Old Res Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 120706
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
306 AM EDT Sun Oct 12 2025

.SYNOPSIS...
A coastal storm brings rain and strong coastal winds into Monday 
night, along with the minor coastal flooding and erosion.
Unsettled weather lingers into Tuesday, especially across the
eastern half of southern New England. Then blustery and
generally dry with below normal temperatures for mid to late 
this workweek as an unseasonably cool air mass moves in. High 
pressure builds into the region next weekend with milder 
conditions and less wind.

&&

.NEAR TERM /THROUGH TODAY/...
Key Messages:

* Rain arrives from south to north, especially this afternoon
  for most

* Increasing E-NE winds, strongest across the Cape and islands

* Pockets of minor coastal flooding during high tide

Latest guidance suite did not provide much reason to alter the
overall forecast. Did try to improve the onset timing of
rainfall across out region. Really like the last few runs of the
HRRR and the latest HREF for that aspect of this forecast.
Thinking rainfall remains mainly south of the northern CT/RI and
MA border this morning, although there is a chance for more
scattered rainfall farther north by late morning. The widespread
rainfall should really start to arrive through this afternoon.

Gusty E-NE winds develop as the coastal low pressure to our
south gets closer to the high pressure over the Maritimes.

Expecting slightly below normal high temperatures.  

&&

.SHORT TERM /TONIGHT THROUGH 6 PM MONDAY/...
Key Messages:

* Steadiest and heaviest rain tonight into Monday

* Strong E-NE winds developing into Mon along the coast,
  especially the Cape/Islands where gusts to 50+ mph expected 
  with some power outages possible

* Pockets of minor coastal flooding during high tide

Rainfall...

The brunt of the impacts from this coastal storm are expected
tonight into Monday. This is the time period where we could see
1-3 inches of rainfall, especially across RI and eastern MA. 
The prolonged duration is important, because it is unlikely to 
result in significant flooding. The exception to that would be 
clogged storm drains possibly leading to poor-drainage flooding.

There is not a tremendous amount of instability expected.
However, there is relatively strong shear which may be enough to
focus enough energy to result is a few thunderstorms. this would
mainly be on Monday.

Strong winds...

E-NE winds will be ramping up this afternoon with the peak of 
the winds tonight into early Monday. Still looking like the
925 mb jet weakens late tonight into Monday. Contemplated
expanding the Wind Advisory to Cape Ann and parts of the eastern
MA coastline, but do not have enough confidence yet that the we
will see 45+ mph wind gusts that far north. It is something that
will need to be monitored. No changes to the current wind
headlines at this time. Given most trees remain fully leaved, 
some tree damage and power outages are possible, mainly over the
Cape and Islands.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Key Messages:

* Coastal low slowly pulls away by Tue. Steadiest rains over
  eastern and coastal portions of RI and MA Mon night and Tue,
  with gradually decreasing north to northwest winds. 

* Minor coastal/tidal flooding possible at Nantucket for Tue
  aftn high tide, but water levels are slightly lower than what
  we will have with the afternoon high tides today and Mon.

* Blustery and dry with below normal temperatures for mid to 
  late week, as much as 10 degrees below normal. Generally dry, 
  but could be some spotty showers over the Cape and Islands. 

Details:

Monday Night and Tuesday: 

Still dealing with rain and northeast to northerly winds as we 
remain under the influence of the coastal low from the weekend.
There is some solution spread with regard to how quickly the
coastal low moves eastward/offshore from the mid-Atlantic
states, with some deterministic models (00z ECMWF / 12z
Canadian) showing a secondary low meandering around the NJ coast 
Mon night/Tue; we view this as an outlier outcome right now
given limited support in ensemble membership analyses. 

Rain will continue to fall at a steady light to locally moderate 
clip early Mon night; as we move into the overnight Mon night to
early Tue timeframe, the character of the rain trends more
intermittent/showery or even drizzly for much of the interior as 
drier air starts working in aloft. Focus for steadier rains
later Mon night through Tue is along the eastern MA coast
aligned along an inverted trough, and it very slowly trends more 
intermittent in coastal eastern MA by Tue night. Additional
rains covering the Mon night to Tue night period are around a
half inch or less for much of Southern New England, but with an 
additional inch of rain still possible for coastal eastern MA.

Winds will continue out of the NE Mon night with gusts 20-25 mph 
over the interior and around 30-35 mph in gusts for the Cape and
the Islands. These will be coming around to the N and eventually 
NW with a decrease in speeds as we move into Tue, with gusts
over the Cape and Islands around 25-30 mph for Tue. That
probably will not translate to any additional wind-related
impacts, but as winds come around to NW Tue, that could
influence the coastal flood forecast for Nantucket, with Stevens 
Institute showing a continued 1 ft surge around the Tue aftn 
high tide which could support a worst-case minor coastal flood 
forecast for that high tide cycle. 

Wednesday thru Friday:

The coastal low moves far enough away into the Canadian
Maritimes but ends up slowing/stalling out as a deep upper
trough sets up over New England. As this happens, it draws down 
an unseasonably cold airmass on NW winds. 925 mb temps drop to 
around zero Celsius or even a touch colder. 

This period is generally dry with strong sfc high pressure in  
control, except for possible ocean-enhanced cloud cover and
limited chances at ocean-effect rain showers out over the Cape
and Islands. However below normal temperatures are favored to go 
along with blustery NW winds which will make it feel cooler. 
Highs on Thurs may struggle to reach the low 50s!

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent. 
Moderate - 30 to 60 percent. 
High - greater than 60 percent.

Today: High confidence in trends. Moderate confidence in 
timing.

