546
FXUS61 KBOX 111907
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
307 PM EDT Sat May 11 2024

.SYNOPSIS...
Increasing clouds tonight ahead of an approaching system across the
eastern Great Lakes. A few showers possible late tonight with a hit
or miss shower on Sunday, not expecting a washout. Another cooler
than normal day is expected Sunday. Milder next week with the
risk for showers increasing Tuesday into Wednesday, then mainly
dry and seasonable toward the end of next week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Highlights:

* Mixture of sun and clouds to wrap up this afternoon, but
  increasing mid and high clouds this evening to likely obscure the
  aurora overnight.

Diurnal cumulus clouds this afternoon and cooler temperatures across
southern New England. Many locations as of early this afternoon are
in the 50s to mid 60s, warm spot in the CT River Valley. Southern
New England is positioned between an area of high pressure near the
mouth of the St. Lawrence River and surface low pressure well to the
southeast of Nantucket. Due to this setup, a northeast flow has kept
our temperatures below normal... The normal high for today ranges
between 65 to 70 degrees!

Diurnal clouds dissipate late this afternoon/early evening, but a
robust shortwave to our west will advect moisture and cloud cover
for this evening and overnight hours. Not the best news for those
seeking to get a glimpse of the aurora overnight. While there could
be a few breaks in the cloud cover, do think there will be blanket
of mid and high clouds aloft before midnight and remains with us
into Sunday.

A few showers are possible, mainly areas west of the CT River Valley
as the shortwave moves in from the west. Otherwise a dry night.

Temperatures aloft are fairly cold, 850mb temperatures are between
+1C to -2C, which is -5C to -10C below the climatological normal.
That said, a cooler night ahead despite the cloud cover, look for
overnight low temperatures in the upper 30s to middle 40s.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Highlights:

* Another cooler day with a few showers possible.

Sunday & Sunday Night:

A weak surface low pressure develops around the eastern Great Lakes
and moves southeast, promoting shower activity over New York, but a
few showers are possible in western Connecticut and Massachusetts.
While the day is mainly dry, an anomolously cold airmass aloft and
shortwave pushes across southern New England, the cold pool could
trigger a few spot/pop-up showers across all of southern New England
as seen on the 12z CAMs. Good news, not a washout, showers will be
isolated and brief. Winds are generally out of the southeast, but
along the east coast of Massachusetts do think a seabreeze develops
which will keep the wind direction out of the east. Another cooler
afternoon with highs in the upper 50s and low 60s away from the
coast, near the coast temperatures are in the mid 50s. Clearing sky
overnight with high pressure settling back into the region,
temperatures aloft are increasing, despite the clear sky don`t
expect low temperatures to be much cooler than the night before, in
fact a few degrees warmer int he low and middle 40s.

&&

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

* Warming up Monday and Tuesday with afternoon high temperatures
  near or above 70 degrees

* A coastal low-pressure system is forecast to bring a period of
  substantial rainfall and gusty winds to the region Tuesday night
  into Wednesday

* Drying out late week with more seasonable temperatures in the 60s
  and 70s

Monday and Tuesday

The week begins with an upper-level low and cold pool aloft shifting
east of southern New England. Behind this system a broad upper-level
ridge will build over the eastern US and replace the anomalously
cool air mass currently in place with a warmer and more seasonable
air mass for mid-May. 925 hPa temps rise to 10C on Monday afternoon
and 15C on Tuesday afternoon. This should support warmer
temperatures in the upper 60s on Monday afternoon and low to mid 70s
on Tuesday afternoon. Sea-breezes may keep the coastal areas a bit
cooler on Monday.

Precipitation chance begin to increase late Tuesday in response to
warm advect ahead of a fairly robust short-wave trough advancing
over The Midwest/Ohio River Valley. Most areas stay dry on Tuesday,
but can`t rule out a few spot showers Tuesday evening.

