528
FXUS61 KBOX 210155
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
955 PM EDT Sat Jul 20 2024

.SYNOPSIS...
Seasonable and mainly dry to round out the weekend, although a
rouge shower or thunderstorm remains possible each afternoon.
The pattern turns more active again next week with increasing
humidity and periods of wet weather with heavy rain possible.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
10 PM Update

Light showers have formed in western CT off of a weak surface
trough along with 250 J/kg of MLCAPE. hi-res guidance is
capturing these showers quite well. As the surface trough moves
east tonight, it will find more moisture and some residual
instability to work with and bring scattered light showers to
the south coast tonight. Showers should end by day break as the
better forcing moves offshore.

Highlights:

* A mainly dry and warm afternoon under a mixture of sunshine and
  clouds. A rouge shower or thunderstorm is possible this afternoon
  mainly area west of the CT River Valley.

* A few showers or thunderstorm is possible overnight for locations
  along and south of the Mass Pike.

Satellite imagery shows thickening cirrus over southern New England
leading to filtered sunshine. Overall, a warm day with temperatures
in the low and middle 80s. Dew points are rising too, leading to a
slight humid feel as compared to yesterday afternoon. The day has
remained dry, but still cannot rule out a brief shower this
afternoon and this evening with the passage of a surface trough. The
latest surface observations show the trough over the Catskills and
that is where we find a cluster of showers. As these showers push
east, it will interact with some SB CAPE, around 1,000 J/kg and bulk
shear of 25-30 knots. Not expecting any severe storms, but a garden
variety thunderstorm or two are possible, and should be confined to
areas west of the Connecticut River Valley.

Tonight, a broad mid-level trough and shortwave energy moves over
southern New England and with PWATs 1.5 to 1.6 inch, leading to a
few showers/rumbles of thunder after midnight through sunrise
Sunday. While not everyone receives a shower or thunderstorm, do
think the area with the greatest potential are along and south of
the Mass Pike.

Temperatures are a few degrees warmer tonight, generally middle to
upper 60s, though city centers, Boston, Hartford, Providence are
near 70 degrees. A few degrees cooler for those communities in the
northern Worcester Hills and east slope of the Berkshires, there low
60s to upper 50s are possible.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Highlights:

* Slightly warmer for Sunday with a weak cold front approaching from
  the a north, a spot shower or thunderstorm cannot be ruled out.

Sunday:

A dry day ahead with low probability of a shower or thunderstorm as
a weak cool front dives south from northern New England. The general
weather pattern shows the broad mid-level trough moving east and
subtle height rises. Still, seasonable PWATs are around 1.0 to 1.2
inch and the steep low-level lapse rates, around 8-9 C/km, should
lead to diurnal cumulus clouds at the very least. CAMs do show a few
hit and miss showers developing along the leading edge of the front,
but nothing that would washout and cancel outdoor plans.

Highs are 2-3 degrees warmer than today, topping out in the middle
to upper 80s away from the coast. Near the water it is in the lower
80s.

Sunday Night:

If any spot showers from the cool front area still around, they
should diminish shortly after sunset. Mainly clear overnight with
lows in the lower 60s north to about 70 degrees south.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Monday through Saturday

The work week begins with a seasonable/sunny day on Monday as a weak
area of surface high pressure builds over and eventually east of
southern New England. 925 hPa temps continue to hover in the 18-20C
range which will translate to close to normal surface temperatures
in the low to mid 80s across southern New England. As high pressure
shifts east, onshore flow will develop along the east coast which
will keep Boston and the north/south shores slightly cooler with
comfortable high temperatures in the upper 70s to perhaps low 80s.
There is a low risk for a spot shower west of I-495 during the late
afternoon hours, but overall it should be a dry day to start the
week.

