Londonderry, New Hampshire 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

722
FXUS61 KGYX 070633
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
133 AM EST Sat Mar 7 2026

.WHAT HAS CHANGED...
Little has changed in the short term other than the expansion of
of the winter weather weather advisory to portions of southern
NH for early this morning as areas of freezing drizzle may cause
slippery spots.

&&

.KEY MESSAGES...
1. Some slippery spots likely for this morning`s commute, mainly
where surfaces are untreated. Thereafter, a rather gloomy day
takes shape before we warm up for Sunday.

2. Spring-like warmth to start next week, inducing rapid snow melt
and a low chance for river flooding.

3. The next chance for widespread precipitation returns the second
half of next week with temperatures returning closer to seasonal
normals.

&&

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

Cold air damming will hold on early this morning allowing for
areas of freezing drizzle. Therefore a winter weather advisory
remains in effect early this morning for many areas for the
potential for slippery spots. Fog will likely develop later
tonight and last through this morning in spots as the moist low
level air mass lingers.

Thereafter, we expected a mostly cloudy day today with
warmer temperatures, but still a bit cool with areas of fog.
The cold air damming will likely hold tight in much of Maine,
keeping temperatures lower there than across western NH where a
warm-up should commence.

A cold front approaches tonight with showers likely.
Temperatures will have warmed up enough to allow for plain rain
all zones. Lapse rates in the mid levels become steep, so a few
thunderstorms cannot be ruled out, especially across western and
northern zones.

We return to dry weather on Sunday with highs well into the 50s.

KEY MESSAGE 2 DESCRIPTION...

The upper-air pattern shows a 500 mb ridge cresting over New England
the first half of next week as a trough begins to dig towards the
region out of the Upper Midwest. This puts the region in a warm air
advection pattern, and will bring a long awaited taste of true
spring warmth to the region. However, how warm exactly it gets still
remains to be seen.

850 mb temperatures are generally between 5-10C on Monday and 3-8C
on Tuesday. From yesterday we have seen a bit of an upward trend for
Monday while Tuesday has trended modestly cooler. The depth of
mixing also looks more limited on guidance which should put a cap on
how warm it gets but at minimum 50s look likely with the potential
for 60s across the lower elevations of S NH and SW ME. One wildcard
to watch will be a bit of a backdoor cold front on Tuesday which may
result in cooler temperatures across the northern mountains.

The sudden warm up is likely to result in significant melting to the
snow pack and some river ice movement. One note is dew points stay
rather low which should keep the rate of melting in check, as well
as no precipitation through Tuesday.

KEY MESSAGE 3 DESCRIPTION...

Widespread precipitation chances return on Wednesday as a cold
front approaches and we start the day in low amplitude
southwest flow aloft. Widespread cloud cover/precipitation along
this front will likely work to keep temperatures on the cooler
side of the guidance. The current 25th to 75th NBM percentile
high temperature spread at GYX on Wednesday ranges from 39 to 52
so it seems like the ensembles are struggling to resolve many
of the finer details this far out. Given pattern recognition, I
lean towards the cooler side of the guidance for temperatures
Wednesday and Thursday.

Precipitation chances will increase starting early in the day
on Wednesday as a surface low deepens to our west along the
approaching cold front. Some guidance then has a secondary low
forming along the front and lifting up into our area on
Thursday. The latest cluster analysis suggests that the
strongest synoptic forcing will remain over Canada and northern
Maine, but there will be enough lift along the front to produce
widespread precipitation through the end of the week. While it`s
still too far out to speculate on precipitation type, it mainly
looks like rain with snow mixing in for now. That being said, a
fair amount of ensemble members would lead to some freezing
rain and/or sleet mixing in at times so it will certainly be a
time frame to watch closely.

Looking beyond, the active signal continues in much of the long
term ensemble guidance.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
Widespread IFR or lower conditions are expected south of the
mtns for much of today. Freezing drizzle will also be possible
at all TAF sites until temps begin to warm early this morning.
HIE may remain VFR or MVFR as low cloud cover struggles to make
it past the mtns. Showers and lower conditions likely at times
tonight. Becoming VFR Sunday, except in the mtns where MVFR CIGs
may linger. Westerly surface gusts to 25 kt possible in the
afternoon. Widespread enhanced low level wind shear will also be
possible late this afternoon through tonight.

Outlook:

Sunday night-Tuesday: VFR conditions expected.

Tuesday night: Conditions becoming MVFR/IFR as rain and snow move
into the area overnight.

Wednesday-Wednesday night: MVFR/IFR conditions continue. There is
uncertainty in precipitation type for this time period, so
widespread IFR is not out of the question if the forecast trends
colder and terminals see more of a mix or snow.

&&

.MARINE...
Short term...SCA has been extended into Sunday for winds and
seas. SCA conditions may linger outside of the bays through
Monday before starting to diminish at night.

Long term...Wave heights will remain around 5-6ft into early
Tuesday morning but we will likely see a break in SCA
conditions later Tuesday morning through Tuesday night. Winds
and seas then ramp up again Wednesday as a disturbance moves
through the Gulf of Maine. There is even some suggestion that
gale force gusts may be possible at times through Thursday. Seas
remain high with gusty winds through Friday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory until 10 AM EST Saturday for
     MEZ007>009-012>014-018>022-033.
NH...Winter Weather Advisory until 10 AM EST Saturday for
     NHZ001>006-009.
     Winter Weather Advisory until 5 AM EST Saturday for NHZ008-010-
     012-013-015.
MARINE...Small Craft Advisory until 5 PM EST Sunday for ANZ150-152>154.

&&

$$

DISCUSSION...Barker/Ekster/Hargrove