Hampstead, New Hampshire 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

700
FXUS61 KGYX 201021 AAA
AFDGYX

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
621 AM EDT Sun Jul 20 2025

.SYNOPSIS...
Chances for rain and thunderstorms increase today as weak low
pressure crosses New England. Some storms may be strong to
severe and bring a threat for hail and damaging winds. Once that
front clears the area Sunday night, next week will return to
fair and seasonable weather with high pressure building in for
much of the week. Temperatures moderate through the week, with
increasingly humid conditions by late week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Update...Adjusted PoP to better match latest radar trends.
Generally showers with isolated thunder will track across the
mtns this morning. Turning towards this afternoon...additional
CAM runs are starting to coalesce around an evolution for this
afternoon. It looks as if one round of convection is forecast to
go up in the vicinity of the ME Capital Region. This may help to
reinforce or at least sharpen the gradient between warm/moist
air mass and rain cooled. The second round of convection late
afternoon and early evening looks to be the more robust of the
two and will likely carry the greatest severe threat.

Previous discussion...This morning will see showers continue to
develop and stream eastward along the slowly sagging cold
front. Embedded within those showers may be one or two stronger
cells capable of some briefly heavy rain...but things are moving
along quickly right now.

I have also backed off fog a little bit near the coast. There is
currently not much visible on the nighttime microphysics
satellite product...so anything that does form will be later and
likely confined to the waters or very near the coastline.

Most of the attention however is on the threat for severe storms
this afternoon. CAM guidance continues to be rather robust with
convective development around mid afternoon thru the evening.
Forecast lapse rates are not overlay impressive...but warm temps
and a rapidly moistening boundary layer should support CAPE
climbing over 1000 J/kg. We will have plenty of shear...with
most guidance right around 40 kt thru 6 km. We are also looking
at largely southwest winds at the surface...which will reduce
the influence of the cooler Gulf of ME. I suspect that storms
should have no problem maintaining strength to the coastline. If
anything the severe threat has shifted slightly
northward...based on CAM guidance and 20.00z HREF. If I were a
betting man I would say that should result in a strong severe
threat along the pseudo-warm frontal boundary gradient that is
forecast somewhere roughly along an IZG to RKD line.

On the severe hazard front...given the adequate CAPE and strong
shear all hazards should be in play. The forecast hodographs are
long but do not feature much curvature...so a traditional
tornado threat is pretty low. However 0-3 km shear is forecast
to be strong as well...which should support a QLCS tornado
threat as mesovortex formation will be favored with any clusters
of storms that surge out to the east. It will be warm with
higher than normal freezing levels...but certainly sufficient
shear and hail CAPE for some large hail. And otherwise the most
likely threat will be damaging winds from strong largely
westerly flow and precip loading as PWAT values creep up to near
1.75 inches. This threat is mostly confined to areas south of
the White Mtns and the aforementioned areas south of the IZG to
RKD line. To the north of that I cannot rule out an isolated
stronger cell that is capable of gusty winds and small
hail...and that could even include morning convection in the
mtns.

Convection will be weakening and/or moving off the coast by this
evening...generally around 8 PM.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Behind the front it will be a relatively quiet night. Much drier
air will arrive and temps will fall into the 50s again. It will
also be a little breezy...which should preclude widespread
radiation fog. However some of the more sheltered valleys may
still see some develop.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Overnight long term update...01z NBM has been incorporated into
the latest long term forecast and little significant change has
been made to the going forecast.

Breezy conditions with mountain showers will be the case on
Monday the deeper cyclonic flow in the wake of low pressure.
Fair and seasonable weather continues Tue through Wed. Models
are in reasonable agreement with the initiation of a WAA pattern
on Thu with hot weather possibly returning by Fri depending on
how far north the Mid Atlantic ridge extends. Shower and
thunderstorm chances increase then as well.

Previously...

Overview...

A trough progresses through early in the week with a cool and
dry airmass. A ridge then builds across the Northeast for the
middle and later portions of the week, bringing a warming trend
and a return to more humid conditions.

Details...

The week starts off with a seasonably cool and dry airmass in
place with a northwesterly breeze. Highs range from the mid 60s
across the north, to the upper 70s through southern New
Hampshire. The airmass will be noticeably dry, with dew points
in the 40s and 50s across the area. Lows will also be cool
Monday night, with temps falling into the 40s to mid 50s.
Temperatures moderate by a few degrees on Tuesday with
widespread 70s and dew points remaining in the 40s and 50s.

The trough moves east, and a ridge begins building across the
Northeast by Wednesday. Humidity begins to increase again on a
southerly flow as well. Highs range from the mid 70s to mid 80s
on Wednesday. More widespread 80s to low 90s return for
Thursday, with low mid 90s increasingly likely for southern
areas by Friday.

Additionally by Thursday, more moisture returns with dew points
climbing into the mid to upper 60s, and likely reaching the low
70s by Friday. At the same time, a slow moving cold front
approaches from the northwest on Thursday. Afternoon showers and
storms likely move ahead of the front to reach northern areas
during the late afternoon and evening, but the timing of these
is still uncertain from this far out and will be dependent on
the progression and timing of the front. The front then most
likely moves through during the day on Friday, with more showers
and storms possible, but to what extent will be determined by
the timing of the frontal passage.

&&

.AVIATION /10Z SUNDAY THROUGH THURSDAY/...
Short Term...Widespread VFR conditions currently ahead of a slow
moving cold front. Eventually marine fog will try and form ahead
of it...but I believe that will occur too late and confidence is
too low to include in the TAF at RKD. Otherwise SHRA/TSRA will
really begin to grow in coverage and intensity around mid
afternoon. Local MVFR or lower conditions are possible in any
convection...and some of the stronger storms may contain hail
and strong wind gusts. Behind the front it will clear out...but
some local valley fog is possible where it rained during the
day.

Long Term...VFR conditions prevail Monday through Wednesday,
with valley fog possible at HIE and LEB each night. MVFR
conditions remain possible in the mountains on Monday. VFR then
prevails most of the time Thursday and Friday, but with
moistening air mass we could be looking at the generation of
coastal fog and stratus and also increasing chances for
thunderstorms.

&&

.MARINE...
Short Term...A cold front will approach the waters today and
cross overnight. Showers and thunderstorms will be likely by
evening...some of which may be strong to severe. Once the front
passes thru it will become drier again but breezy thru Mon.

Long Term...Some northwesterly gusts to 25kt are possible on
Monday. Afterwards, high pressure steadily builds across and
progresses through the water for mid to late week. A cold front
approaches from the west on Thursday, and most likely crosses on
Friday.

&&

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

&&

$$

NEAR TERM...Legro
SHORT TERM...Cornwell/Ekster
LONG TERM...Clair/Ekster