Merrimack, New Hampshire 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

683
FXUS61 KGYX 042239
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
639 PM EDT Sat Jul 4 2026

.WHAT HAS CHANGED...
Heat advisory in southern NH has been cancelled. Isolated
showers and perhaps a thunderstorm remain possible early this
evening but should dissipate around sunset. A much drier and
cooler night is expected.

&&

.KEY MESSAGES...
1. Showers and thunderstorms exit to the south this evening with
more comfortable overnight low temperatures expected areawide.

2. An area of rain will slowly move northward Monday afternoon
through Tuesday. In addition, this will also bring cooler
temperatures to begin the week.

&&

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

A cold front continues to push through the forecast area north
to south this afternoon. Ahead, RAP sfc CAPE 500 to 1500 j/kg is
fueling showers and thunderstorms. The overlap of moisture and
forcing is greatest across southern NH, with rounds of showers
and storms expected to continue through early evening. A few
storms may be strong, with gusty outflow winds and heavy
downpours. One such storm went through Concord and then the NH
Seacoast with gusts to 45 mph.

Behind the cold front, more stable and cooler air arrives,
shutting off convection. Overnight lows dip into the upper 50s
to lower 60s tonight, welcome relief after this stretch of heat.
Could see some pockets of fog develop overnight, especially
where rain fell through the afternoon. Otherwise, the lower
dewpoints may inhibit much widespread fog development.

Sunday will be a couple degrees cooler than Saturday, with highs
in the low to mid 80s. RH values will run about 30 to 40 percent,
so it will feel less humid. Clouds begin to thicken in the
evening and overnight into Monday as the next rain system
approaches.

KEY MESSAGE 2 DESCRIPTION...

Low pressure shifts east towards the Mid-Atlantic Monday,
advecting moisture back into central to northern New England.
The low is broad, and not very deep. This results in a wide
influence amid otherwise stagnant moisture. Guidance tries to
take the center through the Delmarva region and south of Cape
Cod through Tuesday.

This track would support a rain shield pushing north into
southern NH and southern ME Monday afternoon and much of
Tuesday. Expansive and thick cloud cover would also support mild
temperatures perhaps with highs only around the upper 70s to
around 80 Mon/Tues.

There remains some timing differences as well as coverage amid
guidance flavors, but consensus was enough to include likely
rain mention for southern NH. If some of the further south
solutions verify, that could mean points towards central ME see
a bump in temperatures Mon/Tues under thinner clouds and less
precipitation.

NBM 50th percentile QPF shows a tight precip gradient, focused
across southern to central NH. This indicates some of the spread
still in contention, but also confidence in that region being
the only spot to see much measurable precipitation. A half to
three quarters of an inch of rain is possible for the southern
tier of NH counties through Tuesday evening.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Through 18z Sunday...SHRA with occasional TS continues for
southern NH terminals through 00 to 02z. Occasional gusts 35 to
40 kt have been measured out of the stronger cells, but these
should remain fairly isolated. These heavy downpours have
produced occasional IFR vis. Areas north of SFM to LCI seem to
be in more stable air now, and significant convection here has
ended. VFR is expected tonight, but could see some FG develop in
valley locations, especially where rain fell this afternoon (LEB
in mind). VFR Sunday, with slight chance of -SHRA towards AUG in
the afternoon.

Outlook:

Monday: Increasing rain chances and clouds south to north in the
afternoon. Patchy MVFR cigs across southern NH possible,
otherwise VFR.

Monday Night: Continued rain chances across southern NH. MVFR
possible.

Tuesday: Rain departs east late, with improving cig in the late
afternoon. VFR likely.

Wednesday: VFR likely under high pressure in the region.

Thursday: SHRA arrives from the NW, otherwise VFR.

&&

.MARINE...
Below SCA conditions are anticipated through midweek. A storm or
two could bring locally gusty winds this afternoon ahead of a
cold front. This front will pass tonight, shifting winds
offshore. Weak wind fields will promote some onshore breeze
Sunday and Monday as broad low pressure moves east from the Ohio
Valley and passes towards the Delmarva region Tues. Winds then
shift east Tues, with building waves into Wed 4 to 5 ft.

&&

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

&&

$$

DISCUSSION...Cornwell/Ekster
AVIATION...Cornwell
MARINE...