818
FXUS61 KBOX 051750
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
150 PM EDT Sun May 5 2024

.SYNOPSIS...

Cloudy and cool weather is on tap for today with a period of
widespread showers arriving from the west this afternoon and
continuing tonight. Mild and dry to start the work week before
cooler and unsettled conditions Wednesday through next weekend

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

845 AM Update...

* Cloudy with showers moving into the interior mainly this
  afternoon & late afternoon/early evening on I-95 corridor

* Remaining cool this afternoon with highs only in the 50s

Previous forecast is pretty much on track. High pressure over
the Canadian Maritimes will continue to shift further east today
as shortwave energy approaches from the west. The
stronger/forcing deeper moisture will not impact the interior
until this afternoon. So while a few spot showers are possible
this morning across the interior...expect the main threat of
showers to arrive this afternoon. Meanwhile...in the Boston to
Providence corridor the showers should not arrive until late
afternoon/early evening but it still will be cloudy.

As for temperatures...they will remain cool today with cloudy
skies and onshore low level flow. This should keep high
temperatures in the 50s across the vast majority of the region.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...

Tonight

Showers associated with an upper-level short-wave traversing over
The Northeast spread west to east this evening. Expect widespread
light showers across southern New England with new rainfall
accumulations totaling 0.25 to 0.5 inches. Winds remain steady out
of the south which will keep dewpoints elevated and support some
patchy fog formation. Low temps will be bottom out early in the
evening as southerly flow and low-level warm advection will begin to
support increasing temperatures after midnight and into tomorrow
morning.

Tomorrow

A substantial warm up tomorrow as southerly flow advects a near 15C
air mass at 925 hPa over the region. Still expecting a good amount
of low to mid-level cloud cover across the region for the first half
of the day, but breaks of sun in the afternoon should support warm
temperatures in the low to mid 70s across areas of southern New
England away from the coast. Winds may be light enough to support a
sea-breeze along the coastline which would result in cooler
temperatures in the mid 60s.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...

* Dry with warmer than normal temperatures Tuesday

* Cooler with periodic showers Wednesday thru Saturday

Temperatures...

Warm airmass over SNE with good model consensus of 925 mb temps
ranging from +16C to +18C...and +10C at 850 mb. These temps aloft
combined with good blyr mixing via strong/high May sun angle and a
dry airmass (dew pts in the 40s) will support highs 75-80. Ensembles
have 100% probability of 70+ temps away from the immediate coast
Tue. These temps are much warmer than normal (60s) for early May.
Thus, a dry heat for Tue. A weak pressure gradient combined with
ocean temps in the 40s, will result in a wicked seabreeze, hence
much cooler along the coast, Cape and Islands. However, coastal
locations including Boston, could briefly hit 70+ before the
seabreeze arrives. Nonetheless, Tue definitely the pick of the week,
then a pattern change develops around Wednesday and continues thru
next weekend. A stalled frontal boundary sets up over or near SNE,
yielding a cooler regime, with lots of clouds, onshore flow and risk
of showers from time to time. Temps likely become progressively
cooler each day, beginning Wed and continuing into next weekend.

Precipitation...

Any leftover scattered showers Monday evening associated with weak
cold front, quickly come to an end as post frontal airmass
overspreads the region later in the evening and overnight. Turning
less humid Monday night, as dew pts fall from 55-60 into the upper
40s/low 50s by 12z Tue. Dry NW flow prevails Tue followed by a
pattern change with a stalled frontal boundary setting up over or
near SNE, beginning Wed and continuing into next weekend. Lots of
uncertainty on the exact placement of this boundary and timing and
amplitude of frontal waves traversing this boundary. There will be
periods of dry weather during this time as well, hence not raining
every hour of the day.

&&

.AVIATION /18Z SUNDAY THROUGH THURSDAY/...

Forecast Confidence Levels:

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

18z TAF Update...

This afternoon through tonight...High Confidence.

Mainly lower end MVFR/IFR conditions will tend more towards IFR
cigs/vsbys tonight with even localized LIFR conditions with the
cooling boundary layer. Showers were currently working into
interior MA & CT at mid afternoon and will overspread the
coastal plain by late afternoon/early evening. Generally expect
a 3 to 6 hour period of showers working from northwest to
southeast into tonight. Light SE winds will tend to shift more
to a S direction tonight. A period of LLWS will also impact
areas to near the south coast toward daybreak with a modest SW
low level jet.

Monday and Monday night...High Confidence.

MVFR-IFR conditions Monday morning will tend to improve to
mainly VFR thresholds by mid afternoon and persist Mon night
outside localized patchy ground fog. However...MVFR-IFR
conditions in low clouds and fog may persist near the south
coast well into Monday night with moist light SW low level flow
ahead of a slow moving cold front. Bulk of the showers will exit
the Cape/Islands Monday morning. Dry weather should then
dominate later Monday into Monday night...but a round of
scattered brief showers will work southward along a slow moving
cold front Monday afternoon and evening but they will not last
long in a give location. Light SW winds Monday will shift to a
light NW wind Monday night behind a weak cold front.

KBOS TAF...High Confidence in TAF.

KBDL TAF...High Confidence in TAF.

Outlook /Tuesday through Thursday/...

Tuesday: VFR.

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

Wednesday: Mainly MVFR, with local IFR possible. Breezy. Chance
SHRA, isolated TSRA.

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

Thursday: Mainly VFR, with areas MVFR possible. Breezy. Chance
SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Tomorrow

Seas increase by about a foot over the next 48 hours as winds become
more steady out of the south. Nonetheless, conditions remain on the
quiet side with wind speeds topping out at 10-15 knots and seas in
the 2 to 4 foot range. A period of stronger gusts up to 20 knots is
expected to develop tomorrow afternoon over the outer southeastern
marine zones.

Outlook /Monday Night through Thursday/...

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

Tuesday through Tuesday Night: Winds less than 25 kt.

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

Wednesday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain showers.

Thursday: 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...Nocera/RM
NEAR TERM...Frank
SHORT TERM...RM
LONG TERM...Nocera
AVIATION...Frank/Nocera
MARINE...Nocera/RM