228
FXUS61 KBOX 192342
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
742 PM EDT Thu Sep 19 2024

.SYNOPSIS...
Rain continues for the Cape and Islands through tonight into
tomorrow, with chances to the northwest decreasing going into
the weekend. Gusty northeast winds will keep temperatures near
or below normal for much of the region tomorrow into the
weekend. Next chance of rain comes around mid week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
730pm update...

made a few minor adjustments to the PoP, weather and wind
aspect of the forecast for tonight based on current trends and
most recent hi-res model data. Models are struggling with the
overall coverage of the precip, and although they were
indicating there would be some local maximum of rainfall
somewhere near the Cape, they didn`t get the location. Radar
estimates of 2 to 3+" of rain has fallen since noon, but the
axis was over the water just south of the Cape and north of the
Islands. Still about 1.5" has fallen at MVY and ACK. No flood
concerns however given that it`s fallen over a relatively long
period of time. Mesonet obs have indicated some gusts of
40-45mph across the Cape and Islands. Did increase the wind
forecast a little based on those obs. Model soundings show the
gusty winds will continue overnight, and although a rogue gust
to 50 mph can`t be ruled out, it`s not enough to rate the need
for any sort of wind advisory. Of course over the water, the
winds are more impactful, thus the Gale Warnings we have.
Meanwhile once you get west of about I-95, not much is going on.
Should be enough clear skies out west that some patchy fog is
possible in the CT River Valley, especially in sheltered areas,
late tonight.


Previous Discussion...

A stalled low looks to remain off the coast of southern New England
due to a blocking high to the north. Unsettled weather will continue
for the Cape and Islands through Friday morning. Cloudy conditions
expected to continue through tonight for the rest of eastern MA and
RI into parts of central MA, but clearer conditions out to the west.
Temperatures tonight expected to be primarily in the lower 60s and
upper 50s.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Tomorrow and Tomorrow Night

The stalled low looks to stick around through the weekend,
continuing the trend of cloudy skies and chances for rain for
eastern MA. Pressure gradient between the blocking high and the low
in question will encourage NE gusts up to 35 mph (30 knots) down to
the Cape and Islands, reaching up to 25 mph near Boston. Highs
tomorrow look to remain in the 60s for much of eastern MA into RI
with persistent cloud cover and showers throughout the day, but
confidence in consistent showers northwest of the Cape remains a bit
low. Highs in the CT River Valley are currently expected to be in
the mid 70s. However, considering today`s highs ended up a bit
higher than forecast, it could reach the upper 70s to lower 80s.
This will depend on cloud cover, which is a bit uncertain at this
time. Chances for showers continue Friday night going into Saturday
morning and strong NE flow is expected to continue.

&&

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

* Some rain and breezy conditions Saturday
* Dry to start next week, becoming unsettled mid-week


No huge changes with the 12z suite of model guidance with respect
the long term forecast period, though we have more consistency with
the evolution of the slow moving coastal low Saturday and Sunday
which gives increasing confidence for this part of the forecast. The
low center Saturday morning will be just southeast of the 40n/70w
benchmark and be slowly drifting south. Models all show deep
moisture across the eastern half of southern New England, so that is
the area with the highest chance of rainfall. The PoP gradient might
need to be tightened up in later forecasts as it could end up being
totally dry across northern CT and the Worcester area westward.
Certainly a damp and breezy day close to the east coast with NE
winds gusting over 30 mph at times. Kept with the model blend for
QPF, so perhaps another 1/4 to 1/2" of rain during the day.  Low
pressure moves further away Saturday night and Sunday morning, we
will see improving conditions from northwest to southeast. Still
have some lingering PoPs (30% or so) for far SE MA, Cape and Islands
for Sunday morning. That could end up being pessimistic. 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. Further inland looks to feature a good amount
of sun.

High confidence that a ridge of high pressure will re-establish
dominance in our weather for the second half of Sunday into Tuesday.
Beyond that, confidence starts to decrease again as an upper trough
tries to move in from the west. How quickly that trough can break
down the ridge is still up for grabs in the models, given some
significant differences between models and model runs with regard to
the amplitude and timing of that trough.  For now stuck with NBM
guidance and have 30-40% PoPs from late Wednesday through Thursday.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:

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

00z TAF update

Tonight... Overall moderate confidence.

Big differences in weather conditions will continue overnight.
IFR to LIFR conditions across the Cape and Islands since they
are closer to the coastal low. As you go west, conditions
improve to MVFR and then VFR. Gusty surface NE winds, especially
near the coast. LLWS also in play with 50kts of wind as low as
2000ft down across the Cape. Could see some patchy fog and
stratus develop after 06z in parts of the CT River Valley.

