591
FXUS61 KBOX 051049
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
649 AM 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 overnight. Mild and dry to start the work week
before cooler and unsettled conditions Wednesday through next
weekend

&&

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

650 AM Update...

1030 mb high over the maritimes providing a cool and moist
easterly flow across SNE. Meanwhile, warm air aloft is gliding
over this shallow cool airmass. However, strongest thermal and
moisture advection is across NY state into VT. Hence, rain
shield is focused over this region. However, the ridge over
eastern MA advects offshore today, showers to the west will
slowly traverse eastward. Thus, a dry start for much of SNE, but
it will be wet finish for most of the region, with Cape Cod
possibly remaining dry much of the day. Otherwise, a cool day
with east to southeast winds streaming across ocean temps in the
40s. Earlier forecast was capturing these details, therefore no
major changes with this update. Earlier discussion below.

-------------------------------------------------------------------

Today

Southeast winds gradually shift south during the afternoon today.
Skies will be consistently overcast today which will limit high
temperatures to the mid to upper 50s across the region. Shower
chance will gradually increase into the mid-afternoon hours as a mid-
level short-wave approaches from the west. Most areas stay dry
today, but locations near and west of the CT River Valley may start
to see some light showers in the 5 to 7pm time frame.

&&

.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 /12Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:

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

12z TAF Update...

Marginal MVFR/IFR will slowly lift to mainly MVFR but then
likely lower this afternoon and especially late in the day as
showers overspread the region from west to east. Light E-SE
winds. Earlier discussion below.

---------------------------------------------------------------

Borderline IFR/MVFR ceilings between 008-012 feet with light
easterly winds.

Sunday...High Confidence.

IFR/MVFR ceilings will trend to mainly MVFR thresholds with
some diurnal heating despite the cloudy skies. Some showers will
work into mainly interior MA & CT during the afternoon hours, but
will not reach the coastal plain until late Sunday
afternoon/evening. SE winds 5 to 10 knots.

Sunday night...Moderate Confidence.

IFR/LIFR ceilings develop with light showers spreading west to
east across southern New England overnight. SE winds shift to
more of a S direction at 5 to 10 knots.

Monday...

IFR ceilings lifting to VFR levels by late morning/early
afternoon. Though lower IFR ceilings may persist longer over
The Cape Islands. Light southwest winds becoming more westerly.
Winds may be weak enough to support a sea-breeze circulation
along the coastline.

KBOS TAF...High confidence

KBDL TAF...High confidence

Outlook /Monday Night through Thursday/...

Monday Night through 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...Nocera/RM
SHORT TERM...RM
LONG TERM...Nocera
AVIATION...Nocera/RM
MARINE...Nocera/RM