Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 131628
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1128 AM EST Wed Dec 13 2017

.SYNOPSIS...
Behind the departing low pressure a strong cold front has moved
through the region. Snow showers persist in the mountains
today. Temperatures today will likely fall through the
day...ending up the teens by the evening. Wind gusts in excess
of 35 mph will make that air feel bitterly cold. The coldest air
of the season will move into the region behind this system for
the remainder of the week...with a few chances for additional
snow showers.

&&

.NEAR TERM /TODAY/...
1130AM UPDATE...
Have updated to drop the Winter Storm Warning in the mountains.
Although snow will continue through the day, it will be light
and only amounting to an inch or two. The warning level impacts
have ended.

1030AM UPDATE...
Have updated the forecast primarily to tweak PoP and
temperatures based on latest observations. Front has cleared the
area but upslope snows continue in the mountains. This may
decrease in coverage this afternoon when flow becomes more well
mixed. Additional accumulations are possible, so will maintain
ongoing Winter Storm Warnings.

730AM UPDATE...
Bulk of the precip outside of the mtns has moved E of the
forecast area at this hour. Minor adjustments to temps and dew
points. Otherwise no significant change to the forecast.

ORIGINAL DISCUSSION...
Upper low pressure is beginning to approach Northern New
England this morning. At the moment lift ahead of it...along the
H8 cold front...is leading to a band of precip across the
Midcoast. I have increased PoP to likely...and have a mixed bag
of ptypes. There may be some rain along the immediate coast
where warmer air still lingers...but inland temps at or below
freezing are probably leading to a little bit of everything with
mid level temps still just above freezing. This will be short
lived precip however...as the surface low moving into Downeast
ME will drag precip with it.

The upper low itself will likely provide for fairly widespread
precip early in the day. The cooling column will support snow
showers vs mixed precip by then though. The real cold air will
move into the region behind the trof axis...which will also help
mix down stronger winds aloft in CAA. There does appear to be a
window of possible 40 kt gusts from about 21z to 00z. Given the
recent snow and ice...tree limbs may be more susceptible to
breaking and leading to power outages...so I have issued a wind
advisory for Southern NH and adjacent SW ME. Elsewhere gusts of
25 to 30 kts are likely in the afternoon.

The developing strong W winds will also help to focus snow
showers in the higher terrain. Very low snow growth
zones...lingering low level moisture...and orographic lift will
likely result in numerous snow showers...and efficient snow
accumulation despite low QPF. Several inches additional
accumulation are possible today...and given that there is no
discernible break in snow for the mtns...I have extended the
winter storm warnings thru the evening for those areas. Given
the well mixed boundary layer...snow showers may be able to top
the mountains and move downstream...but significant
accumulations are not expected there.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Chilly night on tap...especially considering the gusty W flow
that will be continuing. Temps will fall into the teens S of the
mountains...where downsloping and a well mixed boundary layer
will keep readings relatively mild considering the air mass
moving in. In the mountains and N readings will bottom out in
the single digits. With winds staying gusty overnight...wind
chills will fall to as cold as -10 in the northern zones...and
to near zero S of the mountains. Cross barrier flow...cold
temps...and lingering low level moisture will keep snow showers
going along and upwind of the mountains as well...though
coverage should be less widespread than the afternoon.

On Thu a trailing S/WV trof will pass S of the forecast
area. Though at this time it looks far enough S to avoid
significant impacts...it will likely spread some cloud cover
into southern zones...and may even bring a period of very light
snow to southern NH. The main story however will be the cold
temps...with afternoon highs staying in the 20s S of the
mountains...and teens and even single digits in the higher
terrain.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
The mean long wave trof position remains anchored across the
eastern US while the high amplitude ridge across the west coast
remains in place. The coldest air of the season will move into
the region with this long wave trof as a series of clipper
systems move through this long wave trof over the outlook
period. These clipper systems will each have very limited
moisture due to their source region, but enough to allow
scattered snow showers and reinforcing shots of arctic air in
their wake. The first of these systems will arrive Fri night and
exit by late Sat. Then another similar clipper Sun night into
Mon. Generally stayed very close to superblend models for the
outlook period.

One item to note, min/max temps may not be cold enough for Thu
night through Fri night due to the fresh snow cover.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Short Term...SHSN will be likely in the mtns...with LEB and HIE
possibly seeing local IFR or lower conditions thru the day.
Scattered SHSN are less likely downwind of the mtns...but it
cannot be ruled out. In addition after 18z thru about 00-01z
surface wind gusts at or above 30 kts are possible at all
terminals...especially across southern NH and MHT/PSM/CON.
Gusty W winds will linger into Thu.

Long Term...VFR conditions except MVFR/IFR in any snow showers
with the next clipper system to move through the area Fri night
and Sat.

&&

.MARINE...
Short Term...A strong cold front is expected to cross the waters
today. Strong W winds will develop in the CAA behind the
front...with gale force gusts expected for all waters. A strong
gale is possible outside of the bays. Winds will diminish in the
bays this evening...but gale force gusts will linger outside
the bays thru the overnight. Winds and seas will remain above
SCA thresholds thru Thu.

Long Term...Strong gusty west winds continue into Thu night due
to the combination of strong CAA over the warm waters and the
pressure gradient. High pres beings to settle south of the
waters Fri allowing winds to diminish.

A strong northwest flow develops with possible gale force winds once
again in the wake of the next clipper system which exits off
the coast Sat night.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Wind Advisory until 9 PM EST this evening for MEZ018-023.
NH...Wind Advisory until 9 PM EST this evening for NHZ008>015.
MARINE...Gale Warning until 11 AM EST Thursday for ANZ150>154.

&&

$$

NEAR TERM UPDATE...Kimble
SHORT TERM...Legro
LONG TERM...Marine



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