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058
FXUS61 KGYX 270020
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
820 PM EDT Wed Jun 26 2024

.SYNOPSIS...
Low pressure will move through the region along a cold front
tonight...bringing showers and thunderstorms to the region.  Cooler
and drier air will begin to filter in on Thursday with a few
afternoon showers again possible.  A cool night is expected Thursday
night with seasonably cool and dry conditions for the day on Friday.
Unsettled weather returns to the region for this weekend with
additional showers and thunderstorms expected as low pressure moves
north of New England.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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8pm Update...Not many changes from the day crew. Despite evening
convection across MA setting up north of 12z HREF guidance,
believe this activity pushes east before sfc low pushes across
NH/ME tonight. RAP soundings in southern NH keep low levels dry
through midnight, but upper level saturation should allow
showers to reach surface. With low but nonzero MUCAPE overnight
for the mountains and then towards the Midcoast, have continued
thunder chances here overnight.

Previous Discussion...
High Impact Weather Potential: Some low probabilities for
excessive rainfall across southern areas as well as a severe
thunderstorm risk for far SW New Hampshire.

Pattern:  A potent shortwave trough can be seen moving through the
Great Lakes region early this afternoon as a surface cold front
drops toward northern New England.  This shortwave will help spawn
low pressure development along the front as it slows while passing
overhead.  Thus...forecast concerns will center around shower and
thunderstorms associated with this low and more specifically 1)
where heavy rainfall may occur and 2) whether there is any
severe threat with the thunderstorm activity.

Through this evening: Initial batch of showers is passing east
of the area with a sprinkle or two in it/s wake. While llevel
cloud cover will wane through this evening...high cloudiness
will continue to increase as convection develops across NY/PA.
8pm temperatures will remain warm...only falling to the 70s to
around 80.

Tonight: Overall trend over the past 24 hours has been to lower the
QPF in the mesoscale guidance suite...with low pressure riding just
south of the forecast area overnight as the cold front makes it to
the coast before the surface low arrives.  The net result is that
any surface-based instability remains south and east of the forecast
area overnight. There is a small amount of elevated instability
north of the cold front...so a few rumbles can/t be ruled out...but
feel that the severe convective threat will be confined to areas
south of the CWA.  With more significant convection south of the
area...the majority of our rainfall overnight will be tied to QG
forcing associated with mid level shortwave and the developing
surface low.  This favors more light-moderate rainfall rates with
the heaviest amounts potentially towards the midcoast where some
weak deformation will have the chance to develop depending on how
quickly the surface low spins up. Temperatures will remain generally
mild overnight as more significant cold air advection holds off
until daytime Thursday.  Therefore...expect lows in the 50s in the
mountains and the 60s to the south.
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&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
High Impact Weather Potential: Minimal.

Pattern:  Shortwave trough over the eastern portion of the forecast
area will move east of the region with a secondary shortwave and
associated trough dropping through the region.  Forecast focus will
be on departing morning precipitation...any shower/storm potential
with the secondary trough...and then cooler temperatures Thursday
night.

Thursday: With low pressure pulling northeast of the forecast area
and initial surface cold front offshore...could see a few residual
showers across the Midcoast to start the day before attention turns
towards a secondary trough that will drop through the region during
the day with very weak height mid level height falls continuing as a
secondary shortwave passes north of New England.  While the overall
profile will be drying through the day...some modest moisture
pooling ahead of the secondary trough should allow for a few hundred
J/kg of SBCAPE to develop ahead of the trough.  Thus...expect some
afternoon showers to develop with a few rumbles of thunder possible
though instability appears too weak to support a severe threat.  T8s
will have fallen a few degrees C since Wednesday...though downslope
assistance will allow southern NH/southwestern ME to push into the
lower 80s again while highs in the 70s with gradually decreasing
dewpoints are expected elsewhere.

Thursday Night: Canadian high pressure helps drive a continental
polar airmass into the region Thursday night with PWATs falling
below 0.25".  Thus...a quieter and much cooler night is in store.
Northerly 1000 mb geostrophic winds remain in the 20-30kt range
overnight which should keep all but the deepest valleys coupled.
Some of the statistical guidance drops the northern valleys /BML-
HIE/ just below the 40F mark.  Given the remaining winds...this may
be a bit too low...but do expect lows in the lower 40s in the
mountains with lows south of the mountains in the mid 40s to lower
50s...warmest in the urban centers.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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A quiet start to the long term before a little more active weather
pattern returns. On Friday high pressure will be centered over New
England resulting in mainly clear as seasonable conditions.
Friday Night into Saturday the high will drift offshore as low
pressure over the upper Great Lakes pushes east. A warm front
followed by a cold front that are associated with this low will
cross the area later Saturday Afternoon and Night. This will
result in increasing clouds during the day on Saturday with rain
developing during the afternoon over NH...reaching western
Maine by late afternoon or early evening. Rain will continue
into the overnight hours of Saturday Night before tapering to
showers by daybreak from west to east. With an upper level
trough approaching the area on Sunday scattered instability
showers and thunder showers will be possible. This upper level
trough will cross the area on Monday meaning a few showers may
linger on Monday although the bulk of the day should be dry. As
the upper level trough reaches the Gulf of Maine there are
indications that low pressure forms. Right now the models have
this east of the area allowing high pressure over the Ohio
Valley to slowly build east for Tuesday into Wednesday. As long
as the low just east of the area does not form further west, we
will see a return of dry and seasonable conditions for Tuesday
into Wednesday.
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&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Short Term...

Summary: Low pressure moves through the region tonight along a cold
front with showers and a few thunderstorms.  Partial clearing is
expected on Thursday before a few afternoon showers develop.  High
pressure builds toward the area Thursday night with clearing skies.

Restrictions: VFR ATTM with conditions deteriorating to MVFR/IFR
in SHRA and fog after midnight. A few embedded thunderstorms
will be possible. Improvement to VFR occurs on Thursday with VFR
Thursday night.

Winds: West southwest winds 10g15kts through this evening will
weaken to 5kts or less overnight before strengthening to 8G14kts
from the west Thursday.  Winds shift to the northwest 5-10kts
Thursday night.

LLWS: LLWS is not expected through Thursday night.

Lightning: There is a low potential for lightning through 19Z at
AUG/RKD.  Tonight...an isolated thunderstorm is possible...esp for
southern NH and southwestern ME.  Thursday afternoon, an isolated
thunderstorm is again possible.

Long Term...

VFR conditions Friday into Saturday morning. IFR
conditions in developing rain late Saturday over NH overspreading
western Maine Saturday evening and continuing Saturday night. MVFR
with areas of IFR in showers on Sunday as a upper level trough
crosses the area. MVFR to VFR conditions return on Monday as High
pressure builds east from the Ohio Valley.

&&

.MARINE...
Short Term...Southerly winds will weaken tonight as a cold
front settles over the waters. Light winds become southwesterly
on Thursday before shifting northwest and strengthening Thursday
night.

Long Term...Wind and waves to remain below SCA conditions
through Saturday Afternoon.  A frontal system crossing the waters
Saturday Night and Sunday will result in SCA Winds and Waves with
areas of rain. Conditions to fall below SCA levels Sunday Night and
Monday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.

&&

$$


NEAR TERM...Arnott/Cornwell
SHORT TERM...Arnott
LONG TERM...Lulofs