073
FXUS61 KBOX 220531
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
131 AM EDT Fri Aug 22 2025

.SYNOPSIS...
Strong NE winds will impact the Cape, Islands, and coastal
waters tonight. Hurricane Erin will pass well southeast of
Nantucket on Friday, with the only impacts being limited to
southeast coastal New England. High surf and dangerous rip
currents along with areas of coastal flooding and beach erosion
are anticipated on south-facing beaches. Dangerous marine
conditions from gale force wind gusts and high offshore waves,
and potential minor coastal flooding are also expected impacts.
Seasonable weather expected Friday and Saturday with breezy
conditions. Turning more unsettled for Sunday through Tuesday
with daily chances for showers and thunderstorms.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Key Messages:

* High winds tonight-Friday, likely greater than 40 mph for the
  Cape, islands, and the offshore waters. Potentially up to 50
  mph in spots.

* Hurricane Erin will continue to pass well offshore of southern
  New England tonight, but high surf, dangerous rip currents,
  coastal flooding, and beach erosion are expected to impact the
  coastline.

Lower clouds continued to move offshore to the SE this evening.
Gusty winds will only increase across southeastern New England
as Erin makes its closest approach tonight. Current forecast
appeared to be handling current conditions well, so no major
changes.

Previous Discussion...

High pressure settled over New England combined with the
approaching deep low pressure center with Erin will result in
a tightening pressure gradient. This will result in higher
magnitude northeast winds developing this evening, especially
across far SE MA where the gradient is strongest. 925mb winds
show 35-50 kts brushing across the Cape from Erin`s fairly large
wind field. Model soundings show mixing close to that level
which would support the potential for high magnitude gusts to
reach the surface. HREF ensemble guidance shows high
probabilities (70%+) for gusts over 40 mph for the outer Cape,
Nantucket, Martha`s Vineyard, and Block Island and their coastal
areas. The 75th percentile shows gusts up to 50 mph for
Nantucket and just off the outer Cape possible by early Friday
morning, so this is not out of the question. A Wind Advisory
will be in effect this evening for Cape Cod and the Islands from
5 PM Thursday through Friday afternoon.

Elsewhere, expect breezy N/NE winds overnight with temperatures
dropping into the 50s for western and central southern New England.
Breezier conditions further east will keep lows from dropping as
much with lows in the low to mid 60s.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 AM SATURDAY/...
Key Messages:

* Strong winds gradually decrease across the Cape/Islands, SE MA
  Friday-Friday night.

* High surf, dangerous rip currents, coastal flooding, and
  possible beach erosion will remain a threat Friday/Friday
  Night.

Friday:

As Hurricane Erin continues to pull away to the northeast, the
pressure gradient will slowly relax through the day Friday
resulting in a gradual downward trend in winds/gusts. However,
there will still be residual impacts to the coastal areas such
as dangerous rip currents and high surf. Minor coastal flooding
and beach erosion will continue to be a threat as well,
particularly during the high tides. More details are provided in
the coastal flooding section below. High pressure remains over
the region keeping conditions dry with temperatures in the 70s
to low around 80.

Friday Night:

Winds continue to decrease Friday night with gusts diminishing
by early Saturday morning. Minor coastal flooding will be a
threat for the evening high tides for the Islands and south
coast with splash over to minor coastal flooding possible for
areas of the east coast. High surf and dangerous rip currents
will also continue to be a threat.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Key Messages:

* High surf, dangerous rip currents, gale-force wind gusts, and
  possible beach erosion will be a concern into Saturday

* Warming trend this weekend will bring temperatures back to
  more normal values

* Unsettled conditions expected for late Sunday into Monday

High pressure briefly crosses southern New England Saturday, as
Erin moves farther east over the North Atlantic past
Newfoundland. South winds ahead of an approaching cold front
will continue our warm up. Despite weaker winds, still expecting
yet another day of rough surf and rip currents along the coasts,
although it should continue to diminish with Erin moving
farther away.

An approaching cold front from the west may slow down late
Sunday, before finally moving past our region Monday. This is
looking like our next chance for a period of showers, from late
Sunday into Monday night. Guidance continues to show a modest
potential for some thunderstorms as well, but confidence remains
low in the details as this is several days away.

After that, another large high pressure should move from the
northern Plains to the central Appalachians. Thus, anticipating
mainly dry weather with slightly below normal temperatures for
most of next week.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...

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

06z Update...

Through 12z...High confidence.

VFR. N to NE winds continue to gust over PVD 20-25 kts tonight,
with more infrequent ones possible over BOS. These have now
diminished over interior terminals. Stronger gusts up to 40 kts
for the Cape/Islands expected to remain possible.

Friday...High confidence.

VFR. N winds sustained at 10 kts across much of the region,
25 kts over the Cape and Islands in the morning. Gusts start
around 20 kts for BOS/PVD and up to 40 kts over the Cape and
Islands before overall winds diminish heading into the afternoon
and evening.

Friday Night...High confidence.

VFR. Winds become light overnight, varying between S and W.

Saturday...High confidence.

VFR. Winds from the S/SSW up to 10 kts with occasional gusts
close to 20 kts over eastern MA.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Saturday through Tuesday/...

Saturday through Saturday Night: VFR. Breezy.

Sunday: VFR. Breezy. Slight chance SHRA.

Sunday Night: Mainly VFR, with local MVFR possible. Breezy.
Chance SHRA.

Monday: Mainly VFR, with areas MVFR possible. Chance SHRA,
slight chance TSRA.

