South Portland, Maine 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

223
FXUS61 KGYX 280011
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
711 PM EST Mon Jan 27 2025

.SYNOPSIS...
A sharp cold front will pass across the forecast area early
Tuesday, with scattered snow squalls likely in some areas
tomorrow morning. A fresh Arctic airmass moves in tomorrow
afternoon and evening. A clipper system likely brings some light
snowfall accumulations on Wednesday. High pressure crosses
through the area on Thursday, and then another weak system is
possible by Friday and Saturday.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
705 PM...Did some fine tuning to the POPS and temps just to
better define the temporal resolution of the fropa, and best chc
for SHSN, which looks to happen in the predawn to about 13-14Z.
Also brought min T up a degree or two in some spots given where
temps are now and the steady overnight SW flow, which should be
enough to prevent them falling much ahead of the front.

Previously...Southwesterly flow continues ahead of an
approaching cold front overnight tonight, along with increasing
cloud cover. With this set up, temperatures fall into the 20s in
most spots this evening, and near 30 degrees along the coast.
These temps then hold steady most of the night until the passage
of the cold front late tonight and tomorrow morning.

Ahead of the front, widespread snow showers and some heavier
snow squalls move into northern areas by around midnight. The
shield of snow showers across Canada today only gradually
lessens in coverage through the overnight hours. This brings
scattered to widespread snow showers north of the mountains
through most of the overnight hours. As we get closer toward the
predawn hours, some heavier snow showers and snow squalls are
expected to reach into central and southern New Hampshire toward
the morning commute time. These squalls look likely to move
from the Lakes region through southern New Hampshire between the
5-9am timeframe. Maine is also likely to see some heavier snow
shower activity move south of the mountains by sunrise tomorrow,
but the heaviest ones look to be across New Hampshire.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Scattered snow showers are likely to move through the urban
areas of Concord, Manchester, and Portsmouth during the morning
commute time tomorrow. They may arrive a little later toward
Portsmouth, but drivers should plan for rapidly changing
conditions during tomorrow morning`s commute in these areas. The
high res guidance has been consistent on bringing these in
during this timeframe, and it`s worth noting that the guidance
often tends to under-do the extent and intensity of these
features from this far out. Again, Maine is also likely to see
some heavier snow showers reach the coastline during this
timeframe, but they don`t look to be as heavy as the ones across
New Hampshire.

Behind the front and the snow squalls, temperatures quickly
fall as a fresh Arctic air mass moves into Northern New England.
Despite temps holding in the 20s most of the night, northern
areas see temps fall into the single digits by midday. Teens to
low 20s are expected in most areas south of the mountains during
the daytime after morning highs in the upper 20s to low 30s.
Gusty winds will also accompany these falling temperatures,
with gusts around 30-35 mph for the late morning and afternoon
hours.

Tomorrow night, temps continue to fall through the evening.
Lows bottom out in the single digits below zero across the
north, to the low teens along the coast. By midnight however,
the winds ease and clouds increase ahead of an approaching
clipper system.

The leading edge of the light snow likely reaches into
southwest New Hampshire around midnight, but is expected to
mostly dissipate in the dry airmass. The next push of moisture
arrives a few hours later, with a more steady snow likely moving
into southwest and southern New Hampshire during the 3-5am
timeframe. The snow continues to spread northeastward across the
area through daybreak, likely reaching western Maine and into
parts of the MidCoast by sunrise. Once again, the morning
commute is likely to be impacted across southern New Hampshire
with 1-2 inches of snow possible by sunrise on Wednesday.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As alluded to already, light snow is expected to already be
falling over much of the area to start the morning on Wednesday
and will probably continue through much of the morning, making
for slick travel. The steadier snow should begin tapering off by
the afternoon but could be earlier across NH per some of the
incoming 18Z hi- res guidance. However, there will be a
continued chance of light snow showers through the rest of the
day with upper troughing still overhead. QPF is forecast to be
around a tenth of an inch with this system, give or take a few
hundredths either side. This snow will be the light and fluffy
variety, and the fairly high snow to liquid ratios (model blend
of 17:1 to 19:1) yield snow amounts of 1 to 3 inches across the
area. The ECMWF and GFS are both hinting at localized instances
of closer to 0.20" QPF, which could boost snow amounts closer to
4 inches in some areas.

