Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 130236 AAC
AFDGYX

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
936 PM EST Sun Feb 12 2017

.SYNOPSIS...
Low pressure tracking near the southern New England coastline
will spread snow, heavy at times, through New Hampshire and
Maine overnight. By Monday morning the low will be intensifying
rapidly in the Gulf of Maine with northerly winds increasing
during the day Monday causing widespread blowing snow and
near blizzard conditions. Snow ends from west to east during the
day as the low moves off to the east, though the strong winds
will last into Monday night. Expect a brief break on Tuesday as
a narrow area of high pressure crosses the region. Another low
pressure system dropping in from the north will bring more snow
on Wednesday, with the heaviest accumulations in the east. Below
normal temperatures continue through the end of the week as high
pressure builds in from the west.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
935 PM Update...
Have seen a changeover to all snow with winds becoming northerly
a couple hours ago at Portsmouth and over the remainder of
southern NH and interior ME. Offshore winds are easterly with
the coastal front hugging the seacoast. Low pressure has
deepened to at least 996 mb near Nantucket and will be ejecting
into the Gulf of Maine over the next few hours. Snowfall amounts
are moderate so far and generally around or less then 6-8". As
bombogenesis occurs expect snowfall rates to increase to 2-3" an
hour in any heavier band(s) that develop.


735 PM Update...
IR satellite imagery now showing strong upper level short wave
digging into NY State and Pennsylvania. As it becomes negatively
tilted a jet max will continue to make its way into the Gulf of
Maine, aiding rapidly deepening low pressure near Long Island/
Cape Cod. This low will approach later tonight bringing heavier
snowfall to NH and ME. Currently portions of NH are experiencing
lighter snowfall and in a few areas (but not most) the heaviest
snow may have fallen already. Most locations will see
additional substantial snowfall overnight as deepening low
pressure reaches the Gulf and intense banding sets up.

NNE winds being pulled into the secondary low are keeping cold
air entrenched across the region with the coastal front
offshore everywhere except coastal NH and eastern MA. Have
included sleet in the forecast for these areas which are
reporting IP mixing in a times with the snow. No other major
changes at this time.

On the backside of the storm and towards morning, winds will
ramp up quickly as precipitation comes to an end. This overlap
will cause blizzard conditions for coastal areas east of
Portland. For now have not changed the placement of the blizzard
warnings but will continue to monitor in case the winds occur
farther east/earlier than forecast.


Previous discussion...
Strong cyclogenesis now occurring near the eastern tip of Long
Island as left exit region of the upper level jet noses into the
Gulf of Maine. Denser air now over Maine and central NH is
digging in as the storm organizes. Many areas are less than a
mile in heavy snow. Portsmouth is still holding onto 33 degrees
this hour on the south side of the coastal front. Some mixing is
being reported over southern NH and SW Maine however snow is
still the dominant p-type and any mixing will be brief. Winds
are beginning to increase over the waters.

No major changes to the forecast at this time.


Snow, already heavy at times, continues to overspread the CWA as
of late Sunday afternoon as WAA out ahead of an amplifying short
wave trough strengthens. As low pressure continues to develop
overnight the snow will continue.

Most of the temperatures around the region are pretty cold, but
the coastal front has worked into the seacoast of NH and may
continue working westward perhaps as far west as the
Manchester/Nashua corridor this evening. This will allow
temperatures to rise to around or just above freezing, perhaps
allowing for a heavier, wetter snow that could aid in power
outages. Otherwise, winds will increase overnight, allowing for
poor visibilities as well as some blowing and drifting.

We have decided to upgrade to a Blizzard warning on the
midcoast of Maine where we think intense snow banding will
coincide with very strong winds. We are not confident that this
juxtaposition of factors will occur further south, at least for
a long enough time to allow for 3 hours of true blizzard
conditions. Nevertheless, near-blizzard or occasional blizzard
conditions are expected. The strongest winds are expected during
the day Monday, but they will become strong enough to allow for
considerable blowing and drifting overnight.

Overall, the snowfall forecast has not changed terribly much.
Perhaps a slight down-tick on average in most areas but no
significantly so. Mesoscale banding may lead to locally higher
amounts though. We did however lower amounts a little bit more
across western NH due to shadowing, as well as the fact that
coastal redevelopment likely occurs a little too far east to hit
them with a deformation band late tonight or Monday morning. In
fact, the snow may very well be pretty much done in SW NH
around 12z Monday.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Heavy snow and strong winds will be the theme Monday morning
across the region - Mainly on the coastal plain. Blizzard
conditions are expected on the midcoast of Maine, with near
blizzard conditions elsewhere. The snow will taper off quickly
across western zones in the morning, with snow gradually
tapering off and ending from west to east during the morning and
early afternoon hours. The mid coast will hold onto it longer.