Monday Night: VFR. Chance SHRA.

Tuesday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Friday...High confidence.

Large southerly swell from Hurricane Erin will result in
increasing seas approaching 15 ft offshore by this evening. This
will continue to ramp up tonight through Friday, extending
northward across the eastern zones.

A High Surf Advisory remains in effect for southern coastal
areas, including the Cape and Islands. Waves up to 20 feet are
possible for the southern outer waters off the south coast and
off Martha`s Vineyard/Nantucket overnight, gradually decreasing
Friday. Rip currents will stay a significant concern with the
elevated surf through at least the first half of the weekend.
High Surf Advisories continue through Saturday evening.

A Gale Warning will remain in effect through Friday afternoon
with potential for gusts to 40 kts as the gradient between the
high pressure over southern New England and passing Erin will
tighten greatly. Northern outer waters could see a period of
gusts 35-40 kts tonight. Elsewhere will see Small Craft
Advisories to cover the high waves and elevated wind gusts.

Outlook /Saturday through Tuesday/...

Saturday: Winds less than 25 kt. Areas of rough seas.

Saturday Night: Winds less than 25 kt. Seas up to 5 ft.

Sunday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft.

Sunday Night through Monday: Winds less than 25 kt. Areas of
seas approaching 5 ft. Chance of rain showers, slight chance of
thunderstorms.

Monday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers.

Tuesday: Winds less than 25 kt. Seas up to 5 ft.

&&

.TIDES/COASTAL FLOODING...
Key Messages:

* Significant beach and dune erosion on south facing ocean
  beaches.

* Minor coastal flooding for Martha`s Vineyard, Nantucket, and
  MA/RI South Coast including Narragansett Bay.

The main concern is for significant beach and dune erosion along
south facing ocean beaches, especially along the south coasts of
Martha`s Vineyard and Nantucket, as well as South County (RI)
due to persistent long-period southerly swells that will peak on
Friday, before slowly subsiding Saturday. Offshore buoys are
already showing significant wave heights around 15 ft at periods
of 10-15 seconds, which is indicative of a lot of swell energy.

Breaking waves on the ocean beaches could get as high as 15 to
20 feet resulting in significant beach and dune erosion or
loss. It is tough to determine how much loss could occur but
this could rival what we normally see with stronger nor`easters
during the winter. Both of these islands and the South Coast
have already seen significant beach, dune, and shoreline loss
over the past few winters and are especially vulnerable to
further loss.

Regarding coastal flooding, we`ve added South Coastal MA/RI,
including Narragansett Bay communities, to the Coastal Flood
Advisory. The high tides of concern are Friday morning and
especially Friday evening when we should see a storm surge of 1
to 2 feet (2 feet being the higher end). Normally we`re not
concerned with the South Coast with an offshore (N/NE) wind, but
the combination of persistent southerly swell and the large
envelope of wind on the fringes of Hurricane Erin are expected
to be sufficient to produce this amount of surge.

Flooding should remain well within the Minor category with
flooding up to one foot deep confined to vulnerable shore
roads and low lying areas.

For Martha`s Vineyard and Nantucket, we expect a similar surge
of 1 to perhaps 2 feet during high tides late tonight and late
Friday night. Minor coastal flooding (up to one foot deep)
should occur in the more vulnerable sections of Nantucket
Harbor, Edgartown Harbor, Vineyard Haven, and Oak Bluffs around
high tide. Seas up to 8 feet on Nantucket Sound could bring some
debris onto coastal roads such as Seaview Avenue in Oak Bluffs
near the seawall.

Along the E MA coast including Cape Cod, no significant coastal
flooding is expected but water levels could reach Action stage
due storm surge of 1 to 1.5 ft combined with somewhat high
astronomical tides. We would be more concerned if we had
stronger pressure falls and higher surge ahead of the hurricane,
or higher seas into the eastern MA waters, which are all
unlikely given the track well offshore.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Surf Advisory until 8 PM EDT Saturday for MAZ007-019>024.
     Coastal Flood Advisory from 6 AM to 10 AM EDT this morning for
     MAZ020.
     Coastal Flood Advisory from 6 PM to 10 PM EDT this evening for
     MAZ020.
     Wind Advisory until 2 PM EDT this afternoon for MAZ022>024.
     Coastal Flood Advisory until 2 AM EDT early this morning for
     MAZ023-024.
     Coastal Flood Advisory from 10 PM this evening to 2 AM EDT
     Saturday for MAZ023-024.
RI...High Surf Advisory until 8 PM EDT Saturday for RIZ006>008.
     Coastal Flood Advisory from 6 AM to 10 AM EDT this morning for
     RIZ002-004>008.
     Coastal Flood Advisory from 6 PM to 10 PM EDT this evening for
     RIZ002-004>008.
MARINE...Small Craft Advisory until 2 PM EDT this afternoon for ANZ230-
     236.
     Gale Warning until 8 PM EDT this evening for ANZ231-232-250-
     254-255.
     Gale Warning until 2 PM EDT this afternoon for ANZ233>235-237-
     256.
     Small Craft Advisory until 8 PM EDT this evening for ANZ251.

&&

$$

SYNOPSIS...Belk/Mensch
NEAR TERM...Belk/Mensch
SHORT TERM...Mensch
LONG TERM...Belk
AVIATION...Belk/Hrencecin/FT
MARINE...Belk/Mensch
TIDES/COASTAL FLOODING...Mensch/JWD