903
FXUS63 KAPX 242300
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
600 PM EST Sun Nov 24 2024

.KEY MESSAGES...

- Rain and snow for northern lower move in after midnight
  tonight

- Accumulating snow likely for eastern upper early Monday
  through the day. Transition to widespread lake effect snow
  Monday night into Tuesday


-Lake effect snow continues, albeit slightly less robust, Tuesday
night into Wednesday.

-Turning colder with the potential for a prolonged period of
 lake effect snow Wednesday night through the remainder of the
 forecast period. Potential for higher-end impacts is non-zero.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 320 PM EST Sun Nov 24 2024

Pattern Synopsis / Forecast:

Current satellite and surface obs show a surface cyclone centered
over SW IA this afternoon. South winds over MO/IL are advecting
around 0.5" PWATS northward. At the same time around 0.55" PWATS of
continental moisture exists over the central plains as remnant
moisture from an AR exits the central Rockies. An upper level long
wave trough will dig southward from Manitoba CA and reach into the
central plains. The aforementioned surface cyclone will deepen and
race to the north east - just ahead of the trough axis tonight. A
mid to upper level jet streak and some vorticity will be around 100
miles to the north of the center of the surface cyclone by midnight
tonight. This synoptic scale forcing will help deepen the low
towards the north, resulting in a more northward stack of this
system. Due to this, guidance has been tracking the center of
the surface low over MI - either over central MI or southern MI.
CAMs and global deterministic/ensembles are split, CAMs
slightly favor the track of the entering near Grand Rapids and
drifting towards Saginaw Bay by Monday evening. Global
ensembles have more spread but somewhat favor a track closer to
Detroit. The differences in track lead to the differences in
where the 0C 850mb line sets up - who will see rain, a rain/snow
mix, or mostly snow. Current forecast thoughts are that as
precip moves in tonight it will fall as mostly a rain/snow mix,
with the exceptions being Manistee, Benzie, Gladwin, and Arenac
counties who should see mostly rain through the event. Snow will
likely be seen through the whole event over eastern upper
(besides near the southern coasts). Snow will likely hold on in
the higher terrain of northern lower through Monday morning but
will likely switch back to rain during the afternoon hours.
Lower elevations of easter upper will start with a rain/snow mix
and have little difficulty transitioning back to rain Monday
morning. East winds will start to pick up and become breezy late
Monday morning, especially near the Lk Huron coast and through
the Straits.

Forecasted Snow Amounts for tonight through 7 PM EST Monday:

* Eastern Upper: 1 - 3 inches possibly up to 4 in a spot or two

* Tip of the mitt: T - 0.5"

* Higher terrain of northern lower: T - 0.4"

* Lower elevations of northern lower:  0 - 0.1

Primary Forecast Concerns:

The surface low still has a lot of ground to cover before it
reaches the state Monday morning, this naturally leads to some
uncertainties with the forecast above. The possible tracks that
the surface low can take across the state as it treks from the
SW to the NE leads to various thermal environments aloft. Most
model soundings depict very little change in temperature up
until ~ 4-6kft, and most are right around 32. If the
temperatures in that layer shifts by a degree to two, it could
result in very different outcomes for precip type and snow
amount (if snow does fall). The place where this will be the
most sensitive is over northern lower. The other important
uncertainty that results from a deviation in track is snow
amounts for easter upper. Some CAM guidance places them in an
ideal spot for forcing and moisture - resulting in up to 5 or 6
inches falling by late Monday. This is more unlikely at this
time, as the track of the low would have to be more over
northern MI and guidance is trending more SE at this time.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 320 PM EST Sun Nov 24 2024

Pattern Synopsis / Forecast:

Ridging will be well on its way out at the start of the forecast
period, with height falls commencing due to intruding waves: one a
clipper, and the other a Pacific impulse. This will be enough to
drum up some moisture advection, and with pretty stellar forcing
aloft, should bring plenty of lift to the region, along with surface
cyclogenesis as developing low pressure passes through downstate.
Result will be an initial mix of rain and snow for northern lower
that changes over to mainly snow with time Monday night... and
mainly snow, if not, all snow across the eastern Yoop. Once the main
area of system snow departs Tuesday morning, a transition to lake
effect snow will occur as flow turns more WNW. The traversing waves
then cut off to our east, and following another wave passage to our
south, a much more progressive flow is set to materialize to close
out the forecast period, which may bring about potential for higher
end impacts that coincide with big holiday travel.

Primary Forecast Concerns:

Monday night / Tuesday: Current setup favors mainly snow for the
eastern Yoop, and rain transitioning to snow across northern lower
(especially the interior terrain). Guidance has trended just a touch
more bullish on snow totals by Tuesday morning, with a general 2-5"
across the eastern Yoop, potentially as high as 6"+ in places
considering how good the forcing is, and with lift in the DGZ,
supports good dendritic growth (larger snowflakes). Somewhat less
clear across northern lower, with precip potentially starting as
rain, but a quick flip to snow will be possible across the Straits
and the interior higher terrain given dynamic cooling and slightly
colder temperature potential. This could open the door for a couple
sloppy inches of accumulation by Tuesday morning in these areas,
with perhaps some locally heavier totals, but there remains
uncertainty for this particular portion of the forecast. Eventually,
activity turns to a much more WNW flow lake effect regime as colder
air behind the system streams into the region. Given the daytime
timing of the cold air advection, could see a more cellular lake
effect regime as daytime convection disrupts the banded structures.
Nonetheless, an additional 1-3" (locally higher) possible in the WNW
flow snowbelts.

Rest of the Forecast Period: Lake effect will continue, albeit,
probably a little less efficient through the day Wednesday. Things
change rather considerably on Thursday (Thanksgiving Day) and
beyond. Sharply colder air pouring over the lakes should be able to
easily produce efficient lake effect snowfall, and barring drastic
wind shifts, could produce some beefier banded snowfall structure
just in time for Thanksgiving travel. Considering progressive flow
should be able to bring about numerous shortwaves to keep forcing
and lake induced instability rolling, there is potential for this to
turn into a higher end event over several days if everything can
come together perfectly, and could impact travel (mainly those that
travel Thursday and beyond for the holiday weekend). This trend will
continue to be watched and fine tuned in the next several forecast
cycles.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 600 PM EST Sun Nov 24 2024

Low pressure will eject out of the Central Plains tonight and
will ride thru Lower Michigan on Monday. Widespread rain and
snow will develop ahead of and around this system...impacting
all of Michigan over the next 24 hours. Prevailing conditions
will deteriorate from low VFR/MVFR to IFR as this mixed precip
develops from SW to NE late tonight into Monday. Surface winds
will become easterly and strengthen to 10 to 20 kts with some
higher gusts expected.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 10 AM to 10 PM EST Monday for
     LHZ345>348.
     Small Craft Advisory from 10 AM to 10 PM EST Monday for LMZ342.

&&

$$

SHORT TERM...ELD
LONG TERM...HAD
AVIATION...MLR