739
FXUS61 KBOX 250641
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
241 AM EDT Tue Jun 25 2024

.SYNOPSIS...

A disturbance aloft over the Northern Adirondacks moves
southeastward tonight, bringing evening cloudiness, northwest
breezes and a drier air mass to Southern New England. Warmer
temperatures then return for Tuesday but humidity levels remain
comfortable. Increasing humidity levels on Wednesday with the risk
for showers and thunderstorms, and some could become strong. Drier
and less humid to end the workweek, although summerlike warmth and
humidity return by this weekend.

&&

.NEAR TERM /THROUGH TODAY/...

220 AM Update...

Forecast remains on track. No changes in the latest update.

11 PM Update...

Have added likely showers across eastern MA. Latest NSSL WRF
handling activity associated with the upper trough swinging
through quite well. Should see these showers through roughly 1-3
AM as they diminish with the upper wave lifting offshore.
Otherwise forecast generally on track at this point with only
minor adjustments.

Previous discussion...

So for tonight, shortwave disturbance aloft and its cool pocket
of air aloft will be moving through the interior Northeast and
offshore through midnight. The approach of this disturbance
should at least maintain cloud cover if not increase it a bit.
Think cloud cover should trend more partial to mostly cloudy. An
outside chance (20% or less) of a sprinkle or light shower as
the shortwave moves through. Am a little skeptical the coverage
will be as numerous as some of the high res models indicate with
drier air moving into the lowest hundred or so mb of
atmosphere. Carried a mention of isolated showers but with nil
QPF over northern and northeast portions of Southern New
England, but many areas however stay dry. Should also see more
northwesterly breezes for the evening and overnight, which will
continue to usher in lowering dewpoints and a more comfortable
air mass. Humidity levels should be low enough tonight to give
fans/ACs a break for more open-windows. Lows tonight in the mid
50s to lower 60s, with mid 60s out over Cape Cod.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/...

Brief shortwave ridge and weak high pressure will bring very
pleasant weather again tomorrow. Mid level winds turn SW
Tuesday afternoon allowing for 850mb temps to warm from +13C to
+17C. This will bring high temperatures back into the upper 80s
to low 90s. With westerly surface winds, dewpoints will remain
in a comfortable range in the upper 50s. Skies should remain
mostly sunny through the day with subsidence aloft helping
suppress diurnal cumulus. Late in the day, mid to high level
cirrus clouds may bring some filtered sunshine ahead of a weak
shortwave moving through overnight.

Surface winds turn southwest overnight, brining moisture rich
flow into the region. This will bring dewpoints back into the
low to mid 60s. Winds overnight also turn gusty at 15-20mph as
the pressure gradient tightens ahead of the next system for
Wednesday. This will keep overnight temps quite warm in the
upper 60s to low 70s near urban centers.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...

Highlights:

* Wednesday is hot, muggy, and late day thunderstorms. A few showers
  could linger into Thursday morning across southeastern parts of
  southern New England.

* A post-frontal airmass provides relief from the heat and muggies
  late this week, along with drier conditions.

* Upcoming weekend looks splits, with the unsettled conditions
  likely on Sunday.

Rain and thunderstorm chances increase the second-half of Wednesday
with a mid-level trough and shortwave passage. For now, most of the
daylight hours Wednesday appear dry. Deep southwest flow ahead of
the approaching front advects a warm/moist airmass into southern New
England. Likely a hot and muggy day with highs in the upper 80 to
lower 90s, with dew points near 70F, courtesy of PWATs nearing the
two inch mark. Combination of heat and humidity provides instability
for storms late day. Best forcing at this time comes around late
afternoon and evening and exits during the overnight hours. The
discussion earlier stated a remnant EML from the upper Midwest could
be in the vicinity late in the day, 21z-ish, but latest 12z model
guidance suggests this feature could be over us by 12z/15z. There is
still some uncertainty with how strong and widespread these storms
could become. But there are signs for a few stronger storms, SREF
has surface based CAPE around 1,000 to 1,500 J/kg, along with
modest wind shear, 30 to 40 knots. Additionally, the 12z CSU
machine learning probs for severe weather/winds did back off
slightly across the northeast, though maintained the greatest
risk for severe weather across the Mid Atlantic states. Did
maintain the greatest pops between 00z and 10z, though there
could be lingering showers on Thursday morning as the front is
slow to exit the coastal waters. Places like Cape Cod and the
Island could see a few showers up until lunch before improving.

