Portsmouth, New Hampshire 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

807
FXUS61 KGYX 150745
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
345 AM EDT Thu May 15 2025

.SYNOPSIS...
High pressure continues to drift east of New England through
the week. The weekend will feature a slow moving low pressure
system that will increase rain chances. It does not look like a
washout at this time, but showers and thunderstorms will be
possible each day beginning today. The system slowly moves
through during the weekend, and likely still lingers nearby
early next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Deep layer ridging will gradually give way to troughing today,
or more like a high over low block in which the troughing
portion will begin to affect our forecast area today. The result
will increasing weak forcing for ascent within a modest WAA
regime. Showers and a few thunderstorms are already occurring
across southern New England as of 0730z this morning and these
may affect southern NH early on this morning before generally
weakening or dissipating as they move farther northward. Chance
to low likely PoPs have been placed across southern NH for early
this morning.

Thereafter, organized forcing for ascent generally decreases
allowing for most locations in the forecast area to remain
mostly dry late morning into the afternoon hours. However, we
cannot rule out of a few showers and perhaps a thunderstorm with
the heating of the day, mostly over the far interior. Coastal
locations will be cooler with fog and low clouds a possibility
from time to time.

The highest temperatures across the forecast area today will be
in the far west and north where mid 70s are likely. However, at
the coast readings will be a good 10 degrees colder owing to the
easterly flow off the water.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Fog and low stratus is expected to move back into tonight on the
coastal plain, with dense fog a possibility. Otherwise any
diurnal showers and thunderstorms during the day today should
dissipate this evening and overnight with the lack of heating
allowing for a mostly dry night aside from any fog and drizzle.

Not much in the way of forcing for ascent foreseen on Friday.
Scattered daytime showers and thunderstorms are possible across
interior zones, especially later in the day and early in the
evening. No washout expected by any means but low clouds and fog
may remain pesky at the coast.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
1047 PM Update...An upper low over the Great Lakes region will
spread waves of precipitation into New England Friday night
through Sunday. The best forcing for ascent will arrive Saturday
afternoon and Saturday night when there could be bouts of
moderate rain. The upper low will move east Sunday night and
Monday but may keep things unsettled followed by a drying trend
towards the middle of next week.

Previously...

Key Points:
-Warmer day expected Friday, with a few thunderstorms possible
across the interior Friday evening.

-An low arrives Friday night, with a mostly showery/rainy
 weekend ahead.

-Best chance of widespread rain and thunderstorms should be
 Saturday afternoon/evening.


Details:
An upper-level ridge, light winds, and breaks in the clouds
tomorrow should allow for temperatures to rise quickly Friday
morning. The quick rise in temperatures may destabilize the
atmosphere, with a possibility to see showers and thunderstorms
Friday evening. An upper-level low moves in Friday night, likely
bringing many rounds of showers and storms.

Cooler temperatures are likely over the weekend as dense cloud cover
associated with showers and storms persist over northern New
England. Though this weekend is looking more wet than dry for most,
confidence is higher to see steadier rain and thunderstorms
across NH and western ME Saturday afternoon, with locations
north of the mountains getting more widespread light rain
through the day Sunday as well.

Showery conditions may kick off the next work week, with mostly
cool and wet conditions likely continuing through the remainder
of the week. The aforementioned upper-level low will exit the
area by Monday evening, and should be followed by another
system later on next week. At this time, the lowest chances for
showers next week looks to be Tuesday.

&&

.AVIATION /07Z THURSDAY THROUGH MONDAY/...
Short Term...As of 07z low stratus has spread into the midcoast
terminals but has remained away from others along the coast. Low
stratus may work its way into PSM and PWM early this morning,
but much of the day should be VFR. A few showers and
thunderstorms may temporarily lower conditions in southern NH
early this morning and the rest of NH this afternoon, but
widespread low conditions are not expected. By later this
afternoon fog and low stratus may work its way into the coastal
plain as onshore flow increases some.

Long Term...
VFR expected Friday morning, as marine fog mixes out along the
coastal plain. Restrictions may lower with thunderstorms,
showers and steady Friday afternoon through the weekend.
Unsettled weather may keep restrictions down at least
intermittently through most of next week.

&&

.MARINE...
Short Term...Winds and seas are expected to remain below SCA
thresholds. Areas of fog are expected as moisture advection
continues over the Gulf of ME. Areas of fog will linger over the
waters thru Fri.

Long Term...
Light southerly winds and 2-3ft seas are expected Friday.
Saturday morning, winds shift to southeasterlies and strengthen
to 10-15kts by the end of the day. Winds shift to
southwesterlies by Sunday morning, with 7-12kt winds expected.
2-3 ft seas are expected through early next week.

&&

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

&&

$$


NEAR TERM...Ekster
SHORT TERM...Ekster
LONG TERM...Palmer/Schroeter