112
FXUS61 KBOX 181118
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
718 AM EDT Mon Aug 18 2025

.SYNOPSIS...
Canadian high pressure will bring below normal temperatures/low
humidity to the region for much of the week. Temperatures will then
moderate to more seasonable levels by Friday into the weekend with
the next main chance of showers not until Sunday. The biggest
concern this week though will be high surf and dangerous rip
currents from powerful Hurricane Erin in the Atlantic.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Key Messages...

* Much cooler & less humid today with highs mainly in the 70s
* NE winds gust 20-30 mph along the coast and perhaps 35 mph Cape/ACK

Details...

Today...

Large high pressure across Quebec noses down in the wake of last
evening/s cold frontal passage. The result is a much cooler/much
less humid airmass that will be working into the region. Despite
plenty of sunshine today...high temperatures will be held in the 70s
across the region along with a stiff NE breeze especially along the
coast. In fact...high temperatures along much of the eastern MA
coast/Cape and Nantucket will be held in the upper 60s to lower 70s
with a gusty NE wind. Dewpoints will drop into the 40s so very
comfortable humidity as well. The NE wind gusts of 20 to 30 mph near
the coast today and perhaps briefly up to 35 mph across parts of the
Cape/Nantucket. Those winds may bring in a touch of an early fall
feel. Overall...a beautiful day with low humidity bringing ideal
weather for outdoor activities.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
Key Messages...

* Unseasonably cool tonight with overnight lows in the 40s & 50s
* Another beautiful day on Tue with low humidity & highs in the 70s

Details...

Tonight...

High pressure continuing to nose down from Quebec will result in
diminishing winds tonight. This coupled with mainly clear skies and
a very dry airmass for August standards will bring an unseasonably
cool night to the region. Lows should bottom out in the 40s across
many locations outside the urban centers. And even the urban centers
will see overnight lows bottom out in the lower to middle 50s.

Tuesday...

High pressure over Quebec will bring us another gorgeous day on
Tuesday. Plenty of sunshine, comfortable humidity with highs in the
70s. Less wind than today especially along the coast...so it will
feel a bit milder in the afternoon.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Key Messages...

* Beautiful Tue-Thu...highs mainly in the 70s to near 80
* High Surf/Dangerous Rip Currents from Erin TUe PM through Fri
* A bit warmer Fri/Sat/Sun with highs upper 70s & 80s
* Prolonged stretch of dry weather with risk of showers not til Sun

Details...

High pressure over Quebec slowly shifts further east into the
Maritimes by the end of the week. This high will keep our weather
quiet/mainly dry with temperatures below normal for this time of
year. Highs will mainly be in the 70s to near 80 Tue through Thu.
Temperatures will moderate a bit Friday into the weekend as the next
shortwave trough approaches...so expecting highs to recover into the
upper 70s and 80s.

A prolonged stretch of dry weather this week given high pressure/s
influence to our north. We can not rule out a spot shower or two
with some mid level energy working across the region Wed...but
nothing more than that. The next main chance for showers will likely
not arrive until next Sunday ahead of an approaching cold front.

The main concern this week though is for High Surf and Dangerous rip
currents to ocean exposed beaches Tue PM through Fri. Major
Hurricane Erin will begin to turn more N then NE and not directly
impact southern New England. That being said...large southerly swell
will result in high surf and dangerous rip currents. This is
particularly true across our south facing beaches with the large
southerly swell. Given the dry/nice weather and the fact that ocean
water temperatures are at their climatological warmest there are
likely to be a lot of beachgoers/swimmers. A High Surf Advisory will
need to be issued shortly as early as for Tue afternoon and perhaps
continuing through Friday. Ocean exposed beaches especially those
that our south facing are at a particular high risk for High
Surf/Dangerous rip currents.

&&

.AVIATION /11Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

12z TAF Update...

Today...High confidence.

Pockets of MVFR ceilings linger through 13z-14z, otherwise will
have VFR ceilings through today. Breezy, NE winds 7 to 15 knots
with gusting 25 to 30 knots, especially near the coast.

Tonight...High confidence.

VFR. Winds diminish and become light and variable.

Tuesday...High confidence.

VFR. ESE winds 5 to 10 knots.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday Night through Friday/...

Tuesday Night: VFR.

Wednesday through Wednesday Night: VFR. Slight chance SHRA.

Thursday: VFR. Breezy. Slight chance SHRA.

Thursday Night: VFR. Windy with local gusts up to 30 kt.

Friday: VFR. Windy with gusts up to 30 kt.

&&

.MARINE...
Forecaster Confidence Levels...

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

Today through Tuesday...High confidence.

Large high pressure over Quebec combined with a cooler airmass will
be well mixed over the waters today. This will result in NE wind
gusts of 20 to 30 knots and choppy seas...so small craft headlines
are posted for all our waters. The pressure gradient weakens tonight
and Tue allowing winds to diminish below small craft advisory
thresholds. However...large southerly swell from major hurricane
Erin will result in seas at or above 5 feet for portions of our
southern waters overnight into Tuesday. In fact...they will be
ramping up further into mid-week so small craft headlines will
remain posted for our southern waters for an extended period of time.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Wednesday: Winds less than 25 kt. Areas
of rough seas.

Wednesday Night: Winds less than 25 kt. Areas of rough seas.
Slight chance of rain showers.

Thursday: Moderate risk for Small Craft Advisory winds with
areas of gusts up to 30 kt. Rough seas up to 16 ft. Slight
chance of rain showers.

Thursday Night: Strong winds with gusts up to 35 kt. Rough seas
up to 16 ft. Slight chance of rain showers.

Friday: Low risk for gale force winds with gusts up to 35 kt.
Rough seas up to 11 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ230-
     250-251.
     Small Craft Advisory until 4 PM EDT this afternoon for
     ANZ231>235-237.
     Small Craft Advisory until 1 PM EDT this afternoon for ANZ236.
     Small Craft Advisory until 8 AM EDT Thursday for ANZ254>256.

&&

$$

SYNOPSIS...Frank
NEAR TERM...Frank
SHORT TERM...Frank
LONG TERM...Frank
AVIATION...Frank/Dooley
MARINE...Frank