765
FXUS61 KBOX 181126
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
726 AM EDT Sat May 18 2024

.SYNOPSIS...
Unsettled and cool today with scattered showers. Chance for
improvement on Sunday as high pressure begins to nudge in from
the southwest. Early summerlike temperatures expected Monday through
Wednesday, with the warmest days expected to be Tuesday and
Wednesday. A cold front around Thursday offers the next chance
at showers or thunderstorms, with temperatures then cooling to
more seasonable levels by late in the week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
715 AM Update:

Forecast still looks on track as vertically stacked circulation
to our south draws maritime moisture back westward. Unfortunately
that will translate to a cool, raw overcast, with
intermittent/periodic light rain showers mainly in eastern MA
and RI. The showers won`t necessarily be present all the time or
be a washout, but there will be some to dodge. There is some
guarded optimism that western MA could see more of a partly to
mostly cloudy look but most everywhere should be socked in with
lower clouds. A good day for a bowl of clam chowdah! Temps not
likely to go very far from existing values, in the mid 50s to
lower-mid 60s.

Previous discussion:

Today we remain under the influence of pesky mid level low to
our south that has brought unsettled conditions to southern New
England for the last several days. With low to our south, weak
shortwave lifts from the Great Lakes into northern Maine by late
this evening.

Given southern New England is "sandwiched" between the shortwave and
the low, we`ll have a few chances for showers today; actually, the
first chance for showers is already underway with light
precipitation backing in across the Cape and Islands, thanks to
persistent ENE. Showers will become more widespread after 15Z today
as PWATs surge to >1.0", aided by a weak 925mb jet of 20-30kt draped
over eastern MA. General thinking is showers are possible in any
location, but will be more widespread east of the Worcester metro
area. In fact, the CT River Valley may "luck out" with a primarily
dry day as weak high pressure attempts to nudge in from the
southwest. While it will a dreary and rather chilly day, with little
to no diurnal swing in temps from current obs (in the 50s and
low 60s, west), QPF will be minimal, with HREF ensemble mean
QPF around 0.1" across Middlesex and Essex Counties. Should high
pressure be able to scatter out a few breaks of sunshine across
western MA, could see temps warm briefly into the mid to upper
60s in places like Hartford and Springfield.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Pattern of persistence carries through this evening with little
change in the synoptic setup through early tomorrow morning.
Shortwave passing to our Northwest may renew shower activity
between 00-06Z tonight. Widely scattered shower activity across
the eastern half of the CWA will become increasingly sparse
after the midnight hour, giving way to a more drizzle-stratus
dominated environment by early morning. Temps will pretty much
remain stagnant overnight given no change in the pattern with
low sin the 50s.

While Sunday previously looked to be a much nicer day for southern
New England, there are indications that the influence of onshore
flow will persist through the better part of the day across eastern
MA and RI, though conditions should improve across CT and western MA
as weak high pressure is able to take better hold over the region.
Fortunately, pesky mid level low tracks seaward, which will allow
rain chances to decrease significantly by sunrise. As has been the
case with many days this Spring, it`s likely Sunday is another case
of the "haves and have nots", as the CT River Valley breaks out into
sunshine and temperatures warm into the low 70s while strong onshore
flow pins stratus across eastern MA and much of RI where temps
struggle to climb out of the 50s along the immediate coast. It`s
probably safe to say those in the Boston to Providence corridor are
ready to shake this gloomy pattern, but fear not, the long term AFD
highlights a significant pattern chance by mid week!

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Highlights:

* Warming temperatures under partly to mostly sunny weather through
  midweek, with the warmest days likely on Tuesday and Wednesday.
  Could have our first 80 degree day in Boston Tuesday and/or
  Wednesday, with 3 days of lower-mid 80s in Hartford.

* Our next chance for rains is around later Wednesday night or
  Thursday with showers or thundershowers associated with a cold
  front.

* Cooling to more seasonable levels for late-week.

Details:

While the general theme of a substantial warming trend to
temperatures for the early to midweek period is still valid, today`s
00z guidance indicated more potential for continued cloud cover on
Monday with higher RH in the 1000-850 mb layer, especially for
eastern and southeast New England. Ended up bringing highs down from
NBM by a couple degrees for Monday on the basis of this cloud cover,
though the temperature forecast has obvious sensitivities to how
long clouds linger/scatter out, and that is still a bit unclear.
Kept highs in the mid 50s to mid 60s for the coasts and the coastal
plain, but still think highs soar into the mid to upper 70s from
central MA/eastern CT westward with less cloud cover.

