NWS Gray, Maine Area Forecast Discussion



000
FXUS61 KGYX 161017
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
617 AM EDT Fri Apr 16 2021

.SYNOPSIS...
Low pressure will meander over southern New England today and
then head eastward out to sea on Saturday. Rain and heavy wet
snow will occur with this storm, with the heaviest snowfall
amounts expected at higher elevations. The weather will become
fair once again Sunday into early next week with rebounding
temperatures expected. A cold front is expected to cross
northern New England Wednesday or Wednesday night with the
attendant threat for showers.

&&

.NEAR TERM /TODAY/...
6AM UPDATE...
Precipitation has finally become a bit more widespread this
morning, although precipitation type remains variable. Heavier
pockets of precipitation tend to see a drop in temperature and a
change to snow, while lighter periods go back to rain. The
steadier bands will be pivoting through over the next few hours
and this is likely when we`ll see the best chance for snow in
the urban areas, however confidence continues to be relatively
low in accumulation amounts. For now will continue current
winter weather headlines as the situation evolves.

ORIGINAL DISCUSSION...
Low pressure currently south of Cape Cod will occlude today as
the upper low catches up to it. Expect the heavier precipitation
area to pivot northeast toward the coast of Maine this morning.
Temperatures aloft suggest snow should be the dominant
precipitation type in this band, although temperatures at ground
level will be near or a few degrees above freezing. As the low
occludes, a dry slot will wrap around and push into southern New
Hampshire and southwest Maine. This drier air in the 500 to 700
MB layer will cut off the moisture from the snow growth zone,
leading to a change in precipitation type back to rain in this
area. Further north where the band shifts inland, precipitation
type will likely stay mostly snow.

Some models have shown a potential for some stronger easterly
winds along and just ahead of the dry slot as the low occludes.
While this largely affects the Gulf of Maine, these winds would
be arriving onshore in southeast New Hampshire where wind gusts
of 45 to perhaps 50 mph are possible. A Wind Advisory has been
issued in this area with the strongest winds likely around
midday.

Snow accumulation forecast has not changed significantly from
prior forecasts. We still expect the heaviest accumulations in
the higher elevations where temperatures will be closer to
freezing thus allowing more efficient accumulation. However, a
sticky, wet snowfall accumulation is possible within the entire
band as it pivots through the region. The main concern with this
snowfall today will be the snow load on trees which will lead to
sagging and snapped trees and limbs, causing power outages.
These impacts are most likely where snow accumulation is greater
than about 4 inches and still lines up well with our ongoing
Winter Storm Warning headline.

Greatest uncertainty remains along the coastal plain where
temperatures will be largely above freezing making snowfall
accumulation more difficult. The southern New Hampshire urban
areas are likely to see just a few hours of snow this morning
before changing to rain. So total accumulations here are likely
to be low, although how well these accumulations line up with
the morning rush hour has given us some thoughts of expanding
the Winter Weather Advisory here. Ultimately, though, based on
latest observations we expect that it may be difficult to
achieve significant accumulations on roads and we have thus
opted against the advisory. Further east along the coast of
Maine the uncertainty continues. Most models do show the band of
most significant precipitation shifting through this region
today, although not all models show this precipitation falling
as snowfall. It may ultimately depend on how intense the band of
precipitation remains as it moves through, with a more intense
band leading to a snowier scenario. With most of this falling
during daytime hours and with temperatures above freezing, we
have held snowfall accumulations down in this area today.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
After the low occludes and does a small loop in southeast
Massachusetts, it will begin to pull away tonight. This will
cause the band of heaviest precipitation to pivot along the
coastal plain again, especially across western Maine. The dry
slot fills back in and precipitation likely changes back to snow
if it ever changed to rain. This is probably when western Maine
and the midcoast will see the heaviest snowfall accumulation
from the storm with a few inches of snow currently expected.
Models differ on how much precipitation falls, so there is still
some upward potential on snowfall amounts in this area. However,
with temperatures still expected to stay just above freezing
even through the night, we have kept snowfall amounts to only a
few inches storm total in this area.

