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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KGYX 100809
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
409 AM EDT Wed Apr 10 2024

.SYNOPSIS...
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A series of waves will cross the region through the end of the
work week with increasing humidity, cloud cover, and showers
escalating to widespread rainfall. While some places will be
mild and humid, others toward the Gulf of Maine are likely to
remain cool and humid with onshore flow. In any case, a ripening
and melting snowpack combined with rain will lead to river and
stream rises, with a chance for minor flooding. A passing cold
front on Friday will introduce gusty winds, potentially strong
along the coast. Winds remain gusty heading into the weekend
with scattered showers.
-- End Changed Discussion --

&&

.NEAR TERM /TODAY/...
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The upper level synoptic pattern today features a series of
northern stream waves skirting along the Canadian border and a
broad ridge of high pressure spanning the Eastern Seaboard. At
the surface, high pressure sinks south of Nova Scotia and
supports continued southeasterly/onshore flow... leading to a
significantly cooler day for the majority of the area with highs
in the 40s, except in southern and western New Hampshire
outside of the influence of this flow where temperatures are
again forecast to reach will into the 50s to near 60.

Clouds and precipitation chances will increase through the day
as one of those aforementioned northern stream shortwaves
approaches from VT. Early this morning, a cluster of convective
rain showers tracking through northern New York denotes the weak
system`s triple point, supported by a pocket of elevated
instability. The expectation is that this cluster of showers
initially tracks across the region through the late
morning/early afternoon hours... separating from best forcing
and limiting convective potential. Later in the day more
widespread showers are forecast to from along a weak boundary
pushed east by the wave, with ceilings filling in and lowering
heading into tonight.
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&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
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The upper level shortwave lifts north tonight with its lower-
level boundary eventually stalling across our area. Although
shower activity along the front will go through a bit of a lull,
except toward central Maine, continued onshore flow...turning
more easterly and northeasterly with time...and some subsidence
will lead to widespread drizzle and fog overnight south of the
mountains, especially toward the Maine coast.

The upper air pattern grows significantly more amplified by
Thursday as a trough of low pressure curls negatively through
the Great Lakes/Ohio Valley and see-saws a ridge building up
the East Coast. This takes the remnant boundary north in the
form of a warm front with renewed rain, especially toward the
west with better upper air support. Closer to the surface... the
start of a CAD is noted in NE flow through the interior abutted
by onshore flow along the coastal front. This will lead to a
cooler day over Maine and into eastern NH with highs limited to
the 40s, patchy fog, and patchy drizzle as low-level flow just
off the deck continues out of the south or southeast. Further
west, mainly in the CT and lower Merrimack Valleys, mixing
should be a little better and support highs in the 50s.
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&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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Overview...

Slow moving low pressure tracks through the Great Lakes and
Quebec Thursday night through early Saturday. The cold front
associated with this storm passes through New England during the
afternoon on Saturday, bringing drier conditions for the second
half of the weekend. Temperatures moderate next week as a ridge
builds into the Great Lakes and Northeast, but a nearby
backdoor cold front will also be lurking as high pressure builds
across Labrador through midweek.

Details...

A deepening low pressure center moves into the Great Lakes
Thursday night and Friday, and then moves off to our west
through Quebec into Saturday. Weak waves of low pressure will
move along and ahead of the cold front associated with this
storm and bring periods of rain from Thursday night into Friday
night. More scattered shower activity is expected during the day
on Saturday, and then conditions dry out Saturday night and
into Sunday.

Overall about 1-2 inches of rain are expected across most of
the area from Thursday through Friday, with some slightly lower
amounts expected toward the coast and north of the mountains.
Despite these rainfall amounts not being particularly impressive
compared to other recent storms, combined with melting snow
there is still concern for rivers to rise to near flood stage
through the mountains and foothills.

Breezy conditions are also expected, with southerly wind gusts
up to around 40 mph possible on Friday, especially along the
coast. These peak during the daytime on Friday, and then
gradually ease through Friday night. Winds shift around to the
west after the cold front passes through on Saturday, and could
become a bit gusty again behind the front Saturday night and
into Sunday.

The moderation trend in temps begins on Sunday as brighter
skies and downslope conditions help temps return to the upper
50s and low 60s. There is room to temps to go higher through the
week as a ridge builds, with 70s possible across southern New
Hampshire by Monday. The ridge will continue to build through
midweek, but at the same time high pressure will build across
Labrador, a prime spot to produce a backdoor front that brings
cool maritime air this time of year. Models and ensembles
continue to waffle back and forth on this front, but history
suggests in will make it into the area at some point mid to late
next week. The best chance for a cooldown will be across Maine,
especially toward the coast, with the warmest conditions
through the Connecticut River Valley.

