Pembroke, New Hampshire Weather Forecast Discussion

061
FXUS61 KGYX 180605
AFDGYX
Area Forecast Discussion
National Weather Service Gray ME
205 AM EDT Thu Sep 18 2025
.SYNOPSIS...
High pressure remains in place across New England through
today with warm and dry conditions. A cold front moves through
the area tonight, with dry and breezy conditions behind the
front on Friday. High pressure follows for the weekend, bringing
a fresh cool and dry airmass to New England. Mainly dry
conditions continue for at least the next week.
&&
.NEAR TERM /THROUGH TODAY/...
Latest RAP pressure analysis early on this Thursday morning
shows the center of a weak coastal low located south of
Nantucket with clouds streaming to the north of this low
center. Northeast radar mosaic is showing some weak returns
moving towards the ME coast but the 00Z KGYX RAOB report shows
significant dry air aloft with mid-lvl RH around 20%. Therefore
will maintain slight chance PoPs (15-20%) but believe most
locations will remain dry. Otherwise, fog will remain possible
through daybreak, especially across coastal locations as well as
valleys. Current temperatures are primarily into the 50s and
some additional cooling is likely through sunrise.
The aforementioned low will exit slowly to our east today as a
cold front approaches from the north. Skies will gradually clear
from north to south with high temperatures on avg 5-10 degrees
above avg into the upper 70s to lower 80s.
&&
.SHORT TERM /TONIGHT THROUGH 6 PM FRIDAY/...
The sfc cold front will cross tonight, bringing perhaps a few
showers to the far north and mountains along with additional
cloud cover in developing upslope flow. South of the mountains,
it will remain dry with mainly clear skies. Low temperatures
will range from the 40s across the north with lower to middle
50s elsewhere.
Friday will feature mainly sunny skies behind the front along
with cooler high temperatures into the 60s across the north with
lower to middle 70s south. Northwesterly winds may gust up to
around 25 mph at times, which could cause elevated fire wx
concerns. For additional information please see the fire wx
section below.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
06Z Long Term Update... Little change to the long term portion
of the forecast. A frost/freeze remains likely Fri and Sat night
across the interior. Conditions look to remain dry through at
least early next week before some rain chances return mid-week.
Previously...
Pattern Overview: Broad troughing develops at the 500mb level
as a potent upper low moves into the Hudson Bay Region, but with
high pressure building in at the surface this will only act to
advect a cold dry airmass into the Northeast through the first
part of the weekend. Shortwave ridging then builds in for the
latter part of the weekend, and the beginning of next work week,
bringing warmer temperatures. A disturbance may bring our next
chance of precipitation midweek, but uncertainty is high.
Impacts and Key Messages:
* The first widespread frost of the season is possible Friday
  and Saturday night, as well as a freeze for northern zones.
* Continued dry weather will likely lead to worsening drought
  conditions and elevated fire weather concerns.
Details: Clear skies and calming winds look to lead to an
excellent night of radiational cooling on Fri night. This
airmass is going to be of arctic origin so it looks likely that
we will see the 850mb 0C isotherm creep into northern New
Hampshire and northwestern Maine overnight Friday. This may lead
to the first widespread frost of the season as temperatures in
the low to mid-30s extend down into the foothills. This may also
be the first freeze for northern zones as well as the cooler
guidance brings temperatures as low as 30F into Coos county and
the Western Maine Mountains. The coastal plain may stay in the
upper 30s and low 40s depending on if a breeze sticks around.
Saturday and Sunday: Northwesterly flow continues with high
pressure continuing to build in to the region so expect daytime
temperatures to be even cooler on Saturday with highs only
recovering into the mid to upper 60s south of the mountains, and
in the upper 50s to low 60s to the north, after a very cold
night. Dewpoints continue to fall as dry air continues to work
into the region as well, making for even lower relative humidity
values and continued elevated fire weather concerns (see the
Fire Weather section below for more details). It looks to also
be another very cold night as high pressure becomes centered
over the region overnight. Temperatures will be similar, but
frost and freeze potential become a little more widespread as
the freezing mark pushes toward the foothills and upper 30s push
to the immediate coast. Sunday begins a warming trend as
shortwave ridging builds in and high pressure becomes centered
over the Gulf of Maine. High temperatures look to climb into the
low to mid-70s areawide, with noticeably warmer lows Sunday
night (low to mid-40s for much of the area, with upper 40s in
the coastal plain).
Monday-Wednesday: Shortwave ridging, and thusly the warming
trend, lasts into midweek with high temperatures back into the
low 80s by Tuesday. Models are beginning to hint at a
disturbance around the midweek timeframe that may bring some
precipitation to the region, but as expected at this time range,
they all have wildly different depictions of it and the
ensemble spread on QPF is large. Due to the high uncertainty
have left the low chance PoPs from the NBM in the forecast. The
main takeaway is once again going to have to be that little to
no rain through the extended forecast period is going to lead to
worsening drought conditions.
&&
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
Short Term...Localized IFR-LIFR restrictions due to low ceilings
and FG will remain possible through around 14Z this morning. VFR
will then prevail through the remainder of the day and this
evening with light S flow. Some valley FG is possible tonight,
which could result in some localized restrictions. Flow will be
light and variable. Mainly VFR are then expected on Fri,
although some MVFR CIGS cannot be completely ruled out at KHIE
at times. NW winds may gust up to 20 kts at times. No LLWS is
anticipated through the period.
Long Term...Other than the potential for fog at night. VFR
should be the prevailing condition through the forecast period
as high pressure continues to dominate the weather pattern.
&&
.MARINE...
Short Term...Light S flow prevails today before turning NW
behind a cold front on Friday with gusts up to 20 kts possible
and seas of 2-3 ft.
Long Term...Wind gusts and seas are expected to remain below
SCA criteria through midweek as high pressure moves over the
Gulf of Maine. Winds shift around to southerly on Sunday.
Gusts around 20kts are possible Friday night as a front crosses
the waters during the day.
&&
.FIRE WEATHER...
Post frontal northwesterly winds may gust up to around 25 mph on
Friday. This combined with relative humidity values dropping
into the 35 to 40 percent range will make for elevated fire
weather concerns. Saturday will be less breezy, but much drier
as an Arctic originating airmass builds into the region.
Relative humidity values are expected to drop into the 25-30
percent range which, despite light winds, will continue elevated
fire weather concerns, especially if fuels are readily
available.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR TERM...Tubbs
SHORT TERM...Tubbs
LONG TERM...Baron/Tubbs

NWS GYX Office Area Forecast Discussion