South Portland, Maine 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

263
FXUS61 KGYX 040445
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1145 PM EST Mon Mar 3 2025

.SYNOPSIS...
Temperatures continue to warm over the next few days as high
pressure moves off the Eastern Seaboard. Low pressure then moves
through the Northeast Wednesday and Thursday. Warm
temperatures, rain, and gusty winds are all expected Wednesday
into Thursday. Cooler conditions gradually return late week and
through the weekend as conditions remain unsettled.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
1145 PM Update...Middle to upper level clouds are continuing to
track over the region with pockets of clear skies mixed in
between. This is allowing for a wide range in temperatures with
readings below zero in the north to around 20 in southern and
coastal sites. Made some minor adjustments to overnight
temperatures but overall the fcst remains on track.

Previously...
615 PM Update... Minor changes to reflect latest observational
trends. Satellite imagery early this evening shows some high
altitude cirrus streaming from northwest to southeast over much
of the region. These clouds may limit cooling a little but
temperatures are still expected to fall quickly through around
midnight before mid-level clouds arrive, as seen on the latest
HREF.

Previously...
Impacts and Key Messages:
* No significant weather expected

Clear skies continue into the first part of tonight which
likely cause some locations to decouple and radiate early on in
the night. I blended in some cooler MOS guidance to account for
this and, with temperatures only reaching the 20s today, the
window looks to stay open long enough to drop most of the area
into the single digits area wide. Southern New Hampshire and the
immediate coast may only drop into the mid to upper teens.
Latest RAP analysis shows a 500 mb trough offshore, with visible
satellite showing clouds approaching the area from the
northwest. It is these clouds, plus the beginning of the warm
advection return flow that will help to level temperatures off
around the midnight hour. Forcing from the warm advection may
squeeze out some snow flakes in the mountains, but with minimal
low level moisture these would be very light.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
Impacts and Key Messages:
* No significant weather expected

Brief ridging looks to make for a mostly sunny morning, before
the thicker clouds associated with the approaching system move
in. Continued southerly flow and a mostly sunny day should help
high temperatures climb into the low to mid-40s south of the
mountains. The mountains will be the first to see clouds and
precipitation in the form of snow showers early on the afternoon
so those locations likely top out in the mid to upper 30s.

Skies will be mostly cloudy areawide by Tuesday night. In the
mountains temperatures aloft stay cool enough to support light
snow for most of the night with accumulations only in the range
of 0.5- 1.5". Heading toward Wednesday morning warmer air begins
to move in aloft and a brief period of freezing rain may mix
in, but again with very light QPF this likely won`t be of
significance before the low levels warm as well. The Mid Coast
may also see some light plain rain showers Tuesday night ahead
of the main system, as flow turns onshore there and saturates
the column. The bulk of the system begins to move in around
sunrise Wedensday, but that will be covered in the Long Term
section. Low temperatures will range from the upper 20s north to
the low 30s south.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
05Z Long Term Forecast Update... Latest ensemble and
deterministic based guidance continues to be in good agreement
for an area of low pressure within a negatively tilted H5 trof
axis to bring a widespread moderate rainfall to the region
Wednesday night into Thursday. Rainfall amounts of generally up
to 1" is currently expected with locally higher amounts in the
southeastern slopes of the White Mountains. Behind this system,
cooler weather will return with showers of rain and snow at
times.

Previously...
Overview...

Low pressure moves through the Great Lakes and Saint Lawrence
Valley Wednesday through Thursday. A trough then lingers across
the Northeast through the weekend as high pressure gradually
noses in from the west at the surface through early next week.

Details...

Low pressure moves through the Great Lakes during the day on
Wednesday. Light showers are likely through the morning,
especially across northern areas, with some pockets of light
freezing rain across the northern valleys possible through mid
morning. The steady rain then moves in during the afternoon,
gradually expanding from west to east. The steadiest rain moves
through during the overnight hours on Wednesday, with more
scattered showers and shorter periods of rain likely through the
day on Thursday. Overall rainfall amounts generally look to be
in the 0.75-1.25 inch range, with some locally higher amounts
across the higher terrain.

The low tracks through the Saint Lawrence on Thursday, with a
cold front passing through late in the day. Much of Thursday
will be spent in the warm sector of the system, with highs
ranging from the low 40s across the north where the cold front
moves through earlier, to the mid 50s across southeast New
Hampshire where a few breaks of sunshine are possible through
the day.

With the cold deep snow pack across most of the region, the
majority of the snowpack is expected to survive the event.
Southern and coastal locations are likely to the most snowpack
loss, but also see less rainfall. The higher terrain is likely
see more rainfall, but less snowpack loss. So areal flooding is
still not expected, but river rises, ice break up, and ice jams
remain possible. With the warm temperatures on Thursday, the
possible ice movement and ice jams would most likely occur on
Thursday if they were to come to fruition.

The low continues to deepen across the Canadian Maritimes on
Friday, bringing a deepening trough across the Northeast. Gusty
winds are likely to follow the system during the day on Friday.
Weak disturbances transit through the trough through the
weekend, bringing occasional rain and snow showers, mainly to
northern locations. Relatively cooler air returns during this
timeframe, but a cool airmass is not expected as temps mostly
return to near normal into early next week.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Short Term...VFR will prevail through Tuesday morning. HIE may
see some MVFR ceilings as some thicker clouds pass through the
mountains tonight. Tuesday afternoon is when ceilings will lower
in response to an approaching system. MVFR ceilings are likely
at HIE, with IFR visibilities possible in snow showers.
Elsewhere, ceilings and visibilities will remain VFR in rain
showers through Tuesday night. Wind gusts remain generally below
15kts with some gusts toward 20kts possible at coastal
terminals during the day Tuesday.

Long Term...IFR to LIFR conditions are likely at all terminals
Wednesday through Wednesday night with low ceilings, fog, and
periods of rain. Gradual improvement is expected on Thursday
with scattered showers, with southern terminals most likely to
return to MVFR and VFR conditions. VFR then returns Thursday
night, with MVFR ceilings more likely at HIE with upslope
conditions. Northwesterly wind gusts of around 30- 35kt are
likely on Friday, with VFR likely at most terminals, and MVFR
more likely at HIE. Mainly VFR with brief periods of MVFR
prevail through the weekend, with westerly wind gusts around
25kt on Saturday

&&

.MARINE...
Short Term...High pressure moves over the waters tonight
keeping conditions somewhat tranquil. Southwesterly wind gusts
and seas then ramp up above SCA criteria during the day Tuesday
as a system approaches the area. They may then fall below SCA
criteria for a bit heading into Wednesday.

Long Term...A deepening low pressure system tracks west of the waters Wednesday
through Thursday. Southerly gales are possible with this system
Wednesday night through Thursday morning. Westerly gales are then
possible on Friday as the low deepens across Atlantic Canada. The
low then only slowly moves away through the weekend.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory from 10 AM Tuesday to 4 AM EST Wednesday
     for ANZ150-152-154.
     Gale Watch from Wednesday evening through Thursday morning for
     ANZ150>154.

&&

$$

NEAR TERM...Tubbs
SHORT TERM...Baron
LONG TERM...Clair/Tubbs