-- Discussion containing changed information from previous version are highlighted. --
148
FXUS61 KGYX 201859
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
259 PM EDT Thu Jun 20 2024

.SYNOPSIS...
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Heat ridge breaks down this evening as a surface
cold front pushes through the area bringing cooler weather.
Front stalls just to our south and becomes a focus for rain
shower activity tomorrow and Saturday. Warmer again on Sunday
with thunderstorms and locally heavy rain. Quiet weather is
expected by the beginning of next week.
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&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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The backbone of the heat breaks this evening as strong to
severe storms move through the region. The heat threat is
steadily evolving into a severe threat for this afternoon with a
cold front slowly pressing southward through the afternoon
hours. Isolated storms are expected to grow and consolidate
into clusters and slow moving lines of storms through the
afternoon and into the evening. With west- southwesterly flow,
storms are not expected to weaken until after they move
offshore, bringing the severe threat right to the coastline.

A severe thunderstorm watch has been issued for the entire
forecast area, with storms already firing early this afternoon.
Yesterday`s storms proved damaging with just high CAPE and cold
pools. Today, a little more shear and better forcing from the
front combine with the hot and humid conditions to bring severe
storms with a higher degree of confidence than we often see.
Damaging winds are likely to be the most widespread impact, but
some hail around quarter size is also likely with a few storms,
especially in the more isolated ones forming during the mid
afternoon hours.

The lines and clusters of storms push offshore through the
evening hours after sunset, with much cooler conditions expected
behind the storms by late evening. The front slowly moves
through during the overnight hours, bringing in drier air
overnight. Before this drier air filters in, patchy fog is
likely by late evening and into the overnight hours, especially
through the valleys and along the coastline.
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&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
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The front continues to slowly move through the CWA tomorrow,
with temps warming into the mid 80s through southwest NH ahead
of the front. Behind the front, cool and dry northeasterly flow
keeps temps in the low to mid 70s through much of Maine and the
Seacoast of NH. Showers, and some thunderstorms continue near
and behind the front tomorrow as moisture continues to ride
along the front. This makes for a cool and showery day for much
of southern and western Maine and eastern NH. Further behind the
front, central Maine may escape most of the shower activity to
see more sunshine, with temps warming into the mid to upper 70s
accordingly.

Scattered showers continue through the overnight hours tomorrow
night as the front lingers to our south. Placed of the cooler
side of the ridge, waves of leftover convection and periods of
showers likely continue to move through the region as these
features ride around the ridge. The cooling trend continues,
with lows dipping into the upper 50s to low 60s across most of
the area.
-- End Changed Discussion --

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
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Overview:  Relatively progressive flow after the NE CONUS ridge
becomes suppressed with a more active polar jet stream and Canadian
troughs moving across New England. Shortwave ridging is expected
between the troughs bringing a see-saw weather pattern over the next
week.  This will bring periods of active weather with thunderstorms
and temperature swings from near normal to above normal.

Impacts:  Localized heavy rain is possible Saturday across Western
NH with a higher threat for localized flash flooding on Sunday
across the mountains.  In addition, severe weather can`t be ruled
out Sunday at this time across most of the forecast area.

Forecast Details: On Saturday a stationary boundary will be located
in the vicinity of Southern NH with surface ridging to our north.
This will separate the heat and moisture from the Mid-Atlantic and
cooler dry airmass from Canada. Expect showers and isolated
thunderstorms along this boundary with the highest chances for
locally heavy rain across Southwest NH at this time. By Sunday the
stationary boundary becomes a warm front and surges north of the
area bringing the region back into the warm sector. Threat for
severe weather will increase as a robust mid-level shortwave and
associated cold front pushes through the area sometime late Sunday
into Monday morning. There is some model spread on the order of 12
hours or so on timing of FROPA at this time. Monday the shortwave
trough swings through with the potential for much cooler weather and
showers, but this depends on the timing of the trough. Tuesday looks
to have the highest potential for being the driest day of the week
as a shortwave ridge moves over the area with a rebound in the
temperatures. Wednesday could be warm once again as a return to
southwest flow is possible ahead of the next approaching trough. A
period of storms is possible in the Wednesday night into Thursday
timeframe as the next cold front swings through the area.
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&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
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Short Term...Showers and occasional thunderstorms are expected
at all terminals through the afternoon to early evening hours,
occuring first across western terminals and moving to the
coastal terminals by the late afternoon/early evening. These
storms push offshore by late evening, with brief periods of BR
or FG possible in the valleys overnight. PROBs are too low to go
too strong with the fog threat, but IFR to LIFR can`t be ruled
out late tonight at LEB, HIE, and RKD. Conditions improve
tomorrow morning, but periods of MVFR ceilings are likely
through coastal terminals. Showers and brief restrictions are
possible at all terminals tomorrow afternoon and night, but
otherwise mainly VFR to occasional MVFR conditions are expected.

Long Term...Showers and thunderstorms could bring temporary MVFR to
IFR conditions on Saturday with the highest threat across the
airfields of New Hampshire. Similar impact to operations is possible
on Sunday as the threat for afternoon thunderstorms increases along
with gusty southwest winds. Storm coverage should trend downward by
the beginning of next week.
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&&

.MARINE...
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Short Term...A cold front slowly moves southward across the
waters overnight tonight and tomorrow. Thunderstorms with strong
wind gusts are likely near the coast late this afternoon and
early evening. Winds shift to northeasterly behind the front
tonight, but conditions are expected to remain below SCA levels
through tomorrow night.

Long Term...Storms are possible over the waters on Saturday. By Sunday
strong SW winds could develop leading to marginal SCA conditions by
the afternoon and evening hours ahead of an approaching cold front.
Cold front pushes through on Monday with a return to offshore flow
and possible SCA conditions.
-- End Changed Discussion --

&&

.CLIMATE...


&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Excessive Heat Warning until 7 PM EDT this evening for MEZ012-
     018>028-033.
     Heat Advisory until 7 PM EDT this evening for MEZ013-014.
NH...Excessive Heat Warning until 7 PM EDT this evening for NHZ006-
     008>010-012>015.
     Heat Advisory until 7 PM EDT this evening for NHZ002>005-007-
     011.
MARINE...None.

&&

$$


NEAR TERM...Clair
SHORT TERM...Clair
LONG TERM...Dumont
AVIATION...Clair/Dumont
MARINE...Clair/Dumont