Winds will be strong during the day on Monday - especially on
the coastal plain even after the snow has tapered off. Gusts
around 50 mph are quite possible. This will cause considerable
blowing and drifting along with the possibility of power
outages.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Narrow high pressure axis cross the area on Tuesday. Expect
lighter winds and temperatures which top out in the 20s to low
30s with a fair amount of sunshine.

A shortwave trough is expected to dive south through central
Canada and into the Great Lakes on Tuesday before turning east
across New England on Wednesday. With this system having its
origins in the Arctic, it will be difficult to get a lot of
precipitation out of it at least initially. As the trough
reaches the coastline, though, it will intensify and begin
dragging in Atlantic moisture with the possibility for several
inches of snow. Models differ on how to handle this fast-moving
system. One scenario is for this to move through primarily as an
open wave at the surface, with the majority of the snow falling
along and to the east/north of the surface trough axis mainly
over eastern Maine. Another scenario is for a developing
coastal low to become dominant and track near the southern New
England coastline, spreading wrap around moisture into western
Maine and New Hampshire. Given the origins of this wave in the
Arctic and its late tapping of moisture, expect this to
primarily be a central and eastern Maine snowfall event. There
still remains a chance for significant accumulations even as far
west as southern New Hampshire depending on how this evolves.

The upper low takes its time moving out on Thursday and could
allow for some snow showers to persist into the day. These
should primarily impact the northerly upslope areas of the
mountains.

Cool high pressure slowly slides east through the end of the
week. Expect temperatures near or below normal with dry
conditions. A ridge developing over the center of the continent
begins to drift east into New England late this weekend and will
allow temperatures to warm back up above normal.

&&

.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Short Term...LIFR conditions tonight into Monday morning in
heavy snow and blowing snow. SFC wind gusts to 40 kt likely
Monday. Cigs and vsbys improve in southern NH Monday morning -
with improvement foreseen further east during the late morning
and afternoon hours. VFR conditions are expected Monday night
but blowing snow will still be an issue.

Long Term...Expect VFR conditions on Tuesday, but increasing
clouds should bring widespread MVFR to IFR conditions on
Wednesday with snow developing. Conditions are likely to be
worst (possibly 1/4SM in heavy snow) in the east Wednesday
afternoon. Should see a return to VFR on Thursday, outside of
some isolated snow showers. VFR conditions expected into the
weekend.

&&

.MARINE...
Short Term...Dangerous conditions are expected on the waters
tonight and Monday as storms are expected (except for Casco Bay
where gales are in place). Seas may reach 20 ft early Monday on
the ocean. An improvement in conditions is expected Monday
night.

Long Term...Northerly winds behind the departing low will
finally fall below advisory levels during the day on Tuesday as
high pressure moves in. Another low pressure system moving near
the area will provide another chance of advisory level winds
Wednesday through Friday.

&&

.TIDES/COASTAL FLOODING...
A 1 to 2 ft surge is expected around high tide tonight as well
as monday midday. This may present issues for northeast facing
beaches south of Portland as nearshore waves quickly jump into
the 10 to 20 foot range. A few road closures are possible due
to splash- over. NART based wave runup matrices continue to
indicate beach erosion and splash- over for the hot spots of
Camp Ellis, Ferry Beach, and Jennes Beach in York and Rockingham
counties. Minor, nuisance coastal flooding is possible in
Portland, Biddeford, and Hampton as well.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Storm Warning until 7 PM EST Monday for MEZ007>009-
     012>014-018>021-023-024.
     Blizzard Warning until 7 PM EST Monday for MEZ022-025>028.
     Coastal Flood Watch from Monday morning through Monday
     afternoon for MEZ023-024.
     Coastal Flood Advisory until 3 AM EST Monday for MEZ023-024.
NH...Winter Storm Warning until 7 PM EST Monday for NHZ001>006-009-
     010-013-014.
     Winter Storm Warning until 1 PM EST Monday for NHZ007-008-011-
     012-015.
     Coastal Flood Watch from Monday morning through Monday
     afternoon for NHZ014.
     Coastal Flood Advisory until 3 AM EST Monday for NHZ014.
MARINE...Gale Warning from 1 AM to 11 PM EST Monday for ANZ153.
     Storm Warning from 1 AM to 11 PM EST Monday for ANZ150>152-154.

&&

$$

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



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