740
FXUS61 KGYX 141840
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
240 PM EDT Mon Jul 14 2025

.SYNOPSIS...
A cold front will near the region this afternoon with
widespread showers and thunderstorms, some of which could
produce locally heavy rainfall. Drier weather returns Tuesday,
with heat and humidity building in through late week. Chances
for afternoon showers and thunderstorms return late week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Showers and thunderstorms continue to develop this afternoon.
Main concerns with these will be heavy rainfall and gusty winds.
Showers or storms will be capable of 1 to 2 inch per hour
rainfall rates, with stronger storms moreso. Locations that see
multiple rounds or training of storms will be prone to flash
flooding through early evening.

Clouds have thinned through the morning and early afternoon,
allowing insolation to continue building instability. Locked in
a very moist airmass with a high freezing level, the
combination points to great precipitation efficiency via warm
rain processes.

The cold front that will eventually wick away much of this deep
moisture is still draped across southern Quebec, thus expect
scattered to widespread shower development for much of the CWA
through the afternoon and early evening hours. More stable air
is positioned along the Midcoast, and have left a good portion
of this region with lower PoPs through the evening.

The front will take much of the evening to track through to the
coast, and this may prolong shower activity through midnight via
frontal forcing. Will lose a lot of the surface based
instability, but elevated CAPE continues for much of the night.
Despite the current falloff in precip chances, could still see a
couple clusters of showers sustaining for much of the night.

Because of the slow, weakening nature of the cold front, have
kept some mild overnight lows in place for southern and central
NH. Lows in the lower 70s and upper 60s will be a good jump on
warming temperatures into Tuesday.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
Clearing skies across much of the CWA will be a welcome sight
after days of stratus and mixed skies. While the passing front
will help clearing deeper moisture, there remains a moist layer
that will seed a population of cumulus once mixing and daytime
heating takes hold. There will be the slight chance of a shower
in southern NH, with CAMs depicting a few across southern NH.
Not certain on their longevity considering the dry air aloft,
but taller clouds could mute afternoon temperatures.

Temperatures will warm into the 80s and close to 90 for some
interior, southern locations. Remaining humidity across southern
NH will push heat index values close to 95, and have issued a
Heat Advisory for portions of Hillsborough and Rockingham
counties. This heat will start a stretch of hot temperatures
that expand in area and intensity into Wednesday and Thursday.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Pattern Overview: Shortwave ridging peaks overhead on Wednesday
allowing heat and humidity to peak as well. A shortwave trough
crosses Thursday bringing a chance for showers and
thunderstorms, but the better day looks like Friday as
additional forcing comes in the form of a surface front. Zonal
flow through the weekend will keep afternoon showers in the
forecast with some suggestion that a sharper trough may approach
early next week.

Impacts and Key Messages:
* Heat and humidity peak midweek with heat indices reaching the
  mid to upper 90s in southeastern New Hampshire and
  southwestern Maine.

Details: Wednesday: Confidence is increasing in advisory level
heat indices Wednesday as models trend warmer with 850 mb temps
(now approaching 19C). Low level flow turns southwesterly as 500
mb heights peak overhead, driving dewpoints up around 70F.
These combined result in many locations with temperatures in the
low 90s, feeling more like the mid to upper 90s. Dewpoints stay
lower north of the mountains so heat indices will stay closer
to the actual temperatures (in the upper 80s to around 90).
There also may be enough of a sea breeze to keep heat indices on
the lower side along the coast. The main areas of concern are
the inland areas south of the mountains, and Heat Advisories
will likely have to be issues accordingly. Elevated dewpoints
keep temperatures from dropping too much south of the mountains
with fog and low stratus likely to develop as well. Low
temperatures only bottom out around 70 in southern zones, and in
the low to mid 60s to the north. An approaching shortwave
trough also brings a low chance of showers, mainly to the
mountains, overnight.

Thursday and Friday: Thursday sees increasing clouds and
shower/thunderstorm chances as a shortwave trough crosses the
area. CSU machine learning continues to show low probabilities
that a few storms could be on the stronger side. Long range
ensembles are showing another surge in moisture during this time
frame with the continued southwesterly flow driving PWATs up
across the area, so these probabilities are likely stemming from
precip loaded storms. With that being said any storms would be
capable of producing heavy rain which could lead to localized
flooding. Dewpoints peak in the low to mid 70s on Thursday, but
surface temperatures will be a degree or two cooler than the day
before. Despite the cooler temperatures, higher dewpoints
likely will necessitate Heat Advisories for Thursday as well.
Thursday remains a warm night with temperatures similar to
Wednesday night. Friday looks very similar with the addition of
a surface front that would provide further forcing potentially
leading to more widespread showers/storms. Trends will have to
be watched during this time period as timing of fronts is always
tricky, but nonetheless CSU continues to show low probabilities
of stronger storms and WPC has targeted these days with
Marginal Risks for the heavy rain potential. Depending on the
timing of the front there is likely going to be an interesting
temperature gradient with locations behind the front dropping
into the 70s with lower humidity and locations ahead of the
front during peak heating in the mid to upper 80s with humidity
holding strong. If the front does clear the area by nightfall,
it would make for a cooler night as well.

Saturday-Monday: A drier airmass is ushered in behind the front
for the weekend with temperatures feeling much more pleasant.
Zonal flow aloft, with some suggestion of brief shortwaves
rotating through, keeps low chances of pop-up afternoon showers
and storms in the forecast. Global models than suggest a sharper
trough and surface low pressure develop early next week which
may be the next best chance for widespread showers and storms,
but this is still out in time and unsurprisingly models greatly
vary in representation of this feature, so its only worth a
mention for now.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Short Term...There remains scattered MVFR decks today as SHRA
and TS develop. The trend will be for these to raise, with
northern areas seeing thinning this evening. Another night of
IFR to LIFR expected for the Midcoast up to perhaps AUG.
Elsewhere, thinning takes longer through midnight. SHRA and TS
may contain heavy downpours, with gusty winds on the periphery
of any downdrafts. VFR expected Tuesday, with a fog bank
possibly remaining just off the coast. This may continue to
march inland after sunset Tuesday evening. Cumulus develops
through the day, with outside chance of a VCSH in southern NH.

Long Term...Low stratus and fog will be present Wednesday
morning, overnight Wednesday, and Thursday morning bringing
about IFR/LIFR restrictions. Ceilings during the day Wednesday
should be VFR with more in the way of MVFR ceilings looking
likely with widespread shower activity and a few afternoon
thunderstorms Thursday and Friday.

&&

.MARINE...
Short Term...Conditions remain below SCA with fog occasionally
obscuring visibility. A cold front will approach and then stall
over the waters late tonight/Tuesday morning.

Long Term...Wind gusts and seas remain below SCA criteria
through Friday. Increasing southwesterly flow will continue
areas of fog development through at least Friday morning.
Afternoon showers and thunderstorms may also move over the
waters on Thursday and Friday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...Heat Advisory from 11 AM to 8 PM EDT Tuesday for NHZ012-013.
MARINE...None.

&&

$$

NEAR/SHORT TERM...Cornwell
LONG TERM...Baron