The forecast pattern shifts substantially on Tuesday as deep
southwest flow begins to advect anomalously high amounts of moisture
into The Northeast. This will support more clouds than sun between
Tuesday and Thursday. Extensive cloud cover will limit high
temperatures to the upper 70s to low 80s for most of this time
frame. In addition to the cloud cover, the middle of next week looks
to be generally wet and unsettled. A duo of short-wave disturbances
embedded in the broader southwest flow may support periods of heavy
rainfall with embedded thunder Tuesday through Thursday. Timing and
areal coverage of potential showers and thunderstorms is uncertain
given the weak/subtle forcing that will be driving this weather
pattern, but with weak wind fields and anomalously high PWATs up to
2.2 inches, there may be a risk for excessive rainfall and flash
flooding during the Tuesday-Thursday time frame. Wednesday afternoon
is of particular concern as this looks to be the peak of low-level
moisture transport/high PWATs. WPC currently has southern New
England in a marginal risk for excessive rainfall between Tuesday
morning and Thursday morning. Thus, this will be a period of the
forecast to monitor closely as we head into next week.

The wet/unsettled pattern looks to break by the end of the week as
model guidance is in good agreement with respect to a cold front
replacing the moist air mass with a drier air mass sometime Friday.
This should set the stage for a hot/dry weekend.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:

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

00Z update...


Tonight... High Confidence.

VFR. Slight chance of -SHRA or -TSRA for terminals along and south
of the Mass Pike, did not make mention in any specific TAF as there
is fairly low confidence in where these showers will pop-up. Winds
are west/southwest less than 10 knots, but easing towards daybreak.

Sunday... High Confidence.

VFR and dry. Northwest winds around 10 knots, although Cape Cod and
Islands are southwest 10 to 15 knots. Potential for eastern coastal
Massachusetts to seabreeze late morning/early afternoon.

Sunday Night... High Confidence.

VFR and dry. Light north wind.

KBOS TAF... High Confidence. VFR through the TAF period despite
increased high and mid clouds. A pop-up shower or two are possible
overnight, but confidence is too low at this time to include as a
PROB30/VCSH in TAF. Winds overnight are less than 10 knots,
becoming northwest by daybreak through the morning hours, a sea
breeze is possible, easterly wind, by 16z.

KBDL TAF... High confidence. VFR through the TAF period despite
increased high and mid clouds. A pop-up shower or two are possible
overnight, but confidence is too low at this time to include as a
PROB30 in TAF. Southwest wind less than 10 knots, becoming light and
from the south overnight. Wind becomes northwest to west/northwest
for Sunday, wind speed less than 8 knots.

Outlook /Monday through Thursday/...

Monday: VFR.

Monday Night: VFR. Slight chance SHRA, isolated TSRA.

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

Tuesday Night: VFR. Chance SHRA, isolated TSRA.

Wednesday through Wednesday Night: MVFR/IFR conditions
possible. Chance SHRA, isolated TSRA.

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

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Sunday Night... High Confidence.

A weak are of low pressure exits the coast of the Mid Atlantic and
moves well south of southern New England through Sunday. A weak cold
front moves from north to south reaching the waters Sunday afternoon
and evening. Spot shower or thunderstorm is not out of the question
but majority of this time is dry.

Seas are generally two to three feet trough this forecast period.

West/southwest winds for the rest of Saturday, becoming southwest
for the southern waters on Sunday with speeds 15 to 20 knots. While
the northeast waters are less than 10 knots and from the north. And
for Sunday night all waters have light north winds.

Outlook /Monday through Thursday/...

Monday: Winds less than 25 kt.

Monday Night: Winds less than 25 kt. Slight chance of rain
showers.

Tuesday through Tuesday Night: Winds less than 25 kt. Chance of
rain showers.

Wednesday: Winds less than 25 kt. Chance of rain showers,
isolated thunderstorms.

Wednesday Night: Winds less than 25 kt. Seas locally
approaching 5 ft. Chance of rain showers, isolated
thunderstorms.

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

&&

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

&&

$$

SYNOPSIS...Dooley/RM
NEAR TERM...Dooley/KP
SHORT TERM...Dooley
LONG TERM...RM
AVIATION...Dooley/RM
MARINE...Dooley/RM