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000
FXUS61 KGYX 090935
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
435 AM EST Mon Dec 9 2019

.SYNOPSIS...
A milder and increasingly moist southerly flow this morning
precedes a low pressure system approaching from the Great Lakes
today. This system will bring mainly rain to the area Monday
and Tuesday along with unseasonably mild air. The mild weather
and snow melt combined with the rain could push a few rivers to
near bankfull by late Tuesday. Much colder air follows this
system Tuesday night and Wednesday perhaps allowing for a light
accumulating snow for the coastal plain as well as southern New
Hampshire. An active weather pattern looks to continue for late
week into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today, the pattern amplifies in response to a long wave trough
axis driving south from the Plains of Canada into the upper
Mississippi Valley and eventually into the Great Lakes. The long
wave aloft picks up a closed mid-level low and transports it
ENEward across the Great Lakes today and tonight, which drives
sensible weather locally.

Light snow this morning over the mountains lifts northward as
southerly flow strengthens ahead of the approaching trough. Dry
air in place has prevented much of the precipitation from
reaching the ground, except for across the mountains and areas
north where moisture depth is more favorable. Further south, an
area of precipitation presently over the Mid- Atlantic will
expand as it travels NNEward toward New England. Expect
precipitation, mainly rain, to enter southern New Hampshire mid
to late morning, spreading northeastward into western Maine
through mid- day. Chose to err on the slower side of guidance
with 00Z sounding suggesting a stout mid-level dry layer to
erode before precipitation reaches the ground. At the same time,
increasing surface dew points and WAA over snowpack will lead
to the development of patchy fog this morning, lasting through
much of the day.

Mid-level warm advection is well on its way by this point with
h850 temperatures reaching above freezing areawide about 12Z-
17Z. Meanwhile at the surface, some degree of a CAD is expected
to stunt warming initially, and preserve some cooler pockets,
but in general temperatures rise above freezing across lower
elevations by noon. A brief period of mixed precipitation may
impact interior NH and western ME upon onset as h850 warming
outpaces surface warming, but without significant impacts.

The core of strong mid-level winds driving rounds of rain today
strengthens later today into tonight as a short wave trough axis
rotates around the larger mid-level low. This ramps up forcing
and moisture transport, yielding moderate rain and increasing
winds. Better mixing with the crossing jet will allow
temperatures to warm through tonight as WAA continues aloft.
Mixing isn`t however strong enough to transport a strong portion
of h850 winds in excess of 70kts to the surface. The southerly
clip to winds near the surface does however allow strong winds
to develop over the waters and to an extent over the MidCoast of
Maine including the Penobscot Bay area. BUFKIT soundings
generally paint sustained winds 20-25 kts along the coast and
higher terrain of the MidCoast region with occasional gusts
35-45kts. A wind advisory has been posted for this evening into
tonight as a result.

For rain, expecting widespread amounts exceeding an inch across
southern NH and coastal Maine along with in the south-facing
upslopes of the Whites where rainfall totals may approach two
inches. More details on this in the hydrology section below.
Expect a substantial erosion of snowpack as a result tonight
thanks to breezy conditions, high dew points, and rainfall. The
broad area of stratiform rain exits to the northeast late
tonight.

&&

.SHORT TERM /TUESDAY/...
For the better part of Tuesday, a lull in precipitation is
expected behind the departing shortwave trough axis with dry air
intruding in the upper levels, coinciding with a strengthening
jet aloft. New England is placed in the right/exit region of
this screaming jet in excess of 170kts at h300, leading to with
synoptic descent. The exception would be light rain in southwest
facing upslopes. Later in the afternoon into the evening, a
lagging cold front crosses, with some uptick in precipitation
activity but likely without much in the way of significant QPF.
Cold advection does however spill in aloft behind the cold front
and begins an airmass change for the region. Expect remaining
light rain to switch to snow Tuesday evening.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
The long term periods starts Tuesday evening with a cold front
just offshore and cold air bleeding into all of our zones from
the northwest. At the same time a short wave trough will
approach from the west, with some influence from the southern
stream. The various members of the 00z model suite are in good
agreement with some light overrunning precipitation moving
northeastward in the wake the SFC cold front Tuesday night into
Wednesday. With the column becoming colder with time, any light
rain will turn to light snow from west to east as Tuesday night
progresses. An ensemble approach was employed with the QPF and
temperature forecast, allowing for 1-3" of snow on the coastal
plain as well as the southern portion of NH. There will be a
tight moisture/precipitation gradient with northwestern
sections of the forecast are not seeing anything except cirrus
come Wednesday morning.

