Londonderry, New Hampshire 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

755
FXUS61 KGYX 310131 AAA
AFDGYX

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
931 PM EDT Sun Mar 30 2025

.SYNOPSIS...
A warm front shifts N of the area into Canada overnight.gradually
A cold front crosses late Monday and Monday night with high
pressure building in for the middle of next week. Another storm
featuring mixed wintry precipitation is possible Wednesday night
into Thursday.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Update...Showery precip continues across the area tonight. Temps
are very near freezing...so there will be pockets of freezing
rain at times in the valleys. The core of the cold air will be
in the mid slopes of the White Mtns and into western ME. As you
go towards the highest peaks...temps are actually above
freezing. MWN happens to be one of the warmest locations in the
forecast area currently. For now will leave headlines as is.

Previous discussion...The wobbly boundary that has remained
over the CWA since yesterday, sitting just above the cold sfc
inversion, shifts slowly N of the CWA overnight. If we didnt
have the inversion we would sitting in the warm sector. We
should see steadier precip slowly wind down in the N zones over,
although another round of showers is possible anywhere as 500
MB wave move into the weak ridging and loses some steam, but
still has enough to support some showers. P-type is still an
issue, but given that the last of the cold air aloft is exiting
to the NE attm, we are likely to see rain, liquid of freezing.
The N zones are the likely place for some moderate ice
accretion, approaching a quarter in some spots, somewhat
elevation dependent, but if you got to far up. youll be in the
warm air. Temps should stay steady through midnight, and as
stronger S flow picks up above the BL, will the inversion will
start to stretch a little and become a little mixy, so temps
will start to rise.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
On Monday morning that Inversion will mix out, probably by mid
morning in most places, and temps will warm quickly after that.
Any overnight showers should wind down in the early morning, and
it looks mostly dry on Monday, but given we will be in the warm
sector, although still fairly stable, could see a few SHRA pop
up here and there. Highs range from 50-55 across most of the ME
zones, except the far SW where the upper 50s are expected, to
60-65 in S NH and the CT valley. Could see some breaks of sun by
early afternoon in S NH, but it seems mostly cloudy will still
cover it. Another round of showers, with the potential for some
TS will move in from the W late in the day and continue into
Monday evening. Might be hard to get them going in the GYX CWA,
but they could move in from the SW and hold together at least
into S and W NH.

The front slows a bit and should take most of the evening to
work through, so rain is likely through at least midnight, but,
the precip should shift offshore before daybreak Tuesday. Lows
range from the upper 20s in the mtns /where some upslope SHSN
could develop late, to 35-40 in the S.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Any lingering light showers across coastal and eastern areas will
quickly come to an end by mid morning Tuesday as the cold front
continues to push off the east. The incoming dry air behind the
front will result in clearing skies the rest of the morning and
afternoon, although more clouds and a few rain/snow showers will
stick around in the mountains through the morning. It will also be
breezy with gusts of 25-35 mph out of the northwest and up to 40 mph
on occasion. Highs are forecast to reach the 40s south of the
mountains and 30s in the mountains.

Winds will ease going into Tuesday night as high pressure starts to
settle in, and with clear skies, it looks to be a chilly night with
lows in the teens to low 20s and even single digits across the
north. The high shifts off to the east on Wednesday with increasing
clouds during the afternoon as the next low pressure approaches the
Great Lakes region. However, precip is expected to hold off until
after sunset at this point. Highs will again be mostly in the 40s,
but the switch to onshore flow could limit some areas near the coast
to the upper 30s.

Today`s model guidance remains in good agreement with the low
pressure moving across the Great Lakes region Wednesday night and
across southern Quebec on Thursday. This will likely bring
widespread precipitation to the area, which is expected to
overspread the area Wednesday evening through Wednesday night and
then diminish Thursday afternoon. Although it`s still early, there
is a possibility to see all precip types with this system. Guidance
currently favors temperature profiles to be cold enough to support
snow initially Wednesday night and potentially followed by a period
of sleet and/or freezing rain before temperatures climb enough to
switch over to rain from south to north overnight and into Thursday
morning as the warm front lifts to the north. Some areas could have
slick travel for the morning commute on Thursday depending on how
quickly this transition occurs, but this is uncertain at this time.
Precip becomes more isolated to scattered showers Thursday
afternoon, and the increasing southerly flow will bring temperatures
into the 40s to 50s in western ME with 50s to 60s in New Hampshire.

The cold front pushes through Thursday evening into Thursday night
with a few showers as it does so, but after that high pressure
returns on Friday, bringing mostly dry and warm conditions, other
than some upslope showers in the mountains. Highs are forecast to be
in the 50s for most of the area, including the coast as the
northerly flow looks to be able to delay the seabreeze. Southern NH
could see lower 60s.

Model guidance is still advertising another low pressure sometime
over the weekend, but there does seem to be a trend in the guidance
in keeping high pressure over the area a little longer than how it
looked yesterday. So Saturday may end up being dry after all with
the higher precip chances coming Saturday night or Sunday, but
there`s too much spread in the guidance on the low track to get a
feel for precip type(s) at this time.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Short Term...Any improvement in conds this afternoon drops back
to IFR everywhere tonight in fog/rain/low cigs. Could see a
brief period of FZRA when the precip return to KAUG later this
evening, but rising temps after midnight, should shift that back
to rain. I think there may be gradual improvement to MVFR at
most terminals by midday, except for KRKD, and maybe KAUG.
Periods of VFR are possible at all NH terminals as well. A
return to MVFR or IFR expected Monday night, but should things
start to clear to VFR toward daybreak Tue.

Long Term...MVFR ceilings and rain/snow showers remain possible at HIE
through the Tuesday morning, but otherwise VFR expected Tues-Weds.
Northwest winds will be gusty on Tuesday, likely reaching 25-30 kt
and possibly up to 35 kt. Winds will be lighter on Wednesday. The
next low pressure likely brings widespread precipitation and IFR to
LIFR restrictions from Wednesday evening through Thursday afternoon
before conditions start to improve. Wednesday night could feature
all precipitation types with a change to rain from south to north
overnight through Thursday morning, although confidence is low on
when this will occur. VFR return Thurs night into Friday.

&&

.MARINE...
Short Term...S flow ahead of a cold front increases overnight,
and should reach SCA levels by Monday morning, with a period of
gales possible as the cold front gets close Monday afternoon and
evening. Winds shift NW and begin to diminish once the front
crosses the waters after midnight.

Long Term...Winds out of the north to northwest behind the cold front
will likely remain above SCA levels through Tuesday and at least
part of Tuesday night. However, seas will probably stay above
criteria into the early part of Wednesday. Southerly flow is
expected to quickly increase to SCA levels Wednesday night into
Thursday ahead of the next front, and gales appear possible during
this time. The front crosses late Thursday or Thursday night with
improving conditions Friday into the first part of the weekend as
high pressure builds in. Another low pressure could bring increasing
winds and seas toward the later part of next weekend.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory until 6 AM EDT Monday for MEZ007>009-
     012>014-020>022-028-033.
NH...Winter Weather Advisory until 6 AM EDT Monday for NHZ001>004.
MARINE...Gale Warning from 10 AM Monday to midnight EDT Monday night
     for ANZ150-152-154.
     Small Craft Advisory from 10 AM Monday to midnight EDT Monday
     night for ANZ151-153.

&&

$$

NEAR TERM...Legro
SHORT TERM...Cempa
LONG TERM...Combs