NWS Gray, Maine Area Forecast Discussion



000
FXUS61 KGYX 061250
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
750 AM EST Mon Dec 6 2021

.SYNOPSIS...
Low pressure passes to the north today with a wintry mix this
morning transitioning to mostly rain today and gusty winds
developing. Temperatures will turn cooler for midweek with a
light snowfall possible on Wednesday. After a cold and fair
Thursday, we will see a warming trend, but there is a chance for
rain, or snow in the mountains this weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
740am Update...A very sharp temperature gradient exists along a
coastal front that is slowly moving inland. Pockets of below
freezing temps remain throughout the foothills and interior
coastal locations. Fryeburg has reported moderate freezing rain
a few times this morning, so there are bound to be slick spots
amid rapidly changing temperature environments. Expanded the
Winter Weather Advisory to include southern Carroll and int
Cumberland and Androscoggin, although either side of these zones
straddle the tight temp gradient...one above freezing, the
other below. Warm temperatures will continue to slowly move in
through the morning with some fog or mist developing within the
broad warm sector.

Previous Discussion...
Light precipitation this morning will continue in periods as
dry air is slowly whittled away amid warm, moist southerly
advection. As this warm air works in aloft, some lowlands and
valley locations in the mtns will remain cool enough via cold
air damming. A Winter Weather Advisory was issued in the mtns
and foothills in anticipation of this warm nose causing a change
to liquid precip, but falling on antecedent sub freezing
surfaces. A light glaze of ice will be possible here. A shorter
period of wintry mix will affect areas just inland from the
coast where a very sharp temperature gradient has set up. Warm
air will win out over the next hour or two as this first round
of precip tapers.

The next round of rain is advancing over Long Island now, and
will arrive later this morning. Some lightning is being observed
there currently, but anticipate weaker showers over the CWA
later. Highest QPF is expected in upslope locations of the mtns,
as well as w/ any coastal front enhancement.

Wind will be gusty today, but anticipate a stout inversion to
prevent the much stronger winds aloft from mixing to the surface
through the late afternoon. The more potent time period will be
with a cold front passage late this afternoon and evening.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
the cold front will bring southerly winds sharply turning west.
This front impinging on the LLJ in place will create a short
duration of stronger gusts as it traverses west to east across
NH and ME. Gusts up to 40 mph will be possible along with the
chance for a rumble of thunder given some instability and
advancing cold air environment.

Pocket of moderate to heavy rain may accompany the front. Some
hires guidance has depicted an embedded convective line.
Stronger gusts may be associated with this line, and SPSs may be
necessary should it develop.

Behind the front, cold air will push in, transitioning some
remaining precip to snow. Some light accum is possible in the
western ME and northern NH mtns, but otherwise a fairly quick
shut off of precip is expected. Remaining damp spots on the road
may become slick as temps plummet to the mid to upper 20s away
from the coast tonight.

Tuesday will be mostly dry outside of some remaining NW flow
snow showers in the mtns. Some of these showers could trickle
over the mountains into the foothills and towards the coast, but
ultimately drier conditions should win out here.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
A major pattern shift is in store by this weekend as a cool and
unsettled pattern yields to a warm, amplified pattern with
upstream blocking taking shape over the Atlantic. A mid-week
system skirts to our south with cool Canadian high pressure
providing the stiff-arm from the north, then a deep southerly
flow works in behind a warm front Friday into the weekend.
Overall the threat of impacts appears to be low for the time
being, however the gradual passage of a long wave trough and its
surface reflection through the weekend may provide a variety of
precipitation types.