It`s important to note, those seeking a bit of relief from the heat
and muggy conditions at the ocean, there is a chance for stronger
rip currents. While there are no headlines, yet, future updates may
include a statement or advisory for this hazard.

Comfortable conditions Thursday with a post-frontal airmass due to
surface surface high moving down out of central Canada into northern
Great Lakes region. Drier weather to follow the rest of Thursday
into Friday, daily highs in the upper 70s and low 80s, dew points
are in the low 60s on Thursday and 50s on Friday.

Heading into this coming weekend, potentially a split weekend with
drier weather on Saturday with showers and thunderstorms on Sunday.
Model guidance suggests a system developing across the northern
Great Lakes with a trailing cold front. Still too early to get into
the details, but looks as if the later half of the weekend could be
unsettled.

&&


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

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

Through 12Z...High confidence.

Generally anticipating VFR conditions. Though may take until
08-09Z for the Cape/Islands to see improvement at MVFR/IFR
conditions linger as light showers move through. Could perhaps
see some patchy fog at prone BED given recent precip and light
winds until 11Z. Have handled with tempo given not super
confident on the winds completely decoupling. Winds out of the
NW at 5-10 kts.

Tuesday...High confidence.

VFR conditions expected with mid/high clouds beginning to move
in late afternoon/evening. Winds shifting from the NW to the
W/WSW by the afternoon. Should have speeds of 5-10 kts with
gusts of 15-20 kts.

Tuesday Night...High confidence.

VFR with mid to high clouds continuing to increase. Winds out of
the SW at 5-15 kts. Could see some 15-25 kt gusts after 06Z with
the highest speeds along the immediate south coast.

Wednesday...High confidence in AM. Lowers to moderate for PM.

VFR conditions are anticipated for much of the day. Confidence
lowers to moderate during the afternoon/evening as a cold front
triggers showers and thunderstorms. Not certain at this point on
coverage and exact timing, but risk seems highest across CT into
interior MA. If individual storm moves over terminal could see
brief MVFR to IFR conditions. Not out of the question there are
strong to damaging wind gusts if a stronger storm or two can
develop. Winds out of the WSW/SW at 10-15 kts with gusts of
20-30 kts.

KBOS TAF...High confidence.

VFR through the forecast. Winds remain too strong out of the
NW to WSW today, which will keep the seabreeze at bay. Could
have some 15-20 kt gusts through the afternoon before the
boundary layer decouples roughly 23-01Z.

KBDL TAF...High confidence in TAF.

VFR through the forecast. Could see gusty winds developing
around 15-17Z today as the boundary layer deepens.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Mainly MVFR, with areas VFR possible. Breezy.
SHRA likely, slight chance TSRA.

Thursday: VFR. Chance SHRA.

Thursday Night through Friday Night: VFR.

Saturday: VFR. Breezy. Slight chance SHRA.

&&

.MARINE...

Forecaster Confidence Levels:

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

Tonight...
High pressure begins to move in allowing winds to turn north and
weaken to 10-15 knots. Seas also decrease 3-6 feet.

Tomorrow...

Mainly clear conditions with winds turning SSW. Gusts begin to
ramp up again in the southern waters to 20-25 knots. Seas
decrease to 2-4 feet

Tomorrow night...

Southwesterly winds continue to ramp up across all the waters
with gusts up to 30 knots again. Seas ramp back up to 3-6 feet.
Small Craft Advisories will likely be needed for the this
period.


Outlook /Wednesday Night through Saturday/...

Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas. Rain showers likely,
isolated thunderstorms.

Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers, isolated thunderstorms.

Thursday Night: Winds less than 25 kt. Seas locally approaching
5 ft.

Friday through Saturday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 3 AM EDT early this morning for
     ANZ232>235-237.
     Small Craft Advisory until 3 PM EDT this afternoon for
     ANZ254>256.

&&

$$

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