640
FXUS61 KGYX 050346
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1046 PM EST Wed Dec 4 2024

.SYNOPSIS...
A complex series of upper level troughs will cross the forecast area
tonight and Thursday with snowfall across the interior and a mix of
rain and snow closer to the coast. This system will be a followed by
a very cold airmass and gusty winds to finish up the workweek and to
start the weekend.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
1040 PM...One burst of precip, associated with the front of the
low level jet is moving through attm. There may be a little
break for an hour or two before the steadier precip moves back
in. Coastal areas from KPWM south, have bumped temps into the
mid to upper 30s with Tds mostly in the low 30s. I think these
may drop off a bit once the S jet exits after midnight, but I
think these does further limit the chance of accumulating in
these areas.

745 PM...Based on latest obs, specifically Td depressions, and
meso models, I`ve nudged back arrival time of the accumulating
snow by an hour or two across much of the CWA. Should work into
the NH mtns first then the ME mtns and the rest of NH by around
midnight, and then quickly over spread ME post-midnight. This
may reduce snow amounts by a hair, but unlikely will affect
overall impact.

Shortwave ridging is currently overhead per latest RAP analysis,
but this will shift to the east through tonight as low pressure
currently just north of the Great Lakes heads our way. This has
has given a mostly sunny day up to this point, but high clouds
are already pushing into western zones, and these will continue
to increase over the area while lowering and thickening as the
low pressure approaches.

Snow will begin to overspread the region this evening and
persist through the night and is expected to increase in
intensity after midnight as we`ll be in the left exit region of
a 250mb jet streak and forecast soundings also advertising a
small amount of CAPE. Precipitation type favors snow across the
interior with more of a rain/snow mix closer to the coast (even
a period of mostly rain). There is still uncertainty on where
this transition occurs and how far inland it will progress with
the increasing southerly flow. Still, what snow falls is
expected to accumulate, likely resulting in slick roadways and
poor visibility for the Thursday morning commute, even in the
lower amounts outside the Winter Weather Advisory.

All in all no major changes to the forecast with 3-6" across
the Advisory areas (a bit higher in the mountains), but
portions of some counties not in the Advisory could still
approach these totals, especially northern Androscoggin and
northern Kennebec county. However, the zone/county average does
not warrant the expansion at this time. Taking a glimpse at the
incoming 18Z HRRR and NAMnest indicates the rain/snow line may
not progress quite as far inland...and this will have to be
monitored further as amounts may need to be adjusted upward.

The last thing to mention is a period of strong, gusty winds
tonight and very early Thursday, especially along the coast but
moreso the Midcoast where a 45-50kt low-level jet could bring
gusts to around 45 mph for a brief period overnight. For this
reason, have put out a Wind Advisory for Knox and Coastal Waldo
counties.

Guidance continues to advertise precip rates coming down across
southern and central New Hampshire by mid-late morning and then
closer to the late morning or early afternoon hours across
western ME as the primary forcing shifts east. What falls after
is expected to be lighter in nature, but areas that do see
mostly rain or a mix could then see a switch back to light snow
as temperature profiles cool. One more thing to watch for is
that forecast soundings do depict some clearing and steepening
lapse rates across NH, and as the upper trough swings through,
additional snow showers or even a squall or two could develop.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
The region will transition more to upslope flow Thursday
evening/night as the low pressure deepens while lifting toward the
Canadian Maritimes. This will keep snow showers going in the
mountains with additional light accumulations, and steep low-
level lapse rates/high Froude numbers favor some of these making
it downwind of the mountains. Winds also become gusty with the
pressure gradient continuing to tighten with forecast soundings
supporting 25 to 35 mph, sending wind chills down into the
teens toward daybreak Friday.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
1040 PM update...Forecast looks reasonable through Sunday, but
models become very divergent, even withing own their own
ensemble members. The 12Z operational Euro shows a weak wave
moving through Mon or Mon night, with generally dry conditions
Tue/Wed, and because that`s proven to be the model of choice
will lean in that direction. The front lingers offshore until a
wave moves in later in the week, and with fast zonal WSW aloft
this suggests more in the way of subsidence on the NW side of
the front. Chance POPS were kept into Tue night, given that
there are enough EPS ensemble members showing some precip to
ignore the possible of of a wave traveling NE along the front
around midweek. 850 MB temps do bump up to around +5 C Tue-Wed,
o temps warm into the 40s with maybe some places hitting 50F.

