-- Discussion containing changed information from previous version are highlighted. --
593
FXUS61 KGYX 171341
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
941 AM EDT Mon Jun 17 2024

.SYNOPSIS...
A warm front will move into New England today, which will be
followed by a stretch of very hot and humid conditions through
the week. Record high temperatures and potentially dangerous
heat index values are possible. A weak cold front will slowly
cross through the region on Thursday and Friday with an
increasing chance for scattered showers and cooler temperatures
this weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
940 AM...Minor update to reflect observational trends. Much of
the precipitation on current radar over the area has yet to
reach the ground based on surface obs. There are radar returns
upstream over SE Canada that will bring slight chances for
showers across the north as moisture increases in the
atmospheric column.

640 AM Update... Made some minor adjustments to temperatures
and sky cover based on latest trends but the forecast remains
largely unchanged. The mid- levels are beginning to moisten (as
seen from Mt. Washington RH) and therefore the potential for
sprinkles or light showers will continue to increase through mid
morning, mainly over the north/mtns.

Previously...
Surface high pressure is located over southeastern Massachusetts
early this Monday morning with satellite imagery showing high-
altitude clouds continuing to stream into our region while
riding along an h5 ridge axis. Northeast radar mosaic is
beginning to show some light returns over VT and portions of NH
but ASOS reports indicate this activity is simply virga with the
00Z KGYX RAOB report showing significant dry air aloft. This
combined with weak forcing for ascent should continue to allow
for this activity to evaporate before reaching the ground. It
will otherwise continue to be a cool morning with temperatures
beginning to warm a bit from earlier readings in response to the
increasing cloud cover.

A surface warm front will lift northward over Northern New
England today, allowing for increasing WAA aloft. At the
surface, winds will be out of the south at around 10-15 mph,
which will keep much of the coast into the 60s to around 70 and
into the mid-70s inland. Over NH high temperatures will be
warmer with readings into the middle 80s but dew points will
remain comfortable into the 50s to near 60 degrees. Mainly
cloudy skies early will become partly sunny late with a low-end
chance for an isolated shower/sprinkle (mainly over interior
western ME).

Tonight will feature partly cloudy skies and light winds with
dry conditions continuing. Some patchy fog may develop late with
low temperatures into the upper 50s to middle 60s.
-- End Changed Discussion --

&&

.SHORT TERM /TUESDAY/...
The heat and humidity will build on Tuesday under partly cloudy
skies. WAA aloft will help to push 925 mb temperatures up to
around +25C, and given good mixing this places highs into the
lower to middle 90s. The exception will be at the coast where
onshore wind will keep temperatures into the 70s and 80s. Dew
points will also be increasing into the upper 60s to around 70,
which will result in afternoon heat indices into the middle to
upper 90s across interior south-central NH and interior
southwestern ME. As a result, went ahead and issued a heat
advisory, which will run from 12pm to 8pm Tuesday.

Latest CAMS suggest the potential for a few discrete
updrafts/thunderstorms to develop during the afternoon/early
evening hours. Despite weak bulk shear of around 15-20 kts,
there will be high MUCAPE and decent lapse rates and therefore
should a storm develop it could become locally strong with gusty
winds the primary hazard given inverted-v soundings.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Models continue to suggest a large and highly anomalous upper
level ridge will build over the Northeast mid-week. A 600 DM
500 MB high is rare for this part of the country, especially
considering it is mid June. H8 temperatures near +18C and nearly
full sunshine will allow for widespread 90s with a few
communities in southern New Hampshire approaching 100 degrees.
Along the coast, cooler temperatures can be expected as winds
become onshore during the day.

Wednesday will be a similar day as the H5 high remains parked over
the New England coastline. A warm start, nearly full sunshine and H8
temperatures climbing to +20C, expect even warmer temperatures.
Afternoon temperatures will likely approach if not exceed 100
degrees across some interior locations. The atmosphere will once
again be modified along and near the coastline where southerly winds
bring in cooler temperatures. This inland penetration of this
coastal front will not be significant however. A few miles
inland and away from the coast will be extremely hot, hazy and
humid. Surface dew points will climb into the 65 to 70 degree
range.

