FXUS63 KAPX 111711

Area Forecast Discussion
National Weather Service Gaylord MI
1211 PM EST Mon Dec 11 2023

Key Messages:

 - Lingering lake effect snow this morning will bring an additional
   inch or two of snow to Antrim/Kalkaska counties.

 - Snow squall potential early Tuesday morning with a band of
   snow moving across the area combined with 30-40 mph wind
   gusts, possibly creating rapid drops in visibility during the
   AM commute.

Pattern Synopsis:

Expansive longwave troughing will continue to slide over the eastern
half of the CONUS today as an associated elongated cyclone quickly
works northeastward up the Atlantic coast. Meanwhile, ridging will
temporarily work overhead this afternoon/evening before a potent
shortwave digs into the Great Lakes by the end of the period.

Forecast Details:

Ongoing lake effect snow -- most notably the more concentrated
banding over Antrim/Kalkaska counties -- will continue over the next
several hours. An additional inch or two of snow will be possible
underneath this band before sunrise. As aforementioned ridging works
into the region, low-level winds will begin to shift from
northwesterly to southwesterly through the day, disrupting ongoing
lake effect and fanning out light snow showers across portions of
northwest lower and eastern upper into early this afternoon. An
increasingly dry low-level airmass will also move in today,
ultimately ending snow chances for a time later this afternoon and

Snow chances do look to return later tonight into Tuesday morning as
the shortwave punches overhead and the associated clipper passes to
our north. Favorable forcing and moisture provided by this system
will bring chances for at least light accumulations (less than 1")
across eastern upper and the Tip of the Mitt by 12Z Tuesday. While
snowfall amounts will be unimpressive, the primary concern will be
snow squall potential early Tuesday morning. Fine flakes within a
band of snow swinging west to east across the area around 20-30 mph
will combine with background wind gusts of 30-40 mph to bring
chances for rapid drops in visibility during the morning commute.
While confidence is relatively low at this time, this potential will
be monitored in future forecast cycles due to possible impacts
during the morning commute along primary northern Michigan roadways --
including Mackinac Bridge/I-75. Otherwise, high temperatures in the
low to mid 30s are anticipated this afternoon. Overnight lows should
stay relatively mild and only look to cool into the mid to upper


HIGH IMPACT WEATHER POTENTIAL: Moderate...accumulating lake effect
snow Tuesday, along with potential band of snow with the front
Tuesday morning...


160+kt upper level jet now on the downstream side of the trough
axis, stretching the length of the East Coast...with attendant BCZ
stretching through the Appalachians, along with surface low pressure
along the Eastern Seaboard. Southern end of the trough axis turning
negatively tilted over the SE US as potent niblet plows through that
region. Meanwhile...northern portion of the trough axis remains
overhead as of 4z...with NW flow holding on across the Plains and
Upper Midwest; lake convection ongoing over northern Michigan. Brief
shortwave ridging and attendant surface high pressure across parts
of Canada and the US, broken up by NW-SE oriented warm fronts
stretching over Manitoba/Ontario to our north...and from the Mid MS
Valley up to a potent surface low over northern Saskatchewan. This
latter feature is associated with a potent vort max aloft, with
strong flow through the column and some decent moisture along/ahead
of this.

Current trough axis is expected to lift out today...with shortwave
ridging to arrive in its wake. However...shortwave ridging will be
short-lived...as that strong PV max and its attendant tightly wound
surface system dive toward the Upper Great Lakes today into tonight.
Expecting strong winds with this system Tuesday morning...as a cold
front plows through the area with a band of snow and strong winds
(potential snow squall setup?) and attempts to stall out to our
south. Flow to become WNW behind this front...with abundant cold
advection supportive of good overlake instability. Signals still
point strongly toward an intense snowband setting up over Chippewa
County, especially north of M-28, with details to be refined as the
event gets closer.

Another vort max drops into the back of the shortwave trough
Wednesday morning...likely keeping the NW flow cold advection at
least for a time. However...with ridging building into the central
Plains through the period...think there is some potential surface
high pressure will try to seep in from the south at times going into
midweek...though warm advection ahead of strengthening northern
stream ridging could keep things from being totally quiet,
particularly over the EUP.

Primary Forecast Concerns: Burst of snow Tuesday morning followed by
accumulating lake effect Tuesday afternoon...

