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929
FXUS61 KBOX 201135
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
735 AM EDT Fri Sep 20 2024

.SYNOPSIS...
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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.
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&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Main change was to try to refine the western extent of the
precipitation shield. The last few runs of the HRRR matched up
well with regional radar data. So used that as a basis for these
tweaks. Otherwise, overall forecast was 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.
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&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
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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.
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&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...

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 /12Z FRIDAY THROUGH TUESDAY/...
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Forecast Confidence Levels:

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

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
will increase this afternoon with 40+ knot gusts possible at
Nantucket and 30 to 35 knot gusts possible over The Cape. Wind
gusts should be more modest at the remaining terminals in the 20
to 25 knot range. Gusts at Nantucket peak around 18Z before
gradually falling to the 30 to 35 knot range by 00Z tonight.
Expect continued shower activity over The Cape/Islands with some
stray showers possible at the eastern terminals. BDL,BAF,ORH
should stay dry today.

Tonight...High confidence in flight categories, lower confidence
in precipitation potential

Little change to flight categories overnight with more IFR/MVFR
ceilings and -SHRA over The Cape/Islands. Northeast winds remain
somewhat elevated from 10 to 20 knots with gusts from 20 to 30
knots. Strongest winds over The Cape/Islands.

Tomorrow

Interior terminals trend to VFR ceilings by 18Z. Lower ceilings
linger at BOS,PVD, and Cape/Island Terminals (MVFR/IFR ~ 1000
feet) with slow improvements by 00Z tomorrow evening.

BOS TAF...High Confidence

Teetering between MVFR/IFR for much of the next 36 hours. Steady
northeast winds with gusts from 20 to 25 knots. Should see
improvements to VFR by Saturday afternoon/evening.

BDL TAF... High Confidence


Outlook /Saturday Night through Tuesday/...

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.
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&&

.MARINE...
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Forecaster Confidence Levels:

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

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 Tuesday/...

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.
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&&

.TIDES/COASTAL FLOODING...
Coastal Flood Watch has been converted to a Coastal Flood
Advisory. Latest suite of guidance has trended toward lower
surge values for eastern MA as of this evening. If we consult
 the latest 90th percentile PETSS model run, most locations are
falling short of moderate flood stage. While minor coastal
flooding will be more common, some pockets of moderate coastal
flooding will be possible at locations recently impacted by
erosion or locations that are impacted by the elevated wave
heights.

Since confidence is high that steady northeast winds will
persist through at least Saturday afternoon, we`ve included the
advisory to cover the Friday night and Saturday afternoon high
tide cycles. Astronomical high tides will be substantially
lower tonight compared to this afternoon and Saturday afternoon,
but several tide gages in eastern MA are forecast to reach or
fall just short of minor flood stage overnight. Even if
locations fall short of minor flood stage during tonight`s high
tide, we still expect at least pockets of minor coastal flooding
due to the elevated wave action.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None.
MA...High Surf Advisory until 7 PM EDT this evening for MAZ007-019-
     022-024.
     Coastal Flood Advisory from 11 AM this morning to 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.
     High Risk for Rip Currents until 7 PM EDT this evening for MAZ023.
RI...High Risk for Rip Currents until 7 PM EDT this evening for
     RIZ006>008.
MARINE...Small Craft Advisory until 8 AM EDT Saturday for ANZ230-231-
     233>237-250-251.
     Gale Warning until 8 PM EDT this evening for ANZ232-254>256.
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&&

$$

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