Precipitation will likely linger into Saturday over the
midcoast of Maine especially, although accumulations will likely
end as precipitation decreases in intensity. In fact, the light
precipitation will likely switch back over to rain again as it
is ending. Temperatures warm into the 40s across the entire area
on Saturday behind the storm.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Low pressure will move away from our region Saturday night,
allowing for spring to resume. Fair and much warmer weather is
expected Sunday into midweek. However, the air mass doesn`t look
to be totally clean, with a decent low to mid level moisture
hanging around. This will mean a good amount of clouds Sunday
and probably into Monday. With a weak short wave trough moving
across the region on Monday, it`s not out of the question that
some light showers may develop. Will go with slight chance PoPs
for that possibility for the time being.

Thereafter, a low pressure system or cold frontal boundary looks
to approach our region from the west for Wednesday and Wednesday
night. There are differing scenarios with this in the latest
deterministic and ensemble guidance, from a simple cold frontal
passage to a more amplified scenario with more precipitation.
For now will stick to chance PoPs.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
Short Term...
Deterioration to LIFR/IFR with some periods of VLIFR possible
as rain transitions to snow or a snow/rain mix from southwest to
northeast today. Some questions remain with precipitation type
especially for coastal terminals today...but restrictions will
remain LIFR/IFR through the day regardless. Some gradual
improvement to restrictions is possible tonight...but IFR will
remain the norm.

Winds will be northeasterly and strengthen today...reaching
25G35kt along the coast...with 15G25kts inland. Gusts around
40kt possible at KPSM this afternoon. Winds shift
northwesterly and gradually diminish tonight into Saturday.

Long Term...MVFR likely Saturday night turning to VFR Sunday
into Tuesday. However, periods of MVFR will also be possible
Sunday through Tuesday, with Monday having the best shot at MVFR
conditions.

&&

.MARINE...
Short Term...Winds ramp up this morning over the Gulf of Maine
as low pressure occludes over southeast Massachusetts. The
strongest winds will likely be around midday when a few gusts to
storm force are not out of the question. Winds gradually
decrease this evening and tonight as the low weakens and pulls
away. However, it is possible that the Gale Warning may need to
be extended through tonight as winds may linger a bit longer
than initially expected. Will likely see winds fall below
advisory levels by Saturday afternoon with the low pulling
further away.

Long Term...A cold front will approach Tuesday leading to
increasing SW flow with SCA conditions possible late Tuesday
into Wednesday.

&&

.TIDES/COASTAL FLOODING...
System gradually intensifies before retrograding through the
far southern portions of the Gulf of Maine tomorrow. This type
of system usually lends itself to moderately high storm surge
values, and indeed ESTOFS is forecasting about a two foot surge
tomorrow. The coupled wave action should lead to some minor
beach erosion and this is validated by the USGS wave runup
models. However, this is a borderline situation for splash-over
as we are at a low part of the astronomical tide cycle. Will
continue to monitor. If an area were to have minor splash-over
issues, it would be the beaches south of Portland to the
Massachusetts border tomorrow.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Storm Warning until 6 AM EDT Saturday for MEZ007-008-
     012-013-033.
     Winter Weather Advisory from 8 AM this morning to 6 AM EDT
     Saturday for MEZ019-020.
     Winter Weather Advisory until 6 AM EDT Saturday for MEZ018.
NH...Winter Storm Warning until 6 AM EDT Saturday for NHZ002>009-
     011-015.
     Winter Weather Advisory until 6 AM EDT Saturday for NHZ001-010.
     Wind Advisory from 8 AM this morning to 6 PM EDT this evening
     for NHZ014.
MARINE...Gale Warning from 7 AM this morning to midnight EDT tonight
     for ANZ150>154.

&&

$$

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

NWS GYX Office Area Forecast Discussion