Boothbay Harbor, Maine Weather Forecast Discussion

715
FXUS61 KGYX 291755
AFDGYX
Area Forecast Discussion
National Weather Service Gray ME
155 PM EDT Mon Sep 29 2025
.SYNOPSIS...
High pressure remains over New England through early in the
week with dry weather and warm temperatures. A cold front moves
through Tuesday, allowing for much cooler and continued dry
weather for midweek with potential frost. Warmer conditions
return late in the week and next weekend as high pressure
remains in place.
&&
.NEAR TERM /THROUGH TONIGHT/...
Impacts and Key Messages:
* No significant weather impacts expected.
Visible satellite and area webcams show a cirrus deck advancing
into southern zones, at the time of this writing, courtesy of
Tropical Cyclone Imelda. This will continue to advance this
evening making it to about the foothills tonight, before a
frontal boundary and dry air start pushing back. An area of weak
low pressure will be moving along this front with some
accompanying showers, but virtually all guidance suggest they
dry up before reaching our area. I have kept the near zero PoPs
from the NBM, but I suppose a sprinkle near the International
Border can`t be ruled. Temperatures drop into the mid- to upper
40s north of the mountains, and into the low to mid 50s to the
south. Valley fog is likely in the northern valleys as those
temperatures are near the dewpoints.
&&
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
Impacts and Key Messages:
* Long period swell arriving from TC Humberto will pose a
  moderate to high rip current risk Tuesday.
* Frost is likely in northern zones Tuesday night.
Northwesterly flow behind the front advects cooler and drier
air into the region. Surface high pressure building back in will
clear out the clouds that moved in overnight leaving us with
full sun. In turn this promotes very good mixing down of the
drier air aloft, dropping dewpoints into the 30s and 40s. With
high temperatures expected to climb into the low to mid 70s
south of the mountains, and into the 60s to the north, relative
humidity values drop into the 25 to 35 percent range across much
of the area. Post frontal winds also look on the breezy side
with gusts generally 15 to 20 mph. We have had a few days of
good drying since our last rain, so elevated fire weather
conditions may be a concern. Also of note, is increasing long
period swell from distant tropical cyclone Humberto which is
expected to begin arriving at area beaches and pose a moderate
to high rip current risk. At the angle the swell is approaching
the risk is likely going to be higher on the midcoast down
through the Casco Bay area, with York County and New Hampshire
beaches more in the moderate risk. A Rip Current Statement has
been issued accordingly, but the bottom line is that enhanced
caution should be used in the water wherever you are, especially
now that beaches are unguarded.
Skies remain clear Tuesday night and winds calm north of the
mountains. This promotes good radiational cooling and these
locations drop near the freezing mark as a result. With these
temperatures frost formation should be expected as well. These
areas have had a hard freeze already, but a frost advisory may
be issued in accordance with our "fixed growing season" policy
which runs until October 1st for these northern zones. South of
the mountains may sustain enough of a breeze to keep from
totally decoupling, and therefore have kept temperatures in the
low to mid 40s there. Valley fog is possible once again, as
temperatures cool near these low dewpoints.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Impacts: Frost is possible Wednesday night and Thursday night.
Otherwise, the weather will generally be dry and quiet through the
long term.
The center of an expansive ~1038mb surface high will slide into the
region from Canada through the day on Wednesday and into Wednesday
night. The orientation of the high will lead to cooler days on
Wednesday and Thursday with high temperatures ranging from the 50s
across the north to the low to mid 60s south. Breezier winds will
also hang around on Wednesday given a tightening pressure gradient
between high pressure and tropical cyclone Humberto out in the North
Atlantic.
This pattern will also lead to some chilly nights, especially across
the higher terrain and valleys. For Wednesday night, lows will dip
into the upper 20s and lower 30s across the north with values in the
mid 30s to lower 40s south. A few coastal areas could see readings
in the mid 40s. Widespread frost/freeze conditions are likely
Wednesday night into Thursday morning across northern and portions
of central New Hampshire as well as portions of the western Maine
mountains. Thursday night will be a touch warmer as the center of
high pressure slides a bit further south but widespread lows in the
upper 20s and lower 30s across the north should lead to some more
frost.
High pressure continues to drift south at the end of the week,
leading to return flow and warmer temperatures Friday through the
weekend. The NBM currently has highs ranging from the mid 60s to
lower 70s on Friday and then some lower 80s back in the forecast by
Sunday. There are then some signals for a slight cool down to start
the week but NBM spread remains fairly high this far out so
confidence is low. For now, any precipitation chances look to be
minimal at best.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Short Term...VFR prevails through Tuesday night with the only
exception being fog development at LEB tonight and Tuesday
night, which will bring about IFR restrictions.
Long Term...Generally expect VFR conditions through the long
term with the exception of the usual valley fog at night over
KHIE and KLEB. Wednesday will be a bit breezy with north winds
gusting to around 20 knots.
&&
.MARINE...
Short Term...Long period swell from tropical cyclone Humberto
builds in tonight, reaching the 5 foot mark by Tuesday
afternoon. The swell will continue to build through Tuesday
night reaching 5 to 7 feet by the early hours of Wednesday
morning. Wind gusts increase to 25 kts Tuesday night as well.
Winds are generally west-southwesterly tonight before a front
crosses the waters early Tuesday morning shifting them around to
northerly.
Long Term...SCA conditions are likely on Wednesday and Wednesday
night. Winds will start to subside on Thursday but waves will
be a little bit slower to calm. Thus, SCA conditions may hang
around through the afternoon.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...High Risk for Rip Currents from Tuesday morning through Tuesday
     evening for MEZ024>027.
NH...None.
MARINE...Small Craft Advisory from 11 AM Tuesday to 8 PM EDT Wednesday
     for ANZ150-152-154.
     Small Craft Advisory from 8 AM to 8 PM EDT Wednesday for
     ANZ151-153.
&&
$$
NEAR/SHORT TERM...Baron
LONG TERM...Hargrove

NWS GYX Office Area Forecast Discussion