993
FXUS61 KBOX 182000
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
400 PM EDT Wed Sep 18 2024

.SYNOPSIS...

Rain chances increase from south to north tonight into tomorrow,
with the best chances across the Cape and Islands decreasing
significantly to the north and west.  Gusty northeast winds will
keep temperatures near or below normal for much of the region
tomorrow into the weekend.

&&

.NEAR TERM /THROUGH THURSDAY/...

An area of low pressure makes its way north and eventually stalls
somewhere south of Cape Cod and the Islands. Guidance remains in
disagreement on how far south the low stalls, making the QPF
forecast somewhat uncertain for being 12 to 24 hours out. The HREF
ensemble has a large spread between the 25th and 75 percentiles due
to the unknowns on how far south the low stalls. The 25th percentile
QPF from the HREF through 8 am Friday shows 1.75 inches for the Cape
and Islands and 0.5 inches for the I-95 corridor from Boston to
Providence. The 75th percentile shows 3-3.5 inches for the Cape and
Islands, with 1.0-1.5 inches from Boston to Providence. Further
west, rain amounts drop off very quickly due to dry air on the NW
side of the low. There may not even be measurable QPF north and west
of Worcester.  Overall, any rain that falls will be beneficial and
likely not cause flooding impacts, given the antecedent dry
conditions. Regardless of the rain, tonight and tomorrow will
feature overcast skies with a blustery northeast wind. Temperatures
tonight stay warmer in the upper 50s to low 60s with an abundance of
cloud cover and increasing winds. With the onshore flow tomorrow,
high temps in eastern MA and RI will struggle to top 70F, while in
western MA and CT, temps will reach the mid-70s.

&&

.SHORT TERM /THURSDAY NIGHT/...

Uncertainty continues to remain high into Friday night as guidance
struggles with where the low stalls south of the region. Rain should
continue through Friday night with the best chances over the Cape
and Islands, but how far inland rain continues remains a big
question mark.  Low clouds and gusty NE winds will keep far from
ideal radiational cooling conditions from occurring and hedged
toward slightly warmer overnight lows in the low to mid-60s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Not much change in the latest guidance suite compared to the
past couple of days. Broad agreement continued, but there also
remained significant uncertainty in the details. Trended the
forecast with this update towards the consensus solution,
without making large changes just yet.

Overall, expecting a mid level trough to be nearby late this
week into early this weekend. At the surface, southern New
England should be between two features; a large high pressure to
the north, and a low pressure approaching from the south.
Ensembles showed most of the uncertainty was more east-west in
nature rather than north- south. Thus, still have the greatest
confidence in this low pressure center passing near or just SE
of the 40N/70W benchmark Thursday night into Friday. This timing
is highly uncertain, and could change with later forecasts,
even at this relatively closer time range.

Another aspect which will need to be monitored closely with this
low pressure is coastal flooding. Astronomical tides are rather
high later this week. A slow-moving low pressure with persistent
winds with at least some onshore component for the south coast
of New England may result in pockets of coastal flooding issues
late this week.

High pressure should then build into our region from the N this
weekend into early next week, leading to more dry weather.

Temperatures anticipated to trend below normal by this weekend,
and continue into early next week.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
Forecast Confidence Levels:

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

Rest of Today...Moderate Confidence

VFR north of the MA pike, while south of the MA pike has some
lingering MVFR with IFR cigs closer to the Cape and Islands.
Although guidance does show improvements this afternoon, with
higher dewpoints streaming in, am a bit skeptical if the Cape
and Islands will be able to go and maintain VFR.


Tonight...Moderate Confidence

Winds turn NE this evening, which will bring CIGS down to
IFR/LIFR east of the I-95 corridor, while to the west, CIGS
should remain VFR with pockets of MVFR possible. LIFR cigs are
most likely for the Cape and Islands, but could work into BOS
and PVD. Light rain begins to work its way from south to north
overnight, mainly just affecting the Cape and Islands northward
to BOS. ORH and BDL should stay mainly dry.

Tomorrow...High Confidence

IFR continues as winds increase from the NE at 10-15 knots
inland, and 15-30 knots near the waters. Rain becomes moderate
to heavy for the Cape and Islands. The extent that rain reaches
inland remains uncertain, but should remain light outside of the
Cape. Western terminals may see no rain with MVFR/VFR conditions
tomorrow afternoon.

Tomorrow Night... Low confidence

Guidance tries to show some improvements in CIGS, but am rather
skeptical given the continued on shore NE winds. The low stalls
south of the Cape and Islands, but rain could still continue for
eastern terminals, esspically the Cape and Islands.


KBOS TAF...Moderate Confidence

VFR this afternoon with east winds. Winds turn NE overnight,
bringing in IFR CIGS by 00-02z. CIGS could go LIFR late
overnight, but confidence is low at this time. light rain is
possible early Thursday morning, possibly lasting into Friday
morning

KBDL TAF...High confidence in TAF.

VFR today with light winds. Mainly VFR overnight and tomorrow,
but pockets of MVFR possible. Expecting the rain to stay east
of the CT river valley

Outlook /Friday through Monday/...

Friday: MVFR/IFR conditions possible. Windy with local gusts up
to 30 kt. Chance SHRA.

Friday Night: Mainly VFR, with areas IFR possible. Breezy.
Chance SHRA.

Saturday: Mainly VFR, with local IFR possible. Windy with local
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.

&&

.MARINE...
Forecaster Confidence Levels:

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

Marine

Today through Tomorrow night

Worsening marine conditions starting tonight, with northeast
winds increasing to 20-30 knots by tomorrow morning and seas
increasing to 5-8 feet by tomorrow afternoon.  Moderate to heavy
rain moves from south to north tonight and lasts through Thursday
night.  Seas continue to rise into Thursday night and Friday to 7-10
feet.

Rip Currents/High Surf With gusty NE winds, increasing surf and long-
period swells, we decided to issue a Rip Current Statement for
tomorrow. Much of the south and east-facing beaches will have a
high risk of rip currents. The rip current statement will likely
be extended or upgraded to a high surf advisory on Friday as
seas rise up to 10 feet in outer waters.

Outlook /Friday through Monday/...

Friday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Rough seas up to 10 ft. Rain showers likely.

Friday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Rough seas up to 10 ft. Chance of rain
showers.

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

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

Sunday: Strong winds with gusts up to 30 kt. Rough seas up to
11 ft. Slight chance of rain showers.

Sunday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 30 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.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents from Thursday morning through Thursday
     evening for MAZ007-019-020-022>024.
RI...High Risk for Rip Currents from Thursday morning through Thursday
     evening for RIZ006>008.
MARINE...Small Craft Advisory from 1 PM Thursday to 8 AM EDT Friday for
     ANZ231-251.
     Small Craft Advisory from 5 AM Thursday to 8 AM EDT Friday for
     ANZ232>235-237.
     Small Craft Advisory from 8 AM Thursday to 8 AM EDT Friday for
     ANZ250.
     Small Craft Advisory until 8 AM EDT Friday for ANZ254>256.

&&

$$

SYNOPSIS...BW/KP
NEAR TERM...KP
SHORT TERM...KP
LONG TERM...BW
AVIATION...BW/KP
MARINE...BW/KP