-- Discussion containing changed information from previous version are highlighted. --
511
FXUS61 KBOX 130652
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
252 AM EDT Fri Sep 13 2024

.SYNOPSIS...
High pressure over the southeastern waters will continue to
govern our weather through tonight, bringing mainly dry weather
and above normal temperatures. Onshore breezes are expected on
Saturday and into Sunday although temperatures will still be
above normal. Our weather pattern will remain dry for the
foreseeable future, although there are early indications for
rains around mid to late next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
230 AM Update:

Surface synoptic-scale features remain essentially unchanged
early this morning compared to prior days, with our weather
being governed by a ridge of high pressure which extends across
south-coastal New England into the northern mid-Atlc states.
Air temps early this morning were in the 50s to lower 60s,
close to dewpoint temps. Aloft, an anomalously strong upper
level ridge was located over Lake Michigan, leading to
downstream longwave troughing over the Northeast. Water vapor
imagery early this morning shows a low-amplitude shortwave in
that broader cyclonic flow over northern Quebec which could
exert a minor influence on the forecast in northeast MA today.

First things first...talking about the forecast through the
early morning hours. Strong longwave radiative cooling has
forced temps near dewpoints, and with light southerly to calm
winds and light PBL flow, the expectation has been for fog to
develop in eastern CT, RI and southeast MA; indications which
are supported by a large majority of model visby forecasts. As
of this issuance, thus far that has not occurred outside of the
river valleys, or at least not in any persistent fashion. It`s
possible that soils may simply be too dry to support much
development other than near river valleys. Will continue to
monitor trends over the next few hours and if there is more fog
coverage across a wider area than just along the river valleys,
then we`ll be more proactive with fog statements. If we don`t
start seeing development soon, especially by sunrise, then the
risk for fog would be diminishing.

Otherwise, expecting mostly clear to partly sunny skies today,
with a opaque/hazier look per 13/00z HRRR-Smoke forecasts of
elevated concentrations of vertically integrated smoke in the
prevailing WNW flow aloft. Similar to yesterday, this layer is
aloft and won`t be perceptible in lower elevations/cause any
health issues. Should be quite warm with highs in most areas
reaching the lower to mid 80s, with upper 70s near the
coastlines due to seabreezes.

There remains a limited potential for a shower or stray t-storm
moving off the White Mtns in NH and into the North
Shore/Merrimack Valley area late this afternoon (after 3 PM til
sundown). Lapse rates aloft are quite steep but with weak
mesoscale lifting mechanisms around along with some capping.
Also worth mentioning the NAM could be overdone on its
dewpoints/instability compared to other models and could be
painting a more bullish take on the convective setting. I opted
for no better than 15% PoP in northeast MA, and if anything were
to develop, it may be just one or two buildups. Dry weather is
expected for the vast majority of the time.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
230 AM Update:

Tonight:

Low-amplitude shortwave passes into the waters early tonight,
with reinforcing ridge of high pressure then building in from
northern Quebec/Maine. Similar to the last several nights,
should again see good nighttime radiational cooling, although we
should see a lighter northerly wind take hold for the overnight
hrs. Models are also indicating the potential for fog in
eastern CT through southeast MA again tonight...but if we don`t
see any development this morning, I think we`d be hard pressed
to see much develop outside of the river valleys. I did include
a mention of fog for tonight as well, but the development is
still a little uncertain. Lows in the mid 50s to around 60.

Saturday:

High pressure over Maine then continues to progress into the
Gulf of Maine on Saturday. This will bring a modest cooler
airmass to Nova Scotia, and bring an increasing onshore NE
breeze which propagates westward into interior Southern New
England through the afternoon. Full sun will help offset some of
the shallow cooling, but still expect temps to slightly cool off
from east to west by late morning through the afternoon. Overall
continued dry weather should prevail, although a marine cloud
layer could arrive into eastern MA late in the day. Highs should
reach the upper 70s to the mid 80s, then falling into the 70s by
late afternoon (upper 60s/around 70 for the eastern MA
coastline, with upper 70s interior MA and CT).

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
-- Changed Discussion --
Updated: 2:50AM

Highlights:

* Very quiet weather continues into next week and the next
  chance for appreciable rainfall potentially the second-half of
  next week.

* Temperatures are comfortable with slightly above normal highs
  and seasonably cool overnight lows.


Saturday Night through Tuesday...