The system pulls away Wednesday evening into Wednesday night
with northwest winds kicking in and bringing in colder and drier
air. The GFS is suggesting winds could be pretty gusty, but the
NAM holds off on the breezier conditions closer to Thursday
morning. If the gusty winds do kick in, wind chills could fall
below zero, and potentially into the double digits below zero in
the mountains. Otherwise, mainly just expecting upslope
mountain snow showers.

Other than the mountain snow showers, Thursday looks dry and breezy,
but winds will start to slacken in the afternoon as high pressure
builds in, although only briefly. Cold advection will limit highs to
the teens and twenties south of the mountains with subzero wind
chills remains possible during the morning.

Another clipper system could bring light snow to the area Thursday
night into early Friday with the better chance looking across the
north. Also on Friday, a southern stream trough will drive another
low toward the Mid-Atlantic. The ECMWF has trended farther north
with this system which would bring increasing chances for light snow
Friday into Friday night, possibly even rain during the day Friday
across southern NH, but the GFS is still farther south and drier. If
the northward trend does continue, then PoPs will need to be
increased Fri-Fri night.

Broad high pressure then builds in for Saturday into Saturday night,
and Saturday night could be quite cold if the high can settle
overhead and skies stay clear enough. The high quickly shifts east
with models in pretty good agreement this far out advertising
another clipper moving in from the Great Lakes with increasing
chances for light snow Sunday into Monday.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Short Term...Mainly VFR conditions with west-southwesterly wind
gusts of around 20-25kt continue through the evening with VFR
conditions. Winds ease a bit overnight, and then become gusty
again by late tomorrow morning with west-northwesterly gusts of
25-30kt. Scattered snow showers arrive at HIE late tonight, and
move through by mid-morning. Intervals of MVFR ceilings are
possible during this time. Elsewhere, scattered snow showers
likely move through early to mid tomorrow morning with brief
restrictions at LEB, MHT, CON, and PSM. Brief snow showers are
also possible at PWM, AUG, and RKD tomorrow morning, but are
more scattered than the New Hampshire terminals.

VFR conditions return behind this front by late morning on
Tuesday, and continue into the evening. Light snow with MVFR to
IFR conditions then moves into southern New Hampshire late
Tuesday night, reaching MHT, CON, LEB, HIE, PSM, and PWM by
daybreak on Wednesday.

Long Term...A quick-moving system brings IFR/MVFR ceilings and
IFR to MVFR visibilities from light snow on Wednesday.
Conditions will then start to improve by Wednesday afternoon
into Wednesday evening, except upslope snow showers and MVFR
ceilings at HIE into Thursday, although a couple of stray snow
showers can`t be ruled out Wednesday night elsewhere. Mostly VFR
Thursday Another couple of low pressures could bring additional
restrictions Thurs night into early Friday and Friday night
into early Saturday, but details are uncertain.

For winds: northwest winds increase Wednesday evening/night
with gusts 25 to 30 kt, possibly 35 kt, and these gusty winds
will continue into Thursday morning before a downward trend
Thursday afternoon.

&&

.MARINE...
Short Term...Southwesterly gales continue across the waters
ahead of a strong cold front through the overnight, with a few
gusts to near storm force possible over the outer waters
tonight. Gales lower across the Bays tomorrow morning. Gales
continue with a shift to more westerly behind the passage of the
front tomorrow morning across the outer waters, and then ease
across the outer waters by Tuesday evening. A a few hours of SCA
conditions follow the the gales, but then a period of fair
conditions is expected tomorrow night ahead of a weak low
pressure center.

Long Term...A weak clipper system moves from W-E across the
waters on Wednesday into Wednesday night bringing a period of
light snow and reduced visibility. SCA conditions are possible
Wednesday but more likely Wednesday night into Thursday as
northwest winds increase, with gusts to gale force also
possible. High pressure builds in across the Eastern Seaboard
Thursday, centered just offshore of the Carolinas, with westerly
gusts to SCA levels remaining possible. Another quick-moving
clipper system looks to cross Thurs night into Friday morning
while a low pressure also passes south of the waters Friday
night into early Saturday. Broad high pressure then builds
toward the Northeast US most most of the upcoming weekend, but
by late Sunday into next Monday, another low pressure moving
from the Great Lakes toward New England could bring another
period of increasing winds and seas.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Gale Warning until 6 PM EST Tuesday for ANZ150-152-154.
     Gale Warning until 6 AM EST Tuesday for ANZ151-153.

&&

$$

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