Atkinson, New Hampshire 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

496
FXUS61 KGYX 040547
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
147 AM EDT Mon May 4 2026

.WHAT HAS CHANGED...
Increased winds today and Tuesday in anticipation of deeper
mixing while an active jet resides aloft. Can`t rule out some
gusts to 40 mph either day, but winds will decrease come evening
unless conflicting with convection.

&&

.KEY MESSAGES...
1. Temperatures rapidly warm early this week, accompanied by
gusty south to southwest winds during the daytime.

2. Several chances for instability-driven downpours and
thunderstorms Monday-Wednesday

3. A slow moving front will bring chances for beneficial rain
Tuesday night through Thursday night areawide, with the highest
chances centered on Wednesday.

&&

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

The forecast area is set to see three straight days of low
level warm air advection through Wednesday. A broad region of SW
flow stretches from the Gulf coast to New England, in between a
low to the west and Atlantic high pressure to the east. The
quick warmup will be most noticeable today and Tuesday, where
high temperatures look to improve some 10 degrees from each
previous day.

The warmest days of the week will likely be today and Tuesday
with daytime highs pushing into the mid to upper 60s today and
widespread 70s Tuesday. Ample mixing in the low levels should
tap into WAA aloft where +2 to +5C 850mb temps will be advancing
this afternoon. This increases to around +9C come Tuesday as
approaching mid level jet and expanding low level jet aid in
further SW advection.

Overnight lows also increase, and with some background winds
and cloud cover, radiational cooling will be limited. This will
lead to values bottoming out in the 40s to around 50 Monday
night, and widespread 50s Tuesday night.

The expanding low level jet will also bring breezy conditions
to the region. For Monday, accelerating LLJ into the exiting low
pressure in the Canadian Maritimes will coincide with morning
mixing. This could lead to a window of SW gusts around 40 mph,
before slackening into a range of 25 to 35 mph through the
afternoon. Forecast soundings develop a surface inversion into
the evening and overnight hours, leading to a return to light
winds overnight.

Jet dynamics only increase heading into Tuesday as a 500mb jet
impinges on broadening LLJ below it. A second day of mixing
towards 700mb will attempt to mix 40 kt winds aloft. Will
continue to monitor gusts on Tuesday, but can`t rule out a
slight chance of gusts near Wind Advisory criteria inland based
on model soundings. There will be the complicating factor of
increasing cloud cover w/ showers/storms from the west during
the afternoon. This could also limit mixing depth and how well
daytime gusts perform to the west.

KEY MESSAGE 2 DESCRIPTION...

Kicking things off on Monday, a conditional chance for some
scattered showers/downpours, fueled by warm air advection aloft
and a lobe of vorticity moving through the flow. Timing focused
on the midday-afternoon hours, generally along and north of a
line extending from Whitefield to Lewiston. Cannot rule out a
rumble or two of thunder given rather steep mid-level lapse
rates at or above 7 C/km.

On Tuesday a cold front approaches from the northwest late in
the day. This will be the focus for the greatest thunderstorm
threat of the week. Rather deep mixing suggests an environment
with steep low- level lapse rates of 8-9 C/km, and high LCLs
above 1500 m. Moisture will be modest, with surface dew points
at best in the low-mid 50s. Not hard to think there will at
least be a low risk for strong to damaging winds in any
thunderstorms given the favorable environment for mixing winds
downward. 0-6 km BWD approaching 40 kts suggests some storm
organization/longevity is possible. Weak CAPE generally at or
below 1000 J/Kg will put a ceiling on the severe threat. Similar
to Monday, thinking the best chance for activity will be across
the northern half of the forecast area, but there remains at
least an isolated chance for thunderstorms to make it farther
southeast and towards the coast. The threat looks to be focused
in the 3-9 PM window.

By Wednesday we`ll see the front stall out overhead, with a
trough axis that will be taking on an increasingly negative
tilt. Depending on if any of the region can stay in the warm
sector, another chance exists for downpours and thunderstorms.
Given only a few hundred J/Kg of CAPE at best, not expecting
severe storms at this time despite impressive dynamics and
shear, but cannot rule out some rumbles of thunder. Downpours
are likely however; it will be a juicy environment as dew
points surge to near 60 in the Manchester-Portland corridor.

KEY MESSAGE 3 DESCRIPTION...

No significant changes in regards to a round of soaking rain
midweek. There remains uncertainty on the pace of the front, and
therefore how many embedded waves train over the forecast area.
Present forecast supports a slow arrival Tuesday evening,
lingering for the daytime Wednesday (greatest rainfall amounts
fall), and a quicker departure Wednesday evening into Thursday.

For about 24 hours, Maine and New Hampshire will be within a IVT
corridor stretching all the way from the southern Plains. While
not an ideal moisture source region, broad and strong LLJ should
support the quick transport towards New England. Will have to
monitor how the wave train progresses east as well, should more
undulation join the otherwise flat boundary, a second wave could
continue rain chances into late week.


&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Through 06z Tuesday...MVFR ceilings possible at HIE. Breezy
with westerly/southwesterly winds gusting as high as 25 to 30
kt. Can`t rule out a couple of showers near AUG later. LLWS
likely today and Tuesday most terminals.

Surface winds subside this evening, but jet aloft will be
moving in. LLWS likely in the evening as a 35-40kt jet passes
above surface inversion.

Outlook:

Tuesday-Tuesday Night: During the day mainly VFR with southwest
winds gusting 25 to 35 kts. Chances for showers and
thunderstorms increase NW to SE Tuesday afternoon, although
storms are unlikely from CON to AUG and points south. Chances
for showers Tuesday night bring some potential for MVFR. LLWS
possible overnight.

Wednesday through Friday: MVFR cigs likely with rain. Periods
of IFR possible Wednesday into Wednesday night. Shower chances
will bring potential for at least MVFR Thursday with a drying
trend Friday improving conditions.

&&

.MARINE...
SCA conditions continue over the waters through Tuesday with
gales possible across our far outer zones Tue afternoon and
evening.

A cold front sinks through the waters Thursday into Friday
shifting winds offshore.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory until 6 AM EDT Tuesday for ANZ150-152-154.

&&

$$

DISCUSSION...Barker/Cornwell/Ekster