3 PM...Low pressure continues to intensify and exit through the
Canadian Maritimes on Friday as high pressure builds towards
New England. A strong northwesterly gradient will be building
through a deep layer. With sufficient cold air advection and
ample mixing, expect very gusty winds to occur during the day
with a few 35 kt+ peak winds.

It will be chilly with quite a few upslope clouds and possibly a
flurry or two in the mountains. Temperatures will only make it into
the teens north to 20s south.

Over the weekend it will remain chilly across the region with below
normal temperatures for this time of the year. Most of the
clouds and precipitation will be hung up in the mountains on
Saturday with clouds across the entire region on Sunday as a
warm front crosses the region. Snow showers can be expected
despite a moderating regime.

12Z operational models and ensemble solutions suggest a slow moving
and complex weather system will approach the region on Monday with
pops increasing for snow during the day across much of the
region except the coastline. S second piece of energy will
track to our west, allowing a frontal system to become hung up
along the east coast until midweek. This may allow for
prolonged periods of rain and snow which will be very dependent
on the progressiveness of the boundary along and near the coast.
There is considerable uncertainty in this scenario as other
ensembles suggest more progressive solutions to the system.

&&

.AVIATION /04Z THURSDAY THROUGH MONDAY/...
Short Term...VFR for a little while longer, but conditions will
deteriorate to IFR this evening and tonight, possibly LIFR at
some terminals, as precipitation overspreads the area. This will
be mainly snow inland and more of a rain/snow mix or even
mainly rain for the coastal sites. These restrictions will be
primarily tonight through Thursday morning, and then improving
conditions are expected through Thursday afternoon with most
sites returning to VFR. Mostly VFR Thursday night with the
exception of HIE and maybe LEB, where snow showers will also
remain a possibility. There is also a low chance of snow showers
south of the mountains Thursday.

Winds: A period of southerly gusts to 25 to 30 kt is possible
for the coastal terminals tonight (up to 35 kt at RKD) and then
westerly winds will increase late Thursday into Thursday night
with gusts again 25 to 30 kt, possibly up to 35 kt.

Long Term...Mainly VFR conditions expected Friday and into the
weekend with the exception of upslope low cloudiness in the
mountains. On Sunday, all areas will lower to IFR and LIFR in
ceilings during the day with rain and snow. More mixed precipitation
with persistent IFR conditions during the period Monday through
Wednesday.

&&

.MARINE...
Short Term...There will be deteriorating conditions across the
waters this evening and tonight as southerly flow increases
ahead of a low pressure center that will pass just north of the
waters Thursday before lifting into the Canadian Maritimes
Thursday night. Southerly gales are likely ahead of the low
tonight and Thursday over the eastern waters/Penobscot and then
across all the waters Thursday evening and Thursday night as
westerly flow increases with the deepening low.

Long Term...Gale force conditions may remain over the waters as the
extended forecast starts on Friday. Winds back to the southwest and
diminish slightly over the weekend but still remain relatively
gusty.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory until noon EST Thursday for MEZ007>009-
     012>014-033.
     Wind Advisory until 7 AM EST Thursday for MEZ027-028.
NH...Winter Weather Advisory until noon EST Thursday for NHZ001>009-
     011-015.
MARINE...Gale Warning until 7 PM EST Friday for ANZ150>152.
     Small Craft Advisory until 4 PM EST Thursday for ANZ153-154.
     Gale Watch from Thursday afternoon through Friday evening for
     ANZ153-154.

&&

$$

SYNOPSIS...
NEAR TERM...Cempa/Combs
SHORT TERM...Combs
LONG TERM...Cannon
AVIATION...
MARINE...