448
FXUS61 KGYX 250457
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1157 PM EST Sun Nov 24 2024

.SYNOPSIS...
Low pressure in the Canadian Maritimes continues its slow exit
to the northeast tonight. Weak high pressure crosses the area
Monday. Low pressure crosses the region Tuesday bringing a light
wintry mix to start across the interior Tuesday morning with
rain becoming the dominant p-type south of the mountains. Dry
conditions are expected Wednesday into Thursday morning. A m ore
significant low pressure system takes aim at the Northeast late
Thursday through Friday while there is uncertainty in to the
track and ultimate impacts.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...

11:45pm Update... No notable changes with this update, mostly
just fit with trends so far this evening. Did bump up temps
slightly downwind of the mountains where mixing has kept temp
slow to cool so far tonight. Upslope snow showers continue
north of the mountains through the overnight, with flurries
mostly having come to an end downwind of the mountains as the
flow becomes more blocked.

6:59pm Update... Mostly just minor tweaks to fit with trends so
far this evening, but overall the forecast remains on track.
Upslope snow showers continue across the north, with a few
scattered flurries reaching downwind of the mountains. These are
diminishing in coverage as a weak trough that swung through this
afternoon moves away.

Previous...

The forecast remains largely status quo overnight under the
influence of meandering low pressure in the Canadian Maritimes.
Gusty northwest flow continues overnight...occasionally gusty but
should mostly settle down to a steady breeze. This will also result
in low level moisture being forced over the higher terrain and
upslope snow showers are expected to continue. Froude numbers are
forecast to remain above 1 thru around midnight. I have some
isolated snow showers making it into the foothills thru that
time...after which snow showers will be confined to the northwest
slopes. With gradient remaining higher overnight I have blended
2 m raw temps into the min temp forecast to keep radiative
effects out of the forecast...though colder than last night

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Winds will diminish Mon and much of the area will see sunshine.
Clouds should remain banked against the mtns on the northwest side
before scattering out late in the day. As wind direction becomes
more westerly thru the day...upslope snow shower activity will wind
down.

Initially Mon night will be clear with light winds...as a result
temps should drop quickly after dark. However the next front will be
fast approaching from the west. As it nears temps should steady and
begin rising before dawn. I have blended a non-diurnal temp trend
into the forecast. Precip will be approaching near daybreak as
well...and timing will be crucial. If it arrives more quickly temps
are likely to be near freezing and some brief freezing rain is
possible before temps warm. If precip can mostly delay until after
sunrise that should mitigate any freezing precip threat.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...

Long Term Update... The main focus in the long term continues
to be on the Thursday-Friday storm system, with the potential
for impactful winter conditions across at the least the
interior. The evening model runs have offered little new
clarity, with the GFS still mostly out to sea, while the Euro
and its ensembles remain consistent on a deeper low closer to
the coast. One model that did shift a bit was the Euro AIFS,
coming a little closer toward the Euro ENS solution, after
being more closely aligned with the GFS in earlier runs. POPs
have been increased slightly through this time, but uncertainty
remains on Precip type and placement.

Full Discussion...

Overview:
A short wave swinging through the Great Lakes will send a
surface low towards the St Lawrence Valley Tuesday morning. This
system will spread a light wintry mix across the interior with
mainly rain becoming the dominant p-type south of the mountains.
A secondary low tracks near the coast of Maine that will help
change the wintry mix over to snow into the mountains and far
north Tuesday afternoon. This system exits by Wednesday morning
with mostly dry weather Wednesday into Thursday morning. A more
robust low pressure system will track near the Northeast late
Thursday through Friday. Large variance in model solutions
continue with respect to the track and strength of this system,
as well as the resultant p-types. Colder air moves in behind
this system over the weekend with below normal temperatures
favored into the first week of December.

Impacts:
*Slick travel possible across the interior Tuesday morning from
light wintry mix. Precipitation changes to rain south of the
mountains while light snow accumulations could bring slick travel
into Tuesday evening across the north.

*A robust low pressure system tracking near the Northeast Thursday
into Friday will have the potential to bring wintry precipitation
and travel impacts. Finer details of timing and p-types will likely
take several more model cycles to come into focus.

Details:
Warm air advection from low pressure tracking into the St Lawrence
Valley will spread light freezing rain or a wintry mix along a line
roughly from KLEB to KAUG and points northward around the time of
the morning commute. Temperatures will rise above freezing through
the morning with rain becoming the dominant p-type south of the
mountains. A secondary low forming along the coast of Maine will
help draw cooler air into the column that will change the wintry mix
to snow into the mountains and points north with light accumulations
through Tuesday evening.

