Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 200525 AAC
AFDGYX

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
125 AM EDT Sun Aug 20 2017

.SYNOPSIS...
High pressure will build south of the region Sunday through
Monday before sliding to the east on Tuesday. A cold front will
move in from the west Tuesday night and will cross the region
on Wednesday. High pressure will build in behind the front
Wednesday night through Friday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
1124 PM Update: Going forecast in good shape with only minor
tweaks to temperatures...dewpoints and hourly PoPs necessary
given current obs and slower arrival of decaying upstream
convection now entering western MA. Will maintain thunder
mention for now...but MUCAPES are diminishing and expect that
this activity will continue to weaken as it heads north and
east. Watching fog development...with a few locations having
fallen below one mile last hour /PWM-LEW-RKD/. Gradual dry
advection overnight will compete with cooling and for this
reason don/t expect fog to become widespread and dense...but a
few dense patches are possible. Will consider a SPS if VSBY
trends in this direction.

Update...
Have updated the forecast per current observations and trends.
Plenty of Cu remain over northern areas where the terrain kick
will work with limited instability to produce widely scattered
showers and perhaps a stray thunderstorm overnight. This
precipitation will be associated with the passage of an upper
level trough during the overnight hours.

Have also introduced a chance for showers or thunderstorms,
mainly after midnight tonight over southern New Hampshire and
far southwestern Maine. Latest HRRR depicting convection over
eastern New York State surviving the trip through portions of
New England. Sufficient CAPE values to trigger a brief shower or
storm as the moisture potentially rides through York county
Maine by 09Z.

Elsewhere, some low level moisture from yesterdays heavy rain
will become trapped underneath a developing inversion overnight.
This will lead to patchy fog throughout much of the region.

Have made minor adjustments to temperature trends, dew points
and cloud over over the next few hours.

Prev Disc...
At 18z...a 1007 millibar low was off the downeast
coast with a trailing cold front through the Gulf of Maine. A
1001 millibar low was centered over northern Quebec with a
trailing cold front through the eastern Great Lakes. We`re
seeing gradual clearing today behind the departing disturbance
over the Gulf of Maine. However, heating and the approaching
cold front may trigger a brief shower/isolated thunderstorm
through early tonight mainly across the higher terrain.
Overnight...partly cloudy skies with patchy fog and valley
stratus developing in wake of cold front and shortwave impulse
sweeping offshore.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/...
For Sunday...ridging takes hold although we`ll see a few upslope
clouds across the higher terrain. It`ll be a warm day with highs
ranging from the 70s across the mountains...to lower and mid 80s
elsewhere. Partly cloudy Sunday night with some patchy late
night fog and lows in the 50s to lower 60s.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Models remain in fairly good agreement today on extended forecast
for next week. High pressure will crest over the region early
Monday before shifting offshore south of New England. Return flow
will bring warmer and more humid air back into the northeast
through the day under mostly sunny skies. Highs on Monday will
generally range through the 80s.

Summer-like weather will continue Monday night and Tuesday.
Looking for partly cloudy skies Monday night with lows in the
lower to mid 60s. Tuesday will start off mostly sunny with high
clouds on the increase in the afternoon as a cold front
approaches from the west. Looking like a hot one with highs in the
80s to lower 90s. May see some convective activity reaching far
northwest zones by late in the day but expect a majority of the
forecast area  to see a dry day.

Cold front will push in from the west Tuesday night. Looking for
showers and Thunderstorms overnight some of which could be severe
with heavy rainfall. Moderate to strong shear will combine with
PWAT`s approaching 2 inches to produce possible damaging winds
and heavy rainfall. Although timing of the front not ideal...
strong dynamics associated with this shortwave should sustain
convection well into the evening and overnight. Looking for a very
warm and humid night with lows in the 60s to lower 70s.

Cold front will slow as it moves through the region early Wednesday
but  should finally move offshore by Wednesday afternoon. Highs on
Wednesday will range from the mid 70s north to the mid 80s south.

Skies will be mostly clear Wednesday night as high pressure begins
building in from the west. Should see much more comfortable
conditions as cooler and drier air shifts into the region on a
northwest flow.

High pressure will dominate the weather for the rest of the week
and into the weekend. Upper trough settling into the northeast will
result in A mix of sun and clouds during the days with mostly clear
and cool conditions at night. Highs Thursday through Saturday will
range through the 70s with lows overnight in the upper 40s to mid
50s.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
Short term /through Monday/...

Summary: High pressure will build south of the region through
Monday bringing improving flying conditions to the area.

Restrictions: LIFR fog/stratus is gradually eroding from the
west with RKD/AUG likely to improve to VFR around daybreak.
Otherwise...could see some IFR fog develop near LEB around
daybreak with upslope cloudiness bringing MVFR restrictions to
HIE through the morning. VFR this afternoon through Monday
outside of potential fog redevelopment tonight HIE/LEB and
potentially RKD.

Winds: Light and variable winds overnight will become northwesterly
and increase to 10g18kts for the day today before diminishing back
to calm tonight. Winds will become westerly 10-15kts for the day on
Monday.

LLWS:  LLWS is not expected through Monday.

Lightning: No thunderstorms are expected through Monday.

Long Term...
VFR Tuesday. Areas of MVFR/IFR ceilings/vsby in showers and
thunderstorms Tuesday night. Becoming VFR for Wednesday through
Thursday.

&&

.MARINE...
Short Term /through Sunday Night/...Seas continue to diminish
and the small craft advisory for hazardous seas has been
dropped.

Long Term...
SCA`s may be needed Tuesday into Wednesday.

&&

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

&&

$$
SYNOPSIS...
NEAR TERM...Arnott
SHORT TERM...
LONG TERM...
AVIATION...Arnott
MARINE...



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