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-- Discussion containing changed information from previous version are highlighted. --
239
FXUS61 KGYX 221247
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
847 AM EDT Fri Mar 22 2019

.SYNOPSIS...
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Low pressure will deepen and track north to coastal Maine late
today. Precipitation will continue to spread across the area
through morning. This will bring snow and rain at the start to
many locations, except for the higher elevations which will
likely see snow all day. The snow and rain will briefly change
to snow through midday...especially away from the coast. The
low will make its closest approach late today, which will end
the widespread precipitation as drier air aloft moves overhead.
Colder air and gusty winds move in from the west tonight and
Saturday. Snow showers will break out across much of New
Hampshire and western Maine, with moderate accumulations
possible in the higher terrain. After a brief warm up on Sunday,
a cold front will cross the region Monday. Cold but fair
weather follows for Tuesday and Wednesday, with a warming trend
for the end of the week.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...

-- Changed Discussion --
845 AM...the 12z GYX RAOB shows colder profile and thus expect
more snow closer to the coast and along the coastal plain. As
this is a transition season storm...there are likely to be wide
variations in snow amounts based on elevation as well as
precipitation intensity. The winter weather advisory area has
been expanded further south and east to account for more snow
then rain with this ESTF update. Winds over coastal waters in
advance of the low continue to strengthen and Gales for the
outer waters began a short time ago with strong SCA for the
bays.

Prev disc...
625 AM Update...Forecast on track so far early this morning.
Have raised total snowfall for the coastal plain a bit based on
newest forecast sounding information and trends in upstream obs.
Area of strong UVVs just offshore of northeast MA continues to
move northward at this time and will be affecting the our CWA
this morning. A flip to snow (where it starts as rain) can be
expected away from the immediate coast for a few hours (and even
for an hour or two at the coast is possible). Snow could
oscillate with rain for a time this morning as well in
spots...all depending on UVVs and cooling of the column.
Warnings and advisories remain the same but could be expanded a
bit depending on trends over the next 1-3 hours.

Previously...

Tricky, changeable forecast today. Low pressure currently
centered south of Long Island NY will move north-northeastward
and into the Gulf of Maine this afternoon. At the same time,
deepening mid level low will also move to a position just off
the maine coast by this afternoon.

The most concern at this time is the expected slug of heavy
precipitation that is forecast (by consensus of mesoscale
models) to move northward and through the region this morning
into the early afternoon hours. This slug of precipitation will
be forced by a tightening zone of frontogenesis extending to
the northeast of the deepening mid level low (back-bent mid
level warm front). Since much of the model suite has cooled in
the column (current obs are showing a cooler/drier draw of air
coming in from the north), this makes the precip type forecast
tricky outside of high elevations since the temperature trace
may be straddling the 0c isotherm for several hours this morning
through about midday, even close to the coast. Therefore, even
areas outside of the advisory/warning area could flip to heavy
wet snow for a time. As such, have increased snow accums a bit
at lower elevations on the coastal plain away from the immediate
coast. This will be dependent on getting into some really
intense upward motion, but it`s possible. After the heavier band
of precipitation moves through early afternoon, SFC
temperatures will rise, and any snow will go back over to rain.

In the mountains, have issued a winter storm warning for heavy
wet snow as accumulating snowfall is expected to occur today and
well into tonight. This should get zone averages above 6 inches
in the warning area. Highest elevations could see a foot or
more. South of the warning area, have issued a winter weather
advisory for 3-6" of heavy wet snow - with highest amounts in
highest elevations. Power outages will be possible due to the
potential for downed branches in the advisory and warning area.

Precipitation will be considerably lighter this afternoon in
many areas with dry lot moving on in. Winds will increase from
the west this afternoon, especially across southern zones.

Overall, a forecast where near-term updates to follow trends
will likely be needed today as just a degree colder/warmer in
the column will likely mean a big difference in ptypes. Some
areas may waver from rain to heavy wet snow and back again as
the temperatures profile wiggles around the 0c isotherm.
-- End Changed Discussion --

&&

.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Snow to continue in the mountains tonight, with upslope
contributions from NW flow becoming more dominant as the night
goes on. In addition, it`s possible that the coastal plain sees
a period of accumulating snow once again tonight as lobe of
vorticity moves across the region (remnants of merging northern
stream wave). Winds will increase as the night progresses due to
tightening pressure gradient. Drier air moves in on Saturday.
Aside from gusty west winds, we should see a decent amount of
sunshine.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Models to continue to advertise a break of the +PNA pattern by
early to mid-week, but not before we get a shot colder air for
early to mid week as the trough is already in place before the
flow becomes less amplified. The good news it will at least be
dry after Monday and thru the rest of the week. Warming trend
expected Thu-Fri as New England sits in the anticyclonic flow N
of a closed low off the SE coast. The models have been
struggling with srn stream closed lows, though, so not high
confidence.

