Londonderry, New Hampshire 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

879
FXUS61 KGYX 191853
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
253 PM EDT Thu Mar 19 2026

.WHAT HAS CHANGED...
Active pattern will bring at least two systems across the
region from late Friday through Monday morning. While rain will
be the dominant precipitation type south of the foothills, model
solutions have trended colder with more available moisture. Chances
for accumulating snow have increased for Sunday into Monday
system with impacts possible to both commutes.

&&

.KEY MESSAGES...
1. A cold front cross tonight bringing scattered snow showers
followed by a wave of low pressure crossing Friday afternoon into
Saturday morning. A few inches of snow in the mountains could bring
some slick travel in the mountains Friday evening.

2. Active weather continues Sunday into next week with
multiple chances for widespread precipitation. The system Sunday
into Monday could bring accumulating snowfall to much of the region.
Amounts are uncertain, but impacts to the Monday morning and
evening commutes are possible.

&&

.DISCUSSION...
KEY MESSAGE 1 DESCRIPTION...

Onshore flow ahead of a cold front had produced a localized band of
ocean effect snow in the vicinity of Sagadahoc and Kennebec Counties
for much of the morning. Latest radar trends show this band is
weakening while surface temperatures have warmed to near or above
freezing. Therefore, little in the way of additional snow
accumulations are expected with this feature. As the cold front
crosses overnight there will be chances for scattered snow showers,
mainly in the mountains.

Friday will start off mostly dry with partly to mostly sunny skies.
Clouds will quickly increase west to east Friday morning as a wave
of low pressure tracks east out the Great Lakes. This low will track
across the forecast area Friday night and quickly exits Saturday
morning. Temperatures will rise into the 30s north of the mountains
and into the 40s south of the mountains before precipitation begins
Friday afternoon. Precipitation will likely be rain along and south
of the foothills through Friday night. However, some dynamic cooling
may allow for rain to change to snow across portions of
Androscoggin, Kennebec, and northern Waldo Counties that could bring
some slick travel Friday evening. In the mountains and points north
precipitation will likely stay all snow with a couple inches
possible down to the valley floors and several inches above 2500
feet. Dry air aloft will work into the DGZ Friday night that may
allow for patchy freezing drizzle across the mountains and north
into Saturday morning while confidence is not high enough to put
this in the gridded forecast. Drier air arrives Saturday
allowing for clearing skies.

KEY MESSAGE 2 DESCRIPTION...

Global models show a busy 500mb wave pattern from Saturday night
into next week with a quick progression of shortwaves and ridges
crossing through the Northeast.

The next system of interest is Sunday into Monday with a strong
signal in the ensemble guidance for widespread precipitation as low
pressure crosses the Great Lakes and heads for New England. There`s
still timing discrepancies in onset/end times and does have
potential to be longer duration, so the NBM PoPs covering a larger
time window of 40-70% seem reasonable.

For Sunday, precipitation type favors snow in and around the
mountains with both rain and snow possible to the south, but colder
air working in as winds turn more north to northeast could change
this to all snow later in the day into Sunday night and Monday.
Depending on the track of the low it`s possible somewhere will see a
period of sleet or freezing rain as well. While it`s too early to
pinpoint amounts, there`s increasing potential for accumulating
snowfall as ensemble means for QPF are on the order of 0.25" to
0.75". We`ll see how models trend in the coming days, but impacts to
both Monday commutes are on the table, especially the morning.

Based on latest guidance, precipitation should come to an end Monday
night with shortwave ridging building in for Tuesday bringing mostly
dry conditions.

Another wave brings a chance for lighter precipitation Tuesday night
or Wednesday followed by with what looks to be a wetter system
and a better chance for widespread precipitation approaching the
region around next Thursday.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Through 18Z Friday: Mainly VFR through Friday morning. The
exception will be occasional MVFR at KAUG and KRKD.

OUTLOOK:
Friday Afternoon through Saturday...Snow north and rain south
overspreads the area bringing MVFR to IFR into Saturday morning.
Skies clear through the day with conditions returning to VFR.

Saturday night: MVFR possible with -SN.

Sunday-Monday: IFR is looking more likely with a chance for
widespread precipitation. Mostly snow is favored across the north,
and precip could be a rain/snow mix possible to the south
before a change to snow. There may also be a period of PL/FZRA,
but confidence is low on details.

Monday night and Tuesday: Return to VFR Monday night with mostly
VFR Tuesday, except MVFR possible at HIE.

&&

.MARINE...
Winds and seas remain below SCA thresholds through Friday
morning. Southerly flow increases ahead of an area of low
pressure Friday afternoon shifting to the northwest Saturday
morning. SCA conditions will exist from Friday afternoon through
Saturday.

SCA conditions are possible from Sunday into Tuesday as low pressure
crosses New England and then lifts into the Canadian Maritimes.
There remains uncertainty in the track and timing of the low, and a
period of gales can`t completely be ruled out. The pattern remains
active toward the middle and and later parts of next week with a
couple of additional potentially bringing more increased winds and
seas.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory from 5 PM Friday to 8 PM EDT Saturday for
     ANZ150-152-154.

&&

$$

DISCUSSION...Combs/Schroeter