Thereafter fair weather follows for a few days, but the pattern
continues busy with a few more potential fairly high amplitude
weather systems on tap, one for the weekend and another for
early next week. Some mixed precipitation may be involved for
both, but at this time modeled amplification of the mid and
upper level pattern suggest a couple of chances for heavy rain.
Will continue to monitor.

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
Short Term /Through Tuesday/...A transition to MVFR ceilings
from south to north is well underway this morning amid
strengthening southerly to southwesterly flow. IFR in -ra and fg
arrives across the south and coastal terminals by noon today,
early afternoon further north. Additionally patchy fog may
impact sites at times today with warm air over snowpack.

This afternoon, rainfall intensifies with increasingly gusty
southerly winds and widespread IFR or worse ceilings and
visibility. These conditions persist into tonight, with rain and
associated VIS restrictions pulling out early Tuesday morning
with winds turning southwesterly, although patchy may allow VIS
restrictions to linger through the morning. CIG improvements
are possible Tuesday in a lull between rounds of precipitation.

Of note, LLWS is a concern throughout the short term, primarily
this evening with southerly to southwesterly LLWS on the order
of 45-55 kts developing.

Long Term...Rain will change to light snow across
the forecast area Tuesday night and last through a good portion
of Wednesday. This will allow for IFR conditions, especially on
the coastal plain of Maine and southern New Hampshire where 1-3"
of snow will be possible later Tuesday night into Wednesday.
VFR conditions are then expected Wednesday night through Friday
night.

&&

.MARINE...
Short Term /Through Tuesday/...Southerly flow strengthens
through today, ahead of an approaching frontal system. This
evening and tonight, southerly gale force winds develop area
wide with storm force winds impacting the eastern two-thirds of
the waters including western Penobscot Bay. Winds decrease
gradually Tuesday with SCAs persisting under gusty southwest
flow, turning northwest Tuesday night behind a cold front.

Long Term...SCA conditions will linger through Tuesday night and
Wednesday morning before diminishing. However, winds will
quickly ramp up again to SCA levels Wednesday night and
Thursday, with gales not out of the question.

&&

.HYDROLOGY...
Mild temperatures, high dew points, and periods of rain will
impact the area Monday and Tuesday and erode snow cover across
the region, particularly over southern New Hampshire and
coastal western Maine. While the fresh snow will initially
absorb rainfall, the snow will likely ripen and begin melting.
This will lead to an influx of water into local waterways. At
this time, southern New Hampshire has over a foot of snow in
places with liquid equivalent likely exceeding 1", with some
areas possibly closer to 2". Moderate rainfall in excess of an
inch is expected over this area and may lead to instances of
localized flooding in poorly drained areas. River forecasts also
suggests a flood threat for waterways, particularly across
flashy tributaries in the Whites and southern New Hampshire.
Although no flooding is forecast, action stage is expected to be
reached on the Swift (Roxbury), Pemi (Woodstock), Suncook (N.
Chichester), and on the Saco (Conway).

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Wind Advisory from 6 PM this evening to 4 AM EST Tuesday for
     MEZ022-027-028.
NH...None.
MARINE...Gale Warning from 6 PM this evening to 4 AM EST Tuesday for
     ANZ153-154.
     Storm Warning from 9 PM this evening to 4 AM EST Tuesday for
     ANZ150>152.

&&

$$

NEAR TERM...Casey
SHORT TERM...Casey
LONG TERM...Ekster