Quiet weather expected as high pressure is in control. One area
of interest, whether or not we get fog overnight Saturday into
Sunday. BUFKIT soundings show saturation in the lowest 500 to
1,000 feet of the atmosphere, practically ground level. But,
it`s been quite dry, most locations have not received measurable
rainfall over the last one to three weeks (location dependent).
What should tip us off to whether or not fog develops is the
outcome of this morning (Friday) and tomorrow morning
(Saturday). If no fog develops, then it`s more than likely there
will be no fog, widespread at least on Sunday morning. It`s
possible that fog develop along the larger rivers across
southern New England as the waterways do provide a moisture
source.

Still, no significant weather is expected Sunday, Monday, or
Tuesday with high pressure firmly in place across the northeast.
Could have a few fair weather clouds on Sunday with some
lingering moisture in the mid-levels. Trending mostly sunny
Monday afternoon, and by Tuesday afternoon expecting an increase
in high clouds. As for the temperatures, mild afternoons in the
upper 70s to low 80s, with Tuesday possibly the warmer of the
days as some interior locations could top out in the middle 80s.
At night, clear skies will promote radiational cooling with
overnight temperatures settling into the 50s. The coolest night
is Monday with lows between the upper 40s and the low 50s.


Wednesday and Thursday...

There remains uncertainty with this portion of the forecast.
For an example, the global models are not on board with the
development of a coastal low pressure system near the Carolinas
for early next week. In fact, NHC does give this area a 30%
chance of development over the next 7 days. GFS/GEM does show
development with the system lifting north mid to late next week.
GFS would bring in showers by Wednesday, while the GEM is later
on Thursday. It`s worth noting this is the first run we`ve seen
with the northerly shift. As for the ECMWF, it does not show
any development until late on Thursday off the Carolina with
high pressure still over New England.

This would be the next best chance for any wetting rains,
though there is still pounds of time for things to change. Liked
NBM POPs of 10 to 20 during the period of late Wednesday into
Thursday. Given this is day 6 and 7 did not want to deviate.


Tropical Weather...

The tropics are heating up and comes as no surprise since it`s
climatologically the peak for tropical cyclones for the Atlantic
basin. Tropical Depression Seven west of Cape Verde could
become a tropical storm today and as of now, poses no threat to
land. Closer to home, NHC monitors an area of development off of
the southeast coast of the United States and has a 30% chance
of development over the next 7 days.
-- End Changed Discussion --

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:

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

06z TAF Update:

Through 12z Friday: Overall high confidence, but lower
confidence on fog development in CT-RI-Southeast MA.

Mainly VFR. Still monitoring for fog development in and near
some of the airports in eastern CT, RI and southeast MA but so
far that has not developed. TAFs at PVD and the Cape will still
carry a mention of fog, but will AMD if we don`t see much
development by 09z. Light south winds.

Today: High confidence.

VFR today, though can`t rule out a shower near vicinity of BED
after 21z til sundown. S/SW winds 4-8 kt today; seabreezes are
possible today at BOS but it may be slower to set in or be
shorter-lived.

Tonight: High confidence, though low to moderate on fog
development in CT-RI-Southeast MA.

VFR should again prevail. We could see another chance for
radiation fog in CT-RI-Southeast MA airports but this is still
uncertain. Light south winds become NW to N by daybreak Sat.

Saturday: High confidence.

VFR. Main aviation concern this period is timing an onshore
windshift, with initial light N winds becoming NE to ENE around
5-10 kt; timing ~13-15z near the eastern MA coast, then moving
westward thru 22z Sat to the Berkshires.

KBOS TAF...High confidence in TAF. VFR through the period. SW
winds 4-8 kt should prevail until around 16-18z, where winds
become SSE/SE and then more of a seabreeze ESEly around 8-10 kt
by late afternoon. Winds then come around to NW/NNW tonight,
with a windshift to NE by 13-15z Sat.

KBDL TAF...High confidence in TAF, moderate on fog development.
Fog may develop by 09z Fri, then begin to disperse by 13-14z to
VFR. Light south winds today, becoming a light N tonight.

Outlook /Saturday Night through Tuesday/...

VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

230 AM Update:

Through Friday Night: High confidence.

Light SW winds (seabreezes nearest shore) today with seas 2 ft
or less. Patchy fog possible early this morning, with another
potential period of fog tonight as well, but the coverage is
less certain.

Saturday: High confidence, though moderate on windshift timing.

Winds become N to NE and increase to around 10-15 kt over the
waters on Saturday. The exact timing is still a little uncertain
but would start sooner (early to mid morning) in the offshore
waters of NE MA, then build S/SW into Cape Cod and
Narragansett/Block Island waters by the afternoon. Seas 3 ft or
less.

Outlook /Saturday Night through Tuesday/...

Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$

SYNOPSIS...Loconto/Dooley
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...Dooley
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley