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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCAR 211430
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
1030 AM EDT Thu Sep 21 2023

.SYNOPSIS...
High pressure will build in from the west today, cross the area
tonight, then slide south of the region Friday into Saturday.
Low pressure will track to our south on Sunday into Monday. High
pressure slowly builds eastward into the area Tuesday into
Wednesday.
&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Update...
Surface high pressure will build east toward the region today,
while upper level troffing moves across the Maritimes. With
diurnal cloud development, expect mostly/partly sunny skies
across northern and central areas today with mostly sunny skies
Downeast. High temperatures will range from the lower to mid 60s
north, to the upper 60s to around 70 Downeast. Have updated to
adjust for current conditions along with expected afternoon
temperatures and clouds.

Previous Discussion...
Tonight, a 1029mb surface high slides right overhead as the
500mb ridge axis slides into Quebec. This ends the cyclonic flow
over Maine and conditions become very light. Light winds, clear
skies and high pressure means a very good radiational cooling
night expected. One caveat may be the extremely soaked grounds
in Maine since soil moisture in the root zone is in the 95-99th
percentile for this time of the year. However, felt confident in
lowering the colder valleys a degree or two using the NBM 10th
percentile. This will result in lows Friday AM in the low to mid
30s across the North Woods with patchy to areas of frost. The
frost/freeze program is ending today in these zones and given
how basically it isn`t expected to be widespread opted to not
hoist any headlines. Across the rest of the crown expecting lows
around 40F but some upper 30s are possible in the colder deeper
valleys and its here there may be some patchy frost but
confidence is lower so no headlines at this time. Elsewhere,
from the Baxter Region south to the Downeast coast expecting
lows 40-45F with a few upper 40s at the shoreline. Lastly,
expecting patchy fog to develop in the river valleys and over
the ponds/lakes tonight with colder air, moist grounds and
warmer bodies of water. This may reduce visibility for the
morning commute in locations on Friday AM.
-- End Changed Discussion --
&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
A 1030mb high will be parked over the area Friday morning and
slowly drift offshore by Friday afternoon into Friday night.
With little to no cloud cover and light winds, H925/H850 temps
suggest afternoon temps reaching the upper 60s to around 70F. An
emerging onshore flow will limit highs on the coast to the
upper 50s to lower 60s.

For Friday night, light winds and generally clear skies will
produce another night of decent radiational cooling with a
shallow inversion yielding lows in the low to mid 40s. Once
again, fog will be likely in valleys over relatively warmer
rivers and lakes.

After the high retreats to the east, the big question for the
weekend will be the northward transport of deep tropical
moisture advecting from a closed low along the North Carolina
coast.

An omega block will be trying to set up towards the end of the
period. The forecast area will end up on the east side of the
block. Some guidance, most notably the GEMS, brings the deeper
moisture northward into the forecast area Saturday
night...albeit not as far north as previous runs. Meanwhile, GFS
and ECMWF continue to swing a northern stream shortwave and
cold front southward Saturday night that shunts the moisture off
to the east before getting much further north than the Downeast
coast. Have followed this latter scenario in the forecast in
line with NBM guidance. ECMWF trended more northward with precip
on Saturday night with the 21/00Z run and looks more reasonable
than the last few GFS runs.
&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Blocking continues through the period. Again, the evolution of
the tropical moisture on the east side of the omega block looms
large into early next week. GEMS continues to be the most
pessimistic with the cut-off low migrating from the Carolinas to
Maine Sunday into Sunday night while ECMWF and GFS push a
reinforcing northern steam trough southward out of Quebec Sunday
into Monday. This is a considerably drier solution and following
NBM, we maintained relatively low PoPs into early next week.
That said, confidence is not particularly high in a dry start to
next week across the forecast area and do not give much credence
to the GFS solution.

The likelihood of drier weather increases by mid-week as the
expansive surface high associated with the block slowly expands
eastward. Temperatures and cloud cover will be tricky as this
occurs due to the prospect of stratocu in the a northerly or
northeasterly flow in a subsidence inversion. Thus we stuck
towards the NBM and near normal temps towards the end of the
forecast period.
&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
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NEAR TERM: Occasional MVFR ceilings possible across northern
and central areas this morning. Otherwise, VFR today through
early tonight. Variable conditions possible late tonight with
any patchy fog. North/northwest winds 10 to 15 knots with gusts
up to around 20 knots today. Light and variable winds tonight.

SHORT TERM:
Friday...Patchy valley fog is possible early for sites such as
PQI, but otherwise VFR. Light south winds.

Friday night...Patchy valley fog again in river valleys will
possibly affect sites such as PQI and HUL after midnight. Light
winds.

Saturday...Patchy valley fog is possible early for sites such as
PQI, but otherwise VFR. SW winds 5 to 15 kt.

Saturday night and Sunday...VFR from GNR, MLT and HUL northward.
Chance of MVFR cigs/vis in rain for BGR and BHB. Light north
winds.

Sunday night and Monday...VFR with a slgt chc of MVFR cigs.
Light north to northeast winds.
-- End Changed Discussion --
&&

.MARINE...
-- Changed Discussion --
NEAR TERM: Winds/seas below small craft advisory levels today
through tonight. SE long period swells from Hurricane Nigel
which is located 550mi SSE of Cape Race, Newfoundland will be
occurring across the Gulf of Maine today into tonight. Wave
periods 14-15sec today becoming 12-13sec tonight. Waves are
expected to generally be 2-4ft but cannot rule out a few waves
to 5ft across the waters 20-25nm offshore. Waves will subside to
1-3ft tonight.

SHORT TERM: No fog is expected through the period. There are no
clear cut SCAs lurking into the middle of next week either.
Northeast winds will increase Sunday, but gusts should stay
under 20 kt as it looks now. Northerly wind gusts will likely
exceed 20 kt on Tuesday, but confidence is not high in 25 kt
gusts at this time.
-- End Changed Discussion --
&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.

&&

$$

Near Term...Norcross/Sinko
Short Term...MCW
Long Term...MCW
Aviation...Norcross/MCW
Marine...Norcross/Sinko/MCW