This system exits Tuesday night for a drying trend into
Wednesday morning. Fair weather looks to prevail Wednesday with
highs ranging from the mid 30s north to upper 40s south. Dry
conditions likely continue Wednesday night into the first part
of Thursday. Attention then turns to what is now a trough of low
pressure off the Pacific Northwest that will cross the CONUS
the next few days that could spawn a robust low pressure system
near coastal New England.

Large variance continues in the 12Z model suite with respect to a
potential impactful system Thursday into Friday. A somewhat more
consistent signal is apparent in ensembles with a low pressure
system taking a favorable track south of the area to bring
widespread wintry precipitation away from the coast. The ECMWF and
its ensembles have remained the most consistent with the track of
this system while the GFS has had several runs with this system
being a miss to the south.

A review of ensemble low tracks and 00Z cluster analysis reveals three
emerging camps for the system late Thursday into Friday. The first
cluster representing 34 percent of ensemble members (mainly EPS followed
by GEPS) favors a low track from the Ohio Valley across southern New
England and into the Gulf of Maine. This scenario would favor precipitation
starting as snow/wintry mix across much of the area with a change
to rain south of the mountains while the mountains and far north
stay mostly snow. The second cluster representing 25 percent of ensemble
members (mainly GEPS followed by equal weight of EPS/GEFS) favors
better phasing and a more amplified system. This scenario favors more
QPF and more warm air being drawn into the system off the Atlantic.
This would lead to less wintry precipitation south of the mountains
with even the mountains and far north potentially seeing snow change
to a wintry mix/rain. The third cluster representing 22 percent of
the members (mostly GEFS) does not phase resulting in weaker low
pressure system or waves of low pressure passing south of New
England. This scenario could result in a miss south or bring
chances for light snow to much of the area with snow mixing with
rain near the coast and less QPF. The primary feature associated
with this system is still offshore of the Pacific NW with a
secondary feature in the Arctic Circle near Alaska. This will
likely lead to continued run to run and model to model variance
with this system for the next few model cycles. Stay tuned, as
there continues to be the chance for a winter system impacting
the region Thursday into Friday.

Colder air moves in behind this system over the weekend with broad
troughing settling over the eastern CONUS. This will likely bring a
sustained period of winter-like conditions into the first week of
December.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
Short Term...Mainly VFR conditions prevail thru most of Mon.
MVFR CIGs will linger northwest of the mtns overnight and begin
to lift and scatter out early Mon. Surface gusts around 20 kt
will also be possible at all terminals at times tonight. Very
early Tue precip will begin moving in from the west. Timing will
be very important as temps will be cold enough for wintry
precip Mon night. A brief mix is possible on the leading edge in
addition to areas of IFR conditions around 12z.

Long Term...Lowering cigs will likely bring MVFR to IFR
conditions Tuesday. From KLEB to KAUG and points northward there
will be the chance for light freezing rain or wintry mix Tuesday
morning with rain to the south. Precipitation the changes to
rain south to north through the day Tuesday while KHIE may stay
see a wintry mix change to snow Tuesday evening. Conditions
improve Tuesday night with VFR likely Wednesday into Thursday
morning. A more robust system is forecast to track near New
England late Thursday and Friday. Depending on the track,
widespread wintry precipitation will be possible along with IFR
to LIFR conditions.

&&

.MARINE...
Short Term...Winds remain gusty overnight. I have extended gales
into the late evening for most of the waters...while north of
Port Clyde to Stonington will see gale force gusts thru Mon
morning. SCA conditions continue in Casco Bay until Mon morning
as well.

Long Term...Low pressure crossing northern New England will
bring increasing southerly flow Tuesday with winds approaching
SCA conditions along the outer waters. Winds shift out of the
west Tuesday night with SCA conditions likely through Wednesday
morning. Winds and seas drop below SCA thresholds Wednesday
night into Thursday before another low pressure system tracks
near coastal New England late Thursday into Friday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Gale Warning until 7 AM EST Monday for ANZ150.
     Small Craft Advisory until 1 PM EST Monday for ANZ151-152-154.
     Small Craft Advisory until 7 AM EST Monday for ANZ153.

&&

$$


NEAR TERM...Clair
SHORT TERM...Legro
LONG TERM...Schroeter