Sat night should see NW flow break down as sfc high begins to
work in briefly, and winds will diminish,as will mtn SHSN. Lows
will drop into the teens N, to the mid 20s S, and some colder
spots could decouple late with rad cooling for part of the
night. The high shifts offshore Sunday with a Sw flow picking
up and temps warming to 40-45 in the N, and 50-55 in srn and
interior SW ME. Given the onshore flow, the ME coast is likely
to stay in the mid to upper 40s.

Sunday night and Monday will see the passage of cold front as
srn stream energy phases to the south and drags [polar vortex
toward Labrador. We will be on the equatorward of the cold air,
so it will turn colder, and Tue-Wed will likely run below
normal, but highs Tuesday, which will be the coldest day will
range from around 30 in the N, to the mid to upper 30s in the
south, and overnight lows will run from around 10-20 both
Monday and Tue night. The cold air shifts out fairly quickly,
and Wed will be a few degrees warmer than Tue, but still on the
cool side for late March.

Thu and Fri, will see the area under the influence of SW flow
with warmer temps, in the 40s and 50s, with warmest air
interior sections of the south, as onshore flow keeps the coast
cooler.

&&

.AVIATION /13Z FRIDAY THROUGH TUESDAY/...
Short Term...IFR conditions expected today in rain and snow.
Rain mainly at the coast, with snow in the interior. Conditions
improve on the coastal plain and across southern NH tonight with
low conditions continuing in the mountains. VFR returns Saturday
with gusty west winds.

Long Term...Mainly VFR Sat night thru Tuesday. KHIE could see
some SHSN late Sun night early Monday.

&&

.MARINE...
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Short Term...SCA conditions likely today with some gale gusts
possible this morning. Westerly gales later tonight and Saturday
as low pressure moves off into the Maritimes. Will keep a gale
watch going for the bays as confidence in wind speeds remains a
little low at this time.

Long Term...SCA winds may linger through Sat night, but should
subside below SCA on Sunday, and stay below SCA levels through
Tuesday.

.HYDROLOGY...
Warming temperatures and rainfall may produce sufficient runoff
to cause rises on rivers and streams late today through
Saturday. At this time QPF looks to be less than an inch and a
half...with a good portion of that being snow in the mountains.
Even so, some ice breakup will be possible, especially central
and southern ME.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
Winds and seas begin to build right around the time of high tide
tonight. However, the vast majority of increased storm surge of
around a foot will occur around or shortly before the time of
the midday high tide on Friday. With high astronomical tides
already in place, minor coastal flooding is possible from
Portland and points south during this tidal cycle. Most likely
we remain below 13 ft at Portland, so a coastal flood advisory
has been issued from there south. Some splash over or erosion
may occur northward to Penobscot Bay and a coastal flood
statement has been issued.

00Z wave models suggest long period waves arrive Friday night
into Saturday. Therefore, with high astronomical tides still in
place, there is the possibility for beach erosion and splash-
over to continue for subsequent tides. This additional splash-
over has been indicated in wave run-up output.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Winter Weather Advisory until midnight EDT tonight for MEZ012-
     013.
     Winter Weather Advisory until 2 PM EDT this afternoon for
     MEZ018>022.
     Winter Storm Warning until 8 AM EDT Saturday for MEZ007>009.
     Coastal Flood Advisory until 3 PM EDT this afternoon for
     MEZ023-024.
NH...Winter Weather Advisory until midnight EDT tonight for
     NHZ003>007.
     Winter Weather Advisory until 2 PM EDT this afternoon for
     NHZ008>010.
     Winter Storm Warning until 8 AM EDT Saturday for NHZ001-002.
     Coastal Flood Advisory until 3 PM EDT this afternoon for
     NHZ014.
MARINE...Gale Watch from late tonight through Saturday evening for
     ANZ151-153.
     Small Craft Advisory until 5 AM EDT Saturday for ANZ151-153.
     Gale Warning until 8 PM EDT Saturday for ANZ150-152-154.
-- End Changed Discussion --

&&

$$

ES