Starting off around midweek... a persistent trough anchored
near Hudson Bay will send another wave across the eastern CONUS.
Surface cyclogenesis still looks to occur off the DELMARVA or
Carolina coast, well south of our region where high pressure
extending through eastern Canada has a greater influence on
local conditions. Thus Wednesday is the coolest of the week with
highs in the 20s to low-30s. Latest guidance continues to point
toward uncertainty in the north/west position low pressure...
though the overall trend still reflects a southward shift in
track with fewer impacts for our area. While the system will
pass well south, the low may send an inverted trough back over
the Gulf of Maine which would lead to light snowfall given
forcing aloft... or locally higher in the event of a sharper
Norlun trough, to be resolved at the mesoscale and in the near
term along the coast. The timing for this would be the second
half of Wednesday into that night. Leaned on ensemble means from
multiple suites, which gives a light, sub- advisory snowfall
focused along the coast but with the understanding that there
will likely be some winners and losers.

Low pressure whisks away to the east by Thursday in the progressive
jet stream pattern with a ridge of high pressure approaching from
the west. A cool northwest wind will keep temperatures in the 20s
and 30s with upsloping clouds, otherwise mostly sunny skies.
Southwest return flow kicks in as the ridge departs to the east late
in the week. Looking aloft and at the synoptic scale... this
coincides with the Pacific jet carving out a trough through the
Rockies, which lifts the resident Hudson Bay trough northward
and away. This synoptic warm front may bring a round of light
showers Friday... given the cool start, this would likely
starts as snow and transition to rain with a mix possible in
between... but timing this feature out will be key to
determining precip type. Temperatures behind this feature will
warm with highs by Saturday in the 50s, perhaps pushing 60
across southern zones.

Meanwhile the long wave trough and associated surface cold
front will be gradually approaching from the west. Given
downstream blocking... there is a fair amount of uncertainty
with the timing of this frontal passage ranging from as early as
Saturday to as late as Sunday night. WPC cluster analysis
points toward the strength of upstream blocking ... and thus the
persistence of east coast ridging as the primary source of
uncertainty, favoring blocky synoptic flow over progressive. So,
it may take a while for this frontal boundary to finally push
through... the forecast reflects a broad-brushed chance-to-
likely PoP scenario for the weekend, but I doubt it`ll be a
washout. Leaned on an operational blend of models that favored
slower FROPA and warmer temperatures.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Short Term...Ceilings trend MVFR and then IFR this morning. LLWS
is expected through the afternoon with southerly gusty winds
increasing through the afternoon. A strong cold front will shift
winds west sharply this evening, first at KLEB/KHIE, and then
moving into ME and southern NH tonight. RA is expected with the
front, with some -SHSN behind for western locations. Ceilings
improve towards VFR/MVFR after midnight, with VFR Tuesday.

Long Term...Restrictions in SHSN and low ceilings are possible
Wednesday and Wednesday night for coastal and southern terminals
with VFR returning Thursday. Low ceilings and showers may again
produce restrictions Friday.

&&

.MARINE...
Short Term...Gale conditions today and tonight. Winds trend
southerly today, sharply becoming west behind a strong cold
front passing through this evening. Waves will build to 6 to 12
feet through the afternoon and evening, decreasing Tuesday.
Gales will taper by Tues morning, but SCA conditions will
continue for both wind and waves.

Long Term...Low pressure will cross south, near the waters
around the midweek period and may stall for a time outside of
the Gulf of Maine. This may bring a period of SCA conditions to
the outer waters along with rain and snow showers. High pressure
crests the waters Thursday with improving conditions.

&&

.TIDES/COASTAL FLOODING...
High astronomical tides continue early this week. A period of
onshore flow today combined with these high tides may lead to
minor coastal flooding around the time of the midday high tide.
Offshore flow Tuesday should minimize coastal flooding risk.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Wind Advisory from 1 PM this afternoon to 4 AM EST Tuesday for
     MEZ022-027-028.
     Winter Weather Advisory until 11 AM EST this morning for
     MEZ007>009-012>014-019-020-033.
NH...Winter Weather Advisory until 11 AM EST this morning for
     NHZ004-006.
MARINE...Gale Warning until 7 AM EST Tuesday for ANZ150>154.

&&

$$
NEAR TERM...Cornwell
SHORT TERM...Cornwell
LONG TERM...Casey
TIDES/COASTAL FLOODING...Casey

NWS GYX Office Area Forecast Discussion