482
FXUS61 KGYX 111948
AFDGYX
Area Forecast Discussion
National Weather Service Gray ME
348 PM EDT Mon Aug 11 2025
.SYNOPSIS...
High pressure remains in control for the couple of days, and
temperatures continue to rise through Tuesday as a ridge of high
pressure builds over the Northeast. The ridge starts to break
down mid week and that will allow for some chances of showers
and thunderstorms as a cold front approaches. The weekend looks
to be dry at this time with a warming trend possible by Sunday.
&&
.NEAR TERM /THROUGH TONIGHT/...
345 PM Update...Quick update to issue an Air Quality alert for
Rockingham County at the request of New Hampshire DES. Hot
temperatures tomorrow will lead to an increase in ground-level
ozone.
Impacts and Key Messages:
* A Heat Advisory remains in effect through tonight as some
locations only fall into the upper 60s tonight.
Another afternoon with a robust diurnally driven cumulus field
across the area. The difference today is that we have yet to see
any showers develop. Not going to completely count them out
yet, so maintained the isolated wording for parts of the
mountains, but it is looking less likely than past days.
Otherwise, a hot day has come to fruition with many locations
boasting heat index values in the 90-95F range early this
afternoon. They could still go up another degree or two as there
is still some heating left in the day.
Clear skies and light winds should lead to radiational cooling
once again tonight, with temperatures bottoming out in the low
60s. Locations in the heat advisory may remain in the mid to
upper 60s, which is better than what we saw with previous events
in terms of nighttime relief, but may still allow for
additional accumulation of heat stress. For this reason the Heat
Advisory remains in effect overnight. Valley fog can be
expected again tonight. The dry air has been hindering the
development of fog elsewhere, but low level moisture is
increasing, so will continue with a persistence fog forecast as
it becomes more likely.
&&
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
Impacts and Key Messages:
* Heat index values will reach the mid-90s again Tuesday. A
Heat Advisory remains in effect.
The ridge axis remains overhead Tuesday with the center of high
pressure remaining to our southeast. This results in continued
warm, moist southeast flow that will sustain 850mb temps in the
+18C to +20C range and thusly, high temperatures in the 90F to
95F range. A Heat Advisory remains in effect as heat index
values remain similar to today (Monday). The main difference
will be more in the way of offshore flow early on in the day
that will stave off a seabreeze until later in the day. This
will allow these hot temperatures to make it right down to the
water. I think the dry air finally wins out Tuesday and
suppresses the formation of any mountain showers so have taken
the isolated shower mention out.
Radiational cooling should bottom temperatures out in the low
to mid 60s, with some upper 60s in southeast New Hampshire. This
will once again lead to valley fog development, and advection
of marine fog/low stratus onto the Midcoast with continued
southerly flow.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Key Messages
* Heat continues Wednesday, but additional clouds or midday
showers may affect how long heat indices are in the mid 90s.
* Cold front midweek may not be overly strong, leading to an
additional warmer than normal day on Thursday.
* Rain chances in the extended forecast remain focused on the
mid to late week cold front, with high pressure returning for
the weekend.
Details: Approaching cold front will bring clouds and the
chance of showers to another hot day Wednesday. Timing of the
front has narrowed, but strength is in question.
Current guidance keeps the front west of the forecast area
until Wednesday evening, with shower chances mainly focused into
the late afternoon. This gives morning and early afternoon
temperatures an opportunity to jump into the upper 80s and lower
90s for another day. With this question of cloud impact on the
table, opted to not extend the Heat Advisory into Wed at this
time. Best chance for building heat may be the lower Kennebec
Valley where clouds may hold off until the evening.
Showers and thunderstorms linger into the evening as the front
nears. Timing of the day, limited shear, marginal lapse rates,
and dry air give pause to assigning stronger wording for these
storms, but CAPE and some lift will be present.
Front should be exiting the coast come Thursday morning.
Lacking stronger CAA behind the front, it acts more as a lifting
agent vs. a rapid change of airmasses. NBM temps have been back
and forth over the week as to how quickly temps fall. Relief
doesn`t seem to fully take effect until Friday, as Thursday`s
highs again push into the upper 80s to lower 90s. While hot
temps won`t be as widespread, it will still be warm with a core
of warmest temps across the south interior.
High pressure settles over the area for the weekend with
additional rain chances appearing limited until early next
week.
&&
.AVIATION /20Z MONDAY THROUGH SATURDAY/...
Short Term...Valley fog and low stratus may cause restrictions
at LEB and RKD again tonight, with restrictions less likely
elsewhere. Ceilings will be VFR through Tuesday with, valley fog
and low stratus likely again Tuesday night.
Long Term...VFR through Wednesday with some coastal fog and
stratus mainly along the Midcoast towards RKD. A passing cold
front will bring MVFR/IFR conditions Wednesday night into
Thursday morning along with some SHRA. These will trend VFR into
the afternoon with high pressure set to take hold this weekend.
&&
.MARINE...
Short Term...Wind gusts and seas remain below SCA criteria
through Tuesday night as high pressure remains over the waters.
Generally south southwesterly flow will continue with wind gusts
10-15kts. Increasing low level moisture may allow for patchy
fog to develop over the waters tonight and Tuesday night.
Long Term...A cold front will slowly approach the waters
Wednesday night, passing Thursday morning. It will be weak, and
a wind shift may not occur until Thursday evening. Biggest
impact through the period may be occasional marine stratus or
fog that could reduce visibility at times.
&&
.CLIMATE...
Daily record highs and year(s) set for Tuesday, August 12 through Wednesday,
August 13 for Portland, Augusta, and Concord.
Portland Augusta Concord
Aug 12 99F (2016, 1944) 93F (2002) 99F (2016, 1944)
Aug 13 99F (1947) 94F (2004) 99F (1944)
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Heat Advisory until 8 PM EDT Tuesday for MEZ012>014-018>022-
033.
NH...Heat Advisory until 8 PM EDT Tuesday for NHZ010-012-013.
Air Quality Alert from 10 AM to 10 PM EDT Tuesday for NHZ013-
014.
MARINE...None.
&&
$$
NEAR/SHORT TERM...Baron
LONG TERM...Cornwell