Area Forecast Discussion
Issued by NWS Portland, ME-- Highlight Changed Discussion --
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FXUS61 KGYX 100043
Area Forecast Discussion
National Weather Service Gray ME
743 PM EST Fri Dec 9 2016
Cold air from Canada will continue to move into the area tonight
and Saturday, with temperatures likely remaining below freezing
for the weekend. Saturday night into Sunday morning will be quite
cold with some areas falling below 10 degrees. Low pressure moving
through the Great Lakes and toward New England on Monday will
spread snow into New Hampshire and Maine beginning Sunday night.
Expect accumulating snowfall areawide, though there may be a
chance to rain near the coast during the day on Monday. Snow will
come to an end Monday night as low pressure moves east leaving
mountain snow showers in its wake. Seasonably cold weather
continues through the middle of next week.
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
-- Changed Discussion --740 PM...All in all forecast remains on track. HAve kept pops up a
little longer for the upslope, through the evening, but overall
the SHSN should be on the decline overnight. Also lowered sky
cover outside of the mountains overnight, and tweak temps just a
bit based on current obs. The gusty winds are slowly diminishing,
although they will probably persist through the evening before
they settle in around 10 mph overnight. Low will range from the
single digits in the mountains to the mid-upper teens in srn NH
and on the ME coast.
Previously...Cold air continues to filter into the region in the
wake of the cold frontal passage. Snow showers have continued
through the day as the mountain flow remains unblocked. Overnight
the winds will decrease as the pressure gradient lessens. Snow
showers will come to an end around nightfall as the winds
decrease. Overnight lows will drop into the single digits north
and teens south with the light winds preventing further radiative
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.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Saturday high pressure will move over the region with cold air
aloft moving in. Skies will be mostly clear in all but the
northern mountains. Overnight temperatures will drop to the lowest
seen this season. Temperatures will reach the low teens all the
way to the coast. Have dropped temperatures below guidance
especially in the valley bottoms that radiate well such as SFM HIE
and BML. In the mountains the residual moisture may lead to some
patchy freezing fog in the valleys which will help to keep
temperatures above zero through the region.
.LONG TERM /SUNDAY THROUGH FRIDAY/...
A low amplitude shortwave trough will track eastward through the
Great Lakes and into New England on Monday while the broader
upper low (and core of the colder air) slips southeast out of the
Hudson Bay region of central Canada and into northern New England
later this week. This will spell a below normal temperature
forecast through the period with a chance of wintry weather on
Monday. The details:
High pressure moves east across the area on Sunday with light
winds and cold temperatures continuing. Air mass moderation may
lead to high temperatures a few degrees warmer than Saturday, but
still below freezing. Temperatures drop into the teens again
Sunday night for much of the area, while increasing clouds coming
in from the southwest will hold temperatures in the 20s there.
Surface low pressure tracking through the central Great Lakes
Sunday night will begin to occlude as the leading edge of its
influence reaches the Atlantic Coast. Secondary low pressure is
expected to form early on Monday generally near New York City and
tracking northeast toward Cape Cod and southern New England. This
track favors cold air remaining in place over northern New England
and precipitation remaining as snow for most areas. A track closer
to the coast will allow for the coastal front to push further
inland along the Maine and New Hampshire coastline on Monday. The
American models tend to favor a track closer to the coast with a
transition to rain along the coast and even fairly far inland.
Meanwhile the European model tracks the low offshore of Cape Cod
keeping precipitation as all snow even to the coast. Current
forecast thinking favors a blend of the two solutions, with a
greater weight toward the snowfall forecast over the transition to
rain. An easterly low level flow in advance of this system should
maintain fairly deep cold air damming over interior western Maine
and eastern New Hampshire, which should prevent the rain/snow line
from moving much further inland than the Route 1 corridor in
opposition to the NAM/GFS solutions.
Expect the snow to begin from southwest to northeast Sunday night
into Monday morning. By daybreak the snow should be spreading
across the entire region, with a few inches of accumulation
already on the ground over much of New Hampshire. The heaviest
snowfall rates are likely to occur in the morning hours on Monday
as the low moves by offshore. Snow ends from west to east Monday
evening. It is possible that there could be some light drizzle or
freezing drizzle as the system passes by to the east but low level
moisture remains in place below a dry slot aloft. Any impacts from
this should be minor considering the several inches of snowfall
expected beforehand. Total snowfall accumulations are likely to be
in the 4 to 7 inch range for most locations, though there could be
less along the coast if the coastal front is able to move in and
change things to rain before coming to an end.
Low pressure moves east Monday night with lingering snow showers
possible in the mountains and a westerly flow in the wake of the
low. Highs on Tuesday should reach the low to mid 30s, but remain
in the 20s in the mountains. Another surge of colder air arrives
on Wednesday when a northern stream trough tracks through Quebec.
Models are not in good agreement on what to do within the storm
track to the south of the larger Canadian upper low. The GFS would
like to develop a coastal low that brings more snow to our area
Wednesday into Wednesday night, but the ECMWF does not generate a
storm until it is further east out into the Atlantic. At this
point will try to split the difference for the forecast and
include a chance of snow, but the ECMWF solution seems a bit more
realistic given the lack of a sharp trough to drive cyclogenesis.
Either way, temperatures should be cold even for this time of year
as the core of the cold air drops into our area late next week.
.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
Short Term... gusty winds will continue for the next few hours
before decreasing overnight. HIE will continue to see MVFR SHSN
overnight. VFR conditions will prevail for Saturday with a chance
of IFR FZFG for HIE late Saturday night.
Long Term...VFR conditions expected Sunday, but should see
deteriorating conditions Sunday night into Monday morning with
snow moving in from the southwest. Heaviest snow will be Monday
morning, with a change to rain possible along the immediate
coastline during the day Monday. Should see widespread IFR to
LIFR conditions during the heaviest snowfall, even occasionally
going to 1/4SM in heavy snow. Conditions improve Monday evening
into Monday night except for the mountains where lower ceilings
could remain an additional 24 hours.
-- Changed Discussion --Short Term...740 pm update...Lowered the gale to SCA on the
outer waters and dropped the SCA in the bays. Winds are gusting
to around 30 kts outside of the bays, and this will persist
through most of Saturday.
Long Term...Coastal low tracking through the Gulf of Maine on
Monday could produce advisory level wind speeds as it moves
through. There is a low chance that winds could reach gale force
for a time ahead of the low. Winds become westerly to
northwesterly behind the low Monday night and could remain near
advisory levels through Tuesday.
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-- Changed Discussion --ME...None.
MARINE...Small Craft Advisory until 4 PM EST Saturday for ANZ150-152-
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