Guidance seems pretty keen on the idea of an intense band of snow
sweeping across the area with the cold front Tuesday
morning...which, combined with the strong gusty winds of 30-40kts
currently expected with the front, could suggest potential for a
snow squall situation...making the Tuesday morning commute extra un-

Otherwise...after the quick-hitting frontal snowband Tuesday morning
attention will turn to WNW flow lake effect, particularly over
the EUP (and particularly northern Chippewa County). This is where
the best synoptic forcing (with PVA from niblets aloft) should
combine with the best fetch over Lake Superior, with the greatest
overlake instability over this region, deeper into the colder air
aloft. While some of this should begin fairly quickly after the
front Tuesday morning...think the most intense period will be
Tuesday afternoon into Tuesday night, as additional niblets pass
through the flow aloft and help reinvigorate pre-existing snowbands.
Guidance soundings show a bulk of the cloud layer in the DGZ over
the EUP, with potential for the best lift to be pegged in this
layer as well. This certainly suggests potential for snowfall totals
to be amplified by those bigger, fluffier dendrites...and will have
to see how much the strong winds (likely remaining 20-30+kts, esp.
over the EUP during the day) are able to break up the dendrites,
though I doubt it will have all that much impact on snowfall totals.
A more pressing wind-related concern will be blowing/drifting and
reduced visibilities...particularly noting some probabilistic
guidance showing moderate confidence in less than 3mi visibilities
at times Tuesday across Chippewa county. Additionally...with the
cold air mass in place, wind chills could be in the single
digits...which would not be good for anyone who gets stranded amid
the band Tuesday.

Admittedly...inversion heights are not excessively high with this
event (probably closer to 8kft or so, which is decent)...and
moisture may not be as deep in some areas behind the front Tuesday;
though for now, things look more promising for a more saturated
surface-to-cloud-top layer over the EUP, per guidance soundings.
Still think we'll be keeping a close eye on Chippewa county in the
coming hours for a combination of snowfall and related impacts
Tuesday/Tuesday night...particularly noting that probabilistic
snowfall for this 24 hr period (12z Tues-12z Wed) is still strong
for this event, showing greater than a 70 percent chance for at
least 4 inches of snow.




Signals seem to point toward milder air trying to force its way into
the area for the latter half of the week...though northern stream
and southern stream ridging may end up fighting for dominance and to
some degree mar potential for otherwise generally quiet
weather...though for now, am keeping this idea to a minimum in the
forecast. The northern stream remains quite active...with a niblet
expected to zip through Canada Thursday/Thursday night...though
whether this ends up far enough south to have an influence on our
weather is somewhat unclear attm. Either way...looking like another
potent blob may try to dive out of NW Canada for late week/the
weekend...which bears watching, noting this could have potential to
produce a strong northern stream surface low over Canada, that could
also impact our area. Timing/position of this feature remains
uncertain...and will also have to keep an eye on how a southern
stream trough evolves late in the week into this weekend. For
now...guidance keeps these two separate...with potential for a
decent southern stream system to develop as well, perhaps over the
southeast US. It'll be something to keep an eye on going forward, at
the very least, to see how this idea evolves over the next couple
days' worth of model runs.



Scattered lake effect snow showers will continue to diminish through
this afternoon as winds shift more west-southwesterly. Those winds
strengthen tonight with gusts as high as 25-35 kts overnight into
early Tuesday.  Primarily MVFR CIGs expected to continue, although
some generally brief lifts to VFR possible.


Current northwest winds will gradually turn to southwest winds
today, strengthening this afternoon into this evening. Small craft
advisory conditions are anticipated over all northern Great Lakes
nearshore waters by tonight. Gale force wind gusts are expected over
northern Lake Michigan nearshore waters for a time tonight into
early Tuesday morning. Isolated gale force wind gusts cannot be
ruled out over other nearshore waters. Advisory conditions look to
continue over the nearshores Tuesday into Tuesday night with the
potential for gales over Whitefish Bay during the day on Tuesday.


MARINE...Gale Warning from 10 PM this evening to 7 AM EST Tuesday for
     Small Craft Advisory from 7 PM this evening to midnight EST
     Tuesday night for LHZ347-348.
     Gale Watch from late tonight through Tuesday morning for
     Gale Warning from 10 PM this evening to 7 AM EST Tuesday for
     Small Craft Advisory from 7 PM this evening to midnight EST
     Tuesday night for LSZ321-322.