861
FXUS61 KGYX 231954
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
254 PM EST Mon Dec 23 2024

.SYNOPSIS...
A clipper system brings light snowfall tonight into the first
half of Tuesday. High pressure will then build over the region
Wednesday through the end of the week with a gradual moderating
trend and mainly dry conditions.

&&

.NEAR TERM /THROUGH TONIGHT/...
A large ridge of high pressure will continue to exit off the
eastern Seaboard tonight. Meanwhile, a clipper type system will
approach our region from the central Great Lake states. Strong warm
air advection aloft will allow for precipitation to break out late
this evening from north to south. Ptype will be all snow as plenty
of cold air remains in place. In fact, the cold and dry airmass
initially in place may lead to a delay for the onset of
precipitation.

In any case between the clouds and precipitation, temperatures will
not change all that much during the night. Overnight lows will
fall back to the lower teens in the north to the mid and upper
teens across the south.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
The precipitation will be ongoing early Tuesday morning. Low
pressure will reform along the coast of Maine before tracking east
and out of our region by afternoon.

Advisory type snows are expected with this system with an area of 3-
5 inches of snow over northern and eastern portions of our forecast
area. Would go slightly higher in some areas however the track of
the H8 and H7 low to our north is not favorable at this time.

Temperatures on Tuesday will reach the 20s north to the lower 30s in
the south. There will be increasing late day sunshine as drier air
follows the system.

An inverted trough will be situated east of our region Tuesday
night. The most cloud coverage will be in the mountains with this
type of flow. Overnight lows will drop down into the single numbers
in the north to the teens in the south.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Overview: Broad high pressure will be overhead mid week into
early weekend. This will bring a period of mostly quiet weather
to the region as temperatures moderate towards normal. The next
disturbance approaches the region late this weekend and early
next week.

Details: A lobe of high pressure falls into the upper Great
Lakes behind exiting low into Wednesday. The high/ridge will
again be strong, the antithesis of deepening 500mb heights in
the open Atlantic through late week. This will slowly build
overhead, bringing quiet weather conditions for the remainder of
the week. With little to no precipitation in the forecast until
late this weekend, focus will be on the temperature trend,
generally warming into the weekend.

Before that warming trend, will see a good radiational cooling
night Wednesday night. Fresh snow will be on the ground with
mostly clear skies and light wind. There is some uncertainty on
cloud cover, but guidance soundings present much of the moisture
towards the surface. This may wind up being areas of freezing
fog, but also cant rule out a shallow cloud deck lingering NW
of the Whites in subcritical flow. Daytime highs will trend into
the low to mid 30s by Friday for much of the area, absent the
mountains.

Will need to monitor this trend as the next disturbance
approaches late this weekend into early next week. Current
guidance suggests this will be a progressive overrunning event,
but where/when it enters the region relative to the exiting
highs return flow will play a role in precip types. A quicker
high departure would lead to warmer surface air advecting into
the region, while a slower retreat could prove resilient low
level cold air reinforced by tightening pressure gradient and
increasing NE winds. For now kept the forecast representing a
snow to rain changeover outside of the mountains, with further
detail to come if a wintry mix outcome becomes more likely.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
Short Term...Ceilings and visibilities will continue to be
lowering tonight as light snow enters the region. Expect VFR
conditions to become IFR overnight and into Tuesday morning.
Conditions then gradually improve late Tuesday and Tuesday night
to VFR outside the mountains.

Long Term...VFR for most terminals, with pockets of MVFR clouds
possible Wed. This should dissipate as high pressure nears for
mid to late week. There is a chance for freezing fog Wed night
in the mountains, but otherwise VFR continues through late week.

&&

.MARINE...
Short Term...Southwest winds tonight and Tuesday morning will
remain just below SCA thresholds. Winds become north to
northwest Tuesday afternoon and Tuesday night.

Long Term...High pressure will be drifting overhead mid to late
week, leading to lighter winds and slackening wave heights. With
low pressure off towards Nova Scotia, can`t rule out some light
offshore snow showers through Wednesday night. The next system
that could bring SCA conditions will approach towards the end of
the weekend/early next week.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory from 9 PM this evening to 1 PM EST
     Tuesday for MEZ007>009-012>014-021-022-026>028.
NH...Winter Weather Advisory from 9 PM this evening to 1 PM EST
     Tuesday for NHZ004.
     Winter Weather Advisory from 7 PM this evening to 1 PM EST
     Tuesday for NHZ001>003.
MARINE...None.

&&

$$

NEAR/SHORT TERM...Cannon
LONG TERM...Cornwell