
into Lenawee (and to a degree Washtenaw and Monroe) counties. Snow
accumulations of up to an inch still seems reasonable and will not
make any major changes to the ongoing forecast.

Some clearing associated with infusion of additional dry arctic air
with the passage of this shortwave will lead to colder temperatures
tonight, especially as boundary layer winds decouple. Would expect
single digits for lows by early Thursday morning for many locations
with temperatures likely around zero over the interior Thumb.

Widespread light snow is still expected Friday afternoon/evening as
northern stream upper level trough tracks through the Great Lakes
region. This trough is positively tilted and progressive and looks
to outrace upper level wave/energy near Baja California to minimize
phasing of the northern/southern streams (at least in the Great
Lakes region). As it is, the main stormy weather will be confined
largely to this southern system with just a general period of
isentropic lift expected in advance of the northern trough axis
through the Great Lakes. This should amount to an inch or two of
snow on average across the area.

Ridging works into the area this weekend in the wake of this trough
before the next northern stream shortwave works into the region
Sunday night into Monday and brings additional light snow potential.
This system will tap the next pocket of arctic air over southern and
central Canada which will settle into the area during the middle of
next week once the low pressure system associated with this northern
wave shifts to the east of the region. So, temperatures in the mid
to upper 20s in the Saturday to Monday time frame will settle back
into the lower 20s by Tuesday with low temperatures back down into
the lower teens (and likely single digits in some cases) by the end
of this 7 day forecast period.

&&

.MARINE...

An upper level trough axis drops across the Great Lakes this
evening, supporting lake effect snow showers for most of Lake Huron
through Thursday morning. Persistent cold NW flow will also support
pockets of moderate freezing spray. Once the trough departs late
tonight, high pressure builds in on Thursday which will relax wind
speeds and back winds offshore by Thursday afternoon. Small Craft
Advisories are still in effect through 4 PM EST Thursday for onshore
waves of 6 to 8 feet, although the latest wave model guidance
suggests an earlier cancellation may be possible as winds weaken.
The SW flow also ushers in a warmer airmass to bring an end to
freezing spray potential. These quieter marine conditions will be
short-lived with another low pressure system reaching the Great
Lakes by Friday night. Widespread snow and an uptick in wind gusts
to 20-25 knots will be possible Fri night-Sat as a result.

&&

.PREV DISCUSSION...
Issued at 1259 PM EST Wed Jan 8 2025

AVIATION...

VFR conditions through much of the forecast outside of a period of
snow that will drop through SW MI this afternoon for a few hours,
grazing SE MI at the same time. With the NW winds, the best chance
to get MVFR cigs/vsbys will be DTW, DET, and YIP with lesser chances
going north up the taf corridor. High pressure builds back over the
region tonight which may clear skies out. Will keep a few mention
for now as we assess the strength of the inversion this evening.
Northwest winds today with a few gusts possible into the teens with
winds then turning southwesterly Thursday.

DTW THRESHOLD PROBABILITIES...

* High for ceiling at or below 5000 feet through this evening. Low
  tonight.


&&

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

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

$$

DISCUSSION...DG
MARINE.......MV
AVIATION.....DRK


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