Ceilings trend to VFR/MVFR levels all terminals between 12-16z
from south to north. Continued deterioration toward MVFR-IFR 
15-20z timeframe from south to north as wind-driven rain moves 
in. Steady increase in E-NE wind speeds to around 15 kt with 
gusts is the 20s kt range interior airports. E-NE winds near 
the coastal airports pick up to around 20-25 kt with gusts to  
35 kt by this afternoon, with gusts 35-40 kt Cape and Islands. 

Tonight through Monday: High confidence in trends but lower 
confidence on the timing.

IFR-LIFR ceilings with IFR-MVFR visibilities in steady rain. 
Rain could lighten up some for the interior airports later Mon. 
E-NE winds 15-25 kt with gusts 25-30 kt inland, and around 35-50
kt near the coasts. Strongest gusts over the Cape and Islands. 
Strong LLWS up to 60 kt possible, especially towards the Cape 
and Nantucket tonight into Monday morning.

KBOS Terminal...High confidence in TAF trends. Moderate confidence in 
timing.

KBDL Terminal...High confidence in TAF trends. Moderate confidence in 
timing.

Outlook /Monday Night through Thursday/... 

Monday Night: Mainly IFR, with local MVFR possible. Strong
winds with local gusts up to 40 kt. RA, isolated TSRA, patchy
BR.

Tuesday: MVFR/IFR conditions possible. Windy with areas of
gusts up to 30 kt. Chance RA.

Tuesday Night: Mainly VFR, with local MVFR possible. Breezy.
Chance RA.

Wednesday: VFR. Windy with local gusts up to 30 kt. Slight
chance SHRA.

Wednesday Night: VFR. Windy with local gusts up to 30 kt.
Chance SHRA.

Thursday: VFR. Strong winds with local gusts up to 40 kt.
Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

Low - less than 30 percent. 
Medium - 30 to 60 percent. 
High - greater than 60 percent.

Storm and Gale warnings continue across the coastal waters into
Monday. Expecting the strongest winds tonight, with some
improvement Monday. Visibility reduced in rain and fog into 
Mon. Seas of 15-20 ft expected across the outermost coastal 
waters, with 4-8 ft closer to shore outside of the bays and 
harbors.

Outlook /Monday Night through Thursday/... 

Monday Night: Strong winds with gusts up to 40 kt. Rough seas
up to 16 ft. Rain, chance of thunderstorms, patchy fog.
Visibility 1 nm or less.

Tuesday: Strong winds with gusts up to 35 kt. Rough seas up to
13 ft. Rain likely. Local visibility 1 to 3 nm.

Tuesday Night: Low risk for Small Craft Advisory winds with
local gusts up to 30 kt. Rough seas up to 11 ft. Chance of
rain. 

Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 30 kt. Areas of rough seas. Chance of rain showers. 

Wednesday Night: Strong winds with gusts up to 35 kt. Rough
seas up to 8 ft. Chance of rain showers. 

Thursday: Strong winds with local gusts up to 45 kt. Rough seas
up to 8 ft. Chance of rain showers. 

&&

.TIDES/COASTAL FLOODING...
The biggest impact from this coastal storm will be beach erosion as 
significant wave action impacts 3 successive tide cycles today
into Monday. 

Regarding inundation potential, a Coastal Flood Advisory
continues for this afternoon's high tide for the east coast MA 
and RI south coast. We think the greatest impacts with this 
high tide will be along the ocean-exposed RI coast from
Narragansett to Westerly, where highest surge up to 2 ft
expected with minor inundation. Other areas of minor inundation 
include Nantucket and Edgartown on Martha's Vineyard. Along the
rest of the eastern MA coast, storm surge anticipated to be
1-1.5 ft with increasing wave action leading to pockets of 
minor splashover. 

The late high tide tonight is lower, especially along the
eastern MA coast where inundation is not expected. However, 
higher surge and waves will likely lead to minor inundation at 
Nantucket, Marthas Vineyard and ocean exposed RI south coast. 

The Monday afternoon high tide is also expected to be impacted
with widespread minor inundation along the east coast and 
ocean exposed RI south coast. Storm surge of 1.5-2 ft will 
coincide with the highest seas during this time.

Coastal Flood Advisories for future tides of concern will likely 
be issued with later forecasts as we move past each high tide
where inundation is possible.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Coastal Flood Advisory from 2 PM this afternoon to 6 PM EDT 
     this evening for MAZ007-015-016-019-022>024.
     Wind Advisory from 5 PM this afternoon to 8 PM EDT Monday for 
     MAZ022.
     High Wind Warning from 5 PM this afternoon to 2 PM EDT Monday 
     for MAZ023-024.
RI...High Wind Warning from 5 PM this afternoon to 2 PM EDT Monday 
     for RIZ008.
     Coastal Flood Advisory from 11 AM this morning to 3 PM EDT 
     this afternoon for RIZ006>008.
MARINE...Gale Warning from 2 PM this afternoon to 8 PM EDT Monday for 
     ANZ230.
     Gale Warning from 11 AM this morning to 8 PM EDT Monday for 
     ANZ231-233-234-250-251-254.
     Storm Warning from 2 PM this afternoon to 8 AM EDT Monday for 
     ANZ232-235-237-255-256.
     Gale Warning from 2 PM this afternoon to 2 PM EDT Monday for 
     ANZ236.

&&

$$

SYNOPSIS...Belk/Loconto
NEAR TERM...Belk
SHORT TERM...Belk
LONG TERM...Belk/Loconto
AVIATION...Belk/Loconto
MARINE...Belk/Loconto
TIDES/COASTAL FLOODING...Belk/KJC