This forecast sticks with the NBM for now, but if the front
does make its way into our forecast area, it would produce the
kind of setup where it`s in the 40s or 50s along the Maine coast
while it`s in the 80s at the Vermont border. With it being a
week away it`s still too early to try to pin down this gradient,
or even know if it will make it back into our area, but it will
likely be a forecast challenge that will need to be resolved
for next week in the days ahead. So while the warmest potential
temps are midweek next week, the safest bet for warm temps are
early in the week before the high begins to build to our
northeast.
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&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
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Short Term...Starting off VFR this morning with VFR decks
streaming in from the west and light and variable or no flow on
surface obs. Steady, light SE flow picks up during the daytime
with mainly VFR -SHRA entering from the west. More widespread
-SHRA/-RA is likely to develop this afternoon and evening with
 lowering CIGs. IFR/LIFR is expected overnight for most or all
 terminals in low CIGs, with a break in -SHRA but replaced by BR
 and perhaps -DZ/FG especially near the coast. IFR/LIFR CIGs
 persist Thursday with degraded VSBY in -RA and BR.

Long Term...IFR to LIFR conditions are expected at times with
periods of rain and possibly some fog Thursday night through
Friday night. Conditions gradually improve on Saturday, but some
showers remain possible. Gusty southerly winds up to 30 kts are
possible during this timeframe along coastal terminals, with
some westerly 30kt gusts then possible late Saturday afternoon
through Sunday at all terminals. VFR conditions return by
Sunday, and likely prevail through midweek next week.
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&&

.MARINE...
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Short Term...SE winds below 20 kts continue through this
evening with seas generally 1-3 ft. Flow curls E to NErly right
along the coast tonight into Thursday with gusts near 25 kts
over the eastern waters coinciding with seas increasing to
around 4-5 ft.

Long Term...High pressure builds to the east of the waters as
low pressure tracks west of the waters Thursday night through
Friday night. Southerly gales are possible during this
timeframe, and then gradually ease late Friday night. A cold
front crosses the waters late Saturday, with westerly gales
possible Saturday night and Sunday. High pressure then builds
across the waters for the early to middle portions of next week.
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&&

.HYDROLOGY...
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Confidence is increasing in the potential for new and renewed
river flooding Thu-Fri across the region. A storm system will
bring warm, humid, and breezy conditions to produce snow
ripening and melt, and then periods of moderate to locally heavy
rainfall. Rainfall totals of 0.5-1.5" are expected, with
amounts up to 2.5" across the mountains. Windy conditions,
particularly in the higher terrain, will combine with the warm
dew dewpoints to exasperate the snowmelt which could reach 3"
SWE loss in 48 hours.

Antecedent conditions ahead of this event are saturated due to
repeated rounds of rainfall over the past month, and this
additional rainfall and snowmelt will likely eliminate any
remaining infiltration capacity, causing immediate runoff
directly into streams and rivers and generating small stream and
river flooding. The culmination of vulnerable antecedent
conditions, the atmospheric setup, and snowmelt, elevate the
risk for flooding. At this time the conditions favor minor river
flooding with the potential for isolated significant flooding,
particularly in the mountain regions.

Outside of the snow covered areas, locally heavy rainfall may
elicit poor drainage and nuisance flooding in urban areas,
especially if heavier rainfall totals were to materialize.
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&&

.TIDES/COASTAL FLOODING...
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Astronomical tides remain near their monthly maximum this week
with forecast tidal stages reaching action stage with each
cycle. Late night/early morning cycles are the higher of the two
cycles, and have potential to touch flood stage through late
Friday. Although astrotides will begin to decrease now that
we`re past last night`s maximum, surge should subtly increase as
high pressure settles south of Nova Scotia and sets up an
onshore flow through mid-week. A storm surge is then possible on
Friday, however timing of this surge will be critical in
determining what if any impacts occur as astronomical tides will
start to trend downward at that point.
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&&

.GYX WATCHES/WARNINGS/ADVISORIES...
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ME...None.
NH...None.
MARINE...Gale Watch from late Thursday night through Friday evening for
     ANZ150>154.
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&&

$$

NEAR TERM...Casey
SHORT TERM...Casey
LONG TERM...Clair