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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KGYX 090326
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1026 PM EST Sun Dec 8 2019

.SYNOPSIS...
A milder and increasingly moist southerly flow will precede a
low pressure system approaching from the Great Lakes. 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
for the remainder of the week with an active weather pattern to
continue.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --
1020 PM...Overall, forecast seems in decent shape. I think mins
are happening now or have in some spots along the coast, here
the Sw flow is starting to mix down warmer temps. Otherwise
expect a slow rise in temps overnight. POPs were just tweaked a
little, but other than SHSN over the mtns /and maybe a steadier
snow here just before daybreak/, expect it stay dry overnight.

605 PM...Did some tweaking to POPS and temps overnight. This
keeps the overnight dry in all but the nrn zones, and even backs
off arrival of steadier rain in all but the far srn coastal
zones until mid morning. Looks for snow in the mtns,
accumulating after midnight, but generally light. I think temps
may see a slight dip this evening, es[especially away from the
coast, before rising slowly thru the night.


Previously...At 19z a 1036 millibar high was centered southeast
of Cape Cod. GOES imagery showed an area of warm air advection
clouds gradually spreading eastward into the area. Temperatures
had warmed into the upper 20s and lower 30s in the milder return
flow. NWS Doppler Radar mosaic showed an area of light
precipitation upstream across southeast Quebec. For
tonight...light warm air advection precipitation will break out
mainly across northern and mountain sections. The airmass is
cold and dry to start so we should see light snow with some
sleet possible towards morning with a shallow elevated warm
layer across the north. Further south...primarily some light
rain or spotty drizzle late...although it could start as a light
snow/rain mix in a few spots. The forecast soundings suggest we
should see little if any freezing rain as we transition from
frozen to liquid late tonight and Monday morning.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
On monday...steadier and a bit heavier precipitation breaks out
across the area as low pressure intensifies over the Great lakes
and southerly flow increases across the area. Temperatures will
warm into the lower 40s near the international border while we
see mid 40s to lower 50s elsewhere. There will be some light
snow/sleet across the mountains early transitioning to rain.
Given the frigid temperatures the past few nights...we could
see a few pockets of light glaze in the mountains even with
temperatures a few degrees above freezing during the morning
hours. The mild air mass over the snow pack will make for areas
of fog by afternoon. Unseasonably mild Tomorrow night in the
continued southerly flow with steadier rain tapering off
overnight. We`ll be left with areas of drizzle and fog that may
be locally dense. The mild temperatures and fog will contribute
to snow melt. By Tuesday morning...the first round of rain and
snow melt will be pushing a few rivers and streams towards
bankfull.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
The dry slot and some partial clearing will likely push into the
forecast area by midday Tue. Any precip will be tied to the
terrain forcing as WNW flow begins to pick up.

Tricky forecast late Tue into early Wed for coastal zones as the
next S/WV trof approaches. The baroclinic zone will be offshore
at that time...but a strong S/WV trof moving thru the Great
Lakes will help to try and lift it back Nwd. Flow never quite
backs enough for return flow...but it does look like we will try
and advect a little higher moisture into what is overall a dry
air mass. There should be strong moisture transport along the
boundary...but forcing will be rather narrow. Given the dry air
to the NW...I can see a sharp cutoff to any snowfall that occurs
NW of the front. Right now I have light accumulations in the
coastal zones...but not much outside of that. It will take more
amplified flow to get anything more than that out of this fast
moving event.

High pressure builds in for the remainder of the work
week...with below normal temps expected. Next chance of
widespread precip will be over the weekend as a stronger S/WV
trof induces a wave along the leftover baroclinic zone. There is
a lot of uncertainty regarding the track and intensity of the
resulting low pressure...so the multi-model consensus blend was
used for the forecast in that period. I did go with a non-
diurnal temp trend Fri night...as increasing clouds and
approaching precip should keep temps from cooling off thru
morning.

&&

.AVIATION /04Z MONDAY THROUGH FRIDAY/...
Short Term /Through Monday Night/...Ceilings begin to lower
tonight, mainly over northern areas in -SN. Areas of RA/-SN
enter the region from southwest to northeast early Mon with
widespread IFR developing in precipitation and areas of fog.
IFR/LIFR then continues for the remainder of the period.
Southerly winds will gust to 35 kt at coastal TAF sites Monday
night.

Long Term...With flow turning NW much of the area will see
conditions improving back to VFR. Upslope flow will keep MVFR
CIGs and local IFR in SHSN around HIE thru the day. Tue night
some -SN looks like it will try and developing behind the front
and bring areas of IFR or lower to coastal terminals into Wed
morning. Otherwise high pressure builds in for the rest of the
work week and VFR conditions prevail.

&&

.MARINE...
Short Term /THrough Monday Night/...Strengthening southerly
flow between an offshore high and approaching frontal system
will bring two strong surges of wind to the waters this period.
The first will be tonight when Gales are likely all waters with
a few gusts to Gale possible in Casco Bay. The second will be
late Monday and Monday night with an 80+ kt low level jet. We
should see strong Gales all waters with storms possible over
the eastern two-thirds of our outer waters...where a storm
watch has been posted.

Long Term...CAA continues thru Tue with winds and seas only
gradually diminishing...and SCA conditions lingering into Wed.
High pressure builds in for the remainder of the week with winds
and seas falling below SCA thresholds.

&&

.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". Should moderate rainfall occur in
areas with high snow water equivalent, instances of localized
flooding will be possible in poor drainage areas, as well as
some main stem rivers and tributaries rising above action stage
and approaching bankfull by Tuesday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Gale Warning until 5 AM EST Tuesday for ANZ151-153-154.
     Storm Watch from Monday evening through late Monday night for
     ANZ150-152.
     Gale Warning until 6 PM EST Monday for ANZ150-152.

&&

$$
SYNOPSIS...
NEAR TERM...Cempa/Schwibs
SHORT TERM...Schwibs
LONG TERM...Legro
AVIATION...
MARINE...
HYDROLOGY...