Area Forecast Discussion
National Weather Service Boston/Norton MA
749 AM EDT Sun Oct 18 2026
.WHAT HAS CHANGED...
No significant changes.
.KEY MESSAGES...
- Sunny with light winds today. Cold again tonight with clear
skies and light to calm winds.
- Mainly dry for the upcoming work week, except near coastal
areas. Modest warming trend as high pressure builds in over
the northeastern US.
.DISCUSSION...
KEY MESSAGE 1...Sunny with light winds today. Cold again tonight
with clear skies and light to calm winds.
High pressure continues overspreading the region today with
yesterday's/last night's colder airmass shifting out of the region,
along with the upper level trough that's impacted the region over
the last few days. With 925 mb temperatures returning closer to 5C
and yesterday's cold air advection having come to an end, highs will
reach the 50s. Winds also remain light through the day and into
tonight with high pressure firmly in place overhead. Skies remain
clear through tonight, allowing for another good night of
radiational cooling; lows tonight will dip into the 30s and upper
20s.
KEY MESSAGE 2...Mainly dry for the upcoming work week, except near
coastal areas. Modest warming trend as high pressure builds in over
the northeastern US.
The general trend this week is a drier, somewhat warmer pattern
developing as a broad ridge of high pressure settles over much of
the northeastern US and into Ontario. Temperatures moderate through
the week with highs generally in the 50s and 60s, with cool nights
in the 30s and 40s. The only exception to this overall trend is a
chance for showers towards the Cape and Islands this week.
A non-tropical low pressure developing along the cold front from
Friday night settles just offshore of the Carolina coastal waters.
The aforementioned front looks to have stalled out and a bit of
upper level energy from the associated trough broke away and drifted
to that same area, aiding in the development of this low pressure.
Latest HREF members have shown some of the showers associated with
the northern precipitation shield of this low making their way up to
southeastern parts of New England, mainly the Cape and Islands,
finding a weak point in the ridge aloft. Some of the global
deterministic guidance agrees, indicating some showers making their
way over the Cape and Islands. Though across all models, QPF remains
quite low. Latest global guidance (ensemble and deterministic) have
also trended down on rain chances later this week. Despite minimal
impacts in terms of rain expected with this low pressure, marine
impacts are looking a bit more significant as it remains relatively
stationary over the same area, churning over the same waters for
what appears to be most of this week. This will lead to seas up to
15-17 ft offshore of Nantucket.
The gradient between this area of low pressure and the
aforementioned high pressure over the northeast US will tighten
greatly, increasing ENE winds over the waters and towards the Cape
and Islands, RI, and the coastal plain in SE MA. These start to
really build up towards Monday night as the low pressure deepens and
drifts very slightly north. Ensembles have continued to indicate
decent probabilities of sustained winds reaching gale-force over the
southern waters, with the GEFS and Canadian ensemble up to 30-40%
(and even up to 70% in the Canadian guidance over the ocean waters)
just south of the Islands. In terms of gale-force gusts,
probabilities have remained somewhat steady compared to the last
update, remaining in the high (80-100%) range in the ECMWF ensemble
and up to 80% in the GEFS. However, there was a bit of a southward
shift of the core of the highest sustained gale probabilities. This
lines up with the majority of members across the ensemble suites
tracking the center of this low pressure well to the south and east
of the 40N/70W benchmark. Persistent easterly fetch associated with
these winds, along with building rough seas, will need to be
monitored as well, as beach erosion for east- and northeast-facing
beaches may become an issue.
Towards the end of the week, ensembles indicate troughing from
Canada making a pass towards southern New England, which would aid
in steering this low pressure out to sea. Significant ridging aloft
over much of the CONUS looks to persist and even intensify, then
becomes more tilted towards the Great Lakes region towards the
weekend. This would be associated with a strong Canadian high
pressure that looks to strengthen over the northeast after
originating from the Canadian Prairies, which would lean towards
drier conditions for the whole region once again.
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12z Update...
Today...High confidence.
VFR. Calm/light winds continuing through the day today for
interior terminals. For eastern terminals, N winds shifting NE
after 15Z then to ESE mid-afternoon less than 8 kts. Stronger
winds for Cape/Islands between 10-15 kts. VRBL conditions a
possibility across interior terminals during the day as high
pressure continues aloft.
Tonight...High confidence.
VFR. Southerly winds becoming NW/NNW early Mon AM. Gusts to
around 20 kt possible towards the Islands closer to daybreak
Monday as well.
Monday...Moderate confidence.
Mostly VFR with the exception of the Cape and Islands towards
the late afternoon and evening hours where MVFR ceilings may
develop. Chances for -SHRA increase there as well and should
remain generally over the Cape and Islands, along with an
increased chance for gusts to 25 kt. Winds from the NE and light
to calm further inland, 5-10 kt sustained closer to the coasts.
KBOS Terminal...High confidence in TAF.
Light NNW winds this AM shifting to the NE after 15/16Z then
toward the ESE by mid-afternoon. Speeds 8 kts or less.
KBDL Terminal...High confidence in TAF.
Outlook /Monday Night through Thursday/...
Monday Night: VFR. Windy with local gusts up to 30 kt.
Tuesday: VFR. Windy with gusts up to 30 kt.
Tuesday Night: VFR. Windy with gusts up to 35 kt.
Wednesday: Mainly VFR, with local MVFR possible. Windy with
gusts up to 35 kt.
Wednesday Night through Thursday: VFR. Windy with local gusts
up to 30 kt. Slight chance SHRA.
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through Monday...High confidence.
Some marginal lingering small craft advisory conditions may persist
across the southern waters through this morning, but will be
diminishing. High pressure building in from the west will result in
winds/seas falling below small craft today into tonight. However,
distant ocean storm off the mid- Atlantic coast should result in
small craft advisory seas/wind gusts returning for our southern
waters toward daybreak Mon. Additional marine headlines will be
needed for much of the upcoming work week because of this ocean
storm. Seas start to build up to 15 ft offshore, south of Nantucket
and winds gusting to 25 kt in the southern outer waters return by
Mon morning, reaching up to 30 kt in the southern ocean zones.
Outlook /Monday Night through Thursday/...
Monday Night: Low risk for gale force winds with gusts up to
40 kt. Rough seas up to 14 ft. Chance of rain showers.
Tuesday: Strong winds with gusts up to 40 kt. Rough seas up to
15 ft. Chance of rain showers.
Tuesday Night: Moderate risk for gale force winds with gusts up
to 45 kt. Rough seas up to 16 ft. Slight chance of rain
showers.
Wednesday: Moderate risk for gale force winds with gusts up to
45 kt. Rough seas up to 17 ft. Chance of rain showers.
Wednesday Night: Strong winds with gusts up to 40 kt. Rough
seas up to 17 ft. Chance of rain showers.
Thursday: Strong winds with gusts up to 35 kt. Rough seas up to
15 ft. Chance of rain showers.
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 AM EDT this morning for
ANZ232>235-237-250.
Small Craft Advisory until 11 AM EDT this morning for
ANZ254>256.
Gale Watch from Monday evening through Wednesday morning for
ANZ254>256-281>283.
DISCUSSION...Hrencecin
AVIATION...Hrencecin/Mensch
MARINE...Frank/Hrencecin