-- Discussion containing changed information from previous version are highlighted. --
028
FXUS61 KBOX 231306
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
906 AM EDT Mon Sep 23 2024

.SYNOPSIS...
Weak high pressure will build over our region into Tuesday, but
continued onshore winds should keep cloudiness in place, especially
near the coast. Rain chances increase again late Wednesday into
Thursday as a frontal system moves past. Warming trend with drier
conditions expected by this weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
9 AM update...

A few light showers or sprinkles are possible across eastern MA
and RI as radar showing some light returns backing in from the
ocean. Otherwise, it will be a dry day but with considerable
cloud cover from a combination of increasing strato-cu and high
clouds moving in from the west. Forecast on track.

Previous discussion...

* Considerable cloudiness today with highs mainly in the middle to
  upper 60s but near 70 in parts of the Lower CT River Valley

A weak upper level trough will cross the region today. Surface high
pressure nosing down from northern New England/Canadian Maritimes
will result in dry weather prevailing today. There is a low risk for
a brief sprinkle/spot shower...but not worth including in the
forecast at this time. That being said...low level moisture will be
enough to result in a considerable amount of strato-cu. Model cross
sections also indicate a fair amount of mid-high level cloudiness
moving in from the west with the upper trough. This should hold high
temps mainly in the middle to upper 60s to near 70 in parts of the
Lower CT River Valley.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
Key Points...

* Considerable clouds persist tonight with lows upper 40s & 50s

* Considerable clouds on Tue with highs mainly in the middle to
  upper 60s and perhaps near 70 in parts of the CT River Valley

Details...

Tonight...

The weak upper level trough will move east of the region tonight as
some mid level ridging building in from the west. This coupled with
a surface high pressure nosing down from the Canadian Maritimes will
result in dry weather persisting. Again...we can not rule out a
brief sprinkle/spot shower but not worth including in the forecast.
Overnight low temps should bottom out in the upper 40s in parts of
interior southern new England to the 50s elsewhere.

Tuesday...

A ridge of high pressure over the Maritimes will result in persistent
ENE low level flow of air across our region. Lack of deeper
moisture/forcing should result in generally dry weather prevailing
with just the low risk of a brief spot shower. Otherwise...still
expect plenty of strato-cu with the onshore flow. High temps should
generally be in the middle to upper 60s to near 70 in parts of the
CT River Valley.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Highlights...

* Onshore flow will yield clouds and below normal temperatures
  Wednesday.

* Frontal system sometime mid to late week brings our next chance
  for rain

* Warming and drying trend develops for this weekend

Latest guidance suite continued the trend of slower rainfall timing
for Wednesday, but it was not by much. Thinking that most of
Wednesday morning remains dry across southern New England, with the
risk for showers increasing from west to east during the afternoon.
It is possible that far eastern MA remains dry all day Wednesday,
with showers holding off until after sunset.

A low pressure moving east across southern Canada will sweep both
its warm and cold fronts across our region sometime Wednesday night
into Thursday. The timing remains the most uncertain aspect of this
forecast, which makes it harder to identify a specific narrower time
period for rainfall. In most cases, not looking for a lot of
rainfall with only a 30-40 percent probability of more than one half
inch in the 48-hour period ending 8 AM Friday. The main area for
this rainfall should be northern CT and most of MA.

High pressure centered over eastern Canada should push this front
offshore by Friday morning, then settle over our region into this
weekend. Despite a light N to NE wind, expecting high temperatures
to trend slightly higher just from the increased sunshine. Low
temperatures should trend lower.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

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

Today...High Confidence.

A broken deck of mainly VFR bases, with some pockets of
marginal MVFR ceilings. The lower conditions are most likely
towards the coastal plain during the morning hours after
sunrise. ENE winds of 5 to 15 knots with some 20+ knots across
the Cape and up to 25 knots towards Nantucket.

Tonight...High Confidence.

VFR to MVFR broken ceilings are on tap for tonight. The
scattered MVFR ceilings are most likely during the late night
and overnight hours and towards the coastal plain with the
cooling boundary layer. NE winds generally less than 10 knots.

Tuesday...High Confidence.

A broken deck of VFR to MVFR ceilings will tend more towards
VFR during the afternoon. ENE winds of 5 to 15 knots.

BOS TAF...High Confidence in TAF. Greatest risk for a period of
MVFR ceilings will be this morning through about 16z and then
again very late tonight.

BDL TAF... High Confidence in TAF.

Outlook /Tuesday Night through Friday/...

Tuesday Night: Mainly VFR, with areas MVFR possible. Breezy.

Wednesday: Mainly VFR, with local IFR possible. Slight chance
SHRA.

Wednesday Night: Mainly VFR, with local IFR possible. Chance
SHRA.

Thursday: Mainly VFR, with areas IFR possible. Chance SHRA.

Thursday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA.

Friday: VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Tuesday...High Confidence.

High pressure over the Canadian Maritimes coupled with a distant
offshore low pressure system will continue to generate a persistent
NE winds through Tue. NE winds should continue to gust to between 20
and 25 knots over our southeast waters into Tue.  The long NE fetch
and lingering swell should keep small craft seas across our outer-
waters through Tue. However...we should see the seas drop below
small craft criteria against many of our nearshore waters tonight
and Tue.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Wednesday: Winds less than 25 kt. Areas
of rough seas.

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

Thursday: Winds less than 25 kt. Local rough seas. Chance of
rain showers.

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

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

&&

.TIDES/COASTAL FLOODING...
The total water level at Boston peaked at 12.7 ft during Sunday/s
midday high tide cycle resulting in some minor inundation issues
along exposed east and NE facing beaches. Astronomical tides are
about 0.5 ft less this afternoon...so with a similar surge worst
case would be just some very minor splashover but no need for
additional coastal headlines and astro-tides will continue to
diminish the next few days.

A High Surf Advisory continues through today. We probably will need
to either extend this through Tuesday or go with a Rip Current
Statement...but will let the next shift evaluate.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Surf Advisory until 8 PM EDT this evening for MAZ007-019-
     020-022>024.
RI...High Surf Advisory until 8 PM EDT this evening for RIZ006>008.
MARINE...Small Craft Advisory until 5 AM EDT Tuesday for ANZ231-232.
     Small Craft Advisory until 2 AM EDT Tuesday for ANZ233>235-237.
     Small Craft Advisory until 8 PM EDT Tuesday for ANZ250-251-
     254>256.

&&

$$

SYNOPSIS...Belk/Frank
NEAR TERM...KJC/Frank
SHORT TERM...Frank
LONG TERM...Belk
AVIATION...Belk/Frank
MARINE...Belk/Frank
TIDES/COASTAL FLOODING...Frank