Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 271744
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
144 PM EDT Sat Apr 27 2024

.SYNOPSIS...
Quiet weather prevails Saturday, increasing clouds this 
afternoon ahead of a warm front, with scattered rain late 
tonight and tomorrow. Unsettled pattern sets up for Sunday into
early next week, though the best chance for showers is around 
Tuesday or Wednesday and again on Friday. Temperatures turn 
quite mild for interior western New England Monday, but a 
backdoor cold front brings colder air to coastal areas. Onshore 
flow keeps temps cooler Tue/Wed before warming again late week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
9 AM Update... 

High clouds associated with a warm front advancing from the west
have started to make their way into western southern New England
at this hour. Expecting high clouds to continue to increase from
west to east this afternoon, but we will remain dry through the
daylight hours with temperatures surging, away from the coast,
into the 60s. 

ITWS winds, just off the deck, have gone calm as of 13Z, and
with surface winds also calm, expecting the seabreeze to kick in
around 14Z. This seabreeze will keep temps along the coastline
rather cool today, in the 50s. 

Highlights: 

* Frost Advisory continues through 8 AM due to temperatures in the 
  low 30s. Though, a few prone locations that effectively radiate 
  have dropped into the 20s. 

Persistent weather pattern with surface high pressure dominating the 
forecast yet another day. Hard to complain over seasonable afternoon 
temperatures and wall-to-wall sunshine. Visually, the more notable 
difference will be increasing high clouds ahead of a warm front mid 
to late afternoon. Fairly comfortable temperature-wise as we warm 
into the 60s, perhaps near 70 degrees in the CT River Valley and 
Merrimack Valley. Areas along the coast remain cooler, here the high 
reaches the middle and upper 50s due to the seabreeze. At the coast 
wind speeds are roughly 10 to 15 mph, inland winds are light and 
from the southwest.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Highlights: 

* Sct'd rain, mainly western areas, as a warm front lifts across 
  southern New England.

* No washout Sunday, but a rouge shower or two are possible. More 
  clouds than sunshine, though temperatures remain mild. 

Tonight:

As we transition from late afternoon to early evening clouds thicken 
and lower ahead of a warm front that brings sct'd rain chances to 
southern New England during the overnight hours. Think the greatest 
chance for rain are western Massachusetts and Connecticut. Rain will 
be light due to the amount of dry air still at the surface because 
of the persistent surface high pressure system situated over the 
region. In fact, areas east of the I-95 corridor may remain dry and 
not see a drop of rain. Given the cloudy conditions and southwest 
flow the temperatures overnight will remain warm, comparatively to 
the previous few nights - overnight temperatures range from the low 
to middle 40s. 

Sunday:

Warm front lifts through and we are left with variable cloud cover, 
still can not rule out a spot/brief shower as southern New England 
is situated on the northeastern edge of the mid-level ridge. A few 
pulses of mid-level energy traverse through during the afternoon, it 
is from this we maintained a slight chance for light rain - do not 
go canceling your outdoor plans. Despite the lack of full sunshine a 
warmer afternoon is likely with highs away from the coast in the 
upper 60s to low 70s. Southwest will provide an onshore wind for the 
south coast of RI and MA, here it is cooler, upper 50s to low 60s.

&&

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

* Periodic rain chances through the week, first Tue/Wed then again 
  on Friday. 

* After a warm start to the week (moreso for western SNE) temps cool 
  Tue/Wed before warming back up late week. 

Details...

Southern New England will alternate between being on the northern 
periphery of a mid level ridge and beneath a series of passing 
shortwave troughs which will bring periodic rain chances to the 
region with a fluctuating temperature forecast. 

Monday...

Despite mid level ridging overhead a surface low dropping from 
northern New England along with subtle impulses around the top of 
the ridge will bring widely scattered showers to the region, though 
most will stay dry. The biggest forecast challenge is the high 
temperature for the day as, despite a very warm airmass trying to 
move north, the dropping low will deliver a back door cold front 
sometime Monday. Guidance is slowing the arrival of the front which 
would allow more warming to near or above 70F even for portions of 
central/eastern MA (away from the immediate coast). Ensemble 
guidance indicates a 90%+ chance of temps over 70F in western MA/CT 
and even a 70-80% chance as far east as RI. Along the east coast 
temps likely don't break out of the 60s (or even 50s on the outer 
Cape). 

Tuesday and Wednesday...

The first shortwave of the week moves through Tuesday with a weak 
surface reflection. This leads to increasing rainfall chances 
Tuesday into Wednesday. Though a few rumbles of thunder are 
possible, things have slowed down a bit which would keep the better 
instability to our west and limit thunderstorms here if it looses 
the help from daytime heating. Details on exact timing and placement 
of rain showers are unclear at this time, but the temperature 
forecast is more certain; onshore flow should keep temperatures in 
the 50s (east) and 60s (west). 

Thursday and Friday...

Brief mid level ridging on Thursday will bring drier weather and 
decreasing clouds along with rebounding temperatures as SW flow 
returns. Another frontal system from the Ohio Valley then approaches 
on Friday bringing rain back into the forecast. Warmer air surging 
north ahead of this system brings highs back into the low 70s.

&&

.AVIATION /18Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

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

18Z Update... 

Through Tonight... High Confidence

South/southwest flow around 10kt across much of the interior 
with a seabreeze along the eastern MA coast through 22/23Z,
south/southwest overnight. High clouds/VFR through at least 00Z
with mid level clouds and showers developing across western 
terminals after 02/03Z. MVFR to localized IFR by sunrise with
widespread shower activity, though mainly dry for eastern MA
terminals.

Sunday... High confidence. 

MVFR/IFR cigs early in the morning with sct'd -SHRA. Improving cigs 
after 16z, trending VFR some time after 18z/20z. SW winds 8-12 kt. 

Sunday night... Moderate Confidence

Generally VFR away from the Cape and Islands where patchy fog
will develop. Winds SW to start the night, transitioning to the
W/NW across the interior by daybreak. 


KBOS TAF...High confidence in TAF. VFR with seabreeze through
23Z. Mainly VFR overnight with scattered showers possible
between 06/09Z. MVFR develops behind diminishing showers for the
better part of the morning. VFR redeveloping Sunday afternoon. 

KBDL TAF...High confidence in TAF. VFR through 00Z. Scattered
showers/MVFR developing after 02Z. Localized IFR possible Sunday
morning. Winds SW near 10kt before becoming NW late Sunday
night. 

Outlook /Monday through Wednesday/...

Monday through Monday Night: Mainly VFR, with local MVFR
possible. Slight chance RA.

Tuesday: Mainly VFR, with areas MVFR possible. Chance RA.

Tuesday Night: Mainly VFR, with areas IFR possible. Chance RA.

Wednesday: Mainly VFR, with local IFR possible.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Sunday... High confidence.

Tranquil boating conditions for mariners through most of today and 
this evening, there is a low chance for showers on the southern 
waters late tonight into pre-dawn Sunday. 

Southwest winds increase to 10 to 15 knots on all waters today and 
Sunday, though will become east/southeast on the eastern nearshore 
waters late this morning to early evening. 

Seas mainly 3ft or less all waters.

Outlook /Sunday Night through Wednesday/... 

Sunday: Winds less than 25 kt. Slight chance of rain showers. 

Sunday Night: Winds less than 25 kt. Slight chance of rain. 

Monday: Winds less than 25 kt. 

Monday Night through Tuesday: Winds less than 25 kt. Slight
chance of rain. 

Tuesday Night: Winds less than 25 kt. Chance of rain. 

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

&&

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

&&

$$

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