Friday... Moderate Confidence

More MVFR/IFR ceilings and showers at the eastern terminals.
Northeast winds increase to 15 to 20 knots at coastal terminals
and 10 to 15 knots across the interior. Cape/Islands terminals
could see gusts 30 to 40 knots. For the western area (BDL, BAF) After
any stratus or patchy fog early in the morning, expecting VFR
conditions.

Friday Night... Moderate Confidence

MVFR/IFR ceilings look to persist. NE winds continue at 15 to 20
knots, gusting from 20 to 35 knots with the strongest gusts out
towards ACK and the Cape.

KBOS TAF...Moderate confidence. Lots of MVFR/IFR ceilings near
BOS this evening, so any VFR should be temporary. With continued
NE flow, should see IFR ceilings after 03z. Any rain will be
light intensity overnight. Don`t expect much change for most of
Friday, so kept MVFR conditions all day. Uncertainty in how much
rain will make it into the area, so lots of VCSH. NE winds
should gust 25kt for the day.

KBDL TAF...Moderate confidence, primarily in regard to whether
any MVFR ceilings will develop after roughly 09z. If they do
occur, VFR conditions should return by 14z. Should see winds
gust near 20kt.

Outlook /Saturday through Tuesday/...

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

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

Sunday: Mainly VFR, with local MVFR possible. Windy with local
gusts up to 30 kt. Slight chance SHRA.

Sunday Night through Monday: VFR. Breezy.

Monday Night: Mainly VFR, with local MVFR possible. Breezy.

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.

Tonight through Friday Night

Dangerous Marine conditions over the next 24 to 48 hours as an area
of low pressure stalls south of the coastal waters. Confidence has
increased enough to issue Gale Warnings for the southern offshore
zones and Nantucket Sound. Wind gusts in excess of 35-40knots are
likely overnight, lasting into Saturday evening. Gales may need to
be expanded further north into Cape Cod Bay and the Northern off
shore zone, but confidence was not high enough to include in this
update. As for the rest of the near shore waters, winds will still
be gusting 25-35 knots through Saturday night including Narragansett
Bay and Boston Harbor. Seas will continue to build overnight to 8-12
feet in the open waters. High surf will cause dangerous conditions
near the coasts as well with large breaking waves and strong rip
currents. Mariners and swimmers should take extreme caution if
venturing out to beaches or jetties tomorrow.

Outlook /Saturday through Tuesday/...

Saturday: Strong winds with gusts up to 30 kt. Rough seas up to
14 ft. Rain showers likely.

Saturday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 25 kt. Rough seas up to 11 ft. Chance of rain
showers.

Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Rough seas up to 11 ft. Chance of rain showers.

Sunday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Rough seas up to 11 ft.

Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Rough seas up to 11 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...
The persistent northeast winds will produce a surge of roughly
1.5 to 2 feet from late tonight into Saturday based upon
guidance from the Stevens Institute and P-ETSS. Given the
monthly high astronomical high tides, the combination means we
will be reaching minor flood level along the east coast of
Massachusetts over several high tide cycles. Right now it looks
like the highest water levels will be experienced with the
Friday afternoon high tide, and our current forecast has water
levels topping out just a few inches below moderate flood stage.
With the extended period of northeast winds, this will also
build up rough seas and rather significant wave heights over 10
feet offshore. The combination of that wave energy could be
enough to result in impacts that would normally be associated
with higher water levels. That would especially be the case for
those coastal locations (like Plum Island) that are very
susceptible to high water levels. We have issued a Coastal Flood
Watch for the Friday high tide. We will be fine tuning the
forecast overnight and convert that watch to either a Coastal
Flood Advisory or Coastal Flood Warning (if we expect more
significant impacts).

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Surf Advisory from 7 AM to 7 PM EDT Friday for MAZ007-019-
     022-024.
     Coastal Flood Watch from Friday morning through Friday
     afternoon for MAZ007-015-016-019-022>024.
     High Risk for Rip Currents through Friday evening for MAZ023.
RI...High Risk for Rip Currents through Friday evening for RIZ006>008.
MARINE...Small Craft Advisory from 2 AM Friday to 8 AM EDT Saturday for
     ANZ230-236.
     Small Craft Advisory until 8 AM EDT Saturday for ANZ231-
     233>235-237-250-251.
     Gale Warning until 8 PM EDT Friday for ANZ232-254>256.

&&

$$

SYNOPSIS...Hrencecin
NEAR TERM...Hrencecin/Nash
SHORT TERM...Hrencecin
LONG TERM...Nash
AVIATION...Hrencecin/Nash
MARINE...Hrencecin/KP
TIDES/COASTAL FLOODING...Nash/Nocera