506
FXUS61 KBOX 201851
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
251 PM EDT Fri Sep 20 2024

.SYNOPSIS...
Northeast winds strengthen along the east coast, Cape, and
Islands this afternoon with some 30 to 40 mph gusts possible.
Rain continues at times for the Cape and Islands into Saturday
night. Rainfall chances decrease farther to the northwest into
this weekend. Gusty northeast winds will keep temperatures near
or below normal for much of our region into this weekend. The
next chance of rain after this weekend comes around the middle
of next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
10 AM Update:

Not much change from the last update. Lowered winds slightly
based on observations, but gusts still look to reach close to 40
knots down towards the Cape and Islands. Continued to keep the
precipitation shield in the east. Otherwise, the forecast looks
to be on track.

Previous Discussion...

Pressure gradient between an area of low-pressure off the south
coast and a high pressure over Canada strengthens today allowing
for an uptick in the persistent northeast winds we`ve
experienced over the last 24 hours or so. Sustained winds will
range from 10 mph across the interior to 20 to 25 mph along the
east coast Cape and Islands. Winds will be gusty with some 30 to
40 mph wind gusts on The Cape and Islands. Shower activity
should again stay confined to southeast MA and The Cape.
Extensive cloud cover will support slightly cooler temps for
eastern MA and RI today in the mid to upper 60s. Not expecting
temperatures to be as warm in the CT River Valley as yesterday,
but still warmer than the areas to the east with highs peaking
in the low to mid 70s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
The synoptic weather pattern remains largely unchanged through
Saturday with the area of low-pressure off the south coast
continuing to meander south of Nantucket. The pressure gradient
slackens a bit overnight bringing and end to the 30 to 40 mph
wind gusts, but we should continue to see gusts in the 20 to 30
mph range. Shower activity may penetrate a bit farther inland
tomorrow, but again we expect the southeast MA, Cape, and
Islands to see the most rainfall (0.5 to 1 inches tonight
through tomorrow). High temps take a dip again tomorrow
afternoon in the low to mid 60s east of I- 495 and upper 60s to
low 70s in the CT River Valley.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Key Points:

* Becoming drier from NW to SE Sunday
* Dry to start next week, becoming unsettled mid-week
* Near to slightly below normal temperatures for this portion of the
  forecast

Latest guidance suite continued to converge towards a solution with
the timing of a stagnant low pressure SE of our region finally
moving farther offshore as a high pressure moves south from eastern
Canada. Drier conditions develop from NW to SE Saturday night into
Sunday, with the last of the showers expected to move offshore of
the Cape and islands by late Sunday afternoon. It`s possible this
timing may change with later forecasts. Some question as to how long
low level moisture hangs around across southeastern sections, so
that area might end up staying cloudy most of the day Sunday.
Farther inland looks to feature a good amount of sunshine.
Gusty NE winds also start to diminish Saturday night into Sunday.

High confidence that high pressure will re-establish dominance of
our weather Sunday night into Tuesday. Confidence diminishes towards
mid week, as the forecast will hinge on how quickly this high
pressure departs, and opens the door for a low pressure to move into
the Great Lakes towards mid week. Stayed close to the latest
NationalBlend guidance for precipitation chances since it is an
ensemble-based solution.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

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

Rest of Today...High Confidence

MVFR borderline IFR conditions persist at the same terminals
through tonight as area of low-pressure supporting northeast
winds and lower ceilings remains somewhat stationary. Wind gusts
expected to reach up to 40 knots over Nantucket and around 35
knots over the Cape. Gusts elsewhere in eastern MA and RI have
been ranging from 20 to 30 knots today, which is also expected
to continue for the rest of today. Showers are expected to
continue for Cape and Islands into tonight with some rain moving
into BOS within the next hour or so, but rain there should not
stick around into tonight. Stray showers around other eastern
terminals cannot be ruled out. BDL, BAF, ORH should remain dry
for the rest of today.

Tonight...High Confidence in flight categories, moderate
confidence in precipitation potential

IFR/MVFR ceilings expected to continue overnight with -SHRA to
SHRA over the Cape and Islands. NE winds expected to remain at
around 10 to 15 knots for most of the terminals with the
exception of Nantucket, which is expected to be around 20 to 25
knots overnight. Gusts expected to be from 20 to 35 knots, with
the strongest towards the Cape and Islands.

Tomorrow...Moderate Confidence

Interior terminals expected to be MVFR for most of the day.
Lower ceilings linger at BOS, PVD, and Cape/Island terminals
(MVFR/IFR ~ 1000 feet), slowly improving from the north going
into 00z tomorrow evening.

