Small Craft Advisory 48, NWS Boston/Norton, MA

Area Forecast Discussion
National Weather Service Boston/Norton MA
200 PM EDT Sat Apr 18 2026

.WHAT HAS CHANGED...
More guidance starting to indicate the chance for some scattered
showers Monday due to the presence of a possible weak low
pressure.

&&

.KEY MESSAGES...

- Cool, cloudy, and mainly dry today. Splashover possible for
  the east coast during the Sunday morning high tide.

- Strong cold front brings a round of widespread showers
  Sunday, leaves colder temperatures and drier conditions in its
  wake.

- Cooler than normal Monday. While generally dry weather is
  expected, a weak area of low pressure could bring clouds and
  scattered showers.

- Seasonable temperatures Wednesday, though another cold front
  arrives and temperatures fall once more for the second half of
  the week.

&&

.DISCUSSION...
KEY MESSAGE 1...Cool, cloudy, and mainly dry today. Splashover
possible for the east coast during the Sunday morning high tide.

Low pressure remains just offshore today, maintaining onshore flow
and advecting in marine stratus. This stratus has already started to
make its way into southern New England and will continue to do so
from east to west through the day today. With persistent cloud cover
and NE winds, temperatures today will be cooler, maxing out in the
upper 40s and low 50s closer to the eastern coast. The interior
can expect only slightly warmer highs compared to the east,
reaching the low 60s in the CT Valley and the upper 50s
elsewhere. Ridging overhead will help keep the region dry as
well.

There is a chance that spots along the eastern coastline could see
some splashover or minor coastal flooding during the Sunday morning
high tide. High astronomical tides combined with persistent E/NE
winds elevate this risk during this period. Will continue to monitor
over the next forecast cycle and issue headlines if needed.

KEY MESSAGE 2...Strong cold front brings a round of widespread
showers Sunday, leaves colder temperatures and drier conditions in
its wake.

An incoming strong cold front Sunday will likely bring a round of
widespread showers. This front is part of a potent upper level
trough that will be shifting east from the Great Lakes Sunday into
Monday. Ahead of this front and trough, PWAT values climb to
anomalously higher values around 1.25"-1.30" Sunday morning after
dropping mostly 0.5" during the day today. As the front pushes
through, the forcing from it interacting with this elevated moisture
will lead to widespread showers Sunday. High-res guidance still has
hints of MUCAPE around 500 J/kg during the day that could be a
factor in some embedded thunderstorms with these showers. Some
downpours cannot be ruled out as well, especially in any isolated
thunderstorms that may develop. Despite continued rain today, flash
flooding is not a big concern. At most, we could expect some poor
drainage areas to see some ponding.

Colder and drier air is left in the front's wake, reinforced by
breezy W to NW winds starting Sunday afternoon. Gusts to 25 MPH are
a possibility post-front. Showers may end with a mix of some snow in
the higher elevations of the Berkshires Sunday evening as this
colder airmass takes hold, but any accumulations are not expected at
this time. Lows Sunday night will likely fall below freezing outside
of urban areas, while the cities can expect lows in the mid to upper
30s.

KEY MESSAGE 3...Cooler than normal Monday. While generally dry
weather is expected, a weak area of low pressure could bring clouds
and scattered showers.

The upper level trough settles overhead Monday, and with it,
unseasonably cold air moves in in the midst of CAA. 925 mb
temperatures fall below 0C and may even dip to -5C by Monday
morning. Breezy W to NW winds continue, and highs may not climb out
of the upper 40s and low 50s Monday afternoon. These winds will
start to diminish as high pressure approaches from the west, and
lows Monday night may fall into the 20s for much of southern New
England. Even with approaching high pressure, more guidance has
started to latch onto a weak low pressure moving into the region
Monday that could bring increased clouds and scattered showers.
Ensemble members (and deterministic models) from different guidance
suites have started to indicate some showers Monday as a result of
this weak low, though confidence in this feature developing is still
relatively low. Outside of this, incoming high pressure should keep
the region dry for much of the start of the week before it exits
heading into Wednesday.

KEY MESSAGE 4...Seasonable temperatures Wednesday, though another
cold front arrives and temperatures fall once more for the second
half of the week.

Some showers are a possibility once again heading into Wednesday
morning as another shortwave approaches, but more seasonable
temperatures make a return as the trough early in the week exits.
925 mb temperatures recover to around 5C with SW flow returning,
supporting more seasonable highs in the upper 50s/low 60s. NW flow
makes a return towards Thursday/Friday in the wake of another front
passing through sometime late Wednesday, and high pressure builds
back in as ridging approaches, which should keep the region dry yet
chilly.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

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

18z TAF Update:

Through 00z: Moderate Confidence.

MVFR-IFR ceilings and VFR-MVFR visibilities. E winds 8-15 knots. Few
breaks in the clouds across NE MA to VFR through 00z.

Tonight: Moderate Confidence.

Ceilings deteriorate down to IFR-LIFR levels. Fog return, bringing
visibilities down to IFR and possibly LIFR across the Cape and
Islands. NE winds veer around to SE/S 5-10 knots.

Sunday: Moderate Confidence.

IFR-LIFR during the early morning hours with areas of mist or
drizzle. Locally dense fog possible across Cape Cod and Islands
through mid-morning. Cold front brings widespread RA from west to
east, 12z-15z, SW winds around 10 knots, becoming W/NW and
increasing to 10-15 knots with gusts 20-25 knots post-frontal
passage.

Sunday Night: High Confidence.

VFR. Diminishing wind gusts. W wind 5-10 knots.

KBOS Terminal... Moderate Confidence in TAF.

Brief MVFR conditions this afternoon, trending to IFR by 21z as a
bank of stratus and fog returns. Pockets of DZ overnight into early
Sunday morning. RA arrives 14z-16z, LLWS ahead of the cold front
too. Wind shifts to the W/NW by 18z-20z with gusts 20-25 knots.
Becoming VFR late in the day Sunday.

KBDL Terminal... Moderate Confidence in TAF.

Outlook /Sunday Night through Thursday/...

Sunday Night: VFR. Breezy. Chance RA.

Monday: VFR. Breezy. Slight chance SHRA.

Monday Night through Tuesday: VFR.

Tuesday Night through Wednesday: VFR. Breezy. Slight chance
SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

High confidence through the weekend.

Seas 2-4 ft and winds less than 25 kts out of northeast today.
Winds shift SE to S tonight and should remain less than 25 kts.

Passage of stronger cold front Sun may bring SCA conditions to
at least outer waters Sun into Mon. Wind gusts may locally
approach 25 kt late Sunday in the outer waters. Winds shift NW
following this frontal passage.

Outlook /Sunday Night through Thursday/...

Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Rain likely.

Monday: Winds less than 25 kt. Seas locally approaching 5 ft.

Monday Night through Tuesday: Winds less than 25 kt.

Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers.

Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 11 AM to 6 PM EDT Sunday for ANZ235-
     237.
     Small Craft Advisory from 11 AM to 11 PM EDT Sunday for
     ANZ254>256.

&&

DISCUSSION...Hrencecin
AVIATION...Dooley/McMinn
MARINE...Hrencecin