12Z operational models and ensemble solutions remain with some
disagreement with the timing of a passage of a cold front either
late Thursday or Thursday night into Friday morning. This has some
impact on forecast highs. In general, with a possible delay in the
passage of the cold front, the day may be relatively cloud free, at
least over central and southern portions of the forecast. Mainly
sunny skies and some compressional warming ahead of this weak and
broad front may very well lead to the hottest day of the week with
readings above 100 degrees across portions of southwest interior
Maine and southern New Hampshire. The coast may be cooler once again
due to a sea breeze, but high surface dew points will remain in
place in all locations.

The excessive heat watch remains in place over interior southern
NH and it has been expanded to include interior central NH and
portions of interior southwestern ME for Wednesday and Thursday.
Additional heat related products can be expected.

Record high temperatures during the Tuesday through Thursday period
may be in jeopardy as shown in the climate section below.
Even Friday will be in the 90s across the interior despite
additional cloud cover and scattered showers and thunderstorms with
the weak and broad frontal system that will be slowly crossing New
England. Overnight lows will be mild as well during the three day
stretch which will exacerbate heat related issues.

Note the summit of MWN may reach 70 degrees during the period.

Confidence in the heat wave continues to increase as we head into
the week across the interior. Exactly how hot it reaches remains the
question. Any clouds from decaying MCSs to our west for example
would impact the forecast highs. As mentioned above, onshore winds
along the coast may keep things cooler. Will also be monitoring for
any potential development of coastal fog during this period as well
as inland radiation fog at night and during the morning hours.
However, at this time the gradient flow appears to have a sufficient
westerly component to prevent much in the way of maritime moisture
from entering the region. Coolest readings, albeit still very warm,
will be along the Midcoast region where winds will be onshore.

High pressure nosing into our region from Quebec Province will lead
to diminishing heat over the upcoming weekend. Surface winds will
switch to a cooler easterly flow. However, despite a 10 to 15 degree
drop in daytime highs, it will still be very warm over in New
Hampshire and along the Maine border with readings in the 80s.

It will turn mostly cloudy with scattered showers and thunderstorms
over the weekend. Low pressure will track out of the Plains Saturday
and Sunday leading to the precipitation.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
Short Term...VFR conditions will prevail today through at least
Tuesday. Light and variable winds early today will become
southerly at at 10-15 kts, gusts to around 20kts late this
morning through early this evening at KPSM, KPWM, and KRKD due
to a sea breeze. There is a low end chance for patchy FG
tonight but forecast confidence is low. No LLWS is expected
through the period.

Long Term...Mainly VFR conditions through Wednesday followed by more
showers and thunderstorms with a cold frontal passage by late
Thursday into Friday. Areas of IFR conditions are possible as well
during the night time period with patchy valley fog.

&&

.MARINE...
Short Term...High pressure will remain anchored southeast of the
waters through Tuesday. This will result in increasing southerly
winds with a few gusts of near 25 kts possible across the outer
waters this afternoon through early this evening. Persistent
southerly flow will allow seas to gradually increase to 3-5 ft
outside of the bays.

Long Term...Winds and seas will primarily be out of the south during
the extended portion of the forecast and below SCA thresholds.
Highest wind gusts likely will be during the afternoon hours as the
sea breeze attempts to form

&&

.CLIMATE...
Record breaking high temperatures and warm overnight low
temperatures are likely Tuesday through Friday of next week.

Here are the records...

RECORD HIGHS FOR JUNE 19:
Concord-98, 1995
Augusta-98, 1995
Portland- 94, 1995

RECORD HIGHS FOR JUNE 20:
Concord-98, 1993
Augusta-95, 1953
Portland-93, 2020

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Heat Advisory from noon to 8 PM EDT Tuesday for MEZ012-018>020-
     033.
     Excessive Heat Watch from Wednesday afternoon through Thursday
     evening for MEZ012-018>020-033.
NH...Heat Advisory from noon to 8 PM EDT Tuesday for NHZ004>013-015.
     Excessive Heat Watch from Wednesday afternoon through Thursday
     evening for NHZ006-008>010-012-013-015.
MARINE...None.

&&

$$


NEAR TERM...Schroeter/Tubbs
SHORT TERM...Tubbs
LONG TERM...Cannon