-- Discussion containing changed information from previous version are highlighted. --
076
FXUS61 KBOX 022338
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
738 PM EDT Thu May 2 2024

.SYNOPSIS...
A weak low pressure will bring scattered showers near the coast this
afternoon. Northeast onshore flow will bring cloudy and cool
conditions tomorrow. High pressure supplies dry weather with
cooler onshore breezes on Saturday. Increasing clouds later
Saturday into Sunday, with solid chances for rains and cooler
temperatures on Sunday into Sunday evening. High pressure then
brings dry and seasonable weather early next week, with our next
chance for rains after Sunday not appearing until Wednesday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
-- Changed Discussion --
733 PM Update:

Though it is dry into central and western MA and much of
northern CT and adjacent RI. However it`s a different story in
eastern MA as a combo of diurnal heating and dynamic
ascent/midlevel diffluence owing to a potent shortwave
disturbance digging southeast from central NH is responsible
for a cluster of scattered low-topped convective showers, and a
few have deepened enough to produce lightning and some pea/BB-sized
hailstones. We`re approaching sundown now, and that should start
to diminish the potency of these heavier showers/embedded
t-storms, but we still expect scattered showers to continue to
progress southeast towards south coastal MA and the Cape and
Islands through 9 PM, following HRRR guidance. Adjusted PoP/wx
to change weather to areal coverage wording.

Thereafter the story turns to returning stratus and fog, with
northeast flow drawing the ongoing area of stratus over NH/ME
SSW across much of SNE through the late evening and overnight
hours. BUFKIT soundings shows the stratus layer lingering into
the Friday morning hrs.

Previous discussion:

Shortwave trough aloft continues to dig south into SNE this
afternoon. With clouds clearing across much of northeast MA, this
could set the stage for an isolated pop up shower with a low chance
at a rumble of thunder. SPC mesoanalysis is showing around 100
J/kg of CAPE/instability in northeast MA this afternoon. Showers
quickly move south with the passage of a back door cold front.
This back door cold front will switch our winds to the NE
bringing cool air and a low level marine stratus cloud deck over
the region tonight. This cloud deck will keep lows mild again
overnight only dropping into the upper 40s.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Rising heights and high pressure building in will attempt to erode
the marine status deck tomorrow from west to east, but will
likely linger well into the afternoon for the Cape and Islands.
Best chance for sun tomorrow will again be in the CT River
Valley which is where high temps could top 70F. Elsewhere, cool
onshore easterly flow will keep highs in the upper 50s to low
60s.

Upper level ridge axis passes over SNE Friday night with high
pressure directly overhead. Winds become light and variable and
skies should begin to clear as onshore flow weakens. This could
allow for overnight temps to drop into the low 40s, with an
outside shot at upper 30s.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Highlights:

* Increased clouds but dry Saturday, but cooler with better chances
  for rains Sun into Sun night.

* Mainly dry Mon and Tue with seasonable to slightly above normal
  temps.

* Warm front around Tue night or Wed brings next chance for clouds
  and showers.

Details:

Saturday and Sunday:

Sfc ridge of high pressure over coastal New England to very slowly
weaken/shift eastward through the course of the weekend. Meanwhile
on the western periphery of upper level ridging over western New
England and the northern mid-Atlc and associated with pretty
disorganized shortwave trof energy, warm advection driven showers
will gradually shift eastward into Southern New England, mainly
during the latter half of the weekend (Sunday).

Still looks like Saturday is the better day of the two, although
will have cooler breezes near the coast and increased cloud cover in
all areas. Highs should reach the 60s for most interior locales, but
around the mid 50s along the eastern MA coast, with upper 50s/around
60 near the southern coastline.

Sunday on the other hand looks cloudy with periods of rain showers,
which slowly shift offshore during the evening and overnight. There
are some indications that the frontal boundary responsible for the
rains slows/stalls offshore that could keep chances for showers
going well into Sunday night but this isn`t set in stone. Though
expected rain amts aren`t substantial, should be a pretty soggy day.
Despite the warmer air aloft, cooler highs in the 50s given the
cloud cover, rains and limited mixing. Milder-than-climo on the lows
with the continued cloudiness in the mid to upper 40s.

