324
FXUS61 KBOX 171450
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1050 AM EDT Sat Aug 17 2024

.SYNOPSIS...

Dry weather continues for the region today. A slow-moving front
will lead to unsettled weather with showers and isolated
thunderstorms Sunday evening through Monday night. A drying
trend with seasonable temperatures are expected for the middle
of next week. Meanwhile, Hurricane Ernesto will track well
southeast of New England, but it will bring rough surf and
strong rip currents to south-facing ocean beaches this weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

1030 AM Update...

Main change in the latest update was to decrease high temps
several degrees. Running too warm given the cloud cover overhead
along with haze. Have also kept the low clouds lingering longer
into the afternoon given the prolonged onshore flow. Will be
slow to improve today. High temps generally in the 70s today.
Only spot where think there is potential to get into the 80s is
across the CT River Valley. Main concern still is the risk for
strong rip currents across south facing beaches.

Previous discussion...

Widespread stratus trapped beneath a subsidence inversion to
start today. Weak onshore flow may provide some brief breaks in
this stratus towards the immediate east coast of MA. These lower
clouds should dissipate later this morning, only to be replaced
with some higher based clouds and smoke aloft. Thus, despite a
high pressure moving overhead, expecting more clouds than
sunshine today. All things considered, high temperatures should
be slightly below normal, especially towards the east coast
where light onshore flow will also help to keep temperatures
lower.

The prime concern will be the arrival of long-period S to SE
swells from distant Hurricane Ernesto. Headline for High Risk
for Rip Currents for south-facing beaches along coastal RI,
Cape and Islands continues. This is for the entire weekend. We
may need to expand that to cover the coast of Cape Ann as well.
In addition to the expected stronger rip currents, surf heights
will be elevated. Those heading to the beaches this weekend need
to heed the advice of local lifeguards and beach patrols.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...

Surface high pressure moves farther offshore tonight. A slow-
moving front will try to move east, but have its progress
delayed by the offshore high pressure. That said some showers
may reach the western half of southern New England tonight, but
are slightly more likely for Sunday. Could also see some
isolated thunderstorms Sunday. Not looking for any significant
rainfall however.

Near to slightly below normal temperatures continue.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...

Highlights

* Widespread showers with embedded thunder for most of southern
  New England on Monday

* A few lingering showers into Tuesday followed by a cold
  frontal passage that will be followed by a cooler/drier air
  mass settling over The Northeast

* Dry/seasonable weather Wednesday through Friday with
  temperatures gradually increasing each day

Monday

An area of low-pressure associated with an upper-level trough
at 500 hPa moves across southern New England on Monday. With
sufficient moisture in place and PWATs near 1.5 inches, we`re
likely to receive widespread rainfall for much of the day
Monday. This will be a modest rainfall event with accumulations
ranging from 0.25 inches east of I-495 to 1.25 inches across
western MA and CT. Latest model guidance suggests modest
instability with the GFS forecasting MLCAPE values between 500
and 1000 J/Kg so some embedded thunderstorms will be likely on
Monday afternoon as well. Shear is also on the modest side with
only 20 to 30 knots in the 0-6 km layer, so the risk for any
severe thunderstorm development is low. However, some models are
suggesting decent mid-level lapse rates in the 500 to 700 hPa
layer near 6 C/km for portions of southern New England, so an
isolated strong storm can`t be ruled out at this point. CSU
machine learning probs give most of the east CONUS including
southern New England a 5 to 15 percent chance of severe weather
on Monday. Timing of heaviest rainfall remains uncertain, but
look for rain to affect the western areas during the first half
of Monday followed by the eastern areas Monday afternoon into
Monday evening.

Tuesday through Friday

A few showers may linger Monday night into Tuesday morning as a
surface cold front associated with the aforementioned area of
low- pressure pushes through the region. This will be
accompanied by an early fall like air mass that will bring
temperatures down to the upper 60s and low 70s on Tuesday. As
skies clear Tuesday night into Wednesday, 925 temps near 10C and
radiational cooling may allow for surface temps to fall as low
as the upper 40s for select locations in interior southern New
England.

High pressure begins to build in from the west on Wednesday
supporting dry/seasonable conditions across the regions.
Temperatures will be on the uptick between Wednesday and Friday
with highs in the low 70s on Wednesday increasing to the upper
70s to low 80s by Friday. Overall looks like a quiet stretch of
weather between the middle and end of next week.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...

Forecast Confidence Levels:

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

Overall moderate confidence.

IFR stratus with local VFR into the morning push. Then
conditions start to reverse, with mainly VFR across interior
southern New England into this evening and areas IFR towards the
immediate coasts and adjacent coastal waters. IFR could linger
across the Cape and islands through most of today.

IFR returns tonight, then becoming VFR Sunday. Scattered showers
possible across the western half of southern New England tonight
into Sunday.

KBOS TAF...Moderate confidence. VFR, lowering to IFR around the
morning push, then VFR from late morning into this evening.

KBDL TAF...Moderate confidence. MVFR through the morning push,
quickly improving to VFR by mid morning.

Outlook /Sunday Night through Wednesday/...

Sunday Night: Mainly VFR, with local IFR possible. Chance SHRA,
isolated TSRA.

Monday: Mainly MVFR, with local IFR possible. SHRA likely,
isolated TSRA.

Monday Night: Mainly VFR, with local IFR possible. Chance SHRA,
isolated TSRA.

Tuesday: Mainly VFR, with local MVFR possible. Chance SHRA,
isolated TSRA.

Tuesday Night: VFR. Chance SHRA.

Wednesday: VFR.

&&

.MARINE...

Forecaster Confidence Levels:

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

Overall high confidence in the forecast.

Although winds will be 15kt or less this weekend, Small Craft
Advisories are in effect for the elevated wave heights due to
the powerful swells coming in from the SE due to Hurricane
Ernesto. The swells will also be of very long period (13 to 16
seconds), so this will also result in strong rip currents and
high surf developing along south-facing coast lines. This may
also result in rough conditions at the entrances to inlets and
harbors.

Outlook /Sunday Night through Wednesday/...

Sunday Night: Winds less than 25 kt. Local rough seas. Slight
chance of rain showers, isolated thunderstorms.

Monday: Winds less than 25 kt. Areas of rough seas. Chance of
rain showers, isolated thunderstorms.

Monday Night through Tuesday: Winds less than 25 kt. Seas up to
5 ft. Chance of rain showers, isolated thunderstorms.

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

Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents from Sunday morning through Sunday
     evening for MAZ007.
     High Risk for Rip Currents through Sunday evening for MAZ022>024.
RI...High Risk for Rip Currents through Sunday evening for RIZ006>008.
MARINE...Small Craft Advisory until 8 PM EDT Sunday for ANZ235-237-
     254>256.
     Small Craft Advisory from 10 AM to 8 PM EDT Sunday for ANZ250.

&&

$$

SYNOPSIS...Belk/RM
NEAR TERM...Belk/BL
SHORT TERM...Belk
LONG TERM...RM
AVIATION...Belk/RM
MARINE...Belk/RM