714
FXUS61 KGYX 240757
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
357 AM EDT Tue Jun 24 2025

.SYNOPSIS...
Dangerous heat and humidity across parts of the area peaks
today with some of the highest temperatures of the last several
years occurring in many places. Readings will climb well into
the 90s and may even approach 100 degrees in some areas. It will
be 5 to 10 degrees cooler Wednesday but that will still be hot
in places. The relief finally arrives Thursday in the form of a
backdoor cold front. The cooler air will move in on northeast
winds and bring temperatures back down into the 70s. However
with the cooler weather will come higher chances for showers
into the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Like last night and yesterday morning, light winds and mostly clear
skies have allowed valley fog to develop in some areas, but this
will clear up by 8AM, if not earlier. Could also see marine fog and
stratus along the immediate coastline early this morning, but the
low-level flow should keep most of this offshore.

The anomalously strong 500mb ridge remains fully entrenched
over the East Coast and will bring another day of dangerous heat
and humidity with record high temperatures likely (refer to
climate section below) with little cloud cover to help out. The
primary difference is that the heat expands all the way to the
coast today as W/WNW flow increases ahead of a cold front
approaching from the north, which is expected to be strong
enough to prevent the seabreeze. Temperatures will soar well
into the 90s across most of the area with even the possibility
of triple digits in a couple of spots. Combining with the
humidity, heat index values are expect to be at or just above
105F for most locations south of the mountains and away from the
immediate coast, but even the immediate coastline could see
heat indices of 100-105F. It should be noted that the Midcoast
counties remain in a Heat Advisory due to zone averaging not
meeting Warning criteria, but heat indices could still reach
around 105F in those counties just a few miles inland from the
coastline.

Moving to the lower confidence part of the forecast. As the
cold front approaches in the afternoon and evening, heights
start falling slightly, and forecast soundings do show weakening
subsidence aloft. Because of this, there is potential for
thunderstorms, but the coverage is uncertain, and CAMS are all
over the place. There will be a fair amount of dry air aloft,
which I think will help keep storm coverage on the lower side
(20-30%) and generally toward the mountains. Model guidance
generally agrees on MUCAPE increasing to 1500-2000 J/kg with
0-6km shear also increasing to around 30 kt, and storms that are
able to develop could become strong to severe with the dry air
aloft adding more potential for downburst winds.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
Low chances for showers and storms continue for a little while this
evening, mainly across northern portions of NH, and then this same
area may see a few additional showers overnight as upsloping kicks
in behind the frontal boundary. The rest of the area is forecast to
stay dry. After the hot day today, very little in the way of relief
is expected as temperatures will largely stay in the 70s overnight,
except northern areas may reach the 60s. Similar to the past couple
of nights, valley fog will probably develop in some areas.

The front pushes south of the area by Wednesday morning as high
pressure begins to build in to the north. Unfortunately, it will be
another hot day as highs only come down slightly behind the front
with upper 80s to lower 90s still expected south of the mountains.
There is some good news though in that a push of drier air will work
its way southward through the day, which will lower dewpoints and
make it not feel quite as oppressive out compared to today and
Monday. Still, peak heat indices could still reach the low to
mid 90s across southern areas but not sure if a Heat Advisory
will be needed at this time. The pressure gradient should also
be weak enough to allow the seabreeze to develop, but it
probably won`t make it very far inland. Most will stay dry, but
a shower or storm is possible in southern NH before the push of
drier air arrives there later in the day.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Key Message: Heat breaks midweek as a backdoor cold front
provides some relief and return to more seasonable temps.

Impacts: After one more very warm day Wed...no significant
weather impacts are anticipated.

Forecast Details: Ridge axis will tend to retrograde west thru
the end of the work week. This will allow heights to lower
across the Canadian Maritimes and set up the potential for
backdoor cold front to provide some relief from the heat.

The true relief will arrive Thu. With the front thru the area
temps will be back in the 70s. This will also come with a little
more in the way of cloud cover and threat of
showers...especially near the front itself.

For the rest of the period we remain on the northern edge of the
ridging. This will place us outside of the real heat but near
the so called ring of fire. Convective episodes will be expected
to develop over the Plains and roll eastward along the periphery
of high pressure. Some decaying remnants will threaten the area
at times...so much of the extended will feature some PoP. The
highest chance will come with a more coherent forcing
mechanism...so that will likely have to wait until the next
passing S/WV trof over the weekend.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
Short Term...For the most part, VFR is expected today through
Wednesday with a few exceptions. The first is a bit of valley
fog that could bring restrictions early this morning and again
tonight, mainly at HIE and LEB. Another is marine fog/stratus
lurking right near the coast this morning, which could bring
restrictions to coastal sites, but the higher potential would be
RKD. A cold front approaches later today with isolated showers
and storms in the afternoon and evening, potentially in the
vicinity of HIE and LEB.

Long Term...Largely VFR conditions expected in the extended. A
backdoor cold front will bring relief from the hot weather but
bring back a chance of showers. Local MVFR or lower is possible
in any showery weather...but chances are not particularly high
at this time.

&&

.MARINE...
Short Term...SCA conditions are not expected through Wednesday.
Winds will be mostly out of the southwest today as a cold front
approaches from the north. The front crosses through this
evening and tonight with winds veering to the northwest. High
pressure builds in to the north Wednesday with winds briefly
taking on a northeasterly direction before becoming more onshore
as a seabreeze tries to develop in the afternoon.

Long Term...Winds and seas expected to remain below SCA
thresholds. Behind a backdoor front Wed night into Thu a steady
northeast breeze may pick up...but at this time 25 kt gusts are
not anticipated.

&&

.CLIMATE...
Record breaking temperatures remain possible today (6/24).
Below are the records for our climate sites:

  Site                 Record June 24th

Portland Jetport           93 (1976)
Augusta                    93 (1963)
Concord                    95 (1983)

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Extreme Heat Warning from 11 AM this morning to 8 PM EDT this
     evening for MEZ012>014-018>024-033.
     Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for MEZ025>028.
NH...Extreme Heat Warning from 11 AM this morning to 8 PM EDT this
     evening for NHZ006-009-010-013-014.
     Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for NHZ002>005.
     Extreme Heat Warning until 8 PM EDT this evening for NHZ007-
     008-011-012-015.
MARINE...None.

&&

$$


NEAR TERM...Combs
SHORT TERM...Combs
LONG TERM...Legro