676
FXUS61 KGYX 192356
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
756 PM EDT Tue Aug 19 2025

.SYNOPSIS...
A wave of low pressure tracks across southern New England
Wednesday bringing chances for rain, mainly across NH and far SW
Maine. High pressure builds in Thursday and remains over the
area through Saturday for fair weather and warming temperatures.
High pressure shifts offshore Sunday with a slow moving frontal
system crossing the region Sunday night through Monday bringing
widespread chances for showers.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
800PM Update... Loaded in the latest surface observations and
tweaked trends but otherwise no significant changes were made to
the forecast at this time.

Previously...
High pressure will continue to provide dry conditions the rest
of the day with filtered sunshine as high clouds stream overhead
stemming from a shortwave well to our west.

Going into tonight, the wave will approach the region with forecast
soundings depicting a thickening and lowering cloud base. There
will be a quite a bit of dry air to overcome, so I think precip
(if any) probably won`t occur until late or even toward
daybreak, but if any does fall it should be pretty light and
over NH. The cloud cover is expected to keep temperatures
mostly in the 50s overnight while also keeping the potential for
any fog quite low, but far northern and eastern areas may still
be able to reach the upper 40s.

&&

.SHORT TERM /WEDNESDAY NIGHT/...
Guidance for the most part has come into much better agreement
with the previously mentioned shortwave with a southward trend
in highest chances for showers on Wednesday across NH and far SW
ME and even moreso across southwestern NH. There`s still some
uncertainty in amounts with the potential for the axis of the
higher QPF missing to the south and west, but portions of
southwest NH could receive 0.25" to 0.50" of rainfall and
perhaps up to 1.00" per the HREF PMM. The 12Z NAMnest continues
to be an outlier by showing even higher amounts.

Chances for rain and QPF decrease with northern and eastern extent
with not as much moisture and lift to work with (the Augusta and
Midcoast regions may not see any rain), but this is also an area of
uncertainty on how tight of a gradient there will be. The GFS is a
little more optimistic in bringing measurable rainfall across
these areas than other guidance and is more out an outlier on
this side of the coin. So it`s possible PoPs will need to be
further trimmed farther to the north and east in future updates.
Clouds and precip should keep temperatures limited to the 60s
in most places. The risk of dangerous rip currents will also be
increasing along the coast as long-period swells from Hurricane
Erin arrive.

The trend will be for showers to follow a downward trend Wednesday
evening and into Wednesday night once the wave passes to the south
and east. Flow overnight looks very light, so I think there`s a
pretty good chance for fog to develop in areas that receive rainfall
and also in valleys that see clouds clear out. Overnight lows look
to range from the upper 40s to mid 50s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Overview: On Thursday, a short wave will be lifting northeast
away from the area with surface high pressure building in from
the north. The latest forecast from the National Hurricane
Center brings Erin ENE well south of 40N/70W Thursday night
through Friday with the system`s wind field remaining well
southeast of the forecast area. Deep layer ridging will build
into New England Saturday for continued dry conditions and
warming temperatures. A trough deepening over the Great Lakes
will send a slow moving frontal system across New England early
next week.

Impacts:
*Long period swell from Erin will bring an increasing rip current
risk Thursday into Saturday, lingering into Sunday

*Swells from Erin will peak Friday into Saturday when High Surf
Advisory conditions are likely with potential for beach erosion.

Details:

Skies will turn mostly sunny Thursday as high pressure builds back
into the region from the north. Easterly winds ahead of the high
will keeps temperatures slightly below normal with highs in the low
to mid 70s. Temperatures will moderate Friday into Saturday as deep
layer ridging builds into the area allowing for highs back into the
mid 80s Saturday.

High pressure shifts offshore Sunday as a trough deepens to the west
of New England. This trough will be slow to translate east with one
frontal system poised to cross the area late Sunday into
Monday. Models do diverge on the timing, with some models
keeping Sunday mostly dry until late in the day. Have stuck with
the NBM which brings PoPs 30 to 40 percent across NH and NW
Maine with PoPs around 20 percent along the coastal plain Sunday
afternoon. PoPs will increase Sunday night and Monday when a
slow moving front will cross the area bringing the potential for
a widespread soaking rainfall. There is a large spread in
ensembles with respect to QPF with ensemble means around 0.25
to 0.5 inches. Troughing will linger over the Northeast through
the middle of next week keeping slight chances for showers in
the forecast into Tuesday.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Short Term...VFR the rest of the day today and most of tonight.
There could be fog in some spots tonight, but I think with the
cloud cover, chances are too low to put in any TAF. A disturbance
moves through Wednesday with the highest potential for showers
across the NH terminals, especially south of LEB to CON. IFR to
MVFR ceilings and fog are also possible for most areas through
Wednesday night, but highest chances are across NH.

Long Term...Mainly VFR Thursday through Saturday with the
exception being nighttime valley fog at KLEB and KHIE.

&&

.MARINE...
Short Term...Winds and seas will likely remain below SCA levels
through Wednesday night, but seas will start building as long-
period swells from distant Hurricane Erin begin arriving over
the waters on Wednesday.

Long Term...Hurricane Erin is forecast to track well southeast of the
Gulf of Maine Thursday night through Saturday. Long period swell
from this system will bring wave heights greater than 5 feet
Thursday night building to 10 feet Friday night before slowly
subsiding through the weekend. The gradient between this system
and high pressure to the north will bring winds close to 25 kts
Thursday night into Friday morning.

&&

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

&&

$$

NEAR TERM...Tubbs
SHORT TERM...Combs
LONG TERM...Schroeter