986
FXUS61 KCAR 202218
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
618 PM EDT Fri Sep 20 2024

.SYNOPSIS...
High pressure will build southeastward from eastern Canada
through Tuesday, then begin to retreat back into the Maritimes
into Wednesday. A storm system approaches from the west for the
middle of next week.
&&

.NEAR TERM /THROUGH SATURDAY/...
Update...
High pressure centered near Labrador will ridge south across
the region tonight, while a slow moving ocean low remains
southeast of New England. Expect partly/mostly cloudy skies
across northern area tonight, with mostly cloudy skies Downeast.
Isolated showers on the northern edge of the precipitation
shield with the ocean low could also clip the Downeast coast.
Patchy, mostly river valley, fog is also possible across northern
areas later tonight. Low temperatures tonight will range from
around 40 to the mid 40s north, to around 50 interior Downeast
with lower to mid 50s along the Downeast coast. Have updated to
adjust for current conditions along with expected overnight
temperatures, clouds and shower chances.

Previous Discussion...
An upper level Rex blocking pattern remains in place through
the period. The upper low to the south of the forecast area will
slowly drift southward and fill during the period. Meanwhile,
high pressure will continue building southward into the area
from eastern Canada through tonight. The means no measurable
precip for the forecast area Saturday. The sky trend will
generally be towards clearing skies pushing southward during the
period. However, an easterly flow will continue to advect
moisture westward into Saturday morning, bringing cloudy
periods.

As generally cooler air at 925mb and 850mb backs into the area
from the east, the expectation is that high temps on Saturday
will be a bit cooler than today, even with a deeper mixed
layer. Expect highs to top out in the mid to upper 60s. The
easterly flow will also continue the trend towards less elevated
smoke that we have seen today.
&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
A cutoff slow slowly tracks SE from the Gulf of Maine Saturday
night through Monday as deep layered ridging builds in from the
west through Sunday night, with its axis moving offshore on
Monday.

The main question in the short term is how much low level
moisture will remain trapped under the subsidence inversion
building in underneath the deep layered ridge. While the
subsidence will keep things dry, there are some indications
that sufficient moisture under the inversion could result in
some strato-cumulus clouds, especially across the north. This
in turn, will help limit the diurnal temperature range. As a
result, have kept low temperatures generally 40 or above, and
hence frost out of the forecast.

Lows Saturday night should be near to slightly above normal, and
highs on Sunday, lows Sunday night, and highs on Monday near
normal.
&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As the deep layer ridge axis passes farther to the east, it
allows for northern stream shortwaves to pass by Monday night
and Tuesday. The low levels will be too dry for precipitation,
but should see more widespread cloud cover Monday night and
Tuesday across the entire forecast area than over the weekend.

The models continue to disagree on the timing and strength of a
system a northern stream system that should move from south
central Canada Tuesday night to southern Quebec by Thursday
morning. The ECMWF is the strongest with this system, developing
a closed low, the GFS is the weakest and most progressive with
the system, with the CMC in between. For now used the CMC as a
middle of the road starting point to adjust the NBM.

The 12z runs are slower overall with this system than the 00z
runs, so did slow down the timing of widespread chance pops. For
now limit to western portions of the forecast area on Wednesday
night, then have over the entire forecast area Thursday. Have
kept chance pops over the area Thursday night, and should see
some drying from W to E on Friday (unless the ECMWF is correct -
then should see precipitation continue on Friday).

Given the uncertainty with this system, and the natural inherent
uncertainty in the days 5.5-7 time frame, it is too early to
speculate on what, if any, impacts this system may have on the
region.

Temperatures should be near normal Monday night-Wednesday,
followed by lows above normal with highs near normal Wednesday
night-Friday.
&&

.AVIATION /22Z FRIDAY THROUGH WEDNESDAY/...
NEAR TERM: Across northern areas, variable conditions with any
patchy fog late tonight through early Saturday. Otherwise, VFR
tonight through Saturday. Across Downeast areas, VFR early
tonight. MVFR, occasional IFR, overnight through early Saturday.
Isolated showers along the Downeast coast tonight. VFR later
Saturday morning through the afternoon. Across northern areas,
east/northeast winds 5 to 10 knots tonight through Saturday.
Across Downeast areas, northeast winds 5 to 10 knots tonight,
then 10 to 15 knots Saturday.

SHORT TO LONG TERM:
Saturday night-Sunday Morning...VFR, with a low end chance of
MVFR-IFR at mainly southern terminals. NE-E winds G15-20KT
possible, with highest gusts at coastal terminals.

Sunday Afternoon-Tuesday...Most likely VFR all terminals, with
a very low chance of MVFR at northern terminals.

Tuesday night-Wednesday...VFR, with possible chance of MVFR
developing late Wednesday at western terminals.
&&

.MARINE...
NEAR TERM: A Small Craft Advisory remains in effect for much of
the waters, with the exception of the intra-coastal waters,
tonight through Saturday. Isolated/scattered showers tonight.

SHORT TO LONG TERM: Have extended the SCA through Saturday night
on the coastal ocean waters, with gusts up to 25kt and seas
around/maybe just under 5 ft. The intra-coastal waters should be
just under SCA thresholds Saturday night. There is some chance
that SCA conditions could linger on the coastal ocean waters
into Sunday, otherwise decreasing winds and swells will enable
all waters to experience SCA conditions for the early and
middle portions of next week.
&&

.TIDES/COASTAL FLOODING...
High astronomical tides combined with a modest storm surge from
low pressure to the south will lead to potentially minor tidal
flooding at the high tides around 1 PM Saturday. Tides today
underperformed expectations, but the total water levels may be
nominally higher on Saturday. The southernmost east facing
islands and peninsulas will be most subject to erosion, but most
areas will see little wave action due to the east-northeasterly
wind direction relative to the coastline.
&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Small Craft Advisory until 6 AM EDT Sunday for ANZ050-051.

&&

$$


Near Term...Norcross/MCW
Short Term...Maloit
Long Term...Maloit
Aviation...Norcross/Maloit
Marine...Norcross/Maloit
Tides/Coastal Flooding...MCW