Tomorrow Night...Moderate Confidence

Gradual improvement to VFR ceilings from the north progressing
south. MVFR expected to linger for RI, Cape/Islands, and partly
BOS moving into Sun AM.

BOS TAF...High Confidence

Remaining between MVFR and IFR tonight into tomorrow. NE winds
continue, gusting up to 30 knots tonight before mostly remaining
around 25 knots tomorrow. Should see improvements to VFR by
Saturday evening.

BDL TAF... High Confidence

VFR for the rest of today before going to MVFR overnight. VFR
ceilings expected to return for Saturday.

Outlook /Saturday Night through Wednesday/...

Saturday Night: Mainly VFR, with local MVFR possible. Windy
with local gusts up to 30 kt. Chance SHRA.

Sunday: Mainly VFR, with local MVFR possible. Breezy. Slight
chance SHRA.

Sunday Night through Monday: VFR. Breezy.

Monday Night: Mainly VFR, with local MVFR possible.

Tuesday: Mainly VFR, with areas MVFR possible.

&&

.MARINE...
Forecaster Confidence Levels:

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

10 AM Update:

Expanded Gale Warning to include northern coastal waters and
into southern coastal waters, excluding Block Island.

Previous discussion:

Today through Saturday

Dangerous marine conditions through Saturday as an area of low
pressure south Nantucket continues to produce a persistent fetch
over the coastal waters. Persistent northeast winds will result
in building seas and significant wave heights from 10 to 13 feet
off the coast of Wellfleet. The eastern waters may see wave
heights from 7 to 10 feet over the near-shore marine zones. For
the south coastal waters the near-shore zones will be in the 4
to 6 foot range the outer marine zones in the 6 to foot range.

Northeast winds strengthen to gale force over the south coastal
waters today with some gusts up to 40 knots possible. A Gale
Warning remains in effect through this evening. Winds weaken
somewhat tonight into tomorrow but still remain elevated with
gusts up to 30 knots. Small Craft Advisories will likely be
needed through the weekend.

Outlook /Saturday Night through Wednesday/...

Saturday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Rough seas up to 10 ft. Chance of rain
showers.

Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Rough seas up to 10 ft. Slight chance of rain
showers.

Sunday Night through Monday: Winds less than 25 kt. Rough seas
up to 10 ft.

Monday Night: Winds less than 25 kt. Rough seas up to 9 ft.

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

&&

.TIDES/COASTAL FLOODING...

Coastal Flood Advisories have been extended for coastal eastern
MA including the Islands right through the weekend. Offshore
low pressure will continue to generate a long duration period of
NE wind gusts of 25 to 30 knots through the weekend. This will
generally result in a 1 to 1.5+ foot storm surge along our ocean
exposed east facing beaches. This long duration NE flow will
allow for 7 to 13 foot seas across our eastern open waters and
guidance is often underdone in these setups. This combined with
high astro tides will result in widespread minor coastal
flooding during the Saturday and Sunday midday high tide
cycles...with Saturday/s being the one of greatest concern given
the higher astro tide. There also will be pockets of scattered
minor coastal flooding with the overnight/very early Saturday
morning high tide...but less widespread than the expected midday
cycles because of lower astro tides.

In addition...because this is a long duration event there is
also concern for beach erosion. This is especially true for
areas that were hard hit by the storms of last winter.

Lastly...we have gone with High Surf Advisories for all ocean
exposed beaches along both coasts given the rough seas offshore.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Coastal Flood Advisory until 6 PM EDT this evening for MAZ007-
     015-016-019-022>024.
     Coastal Flood Advisory from 11 PM this evening to 5 AM EDT
     Saturday for MAZ007-015-016-019-022>024.
     Coastal Flood Advisory from 11 AM to 5 PM EDT Saturday for
     MAZ007-015-016-019-022>024.
     Coastal Flood Advisory from noon to 6 PM EDT Sunday for MAZ007-
     015-016-019-022>024.
     High Surf Advisory until 7 PM EDT Saturday for MAZ007-019-020-
     022>024.
RI...High Surf Advisory until 7 PM EDT Saturday for RIZ006>008.
MARINE...Small Craft Advisory until 8 AM EDT Saturday for ANZ230-236-
     237.
     Gale Warning until 8 AM EDT Saturday for ANZ231>235-250-251-
     254>256.

&&

$$

SYNOPSIS...Belk/RM
NEAR TERM...Belk/Hrencecin/RM
SHORT TERM...RM
LONG TERM...Belk/Nash
AVIATION...Hrencecin
MARINE...Belk/Hrencecin/RM
TIDES/COASTAL FLOODING...Frank