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599
FXUS61 KBOX 291746
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
146 PM EDT Mon Apr 29 2024

.SYNOPSIS...
Enjoy the warm and partly sunny conditions today, a backdoor
cold front will bring much cooler conditions, clouds, and spot
showers on Tuesday. The greatest risk for a period of showers
will be Tuesday night into Wednesday morning. Temperatures for
late this week and next weekend are uncertain given the
positioning of a backdoor cold front...but are looking more
likely to end up on the cooler side especially along the coast.
After a slight chance of showers Thursday, another round of
showers may arrive late next weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
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140 PM update...

Backdoor front has moved through much of northern and eastern
MA with temps falling into the 60s and through the 50s along
the immediate coast. 70s across RI and CT and may see a max of
80 in Hartford before fropa and falling temps. Area of showers
moving SE from NH and may see a brief shower/sprinkle in NE MA
during the next hour. Otherwise, weak instability with SBCAPES
up to 500 J/kg has developed in CT. Can`t rule out an isolated
shower this afternoon across CT, but higher risk of convection
to the SW where temps in 80s and SBCAPES up to 1500 J/kg.

Increasing cloud cover post sunset as a 850mb warm front lifts
from southwest to northeast. Can`t rule out a few widely sct`d
showers around midnight to 5/6am Tuesday. Maintained 20 to 40
POPs, `Slight Chance` to `Chance` POPs, mainly across northern
Connecticut and western Massachusetts. A mild night as well with
overnight lows in the upper 40s and low 50s.
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&&

.SHORT TERM /TUESDAY/...
Highlights:

* Much cooler on Tuesday, by as much as 10 or 15 degrees cooler due
  to a backdoor cold front.

* Spot showers possible ahead of an approaching cold front late
  Tuesday.

A noticeable difference come Tuesday, temperatures are roughly
10 to 15 degrees colder than the day prior, plus cloudy skies
and chance for spot showers. We can thank a backdoor cold front
for the cooler temperatures, brought on by an east to east-
southeast wind throughout the day. This knocks back the warm
temperatures to a range of what is considered `normal` for late
April. There will be a spread in temperatures from the low/mid
50s in Boston to the mid/upper 60s in Hartford to Springfield.
In between, many locations achieve a high temperature in-between
the lower and middle 60s. Coastal towns are much cooler, with
highs in the low to mid 50s! As for precipitation, have
maintained `Slight Chance` POPs across western Massachusetts and
northwest Connecticut for the early afternoon, but the POPs
increase into the late afternoon. Do think the bulk of any rain
will arrive overnight, which is discussed in the Long Term
section of the AFD.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Key Points...

* Cool Wed with highs in the 50s coast & 60s inland.

* Main threat for a period of showers Tue night into Wed morning.

* Generally dry Thu & Fri but can`t rule out some scattered
  showers on Thursday...large spread in potential high temps.

* Another round of showers possible next weekend.

Details...

Tuesday Night and Wednesday...

High pressure remains in control directing cool, NE flow into
southern New England keeping highs once again in the low to mid 50s
(east) and mid 60s (CT valley). A shortwave passing overhead coupled
with a surface low moving from the mid-Atlantic passing south of the
region will bring a round of showers moving in Tuesday night and
continuing through at least Wednesday morning; there is a low
probability that showers continue well into the evening before weak
ridging moves in and things dry out a bit.

Thursday and Friday...

An upper level ridge tries to build in for the latter half of the
week, but latest guidance now indicates a shortwave suppressing the
eastern periphery of the ridge over SNE on Thursday, so things
aren`t looking as dry for Thursday as they did 24 hours ago. Even
so, weak forcing and PWATs <1" will keep any rainfall from being to
impactful. By Friday with the ridge closer dry weather is more
likely. The biggest forecast challenge for this period will be the
potential for another backdoor cold front to accompany this
shortwave on Thursday which would keep the earlier expected 70s from
materializing. At this point there is a considerable amount of
uncertainty, but odds shifting toward a cooler solution with temps
more likely to be in the 50s and 60s each day rather than the 70s.

Saturday and Sunday...

The ridge axis arrives on Saturday with our next shortwave on its
heels which brings the return of widespread rain chances as early as
Saturday night. Confidence is low given significant spread in how
the pattern evolves.

&&

.AVIATION /18Z MONDAY THROUGH FRIDAY/...
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Forecast Confidence Levels:

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

Through 00z...

VFR cigs. North to east winds 10-15 mph.

Tonight... Moderate confidence.

Cigs lowering to MVFR across central/W MA and northern CT with
scattered showers developing. Mainly VFR in the east. MVFR may
get as far east as PVD but uncertainty with eastward extent of
lower cigs.

Tuesday... Moderate confidence.

MVFR cigs along and west of FIT-PVD with highest risk in
western New Eng. VFR cigs eastern MA. Scattered showers in the
morning in the west. E-SE wind 10-15 kt.

Tuesday night... Moderate confidence.

Cigs lowering to MVFR-IFR with scattered showers. E wind 5-10
kt.

KBOS TAF...High confidence in TAF.

VFR cigs through the TAF period. Sea breeze transitions to land
breeze with wind shift to S this evening then E winds redevelop
late tonight. Traditional sea breeze develops by 14z Tue.

KBDL TAF...High confidence in TAF.

Cigs lowering to MVFR after 02z and persisting through Tue.
Scattered showers developing tonight.

Outlook /Wednesday through Friday/...

Wednesday: Mainly VFR, with areas IFR possible. Chance SHRA.

Wednesday Night: Mainly VFR, with local IFR possible. Slight
chance SHRA.

Thursday: Mainly VFR, with local MVFR possible. Slight chance
SHRA.

Thursday Night: VFR. Slight chance SHRA.

Friday: VFR. Breezy. 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.

Through Tuesday... High confidence.

Low chance for coastal fog to develop early this morning across
the eastern waters, nighttime RGB product does show an area of
low clouds/fog across the Gulf of Maine and high-res model
guidance shows the potential for this to drift south between 6AM
and 10AM. Otherwise, dry and partly sunny Monday with east-
southeast winds along the eastern coast of Massachusetts and
south-southeast winds along the south coast of Massachusetts and
Rhode Island. Winds are 10 to 15 knots and seas 2 to 4 feet.

Tonight winds are light and variable. Tuesday, winds are east to
southeast 8 to 12 knots, gusts around 15 knots. Seas 1 to 3
feet. A few showers are possible ahead of an approaching front
during the afternoon.

Outlook /Tuesday Night through Friday/...

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

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

Wednesday Night through Friday: Winds less than 25 kt. Slight
chance of rain showers.

&&

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

&&

$$

SYNOPSIS...BW/Dooley
NEAR TERM...KJC/Dooley
SHORT TERM...Dooley
LONG TERM...BW
AVIATION...KJC/BW
MARINE...BW/Dooley