Area Forecast Discussion
Issued by NWS Portland, ME

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080
FXUS61 KGYX 071202
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
702 AM EST Thu Dec 7 2017

.SYNOPSIS...
Weak high pressure will gradually build into the region through
Friday with generally fair weather expected for most of the
area. A pattern change begins to take hold this weekend...as a
coastal low will develop offshore Saturday. This may deliver a
little light snow to the coastal plain through Saturday night or
early Sunday. Beyond the weekend we will have to watch for
another coastal low developing offshore...especially
midweek...that could deliver some snow to the region but
confidence is currently low.

&&

.NEAR TERM /TODAY/...
7AM UPDATE...
Have updated the forecast primarily to adjust for sky cover as
clouds are streaming in from the west southwest primarily as a
result of moisture from the lakes. A few flurries are possible
with this even outside the mountains, but do not expect
accumulations for most areas. Best chance for a dusting or more
of snow will be in northern New Hampshire later this afternoon
and evening.

ORIGINAL DISCUSSION...
Deep layer west southwesterly flow continues today as we remain
on the eastern side of a broad upper trough covering eastern
North America. Expect temperatures to be near seasonal normals,
with highs in the upper 30s to low 40s. West southwest flow over
the Great Lakes will cause a stream of lake moisture to spill
into northern New Hampshire where periods of light snow showers
are possible as the day goes on.

&&

.SHORT TERM /TONIGHT AND FRIDAY/...
Flow relaxes just a little bit tonight, allowing a bit more
low level cooling than the previous night. Temperatures should
fall into the 20s areawide, with teens possible in sheltered
valleys. Friday will be almost identical to today though perhaps
a couple degrees cooler.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
The main focus in the long term continues to be the chance for
accumulating snow Saturday night into Sunday and then again
midweek. Prior to Saturday night, the weather will be dominated
by weak high pressure and consequently fair weather.

The degree of amplification of an upstream trough will determine
how close low pressure develops to the coast Saturday through
early Sunday...and this will ultimately determine if
accumulating snows move westward onto the coastal plain. Two of
the better performing models (ECMWF and UKMET) are two of the
most western solutions and much credence has been given to
these solutions. However, several others remain offshore and dry
for the landmass. A quick look at the GFS ensemble mean looks a
bit like the 00z deterministic ECMWF. Have therefore raised
pops for snow to chance to high chance on the coastal plain for
very late Saturday afternoon and night and went with T-2" of
snow (highest on immediate coast). Will continue to watch trends
in amplification though, as higher amounts will be possible
(especially Maine`s Midcoast). Conversely, it wouldn`t take much
for this to whiff. Any snow would end Sunday morning.

Thereafter, more chances for snow and rain exists Tue/Wed with
another shot at coastal low pressure. High uncertainty there and
therefore low confidence. We`ll get through the first one first
before having much meaningful ideas on details for midweek.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
Short Term...VFR conditions expected the next few days with a
light westerly wind. May see a snow shower at Whitefield with
MVFR ceilings possible as well, especially this afternoon and
tonight.

Long Term...VFR Friday night into Saturday. MVFR possible on the
coastal plain and southeast NH Saturday night into early Sunday
morning in snow if low pressure tracks close enough to the
coast.

&&

.MARINE...
Short Term...Westerly flow continues over the waters with wind
gusts near 25 KT possible today and tonight. Wave heights have
come down a good amount, but remain at or above 5 FT especially
over the outer/eastern waters where the current fetch is
greatest. Could see winds finally drop below advisory levels
Friday morning.

Long Term...SCA conditions will be possible Sunday into Monday
in the wake of departing low pressure. More low pressure systems
could affect the waters around the Tue/Wed timeframe with higher
winds.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory until 6 AM EST Friday for ANZ150-152-154.

&&

$$

NEAR TERM...Kimble
SHORT TERM...Kimble
LONG TERM...Ekster



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