779
FXUS63 KAPX 062300
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
600 PM EST Mon Jan 6 2025

.KEY MESSAGES...

- Cold with light snow accumulations in NW flow areas Tuesday
  into Tuesday night.

- Rounds of lake effect snow showers into the weekend.

- Colder temperatures through mid-week before moderating to the
  20s by the weekend.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 343 PM EST Mon Jan 6 2025

PATTERN SYNOPSIS/FORECAST:

PV maxima sliding through the region this afternoon...mesolow
dropping south from Ontario over the last couple hours resulting in
some breaks in the cloud cover, as well as an increase in snowfall
over parts of the area...with subsidence on the increase as well as
ridge axis to our west begins to seep into the area...in the wake of
surface system located over western VA. Some north flow lake effect
along the NW coast picking up this afternoon as well. Next system
remains to our northwest...a cold front stretching from Hudson Bay
to southern Saskatchewan....behind which surface temps are in the
minus teens to minus 20 F across central Canada. Overlake
instability remains present with 850mb temps in the
-10 to -12C range...and some N/NNE flow lake effect flurries remain
present even into this afternoon.

Expecting high pressure to continue to try to build in...though lake
aggregate troughing will remain in play. Think there is potential
for pressure gradient to remain light enough tonight for some
offshore flow...which, combined with weak N/NNW background
flow...could produce some mesoscale lake bands near or just
offshore...particularly for the NW Lower coast. Better potential for
lake effect snow will arrive through the day Tuesday...as another
shortwave trough dives southeastward into the region toward the
afternoon, bringing even colder air into the picture for
Tuesday/Tuesday night...with some potential for a more intense band
to set up over NW Lower MI Tuesday afternoon into the evening
commute...and hang on into the overnight hours Tuesday. Next blob of
PV approaches late Tuesday night from the NW...bringing another
punch of cold (very cold) air...as well as better synoptic
moisture...going into early Wednesday.


Primary Forecast Concerns:

Lake effect snow bands Tuesday/Tuesday night... have some concerns
that guidance may be trending a bit slower with the PV max Tuesday
afternoon/evening. If this indeed is the case...could develop lake
snow bands later in the afternoon, closer to the evening commute,
rather than slightly beforehand. Think the primary area of concern
will be west of I-75 Tuesday afternoon, particularly along/west of
US-131 where there could be slightly better moisture aloft to
enhance otherwise pure lake effect setup. Some uncertainty in
exactly where the bullseye will end up being, as latest prob
guidance seems to also be hinting at a southward shift of that
beefiest band Tuesday afternoon...from a Leelanau/GT band toward
more of a Benzie/Manistee band...though it may yet remain beefy east
of TC into Kalkaska county. Additionally, have some concerns the
band may shift with time Tuesday afternoon into Tuesday night, which
could keep snowfall from achieving worst-case-scenarios (shifting
the firehose instead of keeping it focused for the entire duration).
On the flipside, however...guidance soundings suggest we`ll be
saturated in the DGZ...with best lift focused in this same
area...which could boost snowfall totals (more fluff). Do think we
could end up a little squally at times along the backdoor cold front
that should be dropping through with this Tuesday afternoon/near the
evening commute...noting potential for some surface-based CAPE to
further pump up the intensity of snowbands during the evening
commute. Bottom line...Tuesday evening`s commute may not be pleasant
for some areas along/west of US-131.

Also concerned the overall pressure gradient/background flow may be
light enough to develop some mesoscale nonsense Tuesday night...
We`re currently seeing some mesoscale vortices continue to drift
down from the north this afternoon...currently over Boyne/East
Jordan, and do have to wonder if something similar could take place
Tuesday into Tuesday night, as the setup could remain somewhat
similar (though maybe less high-pressure-y). Will be something to
keep an eye on as we go forward, as these kinds of events can be
difficult for models (even hi-res ones) to predict.

For now...holding snowfall totals at a general 2-4 inches for the
24hr period ending 7am Wed...which seems to be where prob guidance
is hinting attm. Given potential for the main snowband to drift
around with time, as mentioned above...do think this is a reasonable
starting point. However...I do remain concerned for the potential
for snowfall totals to end up higher than currently forecast Tuesday
afternoon into Tuesday night as the more intense bands light up.

Cold temps Tuesday night...highs Tuesday may only reach into the
teens for the EUP as they get into better drainage flow and
clearing. Setup seems very favorable attm for overnight lows Tuesday
night to drop below zero, with a typical diurnal swing of 15
degrees...and we should exceed that with increasingly cold/dry
conditions draining out of Ontario. Question will be, how far south
does the drainage flow get? Not impossible it could get into
northern Lower as winds are expected to drift a bit more
northerly...which could focus the banding closer to the coast...and
clear things out over the interior. We will be making a run at
criteria for an extreme cold advisory (formerly known as wind chill
advisory) Tuesday night into Wednesday morning...but for now we
remain just warm enough to stay out of the advisory criteria for
now. Will warrant additional looks in the coming forecasts.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 343 PM EST Mon Jan 6 2025

Pattern Synopsis:

A digging longwave trough will swing southeast of the Great Lakes
Region through Thursday. Heights will build through Thursday night
into Friday ahead of another digging trough, with its embedded
features, forecasted to track across the area this weekend.


Forecast Details:

- Lake effect snow showers: Northwest to north-northwest flow will
persist and linger lake effect snow showers into Thursday morning
with decreasing intensity. Primary locations of interest are areas
south of the Grand Traverse Bay and along the Lake Michigan
shoreline (including the Leelanau peninsula) stretching to the far
western portions of Kalkaska and Missaukee counties. An additional
1" to 3" is forecasted by Wednesday night, with locally higher
amounts possible the closer you are to the shoreline and the typical
NNW snowbelts of northern Michigan. Winds look to slowly shift more
NNW through the day Wednesday, shifting the lake effect snow closer
to the shoreline as the day progresses. A quick burst of enhancement
from mesoscale features could bring about another round of moderate
snowfall Wednesday morning/ afternoon, but overall, intensity should
decrease through the night into Thursday morning.

- Colder temperatures: Additionally, colder air will continue to
seep into the Great Lakes Region providing below normal temperatures
(approximate normal highs-- mid 20s; approximate normal lows--
teens) through at least Thursday. Daytime highs are forecasted in
the low teens Wednesday with overnight lows in the single digits,
and some areas in the negative single digits (eastern U.P. and
higher terrain across northern Lower) Wednesday night-- factor in
wind chill values and some areas could experience below-zero wind
chills through the middle of the week with negative teens possible
for the eastern U.P. As the week progresses, daytime temperatures
will moderate back to the 20s by the weekend with another system set
to bring back lake effect snow this weekend, especially for the tip
of the Mitt/ Straights area and far eastern U.P. Ice formation
across these areas could play a role in limiting lake effect snow
shower potential for this weekend with some thin ice being noticed
on webcams across shallower areas today ahead of colder weather we
are anticipating mid-week -- More on this to come in the following
forecast cycles.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 600 PM EST Mon Jan 6 2025

Northerly flow lake effect snow showers will continue to target
areas west of US-131 for the most persistent snowfall tonight
thru Tuesday night. A weak wave will drop thru the northerly
flow on Tuesday...serving to enhanced ongoing lake effect snow
showers for this area. Prevailing conditions will remain mostly
MVFR to low VFR for the next 24 hours. Surface winds will remain
from the N/NW at around 10 kts tonight...strengthening to 10 to
20 kts with some higher gusts on Tuesday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 11 PM EST this evening for LHZ349.
     Small Craft Advisory until 11 PM EST this evening for LMZ323-
     342-344>346.

&&

$$

SHORT TERM...FEF
LONG TERM...NSC
AVIATION...MLR