Area Forecast Discussion
Issued by NWS Portland, ME

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000
FXUS61 KGYX 111151
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
651 AM EST Sun Dec 11 2016

.SYNOPSIS...
High pressure will slide offshore south of New England today. Low
pressure will approach from the west tonight and will move through
New England on Monday. Low pressure will continue east into the
maritimes Monday night. An arctic front will approach from the
west on Tuesday and will move through the region Tuesday night. A
second arctic front will approach from the west on Wednesday and
will push through the region Wednesday night. A trough of low
pressure will push in from the west on Thursday and will cross the
region Thursday night. High pressure will build in from the west
on Friday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
650 AM Update...Little change to the going forecast. A clear, cold
morning is in progress with many areas in the single digits.
Clouds will begin to increase later this morning in advance of the
approaching low pressure system. However, the day will remain dry.

Previously...

The coldest morning of the young winter season is upon us with 3
am temperatures across the area anywhere between 5 below and 15
above zero. High pressure will remain over the area today with
partly sunny skies and light winds. Clouds will increase from west
to east today as the next low pressure system approaches from the
west.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Overall, not too much has changed from the previous forecast. A
quick-moving short wave trough will approach from the west tonight
as surface low pressure develops well to our south and moves into
the Gulf of Maine on Monday.

Snow is expected to begin overspreading the region this
evening...first across southwestern NH and then northeastward from
there. Most locations are expected to be snowing by the midnight
to 2 am time frame.

There is still considerable uncertainty in storm total snow
amounts due to the uncertainty in low level thermal profiles. Much
of the mesoscale guidance suite brings low level warm air into the
coastal plain pretty quickly late tonight and Monday morning. This
is a bit unusual for hi-res guidance given the very cold air mass
in place. However, it cannot be completely ignored given the
strong southeasterly low level jet that develops over sea surface
temperatures that are anywhere from 1 to 3 degrees above normal
for this time of year. However, we went colder than this guidance
based on coastal front climo with a cold air mass such as this in
place. The forecast temperatures/QPF/snowfall through monday were
based on a blend of available guidance but most closely resembles
the 00z ECMWF run which seemed to be a good compromise.

The upshot is that snow is expected to overspread the region from
SW to NE tonight, and possibly be heavy at times late tonight and
early Monday morning. The snow then mixes with or changes to sleet
and rain on the coast and perhaps southern NH Monday morning. We
think most areas will see advisory criteria snowfall by the time
this change takes place. Winter weather advisories have been
issued where the highest confidence exists in getting 3 to 5
inches of snow but less than 6.

For those areas where around 6 inches of snow is expected, winter
storm watches remain in place. This is where highest confidence
exists in 6 or more inches of snow falling (coastal front
enhancement, good dendritic snow growth profiles, best forcing for
ascent), but confidence remains too low to issue a warning at this
time. A decision to go warning or advisory will be made during the
day today. Either way, the Monday morning commute will be a
slippery one in all areas.

Due to the fast moving nature of the system, the snow or mixed
precip will end from west to east during the afternoon with some
sun possible by the time the evening commute comes around.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Low pressure will head into the maritimes Monday night as a narrow
ridge of high pressure builds in from the west. Expect clouds and
flurries in the mountains through the first half of the night with
partial clearing after midnight. Downwind of the mountains variable
evening clouds will clear as downslope winds kick in. Should see
lows slightly above normal for a change with mid teens to lower 20s
north and lower to mid 20s south.

First in a series of arctic fronts will approach from the west on
Tuesday. After a mostly sunny morning expect increasing clouds
during the afternoon...mainly in northern and western zones. May
be a few snow showers or squalls in the mountains. Highs will
range from the mid 20s north to the mid 30s south. Cold front will
push east of the forecast area Tuesday night. Looking for variable
clouds in the north and partly cloudy skies elsewhere. Lows will
range through the teens north and lower to mid 20s south.

The true surge of arctic air will head toward the region on
Wednesday. Will once again see a mostly sunny morning with clouds
increasing in the afternoon along with occasional snow showers.
Highs will range through the 20s north and upper 20s to mid 30s
south.

Arctic front will sweep through the region Wednesday night
accompanied by snow showers and squalls. Will likely see several
inches of accumulation in the mountains and a light dusting
to an inch in local squalls downwind of the mountains. Lows will
bottom out in the single numbers north and will range through the
teens south.

Thursday looking blustery and very cold with scattered snow
showers as several spokes of energy rotate around deep upper low.
Highs will range through the teens north and lower to mid 20s south.

Shortwave rotating around upper low will swing through the region
Thursday night keeping snow showers and some squalls in the forecast
along with some light accumulations. Expect northwest gradient to
tighten considerably behind surface trough by Friday morning.
Lows overnight will range from zero to 10 below north and in the
single numbers south.

Very windy and cold on Friday as surface high pressure builds in
from the west. Highs will range from 5 to 15 north and mid teens to
lower 20s south. More cold for Friday night as high pressure crests
over the region. Expect lows of 5 below to near zero north and in
the single numbers south.

High pressure will shift offshore on Saturday as a broad area of
over-running forecast to shift in from the west ahead of intense low
pressure moving north through the Great lakes. At this point looks
like snow Saturday going over to mixed precip Saturday night.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Short Term...VFR today. Conditions deteriorate to IFR tonight in
snow and mixed precip and continue through Monday morning.
Improvement is foreseen later Monday afternoon.

Long Term...VFR Monday night with areas of MVFR ceilings/vsby in
the Mountains. VFR Tuesday Through Wednesday. Areas of MVFR
ceilings/vsby on Thursday.

&&

.MARINE...
Short Term...A gale watch has been posted for the ocean waters for
late tonight and Monday as low pressure moves across the Gulf of
Maine.

Long Term...SCA`s may be needed Monday night and Thursday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Storm Watch from late tonight through Monday evening
     for MEZ012>014-018>022.
     Winter Weather Advisory from midnight tonight to 7 PM EST
     Monday for MEZ007>009-023>028.
NH...Winter Weather Advisory from 9 PM this evening to 7 PM EST
     Monday for NHZ001>003-005-012>014.
     Winter Storm Watch from late tonight through Monday evening
     for NHZ004-006-008>010.
     Winter Storm Watch from this evening through Monday evening
     for NHZ007-011-015.
MARINE...Gale Watch from late tonight through Monday evening for ANZ150-
     152-154.

&&

$$

NEAR TERM...Ekster
SHORT TERM...Ekster



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