488
FXUS61 KBOX 050526
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
126 AM EDT Sat Oct 5 2024

.SYNOPSIS...
Scattered showers move through the region very late tonight
into early Saturday morning with a weak cold front. Conditions
dry out by Saturday afternoon resulting in a mild day. A cold
front moves through Southern New England overnight Sunday
evening into Monday, bringing a period of rain showers. This
cold front will herald a cooler, Fall-like weather pattern as we
move into the middle part of next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
10 PM Update:

Light returns on radar across eastern MA and RI are having a
tough time making it to the ground with dewpoint depressions
still in excess of 5F in most locations. Cold remains to our
east across central NY and east central PA, leaving a window of
clearing across interior MA and most of CT at this hour. This
window of mainly clear skies has lead to some efficient
radiating in the CT River Valley where patchy fog has developed,
with vsby down to 2SM at Orange.

Any shower chances early tomorrow morning will off until after
06Z, though most recent guidance is not encouraging for those
hoping to see a few rain drops. Given the southern end of line
of precip continues to decay as it pushes east, the best shot
for any appreciable QPF remains to our north.

730 PM Update:

Pretty tranquil evening currently across Southern New England,
with current temps in the lower to mid 60s.

A stream of mid to high clouds (which led to a pretty vibrant
sunset scenes) continues to stream in associated with a weak
lead shortwave impulse evident in water vapor imagery over the
Alleghany Mtns in WV/SW PA. High clouds will continue to stream
in as the night goes on, although some lower cloud decks will
need to be watched well offshore of the Cape and Islands
associated with a shallow marine layer, which the (likely
overdone?) NAM-based models and MOS guidance suggest moves
northward later tonight.

A stronger shortwave was noted moving through northeast Ontario
and its associated surface cold front was nearing the St
Lawrence Valley in NY. While infrared imagery shows some cooling
cloud tops and some steadier light rain showers into NW NY,
looks like the best forcing associated with this front passes to
our north. Will continue to carry a low-PoP (< 20%) mention of
showers, but this frontal passage should be a largely dry one
for the pre-dawn to early Sat AM hrs.

So in sum, overall a cloudier evening than the past several, but
nothing necessarily significant. Lows should also be several
degrees milder as well with the cloud cover, mainly in the low
to mid 50s.

Previous discussion:

Weather for this evening into early Saturday morning will be
dominated by an approaching upper level trough and surface cold
front. Mid-level water vapor satellite shows the main wave moving
over the Great Lakes region this afternoon represented by a stream
of higher moisture. Another stream shown ahead of the main wave over
southern New England bringing and mix of clouds this afternoon. Late
tonight through early Saturday morning a cold front moves through
bringing scattered coverage showers. Can`t rule out a batch or two
of weak showers over the Cape/Island ahead of the front tonight.
HREF mean QPF shows a low probability (< 20%) for amounts greater
than 0.1" by midday Saturday. As a result, this will be a brief
round or two of scattered showers overnight with light
accumulations. It`s likely that not everywhere will get rain given
the scattered nature of the showers.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/...
Saturday...

Clouds gradually scatter from west to east Saturday morning. Any
lingering showers further east should diminish by midday. Northerly
surface winds expected post-front. With breaks of sun in the
afternoon, it will be another fairly mild day with highs in the
upper 60s and low 70s.

Saturday Night...

Saturday night, an upper level ridge works into the region.
This will support a clear night with efficient radiational
cooling bringing lows into the low 40s to 50s. A low level jet
streak moves through the flow offshore supporting more elevated
winds extending over the outer waters and across the
Cape/Islands overnight.

&&

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

* Pleasant Sunday with seasonable temps and dry weather.

* Cloudy with periods of rain showers on Monday, which could linger
  into late Monday or early Monday evening in southeast New England.
  Significant or heavy rains are not expected.

* Pattern change toward cooler, Fall-like weather for early to mid
  next week, with possible frost in some locations.

Details:

Sunday:

High pressure over southeast New England will continue to supply dry
weather for the daytime hrs, with increasing clouds later in the
day. Overall a nice close to the weekend with highs in the mid 60s
to lower 70s, with cooler readings near the coast due to seabreezes.

