870
FXUS63 KAPX 122331
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
631 PM EST Sun Jan 12 2025

.KEY MESSAGES...

- Accumulating lake snows develop tonight.

- Lake effect snow ramps up and peaks in intensity Monday night
  into Tuesday. Greatest impacts favor the snowbelt locales of
  northwest lower and near Whitefish Point.

- Another clipper system passes through Wednesday night into
  Thursday bringing another round of light snow.

- A brief lull in the wintry pattern later this week before
  more active weather potentially returns to close out the
  holiday weekend.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 241 PM EST Sun Jan 12 2025

Pattern Synopsis/Forecast:

All attention directed at sharp shortwave trough digging south
across eastern Manitoba early this afternoon...with lead more
subtle shortwave rotating northeast into the western Great Lakes.
Attendant slowly deepening surface low working northeast across
western upper Michigan, with band of warm air advection driven
mostly light snow working out ahead of this system across the
Northwoods. Accumulations have been minor, with both surface
observations and radar trends suggesting most areas have received
under an inch.

Surface low pressure will continue to work northeast, reaching
vicinity eastern end of Lake Superior by early Monday morning...all-
the-while Manitoba wave digs south...eventually opening up as it
cuts across the northern Great Lakes later Monday into Monday night.
Attendant surge of cold air advection will again ramp up the lake
processes...bringing accumulating snow to our traditional lake belts
tonight through Tuesday night.

Primary Forecast Concerns:

Addressing lake snow evolution and attendant amounts/headline
considerations tonight and Monday.

Details:

Widespread light synoptic snow transitions to lake effect tonight as
cold air advection slowly increases behind exiting cold front.
Initial post-frontal boundary layer flow regime is a westerly
one...keeping best Lake Superior induced snows focused into Ontario
and targeting Lake Michigan induced snows mostly along and north of
the M-32 corridor. Over-water thermal gradient is not overly
impressive tonight, with core of coldest temperature anomolies not
arriving until Monday and Tuesday. However, perusal of hi-res
guidance soundings show decent convective cloud depths and synoptic
moisture contribution through the convective layer. Could easily see
a few inches of snow targeting those snow belt areas along and north
of M-32...with a bit lesser amounts across the remainder of
northwest lower Michigan and eastern upper Michigan.

While cold air advection increases on Monday, synoptic moisture
contribution begins to thin some across northern Lake Michigan.
While moisture remains deeper across Lake Superior, maintenance of
west flow will continue to target best snows north of Sault Ste.
Marie. Flow actually backs a smidge for areas south of the big
bridge, theoretically targeting better snows to areas along and
north of M-68. While that backed flow will help with fetch lengths,
decaying large scale moisture contribution should throttle back a
bit on snow shower organization and intensity. Again, looking at
perhaps a few inches in those favored areas, but not seeing any real
evidence of anything too significant. Lake snows will continue
Monday night right through Tuesday night...adding additional
accumulations to the favored snow belt locations. For more detailed
information on that period please visit the long term section below.

With regards to headlines: While accumulating snow is expected in
our traditional snow belt locations through Monday...just not seeing
enough evidence to support snow amounts that are headline worthy.
Could eventually see the need for headlines Monday night and Tuesday
as better lake snow parameters arrive. Will punt that decision to
future forecast shifts.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 241 PM EST Sun Jan 12 2025

Pattern Synopsis / Forecast:

Closed low pressure will slowly navigate eastward with time, with
height rises building on its heels. Result will be a period of lake
effect snowfall across the region as a series of trough axes
traverse the upper Great Lakes. Overall flow will be somewhat weaker
to start the forecast period, which could induce a lake aggregate
troughing / mesolow setup Monday night into Tuesday. Flow then
shifts from westerly and to a more persistent northwesterly regime
Tuesday, bringing about more traditional banded lake effect snowfall
with time on Tuesday. Activity will be muted once the height rises
commence into Wednesday, resulting in lesser moisture. Another
moisture-starved clipper passes through Wednesday night into
Thursday, bringing about another round of light snow to the region.
This will draw in milder air for Thursday and Friday, albeit, most
areas probably stay below freezing through the weekend. Another
system passes through during the weekend, and most indications are
that this system should bring a reinforcing shot of colder air at
the very end of / just beyond the long term forecast period.

