Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 240232
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1032 PM EDT Tue May 23 2017

.SYNOPSIS...
Weak high pressure will hold over the region through Wednesday as
low pressure passes well offshore. A complex area of low pressure
will approach from the southwest Wednesday night and Thursday and
will slowly move northeast through southern New England and the Gulf
of Maine Thursday night and Friday. High pressure will build in from
the west Friday night and Saturday. A cold front will drop south
through the region Saturday night and Sunday.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Update...
Have issued a quick update to account for current observational
trends and mesoscale models. CS shield has expanded to central
areas and is opaque in many areas, while skies remain mainly
clear over northern areas. With this cloud cover, have backed
off on some of the fog forecast for late tonight and primarily
will focus on patchy for over northern areas which are mainly
clear as of 0230Z.

Widespread 40s expected for overnight lows tonight. No signs of
marine stratus as of late this evening.

Prev Disc...
A stratus deck has moved offshore but it did take a
while for coastal locations to clear out today. After some
clearing over the coastal plain and variable sun across the
area, moderately dense cirrus blow off from the west has covered
southern NH and much of western Maine. Elsewhere cumulus had
developed over the mountains. All this developed in WSW/weak
ridging aloft and in advance of a warm front over the Great
Lakes region.

Expect more cloudy skies tonight with light and variable winds.
Overnight lows will range from the mid 40s to mid 50s.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Wednesday will be similar to today but with increasing moisture
due to an increased onshore flow. We`ll see a weak sea breeze
develop tomorrow afternoon with low pressure passing well south of
the Gulf of Maine. That said there may be a stray shower associated
with this low across southern NH or SW Maine. In addition, isolated
mountain showers are possible as the elevated warm front nears
tomorrow. Highs will generally be in the lower to mid 70s. Overnight
lows will be a little warmer for northern zones in the upper 40s
with lower 50s to the south.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
A broad upper level ridge currently over the eastern portion of the
US will shift eastward as the trough moves through the midwest and
onto the east coast. This will set us up for an active pattern with
a series of waves moving along the upper low and up the east coast.

Thursday will start off partly sunny but quickly cloud over as
low pressure develops to our south and moves up the east coast.
This storm will deepen and pass across Cape Cod on Friday
bringing widespread rain. While there is a fairly good consensus
there will be a coastal low, the strength of the storm is still
seeing quite a bit of spread with QPF amounts as high as 2
inches possible along the coast for the stronger solution and as
low as 0.5 inch. Have leaned a bit on the higher QPF both due
to favoring the stronger solution and because of the long
tropical fetch for the moisture source.

The storm departs into the maritimes on Saturday with some
scattered upslope showers. Saturday afternoon and evening will
be a brief break from the rain. The next low will move through the
Great Lakes on Sunday pushing a warm front and overunning
precipitation through the area Sunday night. Another coastal low
will spin up on Monday pushing another round of widespread
precipitation through to start the week.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Short Term...VFR conditions will prevail with some possible
IFR/MVFR in low stratus and fog once again near RKD...AUG...and PWM
late tonight into Wednesday morning. A low deck is lurking just
offshore and should move back towards shore tonight. Additional fog
or drizzle is possible late Wednesday night into Thursday morning.

Long Term... Thursday will begin with VFR and MVFR but rapidly drop
to IFR on Thursday night as low pressure approaches the region. IFR
with rain and fog will continue through the day on Friday with gusty
winds along the coast. Conditions will improve to VFR with MVFR
ceilings in the mountains for Saturday.

&&

.MARINE...
Short Term...Conditions should remain below SCA thresholds today
through early Thursday morning.

Long Term...
A coastal low will cross the waters on Thursday into Friday with
Small Craft Advisories likely and gale force winds possible ahead of
the storm. Winds and seas will subside on Saturday and remain fairly
calm through the start of next week.

&&

.TIDES/COASTAL FLOODING...
In addition to the potential for a lot of rain on Friday morning,
the easterly flow and winds associated with a coastal low will
create a risk for coastal flooding. Onshore flow will develop
Thursday ahead of the storm and strengthen through the day on
Friday. This will result in a storm surge of around 0.5 ft Thursday
night. The highest tides of the year will occur Friday, with the
onshore component plus the storm surge resulting in coastal flooding.

&&

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

&&

$$
JC



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