Sunday Night into Monday:

Frontal system begins to enter into Southern New England later
Sunday night / pre-dawn Monday, a few hrs slower compared to prior
solutions. Unfortunately this will bring a rainy Monday for much of
Southern New England, although with deeper moisture being sparse,
significant and/or heavy rain totals are not expected. There
continue to be indications in the 12z global models of a weak
secondary low or mesoscale low pressure which develops along the
front as it moves east, and that could keep showers going into the
late afternoon to early Monday evening period. Should see clearing
with onset of cool and dry advection and a NWly breeze for Monday
evening/overnight. Highs mainly in the 60s for Monday, with lows in
the 40s (around 50 near the coast).

Tuesday through Thursday:

A rather strong upper-level low builds into the Northeast states on
Tue and continues to slowly meander around New England. Underneath
this upper-level low is a cool pocket of air (e.g. 925 mb temps down
to +4 to +6C) and that will lead to both some NWly breezes but also
a rather cool, blustery airmass that will really ramp up the Fall
vibes. Daytime hours will likely feature a pretty generous amount of
fair weather clouds or stratocumulus, trending mostly clear for each
evening. Airmass is cool enough where we could see frost develop,
but the mitigating factor is there could be enough of a northerly
breeze to keep frost from developing. Highs Tue thru Thurs could
struggle to reach the lower 60s (with upper 50s in the northern
hills and terrain), with lows upper 30s to mid 40s.

&&

.AVIATION /05Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

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

06z TAF Update:

Through this afternoon: High Confidence except across Cape
Cod/Islands

Generally VFR as cold front sweeps across the region this
morning, but patchy radiation fog has developed north and west
of I495 in a window of clear skies ahead of the front. In
addition, MVFR will temporarily impact terminals across the Cape
and Islands briefly through 12Z. Light showers possible, mainly
north of Rte 2 through 13Z. Widespread postfrontal VFR expected
after 14Z. S/SW winds shift to the NW/N behind the frontal
passage this morning, generally less than 15kt.

Tonight...

VFR except patchy radiation fog/IFR/LIFR for interior
terminals. N wind less than 10kt.

Sunday...

VFR with any am fog burning off by 14Z. Winds shift from the
N/NE to the SE first across the interior around 17Z and
eventually across coastal terminals by 22z; except outer Cape
terminals. Some MVFR possible for the outer Cape with lingering
onshore flow Sunday afternoon.

BOS TAF...High confidence in TAF.

VFR ceilings Saturday. A cold front will be progressing east
with passage around 10-12z today, which will bring a windshift
to NW around 10 kt with gusts up to 18 kt upon frontal passage.
NW to N winds decrease in speed by late morning BDL TAF...High
confidence in TAF.


BDL TAF... High Confidence

VFR. Cold front moves through around
08-10z bringing a windshift to N winds.

Outlook /Sunday Night through Wednesday/...

Sunday: VFR.

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

Monday: Mainly VFR, with areas MVFR possible. SHRA.

Monday Night: VFR. Slight chance SHRA.

Tuesday through Wednesday: VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight...High Confidence.

Waves 2-4ft. S/SE winds through early Saturday morning less
than 15 kts.

Saturday...High Confidence

Scattered showers possible early Saturday morning into Saturday
mid-day, though showers may linger across the eastern outer
waters into Saturday evening. Winds shift behind passing front
to the NW Saturday morning; winds less than 25 kts. Waves 2-4
ft.

Saturday Night...High Confidence

Winds 10-20 kts with higher winds confined to the outer waters.
Waves approach 5 ft across portions of the outer waters
overnight into early Sunday. Coverage and confidence not high
enough to warrant a SCA at this time.

Outlook /Sunday Night through Wednesday/...

Sunday: Winds less than 25 kt. Seas up to 5 ft.

Sunday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers.

Monday: Winds less than 25 kt. Areas of rough seas. Rain
showers.

Monday Night: Winds less than 25 kt. Areas of rough seas.
Chance of rain showers.

Tuesday: Winds less than 25 kt. Seas up to 5 ft.

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

Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.

&&

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

&&

$$

SYNOPSIS...Loconto/Mensch
NEAR TERM...Loconto/Mensch/KS
SHORT TERM...Mensch
LONG TERM...Loconto
AVIATION...KS
MARINE...Loconto/Mensch