Primary Forecast Concerns:

Lake Effect Monday Night - Wednesday: Westerly flow will be dominant
for lake effect as the surface low slowly moves away. Result will be
the focus for lake effect favoring areas downwind of Little Traverse
Bay with lesser intense bands continuing south / west through the US
131 corridor. Initially, wind directions will not be overly
favorable for lake effect snows over the eastern Yoop... but lake
aggregate troughing over eastern Lake Superior may be just enough to
induce mesolow development, which will be advected south across the
Yoop later Monday night and into northern lower during the morning
hours Tuesday as a trough axis swings through the region. This
timeframe will likely be when the greatest snowfall rates occur,
likely limited to the proximity to any lingering mesolow and low
level convergence features. In the wake of this trough passage, lake
effect snowfall will shift focus to the more traditional
locations... western Chippewa in the eastern Yoop, and the "Big
Five" of northern lower (Charlevoix, Antrim, Otsego, Crawford, and
Kalkaska counties).

Given the limited moisture and the shallow inversion heights,
expecting more of a gradual buildup to some respectable snowfall
totals by Wednesday morning, as opposed to the impressive lake
effect events in December... with an additional 6 to 10"+ of
accumulation possible from Monday night through Wednesday morning
across parts of northwest lower (specifically that US 131 corridor
from roughly Boyne Falls to Kalkaska, and perhaps leaking SW toward
Fife Lake, Cadillac, and perhaps westward toward Mesick / Buckley
and Thompsonville). For those in the eastern Yoop, a general 3 to
6"+ of snow will be possible across western Chippewa county. All
other locales likely see 2" or less of accumulation during this
Monday night - Wednesday timeframe. After discussion with short term
forecaster, current headline management thoughts are that any winter
weather headlines will wait until Monday night once these heavier
snowfall rates move into the region.

Weak Clipper Wednesday night - Thursday: Another weak / moisture
starved low pressure system passes through Wednesday night into
Thursday, bringing another round of widespread, albeit, quite light
snowfall to the region. Current thoughts are that this looks like
another 1-3" snowfall event... inconvenient? Perhaps a little. Earth
shattering? Not by any means. Will have to see how the post storm
environment evolves... there is potential for some moisture to
linger in the wake of the system, and there are even some
indications that it will be too shallow to induce any strong lake
effect owing to a lack of cold air advection... which usually means
one of two things: minimal lake effect on the backside, or the worst
case... freezing drizzle. Given uncertainty regarding this feature,
more updates to be had.

Upcoming Holiday Weekend: On the heels of the midweek clipper, a
lack of cold air advection will lead to temps riding above normal...
probably anywhere from 26 to 31 degrees inland and 31 to 34 near the
lakeshores Thursday into Friday. Will need to watch how these
thermal profiles remain over the weekend as another system
approaches. It isn`t impossible for some lakeshore areas to see some
raindrops mix in along the lakeshores and far southern areas as warm
air advection commences. This does look to be a very brief hiccup in
the active wintry regime... as most guidance does indicate that
another shot of deep arctic air (and thus, below normal
temperatures) will make a return either at the very end of the
holiday weekend or into early next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 631 PM EST Sun Jan 12 2025

Widespread -SN and IFR conditions will exit APN later this
evening. IFR cigs will last all night at CIU, improving to MVFR
Monday. Developing lake effect -SHSN will help IFR conditions
return to MBL and TVC tonight. Otherwise, MVFR will be most
common. Winds will become sw to w, and a bit gusty by Monday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 7 AM EST Monday for LHZ347>349.
     Small Craft Advisory until 7 PM EST Tuesday for LMZ323-341-342-
     344>346.

&&

$$

SHORT TERM...MSB
LONG TERM...HAD
AVIATION...JZ

NWS APX Office Area Forecast Discussion