133
FXUS61 KBOX 022323
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
723 PM EDT Sun Jun 2 2024

.SYNOPSIS...
Mainly dry conditions tonight and tomorrow with a spot shower
and rumble of thunder possible Monday afternoon. Back door cold
front will cool down daytime highs tomorrow afternoon. Tranquil
and dry weather prevails into midweek. Our weather pattern then
turns more unsettled and a bit more humid too for Thursday and
Friday, with several opportunities for showers and embedded
thunderstorms. Localized downpours are possible. Still a chance
for pop-up showers and t-storms on Saturday, although with less
coverage.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
710 PM Update:

Pretty nice early evening underway across Southern New England
so far, similar to last night. For the vast majority of Southern
New England, expecting quiet weather to continue for the balance
of the evening.

That said, regional radar over the Finger Lakes region and
southern Adirondacks in central NY shows an cluster of heavier
showers associated with low-level warm advection surge; even in
NY, model guidance has insisted this activity would have fizzled
out by now, but that has yet to occur. Airmass remains quite
dry and while we should see at least a general west to east
increase in mid to high clouds overnight, the drier low level
air should keep this activity at bay and didn`t make any
adjustments to PoPs as yet. But given observed trends and that
the 18z guidance is really handling this ongoing shower activity
pretty poorly, we may need to introduce isolated showers in
forthcoming updates for western MA and adjacent portions of
northern CT. Still, any showers that would develop would be on
the light side.

With rising dewpoints over the still-cooler waters, we could
see patchy fog develop over the southern waters later in the
overnight/pre- dawn period, and it`s possible this could affect
the immediate shoreline if it develops at all.


Previous discussion:

Very subtle and weak shortwave drops south across the region tonight
which could bring an isolated spot shower in western MA and CT.
However, weak forcing and dry air below 10kft will likely evaporate
most rain before it can reach the ground resulting in just virga and
perhaps a sprinkle. Increasing mid and high level cloud cover
tonight along with dewpoints in the 50s will keep overnight lows
warmer then last night only dropping into the upper 50s to low
60s.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Upper level closed low and cold pool to the east will send a back
door cold front into the region Monday. High temperatures in eastern
MA will peak early in the day in the mid to upper 70s, before
abruptly dropping down to the upper 60s to low 70s as the back door
cold front arrives. Further west in the CT river valley, the back
door cold front will struggle to reach that far west, and high temps
should be able to reach the low to mid 80s. Mainly dry conditions
again monday as a weak ridge and area of high pressure builds to the
west. There is a low chance for an isolated shower and rumble of
thunder in the late afternoon across western MA and CT as roughly
500 J/kg of CAPE builds. Any convection that does fire will be
fighting rising heights and very meager mid level lapse rates around
5 C/km. With little to no shear, any convection that forms would be
an isolated single cell. There could be sub-severe wind gusts with
any showers/thunderstorms tomorrow afternoon with steep low level
lapse rates around 10 C/km and soundings showing an inverted V shape
in the boundary layer.

Any showers/thunderstorms that form Monday afternoon/evening will
quickly dissipate after sunset with the loss of daytime heating.
Mainly dry conditions overnight Monday with low clouds and fog
possibly rolling in off the waters due to prolonged onshore flow.
Overnight lows drop into the low to mid 50s.

&&

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

* Generally dry Tue and Wed with mild temps inland, cooler coasts.

* Turning more unsettled and muggy into Thurs and Fri with several
  opportunities for showers/embedded t-storms. Localized downpours
  possible. Temps seasonable to slightly cooler than normal with
  clouds/rain around.

* More pop-up showers/storms Sat, although with a bit less coverage.

Details:

Tuesday:

Tranquil conditions expected for Tue with sfc high pressure in
control and midlevel heights rising. With guidance coming into
better consensus on unsettled weather conditions moving into the
latter portion of the week, Tue is likely to be the pick of the
workweek. While coastal areas expected to be kept cooler due to
seabreezes (highs mid 60s/around 70), full sun and dry weather
inland should boost highs into the 70s to lower/mid 80s. A bit more
of an increase in cloud cover over western CT/MA but still dry with
lows in the mid to upper 50s.

