South Portland, Maine 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

349
FXUS61 KGYX 140709
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
309 AM EDT Mon Apr 14 2025

.SYNOPSIS...
Low pressure moves toward NEwfoundland today with a return to
drier and warmer conditions as high pressure builds in over New
England. A cold front approaches from the west Tuesday, with an
upper low influencing conditions into midweek.

&&

.NEAR TERM /THROUGH TODAY/...
500 MB low that has been around all this past weekend finally
begins to track NE from S of Nova Scotia to Newfoundland today.
Between this low and the next one to our west, we will
experience a narrow, but high amplitude, ridge today. This will
bring a mainly sunny day, with some early clouds in the E, and
late cirrus in the W. NW winds will be a little breezy through
midday, as the we still have that weakening pres gradient, but
winds become lighter during the afternoon. IT will be mild with
highs ranging from the 50s in the mtns and on the mid coast, to
the low to mid 60s in the S half of NH and interior SW ME.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/...
The ridge shifts E this evening, and there may be a chance for a
few showers in W NH late this evening, the bulk of this precip
holds off until after midnight. Even after midnight, mainly
expecting hit and miss SHRA crossing the CWA, mainly in weak WAA
at first, and then into the warm sector toward morning, at least
aloft, if not at the sfc, given increasing onshore flow. Lows
range from the mid to upper 30s in the N and E, where, skies
will take longer to become overcast. To the low to mid 40s in
the S half of NH, where the clouds and showers will prevent
temps from falling that much, and the warmer air begins to move
in toward toward daybreak.

Initially on Tuesday morning, will see occlusion shift ENE
across N zones, so the better chc of showers is here, with
maybe a break in the S. But, good chunk of energy dives into the
trough equatorward of the 500MB closed low N of the Toronto
area, and this will tilt that trough negative, while also
developing mid-level FG over central ME and allowing coastal low
to develop along the Downeast ME coast. This means more
numerous showers or steady rain over the ME mtns and central
ME, with some heavier convective showers possible as well during
the mid to late afternoon. Across NH and SW ME still can`t rule
out some SHRA in the afternoon as this system deepens, but it
will also help push the cold front through these areas mid to
late afternoon, and should see things dry out quickly in the S
behind the front late in the day. Highs range from the upper 40s
in the ME mtns and the far E zone, where clouds and more
frequent showers persist through the day, to 55-60 in S ME and
interior SW NH.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
1045 PM Update...No major changes in the extended with the
latest NBM guidance. An upper low will be slowly exiting into
the Canadian Maritimes Wednesday with mainly upslope rain and
mountain snow showers into Thursday morning.

Previously...

Upper low will be centered just south of James Bay to start Tuesday
morning with associated cold front still west of the region. Out
ahead of the front, expecting light rain showers and/or drizzle to
be around Tuesday morning, but coverage of showers will increase
through the afternoon as the cold front begins to push through the
area and synoptic scale lift increases. There has been more of a
trend in the models in showing the 500mb wave responsible in sending
the cold front through taking on a negative tilt, creating a region
of strong diffluence and a secondary low developing over western ME.
There has resulted in an upward trend in QPF and PoPs, especially
over in western ME. Still could see a couple of storms with small
hail out of this system as well, mainly across NH, but heavy
downpours are possible across most of the region. Rain showers will
diminish from west to east during the afternoon and evening, and
it`s possible northern areas may see a brief period of snow mix in
Tuesday evening. Otherwise, there will be a continued chance of rain
and snow showers in the mountains through Tuesday night.


The low pressure system lifts into the Canadian Maritimes on
Wednesday and more or less stays put there until late week. This
puts the area under broad cyclonic flow with breezy conditions
thanks to good mixing and steep low-level lapse rates. Waves
rotating around the upper low and low-level upslope flow will lead
to rounds of rain or snow showers in the mountains while areas
downwind have a lower chance...but still around 20-30% on Wednesday
and around 20% on Thursday as Froude numbers do come up somewhat in
the afternoon. Temperatures will be mostly in the mid 40s to lower
50s for highs, except a bit cooler in the mountains.

The upper low slowly moves east on Friday as high pressure begins to
build into New England with temperatures also trending upward and
winds not as breezy. The next low pressure will quickly follow
though, but it does look the daytime hours stay dry. High
temperatures should be back into the 50s for most with some low 60s
across southern NH.

Although the details of the track and timing of the next low
pressure system are a still a bit in question, there is good
agreement among the ensembles of the next chance at widespread
precipitation over the weekend. The ECWMF continues to be the
more progressive with early start and end times while the GFS is
in the slower camp, but there is more agreement for the higher
precip chances Friday night into Saturday with decreasing PoPs
going into Sunday.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
Short Term...Lingering MVFR cigs should clear out of KAUG by
09Z, and KRKD by mid morning. Otherwise VFR is expected through
this evening. MVFR cigs between midnight and daybreak at NH
terminal and Tue morning in ME. There could be some periods of
IFR Tue morning as well. Improvement to VFR possible late in the
day at KLEB/KCON/KMHT/KPSM, but KRKD/KAUG will likely drop to
IFR during Tuesday afternoon.

Long Term...Expect improvement from west to east through the
Tuesday evening. Mostly VFR Wednesday through Friday with a low
chance of rain showers downwind of the mountains on Wednesday.
The exception will be at HIE, where the potential for MVFR
ceilings and rain or snow showers may continue through at least
Thursday, and possibly into Friday.

&&

.MARINE...
Short Term...NW winds pick up a bit this morning, but are
expected to fall below SCA levels by this afternoon. Winds seas
below SCA conds through Tuesday, but will start to increase Tue
afternoon.

Long Term...Cold front crosses late Tuesday, and then W to SW
winds likely increase to SCA levels Tuesday night as low
pressure lifts into the Canadian Maritimes. SCA conditions will
probably continue through Wednesday and Thursday as the low stay
across the Maritimes, but high pressure may provide a period of
improvement Friday and maybe into Saturday, depending on how
the speed and track of the next front and low pressure that
approach the region sometime next weekend.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory until 11 AM EDT this morning for ANZ150-
     152-154.

&&

$$

NEAR TERM...Cempa
SHORT TERM...Cempa
LONG TERM...Combs/Schroeter