789
FXUS61 KGYX 110504
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
104 AM EDT Sat May 11 2024

.SYNOPSIS...
A cool and unsettled weather pattern is expected through the
next several days as a longwave trough gradually crosses the
area. Although day-to-day details are relatively uncertain,
there will be several opportunities for rain showers through
this time. No days are expected to be washouts, however. Below-
average temperatures are expected through this weekend, then
will start to trend warmer next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
1am Update...Most `impactful` weather tonight is sky conditions
for the ongoing G4/G5 geomagnetic storm that is producing
abundant aurora across the CONUS. Guidance is having a tricky
time simulating current conditions, and this leads to only
marginal confidence in the forecast for remainder of the night.
Dry air has been strong across much of southern ME, but it is
flanked by moisture in eastern ME and NH. Think coastal spots
south of the Midcoast have the best chance for clear skies for
remainder of the night, while interior locations may see
overcast conditions comb overhead over the next couple hours.
This will also have an effect on overnight temps, with a few
locations touching the mid/lower 30s near the coast tonight.

Prev Disc...
Temperatures continue to trop, mostly in the 40s as of 02Z. A
few upper 30s have been reported in the Midcoast region. Most of
the clear skies, light winds and radiational cooling have been
over eastern portions of the forecast area.

Will continue with patchy frost overnight. Some inland fog may
develop as well after midnight. Otherwise, little in the way of
changes to the overall forecast package.

Update...
Only minor modifications to the near term portion of the
forecast package with this update. Diurnal Cu will continue to
diminish this evening with the loss of daytime heating. This
will allow for light winds and a very chilly night with some
radiational cooling, especially away from the coast. Have
introduced patchy frost into the forecast for tonight as
temperatures will reach the mid 30s in some locations by
morning.

Scattered showers over north-central New Hampshire will be
diminishing after sunset as well with a few snow showers on the
summit of Mount Washington expected.

Prev Disc...Diurnal instability and sufficient moisture in and
around the 850mb level has resulted in a pretty expansive
cumulus field today with skies being mostly cloudy with the
exception being those near the coast who have had the seabreeze
move through. The airmass is pretty dry above this layer (and
also closer to the surface), and combined with a subsidence
inversion aloft, not much in the way of showers have been seen
so far. So while we should still see some showers to develop
through the course of the afternoon, this environment will keep
coverage low with the vast majority staying dry. I have
generally 20% PoP across the interior for light showers and/or
sprinkles with 30% over toward the western CT River Valley where
the low-level moisture depth is a little higher.

As the sun sets this evening, showers that do develop will
wane, and the diurnally driven cloud cover is also expected to
diminish through this evening with skies generally partly cloudy
tonight. Forecast lows are currently in the upper 30s and low
40s, but considering how low the dewpoints are right now, it`s
possible that some areas could see mid 30s if skies are able to
remain clearer. If this is the case, patchy frost may occur.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/...
Surface high pressure remains across the Canadian Maritimes on
Saturday while a weak low pressure passes well to our south and
east. Ample low-level moisture will also still be present with
dry air aloft again, so I`m expecting a pretty similar day as
far the weather is concerned. Low-level lapse rates will be
pretty steep, and a cumulus will probably develop by mid morning
with diurnal isolated to scattered showers then following
through the afternoon with a few hundred J/kg of CAPE in the low
levels. Max temps will again be in the mid 50s to lower 60s.

Showers diminish toward sunset as daytime heating is lost and
shortwave ridge builds in very briefly. Skies will be partly cloudy
initially before increasing overnight. Temperatures will range from
the mid to upper 30s across the north and upper 30s to low 40s
farther south.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
An upper level trough crosses New England late this weekend,
with a welcome warming trend following its passage albeit with
some rain (although not a washout). In general, the forecast
continues to trend on the drier side Sunday and Monday...
although light diurnal showers will still be possible, mainly in
the interior and across the mountains. A more organized system
brings better chances for more widespread rainfall around the
middle of next week.

Starting Sunday... the closed off center of an upper level low
shifts through southern New England. At the surface, weak
ridging extends from the Gulf of Saint Lawrence down into Maine
and New Hampshire, as a low tracks northeast into Nova Scotia.
Although the upper level low will keep mixed mid- and upper-
level cloud decks over the area, the surface high supports dry
air in light northeast flow which will keep ceilings up and
allow for good mixing. Temperatures are forecast to warm to
around 60, although that trend will likely be stunted along the
coast with a seabreeze. Weak mixed layer instability combined
with mid-level moisture and cyclonic flow aloft is forecast to
support slow-moving afternoon showers, most likely over the
mountains but possible anywhere given the synoptic support.

Shortwave ridging moves in behind the departing upper level low
Sunday night, with rain shower chances diminishing and some
clearing. Overall it could be a good radiational cooling night
depending on the timing and degree of clearing, with lows most
likely near 40 but potentially down into the mid-30s in more
ideal scenarios. With the growing season active everywhere but
the mountain zones, will have to keep an eye on trends in case a
frost/freeze headline may be necessary.

High pressure slides offshore to the east on Monday with flow
turning more zonal aloft. Meanwhile upstream, another upper
level trough will be spinning across northern Ontario into
Quebec. Ridging should initially suppress precipitation chances,
but it is short- lived and transient so by the time we get into
peak heating/mixing we`ll start seeing pressure falls and
associated warm advection from the west. These will support high
temperatures largely in the 60s, along with diurnal rain shower
activity. With the offshore high, there ought to be a strong
sea breeze that will limit temperatures along the coast.

There is good model agreement by now WRT the aforementioned Canadian
trough bringing a warm front across New England Monday night through
Tuesday, followed by a cold front on Wednesday. This more organized
system brings better potential for more widespread rain to the area
though there`s still quite a bit of uncertainty WRT to QPF at this
range. Though, the majority of ensemble members keep totals
around 0.75" or less which doesn`t raise too many alarm bells
for hydro, however PWATs will likely rise above 1.0 inch and SW
flow parallel to the front gives some pause... so it`ll be
another item to watch trends on.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
Short Term...Mainly VFR through Saturday night. Isolated/scattered
showers remain possible into early this evening, and these are
expected again on Saturday during the daytime hours, mainly away
from the coast. Should these pass over any terminals, brief MVFR
restrictions are possible. For tonight/early Saturday, will have to
watch for fog should skies clear out enough. For Saturday night and
early Sunday morning, while still low, there is a somewhat
better chance for MVFR ceilings and patchy fog.

Long Term...VFR prevails Sun-Mon, except brief MVFR in SHRA
possible over the interior and west. More widespread SHRA/RA and
associated restrictions are likely to develop Tue into Wed, with
VFR returning Wed into Thu.

&&

.MARINE...
Short Term...Conditions will remain below SCA levels through
Saturday night. High pressure to the northeast of the waters and low
pressure passing to the south and east will keep a northeast flow
going the rest of today through Saturday night. However, winds
are expected to veer onshore Saturday once the seabreeze gets
going.

Long Term...Light flow and quiet seas are expected over the
extended forecast period with SCA conditions unlikely to occur.
In general, winds late this weekend will be NE, then will turn
out of the SW to start the next week however daily sea breezes
and a nebulous pressure gradient will muddy this progression a
bit. The best chance for 25+ kt winds, right now, comes around
Tue with a more organized system potentially crossing the
region which also brings potential for rain and fog. This
system likely departs around Wednesday night with drier air
filters in by Thursday, however the trough may cut off near the
coast which will impact timing a bit.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.

&&

$$


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