Londonderry, New Hampshire 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

417
FXUS61 KGYX 281603
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1203 PM EDT Wed May 28 2025

.SYNOPSIS...
Quiet weather and seasonable temperatures continue today with
high pressure over the region. A weak low pressure system will
lift north into the area Thursday bringing a chance for rain
showers. A second and more organized system will lift north
through western Maine Saturday, bringing widespread soaking
rains once again. Cool and damp conditions will likely persist
Sunday with an upper low overhead.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

12:00pm Update... No notable changes to the forecast at this
time as temperatures warm under mainly sunny skies. The sea
breeze is starting to slowly move inland along the coastline,
with temps falling back a bit through the afternoon here.

630 AM Update... Minor changes to reflect latest observational
trends.

Previously...
Nighttime microphysics satellite imagery early this Wednesday
morning shows mainly clear skies over western ME and north-
central NH. Across southern NH cirrus is riding over the H5
ridge axis from distant low pressure located over the Mid-
Atlantic. Current temperatures range from the lower 40s across
the northern valleys to the upper 40s/lower 50s elsewhere.
Additional cooling is likely through sunrise. It will otherwise
remain a dry early morning.

Surface high pressure will move well south east of the Gulf of
Maine today but a secondary high located over Quebec will allow
for another dry and warm day. High temperatures into the lower
80s can be expected for inland locations with highs into the
lower to middle 70s along the coast. Similar to yesterday, a sea
breeze is likely to develop by late morning or early afternoon
and this will cool temperatures behind it. Other than some
cirrus (mainly over NH) skies will be mostly sunny.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Skies will become cloudy from southwest to northeast tonight as
low pressure moves northeastward from the Ohio River Valley. The
combination of a gradually moistening column and increasing
forcing for ascent may allow for the development of scattered
showers after midnight, especially over southern NH. Patchy fog
may also develop with low temperatures mainly into the 50s.

Thursday will be a transition day with mainly cloudy skies
prevailing and scattered showers at times. High temperatures
will be warmest over eastern interior locations due to a later
arrival time of clouds and showers. Highs will range from around
70 from the Capital District of Maine and points east with 60s
elsewhere.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
11 PM Update...No notable changes in the latest NBM regarding
the long term period. Friday may be a decent day as one wave
exits to the east and the next system will approach Friday
night. Recent NWP guidance still show a signal for a deepening
low pressure system to track NNE along the Northeast coast into
Saturday that will bring a widespread soaking rain. There are
some signs of transitioning to ridge dominant pattern across the
eastern CONUS towards the middle of next week that would favor
a warming and drying pattern.

Previously...

There will be a lull as the system dissipates as it lifts
northeast Thu Night, but attention turns to a second and more
organized system for Friday night into Saturday.

Forecast guidance has trended wetter with this system as a deepening
upper level trough swings across the region. As this is happening,
another low drops down from Canada and phases with a coastal low
moving north from Virginia. There are variations in the track of the
surface feature, with it lifting north and inland across either
western or central Maine. These variations in the track and strength
of this deepening low will greatly influence the areas of
heaviest rainfall, and wind potential. The Euro and the Canadian
models shows this low tracking more east and slower than the
GFS. Despite these finer details, the big picture is we are
faced with another rainy weekend with soaking rain Saturday and
cool/showery conditions on Sunday. In fact the cold pool is deep
enough to support some snow at Mt. Washington Saturday night,
but likely not in lower elevations. Upper level troughing
remaining across our region into Sunday, with a cold pool and NW
flow aloft. Destabilization with any heating will support
showers for much of Sunday. Trend has favored dropping
temperatures for Sunday with highs 50s to low/mid 60s in the
south. NW flow will linger into Monday with a additional showers
and below normal temperatures, but ridging returns next week
with a drying out period possible.

&&

.AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
Short Term...VFR conditions prevail today with light
southwesterly flow becoming southerly by this afternoon and
increasing to 5-15 kts. VFR conditions will persist tonight
outside of any patchy FG and scattered -SHRA after 04Z. The
greatest potential for a scattered -SHRA will be across NH TAF
sites. Conditions will then likely begin to deteriorate on
Thursday due to lowering ceilings and scattered -SHRA with at
least MVFR restrictions. No LLWS is anticipated through the
period.

Long Term...Improved flight conditions are likely Thursday
night into Friday. Conditions go back downhill Saturday with widespread
moderate rainfall.

&&

.MARINE...
Short Term...Winds and seas will remain below SCA thresholds
through at least Thursday. A few southerly gusts up to around 20
kts is possible this afternoon though over the outer waters.

Long Term...Winds and seas to remain below SCA thresholds
Thursday night through Friday. The more organized system
Saturday will be deepening as it lifts into the Gulf of Maine.
Trend is favoring stronger gradient with a 30% chance of small
craft winds. Seas have a higher probability of SCA criteria of
>5ft due to the long S fetch.

&&

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

&&

$$


NEAR TERM...Clair/Tubbs
SHORT TERM...Tubbs
LONG TERM...Jamison/Schroeter