Wednesday:

Should be able to eke out another dry day for eastern MA and RI on
Wed as surface high pressure shifts offshore. Some hints in latest
guidance of isolated diurnal convection as 500 mb heights start to
fall with modest instability, although the better risk looks to
reside to our north and west. Left a slight chance PoP mention
during the afternoon for the CT Valley and the Berkshires, although
drier weather to prevail most of the time. Risk for showers then
increases later Wed evening/early Thurs AM as we start to feel the
effects of a seasonably-strong upper level low over the Gt Lakes
region. Thus indicated steadily increasing PoP from west to east
into the solid Chance range (30-50%) by Thurs AM. Should see highs
in the 70s to low 80s, and lows in the lower 60s with humidity
levels rising.

Thursday into Friday:

Models are coming into better agreement that this period looks quite
unsettled with widespread showers and embedded t-storms. Upper level
low combined with rising humidity levels and a modest degree of
instability could favor local downpours, though the lack of stronger
instability would be a deterrent to stronger storms. Thurs looks to
be the wettest period, with NBM 4.2 probs of rain over a half inch
are in the moderate range (30-50%), and are lower to moderate (15-
25%) for 24 hrs rains over 1 inch. Brought PoPs up into the Likely
range for showers and t-storms on Thurs. Most models show we get
into a dryslot of sorts for Thurs evening with decreasing PoP to
around 30-40%, then more pop-up showers/storms on Fri as a secondary
shortwave disturbance moves through. Still unclear if these
downpours may cause any hydro issues, though that risk is mitigated
to an extent by the recent spell of dry weather we`ve had.

With a lot of cloud cover around along with periods of rain and
thunderstorms, expect temps to cool off into the 70s for both Thurs
and Fri, though will feel a little more muggy with dewpoints in the
mid 60s.

Saturday:

Still some risk for diurnal showers/storms on Sat, although the
upper low begins to deamplify and lifts toward the northeast into
Canada.

&&

.AVIATION /23Z SUNDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

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

00z TAF Update:

Tonight: High confidence.

Mainly VFR, though did include a TEMPO mention of MVFR BR over
the Cape airports toward early Mon AM due to possible marine
fog. Winds light southerly to start, though will begin a gradual
clockwise turn to N for most, with NE winds developing along the
immediate eastern MA coast towards daybreak.

Monday... High confidence.

VFR and dry. Back door cold front will turn winds ENE in the
morning eventually turning ESE in the afternoon. Low chance for
an isolated afternoon shower/thunderstorm across western MA and
CT.

Monday Night... Moderate confidence

Continued onshore flow could begin to bring in MVFR/IFR CIGS
for coastal terminals. Winds remain ENE/ESE

KBOS TAF... High confidence.

VFR. Winds turn slowly to the north overnight and become ENE
around mid-morning Mon (~14-16z) as a back door cold front
passes through. Winds slowly trend ESE tomorrow afternoon. Could
see lower CIGS move in late Monday as near surface moisture
increase due to onshore flow.

KBDL TAF... High confidence.

VFR. Light SSW winds, though will trend ENE/E Mon. Low chance
for an isolated shower or thundershower Mon afternoon.

Outlook /Tuesday through Friday/...

Tuesday through Tuesday Night: VFR.

Wednesday: VFR. Slight chance SHRA.

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

Thursday: MVFR/IFR conditions possible. Breezy. SHRA likely,
slight chance TSRA.

Thursday Night: Mainly VFR, with areas IFR possible. SHRA
likely, isolated TSRA.

Friday: Mainly VFR, with local IFR possible. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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


Tonight... High confidence.

Dry conditions with WSW winds turning WNW towards day break at
5-10 knots. Seas 1-2 feet.

Monday... High confidence.

Continued dry conditions. Back door cold front will shift the
wind direction to the ENE late tomorrow morning into the early
afternoon at 10-15 knots. Seas 1-3 feet.

Monday night...Moderate confidence

Easterly flow will likely bring low clouds and fog to the
waters overnight. Winds 5-10 knots and seas 1-2 feet.

Outlook /Tuesday through Friday/...

Tuesday through Wednesday: Winds less than 25 kt.

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

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

Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Rain showers likely, isolated thunderstorms.

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

&&

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

&&

$$

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