Tuesday night and Wednesday

By Tuesday night, the short-wave over The Midwest will be traversing
east with a surface low-pressure system developing at the surface.
This system is forecast to bring a substantial amount of
precipitation to southern New England Tuesday night into much of
Wednesday. This system appears as though it will take a coastal-
storm track south of southern New England. This would presumably
support more stable conditions across the region and limit any
potential for spring convection. Nonetheless, strong synoptic
forcing/FGEN and PWATs approaching 1.5" will allow for precipitation
around an inch or greater by Wednesday night. Ensemble probabilities
of an inch or greater are about 50 percent across southern New
England with a 10 to 20 percent chance of up to 2 inches over the
south coast. Accumulations will be heavily dependent on storm track
and just how much moisture is available, but confidence is
increasing in a substantial precipitation event during this time
frame. Winds may be gusty at times as well with 20 to 30 mph gusts
possible Tuesday night and Wednesday. Latest guidance supports this
system being east of the region by Wednesday night leading to a dry
day on Thursday.

Thursday and Friday

Northwest flow behind a departing area of low-pressure will advect a
drier air mass over southern New England to end the week. This will
support plenty of sunshine on Thursday with highs in the upper 60s
to low 70s. A ridge axis overhead should keep the region dry with
warm/seasonable temperatures to end the week as well. As the ridge
axis shifts east late week, return flow from the south will support
increasing cloudiness and precipitation ahead of our next low-
pressure system which may bring more precipitation to the region
early next weekend.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
Forecast Confidence Levels:

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

This Afternoon... High confidence.

VFR, with MVFR for Cape Cod & Islands. Low chance of a brief
spot showers. East-Northeast winds 10-20 kt, gusts to 30 knots
at ACK.

Tonight... High confidence.

VFR, MVFR CIGs and isolated areas of patchy fog may develop
across the CT River Valley and the Cape and Island. Light winds.

Sunday... Moderate confidence.

VFR, areas of MVFR and scattered showers are possible across
western Massachusetts and Connecticut. Southeast wind 5-10
knots with sea breezes developing after 14z.

Sunday Night... High confidence.

VFR. Patchy fog possible in prone radiator locations. Light
southwest winds.

KBOS TAF...High confidence in TAF.

VFR. Low chance for a spot shower overnight, but otherwise dry
runways. East-northeast winds this afternoon and evening,
becoming light and variable after 04z. Seabreeze possible after
14z.

KBDL TAF...High confidence in TAF.

VFR this afternoon and this evening, low chance of a spot
shower Saturday afternoon, otherwise dry runways. MVFR conditions
become possible after 09z with patchy ground fog, but not high
enough confidence to include in TAF. East wind becomes southeast
tonight less than 5 knots. MVFR CIGS Sunday morning becoming VFR
late morning. Chance of SHRA after 09z. Light south winds
Sunday.

Outlook /Monday through Thursday/...

Monday: VFR. Breezy.

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

Tuesday: VFR. Windy with local gusts up to 30 kt. Chance SHRA.

Tuesday Night: Mainly MVFR, with local IFR possible. Windy with
local gusts up to 30 kt. SHRA, isolated TSRA.

Wednesday: MVFR/IFR conditions possible. Breezy. SHRA likely.

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

Thursday: VFR. Breezy. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Sunday Night...

Pressure gradient brings east/northeast winds this afternoon across
the southern waters to 25-30 knots, becoming light and variable
overnight with high pressure settling over the waters. Residual seas
on the southern waters of 5 foot are the basis for the Small Craft
Advisory through portions of Sunday. A few spot and brief showers
possible Sunday morning then dry conditions into Sunday night.

Outlook /Monday through Thursday/...

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

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

Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of seas approaching 5 ft. Slight
chance of rain showers.

Tuesday Night through Wednesday: Moderate risk for Small Craft
Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Rain
showers likely.

Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 20 kt. Areas of rough seas. Chance of rain showers.

Thursday: Winds less than 25 kt. Areas of rough seas. Slight
chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT Sunday for ANZ254-255.
     Small Craft Advisory until 2 AM EDT Sunday for ANZ256.

&&

$$

SYNOPSIS...Dooley/RM
NEAR TERM...Dooley
SHORT TERM...Dooley
LONG TERM...RM
AVIATION...Dooley/RM
MARINE...Dooley/RM