Plaistow, New Hampshire 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

175
FXUS61 KGYX 290623
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
223 AM EDT Mon Jun 29 2026

.WHAT HAS CHANGED...
An Extreme Heat Watch has been issued for portions of NH and
southwestern ME for Wednesday through Friday. Aviation section
updated for 06Z TAFs.

&&

.KEY MESSAGES...
1. High pressure brings fair weather today.

2. Hot and Humid conditions arrive this week, with near record
breaking heat increasingly likely for mid to late week. Any
preparations, such as installing air conditioning units, would
best be completed early this week before the hottest conditions
begin on Wednesday.

3. Building heat and humidity will provide fuel for
thunderstorms starting Tuesday with chances continuing most days
through the end of the week.

&&

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

Upper trough axis pushes east early this morning with high
pressure building in today from southeast Canada. This will
allow for a pleasant day with highs in the 80s with relatively
comfortable humidity levels. A weak gradient over the area will
allow for a healthy sea breeze to develop by early afternoon
that will be able to push well inland.

KEY MESSAGE 2 DESCRIPTION...

The warming trend continues on Tuesday with widespread highs in
the 80s to lower 90s across the interior. Along the coast,
onshore flow likely keeps highs mainly in the 70s for one more
day. Dew points will generally be into the lower 60s and
therefore heat indices will not differ significantly from actual
air temperatures.

By Wednesday, the significant heat likely arrives into at least
New Hampshire and western Maine as highs warm into the 90s.
What makes this heat event notable is just how much moisture
will accompany the heat. Dew points likely push into the low to
mid 70s on Wednesday, pushing heat indices into the triple
digits where temps reach the 90s. These high dew points continue
through at least Friday. Overnight low temperatures on Wednesday
through Friday night will only be into the 70s across many
locations, which will result in accumulated heat stress.

One possible limiting factor for the heat remains the potential
for rounds of convection originating near the Great Lakes, and
riding around the ridge into New England. Should these arrive
during the midday timeframe, they would serve to limit the
heating potential. But arriving at any other time of the day,
they will likely only serve to increase dew points. We`ll likely
have to wait until tomorrow to have a better handle on how
these will effect temperatures in the Wednesday through Friday
time frames, as the differences will be localized and variable.

Outside of any convection, the heat looks most likely to peak
on Thursday and Friday. Modeled 850mb temps of 22-24C support
the potential for near record high temps of 97-102 degrees,
barring any hinderance from convection or sea breezes. It would
be a misuse of time to tinker with which side of 100
temperatures will reach in the Thursday and Friday timeframe at
this point in time. The main message remains that heat and
humidity hazardous to health is increasingly likely as heat
indices push 110 degrees by Thursday.

As a result, an Extreme Heat Watch has been issued for portions
of NH and southwestern ME for Wednesday through Friday. The
watch covers the locations most likely to see heat indices of
105 degrees or greater each afternoon. Heat advisories will
likely be needed elsewhere as we get closer to the event and its
possible that portions of the watch will later be converted to
advisories. Given the increasing confidence for a potentially
high impact heat event, wanted to go ahead with a watch now to
help messaging and preparation.

Additionally, the trend over the last few model runs has been
for an increasing chance of the heat to continue into at least
Friday or Saturday. The models first trended warmer for
Wednesday and Thursday over the last few days, and now look to
be trending this way for Friday and Saturday as well. We will
continue to watch the progression of this, with a trough and
cooler conditions situated just to our east across Atlantic
Canada.

KEY MESSAGE 3 DESCRIPTION...

Low pressure tracking northeast across Canada will lift a warm
front into the area Tuesday afternoon with this front pushing
through northern Maine Wednesday morning. This front will
provide a focus for showers and storms. While the best
instability looks to remain west of the area there will be
sufficient deep layer shear near the front for organized
convection. Several model solutions are hinting at the potential
for an MCS to track southeastward across the Northeast late
Tuesday with additional rounds of convection into Tuesday
night. SPC has a Marginal Risk for severe storms across Upstate
NY and Vermont that pushes into the CT Valley and could see this
trend farther east based on latest CAM output.

On Wednesday there exists the potential for unusually high
levels of CAPE for this part of the county as models continue to
suggest a remnant EML will bring steep mid level lapse rates
over the Northeast. While there will be a lack of surface
forcing and mid level support for ascent any convective
complexes that can ride atop the ridge could bring the threat
for severe storms across the Northeast. The finer details on
timing and coverage remain unclear Wednesday and beyond while
the overall pattern may continue to support storms through
Friday. Machine learning guidance out of CSU continues to have
this signal.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
Through 06z Tuesday...Mostly VFR expected except for valley
locations that see another night of FG w/ LIFR vis/cig. Fog
shouldn`t be as widespread along the ME/NH coast tonight, but
can`t rule out dips to 3 or 4SM with 1SM towards RKD. Rainfall
that occurred at AUG this evening will also bring potential for
fog tonight. VFR expected through the day Monday.

Outlook:

Monday Night: Chance for the return of fog along the coast
hinges on how robust it is over the coastal waters through
Monday. It is likely this does not return until after 00z.

Tuesday - Friday: Mainly VFR prevails at most terminals, but rounds
of showers and storms will be possible each day. Marine fog will be
possible at RKD.

&&

.MARINE...
Marine stratus or fog seems likely to remain around the coastal
waters for much of the coming week in between systems.

High pressure gradually settles south of the waters by midweek.
Mainly fair conditions prevail, but some seas to near 5ft are
possible Tuesday night in southwesterly flow.

&&

.CLIMATE...
High temperature records at long term climate sites...

 July   1st   2nd   3rd

 AUG    92    93     94

 PWM    93    98     95

 CON    99    98    102

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Extreme Heat Watch from Wednesday afternoon through Friday
     evening for MEZ012-013-018>021-023>026-033.
NH...Extreme Heat Watch from Wednesday afternoon through Friday
     evening for NHZ004-006>015.
MARINE...None.

&&

$$

DISCUSSION...Schroeter/Tubbs