Monday and Tuesday:

For Monday...could still see some leftover light showers into the
morning across southeast MA and the Cape and Islands as frontal
boundary in vicinity slowly sags southward. ECMWF in particular is
slowest to progress the front offshore. Ridging to the north and
west eventually builds into Southern New England later in the day
and especially into Monday evening. Highs in the 60s to lower 70s
and lows in the mid 40s to lower 50s.

For Tuesday...high pressure brings a period of cooler onshore flow
to coastal New England, with temperatures being significantly milder
inland away from the maritime influence. Kept highs in the 60s near
the coast with highs inland into the lower to mid 70s, with
potential spot 80 degree readings not out of the question in the
warmer spots in the CT Valley. Increasing clouds for Tue night ahead
of a warm front but associated rains should hold off until Wed.

Wednesday:

Warm front associated with a rather strong area of low pressure over
the northern Plains drapes itself over or just west of SNE. This
offers the next best chance for rains after Sunday with PoPs in the
medium (30-40%) range for rains on Wednesday.

&&

.AVIATION /23Z THURSDAY THROUGH TUESDAY/...
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Forecast Confidence Levels:

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

00z TAF Update:

Tonight: High confidence in trends, though moderate on timing.

Ongoing area of SHRA/embedded TS over eastern MA to progress
southeast toward Cape Cod airports by 02z, then moving offshore.
Brief/temporary restrictions possible at BOS and the Cape
airports with brief MVFR visby and occasional lightning.

Otherwise, VFR to then deteriorate to IFR/LIFR ceilings as
stratus over NH/ME spread SSW. Expect stratus to develop by
01-02z over the North Shore MA and then spread SSW through the
evening and overnight. Ceilings at BAF/BDL likely more in the
MVFR range, while IFR-LIFR should be more common for eastern and
central airports. Stratus likely to persist well into the AM
hrs. NE winds around 8-12 kt.

Tomorrow: Moderate Confidence

Gradual improvements in CIGS back to MVFR late morning, then to
VFR in the afternoon with the CAPE and Islands seeing IFR
linger longer into the day. Winds turn SSE at 5-10 knots

Tomorrow Night: High Confidence

VFR with light and variable winds.

KBOS TAF...Moderate confidence. SHRA/occasional TS with brief
visby restriction should exit southeast from BOS by 01z. VFR
then becomes IFR-LIFR as soon as 01z but more likely after 02z
as stratus sets in from NH/ME. NE winds around 10-12 kt.

KBDL TAF...Moderate confidence. VFR for most of the first half
of the night, with MVFR stratus developing late overnight into
the pre-dawn hrs. Low prob of IFR ceilings. N winds around 10
kt.

Outlook /Saturday through Tuesday/...

Saturday: VFR. Chance SHRA.

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

Sunday: Mainly VFR, with areas IFR possible. Breezy. Chance
SHRA.

Sunday Night: MVFR/IFR conditions possible. Breezy. Chance
SHRA.

Monday: Mainly VFR, with local MVFR possible. Chance SHRA.

Monday Night through Tuesday: VFR. Slight chance SHRA.
-- End Changed Discussion --

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight: Moderate Confidence

Weak low pressure system will cause scatted rain showers with
isolated thunder this afternoon and evening mainly across the
eastern waters. Cool NE flow will cause a low status/fog cloud deck
to form this evening. Winds will approach 20-25 knots esspically
across the southern waters between 06-12z tonight, but confidence
was not high enough to issue a small craft advisory at this time.

Tomorrow: Moderate Confidence

Low status and fog stick around into the afternoon before possibly
clearing in the evening. Winds become light and variable tomorrow

Tomorrow night: High Confidence

High pressure overhead will keep conditions dry with light and
variable winds

Outlook /Saturday through Tuesday/...

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

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

Sunday Night through Monday: Winds less than 25 kt. Seas
locally approaching 5 ft. Chance of rain showers.

Monday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers.

Tuesday: Winds less than 25 kt. Slight 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