049
FXUS61 KGYX 181810
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
210 PM EDT Mon Aug 18 2025

.SYNOPSIS...
Cooler weather continues through the middle of this week with a
weak trough triggering some showers Wednesday, followed by high
pressure building in from the west through Saturday.
Temperatures will warm back into the 80s by late week and to
start off the upcoming weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Impacts and Key Messages:
* No significant weather impacts expected.

Visible satellite this afternoon shows plenty of high clouds
streaming in from an MCS over the Great Lakes Region. These
shouldn`t effect tonight`s temperatures which are expected to
plummet. Continued to blend in some MAV which handles
radiational cooling well and this suggests temperatures bottom
out in the low to mid 40s areawide, with some upper 30s in
northern New Hampshire and the western Maine mountains. Cloud
cover will eventually get thicker toward day break Tuesday,
which may help keep temperatures from getting even lower and may
also keep fog development minimal, but do expect at least some
degree of valley fog.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
Impacts and Key Messages:
* No significant weather impacts expected.

High pressure remains centered over the Gulf of Maine Tuesday
which will continue a cool dry flow. Skies look to end up more
in the partly cloudy range as low pressure approaches from the
Great Lakes Region. We will see continued drying at the surface
as relative humidity values once again drop to around 40-45%
during peak heating. Overall, it will be another fair weather
day with high temperatures similar to today (Monday); low to mid
70s areawide.

Will start to see cloud cover increase Tuesday night as low
pressure moves closer to the region. This keeps temperatures
from plummeting like we have seen the past few nights, but it
will still be cool with temperatures in the low 50s south of the
mountains, and mid- to upper 40s to the north. The 12Z NAMNest
and 12Z HRRR suggest showers may be see as early as around
sunrise Wednesday morning, but there is still significant
uncertainty between them so kept chances low during that time.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
An upper-level shortwave trough crosses the area Wednesday,
bringing an increase in cloud cover as well as a chance of
showers. Global models as well as ensembles depict the highest
probabilities of measurable rainfall being from the foothills
northward with a tenth to a quarter of an inch of rain possible.
Temperatures will be mostly in the 70s for highs.

Worth mentioning: the NAM and NAMnest are at odds with the
global models with being much more robust with moisture and QPF
by developing a a sharp inverted trough near southern areas and
strong isentropic lift. If this ends up being the case,
temperatures would also be much cooler than the current
forecast, but this seems more of an outlier scenario at this
point. However, we`re getting into that 48-hour window where
additional hi-res guidance should bring more confidence to the
forecast.

Once the Wednesday system passes, another period of mostly dry
weather is expected from Thursday through Saturday with
gradually warming temperatures, although the mountains may see
some diurnal showers on Thursday. This dry weather is owed to an
upper ridge steadily building toward New England as the latest
forecast from NHC has Tropical Cyclone Erin passing well to the
south and east of the area as well as any extra moisture that
would potentially bring any additional rain chances. However,
long- period swells from Erin are modeled to begin arriving from
mid to late week, likely bringing high surf to the coast as
well as high risk of dangerous rip currents. Highs go from the
70s Thursday to the 80s Friday and Saturday.

Global models are in good agreement by shifting the high to the
east of the area by Sunday as an upper low digs in north of the
Great Lakes and sends a frontal boundary toward New England.
Things can always change, but with at this point there is a
pretty good signal from ensembles for this front to bring
measurable rainfall to portions of the area Sunday or Monday,
but amounts are uncertain.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Short Term...Gusty winds subside tonight which will lead to the
development of valley fog effecting LEB. Otherwise, VFR will
prevail overnight into Tuesday. Ceilings look like they may
thicken and lower toward MVFR Tuesday night as low pressure
approaches from the west.

Long Term...A low pressure system will bring increasing shower chances
on Wednesday into Wednesday night and the potential for IFR to MVFR
restrictions. However, confidence in details is low other than it
looks like the NH terminals have the higher chances. After this
system passes, primarily VFR Thurs-Sat other than the
possibility of nighttime valley fog at HIE and LEB.

&&

.MARINE...
Short Term...Wind gusts and seas remain below SCA criteria
through Tuesday night as high pressure remains centered over the
waters. Winds shift northerly tonight, than back to southerly
Tuesday afternoon, with gusts falling below 10kts.

Long Term...Conditions remain below SCA levels Wednesday. Winds remain
below criteria through Friday, but seas will build through late
week as long-period swells from Tropical Cyclone Erin (passing well
to the south and east of the waters) arrive over the waters Thursday
and Friday, likely requiring a Small Craft Advisory. Seas will start
to come down over the weekend but could still remain above SCA
levels based on the current forecast. Southerly winds may also
gust to around 25 kt as the pressure gradient tightens with high
pressure to the east and an approaching frontal boundary from
the west.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.

&&

$$


NEAR/SHORT TERM...Baron
LONG TERM...Combs