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000
FXUS61 KGYX 162240
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
640 PM EDT Tue Apr 16 2024

.SYNOPSIS...
High pressure nearby will ensure a quiet period of spring
weather in New England for much of this week. Temperatures will
trend cooler as an onshore component to surface flow builds,
culminating in the passage of a frontal system with light rain
late in the week. Quiet, mild, and dry weather, this time with
more westerly flow, returns by the start of next week.

&&

.NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/...
645 PM Update... Minor changes to reflect latest observational
trends. As expected, diurnally driven cumulus field is already
showing signs of dissipating with the loss of daytime heating.
Will monitor temperature trends over the next few hours before
making any possible changes to overnight lows. It will
otherwise continue to be a nice April evening weather wise.

Previously...
Sufficient low-level moisture and a small amount of instability has
resulted in a pretty decent cu field across much of the area this
afternoon, but the overall atmosphere is likely too dry to support
any shower activity. The exception may be across the far north where
the moisture is a little better, and I have included a slight shower
chance (20%) into this evening.

Northwest winds will continue to be breezy through this
afternoon generally gusting to around 25 mph, but these will
diminish toward sunset as well as the cu field south of the
mountains. The mountains will stay cloudier a little longer, but
these will erode tonight as a bigger push of drier air works in
from the north. Clearing skies and drier air will allow for
another seasonably cool night, but winds overall look a tad
higher than last night/this morning, so I don`t think
radiational cooling will be quite as efficient in most places.
Still, lows are expected to be in the upper 20s across the north
and 30s elsewhere.

&&

.SHORT TERM /7 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Broad high pressure will be positioned well north of the area
during the day on Wednesday with a light north to northwest flow
in place. The airmass will be very dry with precipitable water
progged to be around 0.25" giving us plenty of sunshine.
Temperatures will again be warm, and given the dry air, I have
gone slightly above guidance putting temperatures in the upper
50s to lower 60s for much of the area. Coastal areas are
expected to be slightly cooler with the flow not being enough to
hold off the seabreeze, which will bring in the chillier marine
air from the Gulf of Maine.

The airmass will remain dry Wednesday night, keeping skies
mostly clear for most of the area, and winds will also be light.
To account for radiational cooling, I have followed more
closely to MOS guidance with the exception being across southern
NH, where an increase in clouds is expected to keep
temperatures milder. So I have forecast lows in the mid 30s to
lower 40s there with mid 20s to lower 30s across the remainder
of the area.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
A mostly dry but quintessential New England Spring period of
weather continues through the long term, starting with a bout of
cool onshore flow with offshore high pressure and eventually
ending in milder westerly flow. Precipitation chances continue
to hold off late this week with a dry ridge overhead shunting
the northern stream trough... though most or all places can
expect a round or two of light rain between late Thursday and
Saturday. High pressure returns after that point, but with a
drier continental source region which should keep conditions
relatively pleasant overall.

Starting Thursday... a ridge of high pressure will be in
control over eastern NOAM, with its surface reflection centered
over Maritime Canada. An upper level trough meanwhile will be
skirting across the Boundary Waters and into the upper Great
Lakes... with a preceding shortwave pushing into the Northeast
ahead of the larger system. The resulting gradient flow will
bring a building onshore component of surface flow, while the
airmass above the boundary layer remains quite dry Thursday into
Friday. The dry air aloft continues to trend tougher to
erode... with the preceding shortwave`s weak forcing unlikely to
overcome this, still only offering a slight/low chance of rain
showers Thursday, mainly in the mountains and CT River Valley.
The bigger question will be, if we can get the cooler marine
layer in at the surface... MOS guidance seems to think so, with
highs on Thursday in the 50s, coolest along the coast and
southern interior.

Should it be a proper marine layer coming in with marine
stratus and weak/no mixing, would expect temperatures near SSTs
in the low-40s along the coast. But, marine stratus looks more
likely to form later Thursday night or Friday if at all... as
low pressure and an attendant cold front approaches from the
Great Lakes region, producing an increasing southerly flow and
bringing deeper moisture, at least enough for widespread light
rain as the system crosses Friday into Saturday. Large-scale,
upper-level cyclonic flow will persist through the weekend with
daily chances for mountain showers. Gradient flow meanwhile will
switch more westerly/offshore... which will allow for better
mixing, and in turn breezier flow and temperatures closer to
seasonal averages in the 50s to low-60s.

The upper air pattern early next week is likely to remain
weakly cyclonic or zonal, with high pressure building to the
south. This sort of set up is likely to result in a pleasant and
dry stretch of weather to start the coming work week, with
varying degrees of southerly onshore flow for the Midcoast
depending on where the high sets up to our south.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Short Term...VFR expected through Wednesday night. Winds
gusting to around 20-25 kt this afternoon will diminish this
evening and tonight. Northerly winds will be lighter on
Wednesday, and this will allow a seabreeze to move inland during
the afternoon. The seabreeze will result in a wind shift at
coastal sites in the 17Z to 19Z timeframe, and it may progress
far enough to inland to reach MHT and CON by 22Z to 23Z
Wednesday.

Long Term...VFR likely on Thu with E or SE winds AOB 15 kts.
There`s a chance that IFR/LIFR CIGs develop for coastal and
interior locations Thu night, and would likely persist through
Fri and into Sat with periods of -RA providing MVFR otherwise.
VFR returns, except perhaps at KHIE in MVFR CIGs, behind this
wave for the start of next week.

&&

.MARINE...
Short Term...Conditions expected to remain below SCA levels
through Wednesday night. Another weak frontal boundary will
cross the waters later this afternoon and evening, turning winds
northerly through early Wednesday along with a slight increase
in gusts. A seabreeze develops Wednesday afternoon resulting in
a more a southerly flow across the waters before high pressure
becomes centered north of the waters Wednesday night swinging
winds back to east to northeast.

Long Term...E to SE gradient flow builds Thu into Fri then
turns S to SW as a cold front crosses on Saturday with winds
generally remaining AOB 20 kts or so, though a brief SCA may be
needed around the time of frontal passage. W flow prevails into
early next week.

&&

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

&&

$$

NEAR TERM...Tubbs
SHORT TERM...Combs
LONG TERM...Casey