Warmest days look to be on Tuesday and Wednesday, with full
sunshine, southwest breezes and continue dry weather. Relatively
strong SW flow should keep sea breezes from making much of any
intrusion landwards, so even sites such as Boston and the North and
South Shore have a solid chance at reaching 80 degrees, having last
occurred at Boston on October 28th of last year. Mid 80s inland seem
reasonable on both days. Despite the breezes, both days should feel
more reminiscent of early summer with dewpoint temps in the mid to
upper 50s.

Dry weather to prevail through Wednesday. Our next chance for
showers or thundershowers isn`t until a cold front arrives around
Wednesday night or Thursday, but the timing and the strength of any
thunderstorms are both uncertain. Latest guidance favors
Thursday for frontal passage so favored the highest PoP around
Thursday but only around 20-30 percent given the uncertainties
in timing. Friday appears to be more entrenched in post-frontal
colder air, with temps seemingly poised to return closer to
late-May climatological levels.

&&

.AVIATION /11Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

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

12z TAF Update:

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

IFR bases were already common over south coastal MA and were
starting to lower into MVFR range the PVD/BOS corridor, with VFR
in the interior. Continued deterioration anticipated in all
areas with MVFR becoming common, and IFR/at times LIFR for
central/eastern MA and RI. Scattered hit-or-miss showers fror
the eastern which was messaged in TAFs as P6SM -RA, although
could be a round of steadier rains developing later today. NE
Winds 5-15kt with a few gusts to 20kt possible along the
immediate eastern coastline.

Saturday Night...Moderate confidence.

Conditions remain consistently MVFR to LIFR from West to
Southeast, lowest on the Cape and Islands. Light showers and
drizzle continue through the first half of the evening. MVFR to
IFR conditions persist due to pesky onshore flow. Winds continue
to blow from the E/ENE gusting to around 10-15kt overnight.

Sunday... Moderate Confidence

Conditions improve from west to east after sunrise from
MVFR/IFR to VFR/MVFR. VFR possible for BOS-PVD line, SE after
18Z, though MVFR to hang on across the Cape for the duration of
the day. NE winds gusting 15 to perhaps 20kt once again.


KBOS TAF...High confidence in TAF through 00Z. Moderate after
this time.

MVFR to deteriorate to IFR late morning/early afternoon, with
periodic -SHRA, though may trend towards a steady light rain
after 00z. NE flow 10-15kt with the occasional gust to 20kt
possible.

KBDL TAF...High confidence in TAF.

Generally VFR but will become borderline VFR/MVFR this
afternoon. Showers most likely stay east of the terminal but a
stray shower may impact the terminal this afternoon or early
evening. Winds NE 5-10kt with gusts to 15kt.

Outlook /Sunday Night through Wednesday/...

Sunday Night through Monday: Mainly VFR, with local MVFR
possible.

Monday Night through Tuesday Night: VFR.

Wednesday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels:

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

Extended the SCA for the eastern outer waters through early
Monday morning for persistent seas.

Saturday... High confidence.

Scattered light rain and drizzle across the waters. Will have
visibilities of 3-5 SM. Persistent 15-20 kts out of the NE with
gusts up to 20 kts. Seas 1-4 ft across the interior waters and
4-6 ft for the outer.

Saturday Night...Moderate confidence.

Scattered light rain and drizzle anticipated to persist. Will
continue to see NE winds at 10-15 kts and gusts around 20 kts.
Visibilities of 3-5 SM and seas 3-6 ft for the outer waters.

Sunday... High Confidence.

Continued NE winds 10-15kt. Seas across the eastern outer
waters will remain above 5 feet through the period, but will
fall below 5 ft elsewhere. Vsby reductions early Sunday morning
should improve through the day.

Outlook /Sunday Night through Wednesday/...

Sunday Night: Winds less than 25 kt. Seas up to 5 ft.

Monday through Monday Night: Winds less than 25 kt. Areas of
seas approaching 5 ft.

Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.

Tuesday Night through Wednesday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 2 AM EDT Monday for ANZ250-254.
     Small Craft Advisory until 8 PM EDT this evening for ANZ255-
     256.

&&

$$

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