FXUS61 KGYX 240158

Area Forecast Discussion
National Weather Service Gray ME
958 PM EDT Tue Oct 23 2018

Low pressure will intensify along the Maine coast tonight before
moving into the Canadian Maritimes on Wednesday. This will
bring of snow in the mountains and rain or snow elsewhere
tonight into Wednesday morning. High pressure will slowly build
in from the west late Wednesday through Friday. Low pressure
passes through the Gulf of Maine Saturday over the weekend.


10pm update.. minor adjustments for current trends, temps have
cooled a bit along the coast. Precipitation continues to have a
sharp back edge.

630pm update... Temperatures across the northern Mountains as
well as interior Maine from Augusta eastwards to Bangor are
running colder than prior forecast and have adjusted
temperatures down for the next several hours. This may allow for the
changeover to snow to occur sooner, and as a result there is a
slight increase in the amounts in the northern valleys, however
the overall snowfall amounts have not changed much.

A very sharp back edge to the precipitation associated with this
first cold front/cold conveyor belt and have adjusted the PoP
down for the next few hours over western New Hampshire.

Along the immediate coastline, onshore flow has kept
temperatures still in the 50s at Portland however those temps
will drop rapidly over the next hour or so as the precipitation
moves through and flow become northerly behind it as cold air
deepens. KGYX 00Z sounding remains in the warm sector with
freezing level around 4500ft, however higher elevation locations
in the White mountains suggest the freezing level has already
fallen to below 2000ft.

prev disc...
WAA overunning light rain has overspread the area in advance of
a s/wv upstream digging southeast. Will continue high POP's thru
the night as baroclinic zone in advance of the approaching
system continues to develop and will enhance overrunning pcpn later
in the evening. US models have finally caught on to EURO
solution allowing strong development of a coastal low along the
ME coast tonight. Strong dynamic cooling should help wipe out
the warmer boundary layer temps in the mtns and foothills
allowing some significant accumulations to occur especially in
central Somerset and northern Franklin counties where a Winter
Storm Warning has been issued for tonight into Wed aftn.
Elsewhere in the mtn areas the rain will change to a mix and
then to snow with some lighter accumulations expected since some
of the QPF will be in the form of rain, so a winter wx adv has
been issued for northern NH and southern Somerset and Franklin
counties. Used a blend of models for temps but then lowered from
there a tad to reflect stg dynamic cooling from aloft. As the
storm winds up late tonight into Wed morning freezing levels
will fall enough closer to the coastal midcoast areas that some
ptype may fall as snow with some light accums possible...esp in
areas such as the Camden hills etc.


The track and timing of the deepening coastal low in fairly good
agreement by models Wed but wraparound snow or mixed ptype should
continue into the eastern and northern mountain areas through
much of the day. Over southern areas winds back to northwest and
downsloping winds will bring a quick end to the pcpn and some
clearing is expected in the afternoon. Used a blend of NBM temps
for Wed but once again nudged a tad lower. Wed night the system
pulls away but CAA and downsloping gusty winds continue.


Very active and complex pattern will continue during the long
range portion of the forecast.

A strong northwest flow and cold air advection will allow for
below normal temperatures across western Maine and New Hampshire
on Thursday. H8 temperatures near -10C and a fresh snowpack in
portions of the higher terrain may make for very chilly
conditions. A northwest breeze will help keep a well mixed layer
for Thursday night however.

By Friday and Friday night, the gradient will relax as high
pressure settles over the region. There will be high level
moisture advecting into the region Friday night, however
northern areas may remain clear long enough for temperatures to
drop into the upper teens by late at night.

Pattern becomes more active for the upcoming weekend. A vigorous
upper level trough will approach the eastern United States on
Saturday. This negatively tilted upper level feature will allow
low pressure to move north from the Mid Atlantic region during
the day Saturday to a position near Long Island, New York
Saturday evening. Strong easterly or northeasterly winds can be
expected late Saturday and Saturday night with winds
particularly gusty along the immediate coastline.

Temperature profiles suggest that snow may accumulate once again
over the far northern, high terrain with mostly a cold rain
elsewhere. The 12Z guidance package is not entirely onboard with
the timing of this system with the GFS being somewhat slower
with the track of the surface low. This surface feature may
drive the coastal front inland by Sunday as relatively warm
ocean temperatures still remain in the Gulf of Maine.

A second, deepening and fast moving coastal storm may effect the
region early next week as a deep, upper level low pressure
system remains over the forecast area.


Short Term...Mainly IFR conditions tonight into Wed improving
to VFR over southern areas with MVFR conditions continuing in
the mountains. MVFR conds continue into Wed night in the
mountains with VFR conditions elsewhere.

Long Term...Mainly VFR conditions and a breezy northwest flow
until this weekend. On Saturday, conditions will be lowering to
IFR in rain over southern areas and snow over northernmost
areas. IFR conditions will continue on Sunday as the system
weakens over the region.


Short Term...Gale warnings have been issued for outer water for
Wed into Wed night with SCA conditions in the bays.

Long Term...SCA thresholds will likely be exceeded as a strong
northwesterly gradient continues on Thursday. East to
northeasterly gales are expected with an approaching coastal
system on Saturday. Winds may briefly approach storm force.


East to northeasterly gales and possibly low end storm force
winds out over the Gulf of Maine will trigger a storm surge over
about 1.5 feet. This combined with already high astronomical
tides may bring the southwest coast of Maine and the Seacoast of
New Hampshire over flood stage. Minor flooding along with beach
erosion and splash-over is possible during the weekend.


ME...Winter Weather Advisory until 11 AM EDT Wednesday for MEZ007.
Winter Storm Warning until 6 PM EDT Wednesday for MEZ008-009.
Winter Weather Advisory until 6 PM EDT Wednesday for MEZ013-
NH...Winter Weather Advisory until 11 AM EDT Wednesday for NHZ001-
MARINE...Small Craft Advisory from 8 AM to 10 PM EDT Wednesday for
Gale Warning from noon Wednesday to 2 AM EDT Thursday for


NEAR TERM...Curtis
LONG TERM...Cannon
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