397
FXUS61 KBOX 050551
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
151 AM EDT Wed Jun 5 2024

.SYNOPSIS...
Mainly dry and warm weather is on tap for Wednesday outside the risk
for a few spot showers. Our weather pattern then changes to a cloudy
and more unsettled outlook by Thursday and continuing into
early next week. Widespread rain showers and embedded
thunderstorms are expected on Thursday. Shower and thunderstorm
coverage for Friday into Monday then becomes more scattered with
some dry periods at times. Temperatures trend slightly cooler
than normal.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
1015 AM update...

Still a few showers across western MA which will soon dissipate,
but a weak shortwave dropping south across the region may lead
to widely scattered pop up showers developing overnight in
central and northeast MA

Some uncertainty regarding potential stratus and fog overnight,
mainly along the south coast with low level SW flow. HREF probs
are highest across southern CT as stratus along the NJ coast
lifts northward, and will also have to watch area of stratus
east of Cape Cod. Lows will be mostly in the mid-upper 50s.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/...
Key Points...

* Warm Wed with highs 85-90 away from the south coast
* A few showers/iso t-storm possible Wed afternoon in NE Mass
* Main risk for showers/iso t-storms develop near daybreak Thu

Details...

Wednesday...

Shortwave energy may result in a few leftover spot showers across
eastern MA early Wed morning...but any of this activity should be
pushing east of the region by mid-late morning. Otherwise...mainly
dry weather is on tap for Wed with partly to mostly sunny skies and
warm temperatures. 850T near +14C/+15C should result in afternoon
high temps between 85 and 90 away from the cooling marine influence
near the south coast, Cape and Islands. Ridge axis building to our
west should result in a mainly dry weather too. That being said...a
few showers/iso t-storm are possible mainly across northeast MA with
some shortwave energy focused to our north and east. Greatest risk
will north of our region...but northeast MA may be brushed by this
activity depending on how far south it can build.

Wednesday night...

Mainly dry weather expected Wed evening as upper level ridge axis
crosses the region. Once this ridge axis crosses the
region...shortwave energy approaching from the west. Timing is a bit
uncertain...but a cluster of showers/isolated t-storms may approach
the region from the southwest toward daybreak Thu. Pwats increasing
to between 1.5 and 2 inches may allow for downpours within this
activity as well. It will be quite mild too with increasing low
level moisture. This may result in low clouds and fog patches to
develop as well. Overnight lows will only drop into the lower to
middle 60s as a result.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Highlights:

* Slow-moving upper level disturbance favors several chances for
  showers/t-storms Thurs thru Mon, with temps trending slightly
  cooler than normal.

* Thurs looks to be a washout with widespread showers/t-storms.

* More scattered/hit-or-miss showers/t-storms Fri thru Mon with dry
  periods in between.

Details:

There are no substantial changes in the anticipated pattern for late
in the week on into the early next week period. An anomalous upper
low for early June over the Gt Lakes region will bring lower than
normal 500 mb heights to the Northeast states. While it won`t be
raining the whole period of time with drier periods interspersed, it
is an unsettled pattern with several chances at showers and t-
storms. This upper level low will close off and gradually fill into
the weekend into early next week. It remains uncertain when we might
see this upper-level feature leave our area; a North Atlantic omega
blocking pattern indicated by GEFS/EPS ensembles would favor very
slow eastward progression through the weekend. There are indications
on Mon that the upper low may make greater northeast inroads then,
with the latest 12z ensembles indicating the North Atlantic blocking
pattern weakening, but that is still to be determined.

Thurs still looks to be a washout and is the wettest day in this
period. PoPs were increased into the Categorical range, as leading
edge of stronger 500 height falls combined with an axis of anomalous
moisture (PWATs 1.2 to 1.4") and warm cloud depths 10-11kft will
favor showers and embedded t-storms with localized downpours,
focused by a surface frontal occlusion. Wouldn`t rule out isolated
instances of street flooding but we still are not anticipating any
significant hydro problems as it has been pretty dry of late and FFG
is on the higher side. Most of these rains move in during the
daytime hrs, then lift into interior New England by early evening
with a decrease in PoPs.

For Fri, the weekend on into Mon, still expect partly to mostly
cloudy conditions with a general sameness to PoPs for showers/t-
storms. More specifically, higher PoPs during the daytime hrs in the
30-55 percent range with the highest north and west closer to the
upper low. Lesser/reduced PoPs around 15-25% for the nighttime hours
during the diurnal-heating minimum. Later shifts will need to adjust
this up/down but level of predictability at this time horizon is too
limited to get into those details. It won`t be raining the entire
time, but the message is that there will be showers/t-storms to
dodge however severe weather potential is quite low.

With cloud cover, showers/t-storms around and with 850 mb temps in
the upper single digits to lower teens, reduced NBM high temps
downward with slightly cooler than normal temps in the lower to
middle 70s and lows in the 50s to lower 60s. Humidity levels are
highest on Thursday and could be pretty muggy with dewpoints in the
mid to upper 60s, then with lower humidity levels Fri thru Mon.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:

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

06z TAF Update:

Through 12z...

Mostly VFR, but localized IFR stratus may develop along the
south coast.

Today...High Confidence.

Any stratus will burn off quickly, otherwise VFR. But patchy
SCT stratus may develop around ACK by this afternoon and become
IFR-LIFR cigs by late afternoon. There is a low risk for an
isolated shower or t-storm across NE MA this afternoon, but
greater risk will be to the north. SW wind increasing to 10-20
kt.

Tonight...Moderate Confidence.

IFR-LIFR stratus and patchy fog expected to overspread the
south coast by early evening then expand northward, but
specific timing remains uncertain. A cluster of showers and
perhaps an embedded t-storm may begin to overspread the region
from SW to NE 09-12z. Light S winds.

Thursday...High confidence.

Widespread IFR-LIFR may improve to MVFR in the CT valley during
the afternoon. Numerous showers and a few t-storms with locally
heavy rainfall possible. SE-S wind 5-15 kt.

KBOS TAF...High confidence today. VFR into this evening.
Lowering cigs to MVFR and possibly IFR later tonight but exact
timing is uncertain. No sea-breeze today with SW wind 10-15 kt.

KBDL TAF...High confidence today. VFR today. Lowering cigs to
MVFR-IFR later tonight but exact timing is uncertain.

Outlook /Thursday Night through Sunday/...

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

Friday: VFR. Slight chance SHRA, isolated TSRA.

Friday Night: VFR. Chance SHRA.

Saturday: VFR. Chance SHRA, isolated TSRA.

Saturday Night: VFR. Slight chance SHRA.

Sunday: VFR. Chance SHRA, isolated TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight through Wednesday night...High Confidence.

The pressure gradient should remain weak enough to keep winds/seas
generally below small craft advisory thresholds through Wed night.
We may see some 20+ knot wind gusts Wed afternoon and night across
the waters. The best chance for these winds will be near the south
coast Wed afternoon with good mixing nearshore...so seas might be
bit choppy near the south coast Wed afternoon.

The other concern will be for areas of fog impacting the waters
especially tonight and again Wed night. Greatest risk for this will
be across the southern waters.

Outlook /Thursday Night through Sunday/...

Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Rain showers, isolated thunderstorms.

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

Friday through Sunday: 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...Frank/Loconto
NEAR TERM...KJC
SHORT TERM...Frank
LONG TERM...Loconto
AVIATION...KJC/Loconto
MARINE...Frank/Loconto