Lexington Weather

Lexington, Massachusetts, USA

55°F

4/27/2024 9:39pm

Lexington Conditions: Clear
Temperature: 55.0°F / 12.8°C
Dew Point: 30.6°F
Relative Humidity: 39%
Wind: SSW Calm, 10-min avg: 2 mph, gust: 11 mph
Barometer: 30.27 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 272306
AFDBOX

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

.SYNOPSIS...
Warm but unsettled conditions for Sunday with a few chances for 
widely scattered showers through early Monday. Mainly dry and 
warm weather is on tap for Monday, except it will be 
considerably cooler along portions of the immediate coast. A 
backdoor cold front will bring cooler temperatures Tuesday and 
Wednesday before it warms up again by late in the week. The 
greatest risk for a period of showers will be later Tuesday into
Wednesday.

&&

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

7 PM Update...

* A round of scattered showers especially inland from the coast
  later this evening and esp after midnight

Approaching mid level warm front/shortwave was resulting in
showers breaking out across NY State early this evening. This
will result in enough forcing/lift for a period of scattered
showers later this evening and particularly after midnight. The
showers will gradually weaken as they move east into some upper
level ridging...so showers will be more numerous inland from 
the coast. However...a few brief showers will probably survive 
it onto the coastal plain after midnight.

Shower activity is expected to come to an end by daybreak, but low 
to mid level clouds will develop thanks to a significant jump in 
moisture in the column. Given increasing cloud cover and dewpoints, 
overnight lows tonight will be much milder than the last several 
days, generally in the 40s, with no risk of frost across the
area!

&&

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

Sunday will be bit of an odd day with widespread morning cloud cover 
giving way to above normal temperatures by mid afternoon. Mid-level 
ridge regenerates and broadens allowing mild temperatures aloft, up 
to 11C, but daytime heating will be slow through ~15Z before breaks 
in the low/mid level cloud deck begin to develop. Once some sunshine 
is able to break through the clouds, we will see temps warm quickly 
into the upper 60s to low and perhaps even mid 70s, warmest across 
the CT River Valley, by early afternoon. Humidity will be quite 
noticeable, as dewpoints climb into the 50s by late afternoon 
thanks to prolonged SW/S flow. 

Convection will generate another round of afternoon showers across 
upstate NY, but with limited instability, up to 100J/kg MUCAPE just 
barely scraping the northwestern edge of MA, not expecting that 
thunderstorms will survive a trip over the Berkshires into our 
region. With that said, convective showers will weaken into widely 
scattered showers as they enter our western zones, highlighted well 
by the 12Z HREF, primarily affecting western MA and CT from 20-00Z 
tomorrow. 

Dewpoints continue to climb after sunset into the mid and perhaps 
upper 50s, which will lead to an unseasonably mild night. Increased 
moisture along with light SW flow will likely result in some pockets 
of fog along the south coast/Cape/Islands overnight, but flow across 
the interior takes a turn for the W/NW, which will limit the inland 
extent of fog formation.  Another weak wave of energy dropping south 
into the region overnight may initiate a few scattered rain showers 
between midnight and sunrise.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...

Key Points...

* Warm on Mon with 70s/near 80...but much cooler immediate coast
* Cooler Tue & especially Wed with 50s & 60s...coolest coast
* Milder again by Thu & Fri with 70s away from the coast
* Greatest risk for a period showers later Tue/Wed 

Details...

Monday...

Upper level ridge axis just to our west will result in a generally 
dry/warm day away from the immediate coast. We will have to watch 
for a backdoor cold front...but thinking for Mon the primary impacts 
will be along the immediate coast. Temps immediately along the coast 
will be in the 60s and probably fall into the 50s across much of 
that region that afternoon with onshore flow. Meanwhile...the 
surface flow is rather weak inland from the immediate coast and 850T 
near +9C/10C. Good mixing should yield highs well into the 70s/near 
80 with the warmest of those readings lower CT River Valley. That is 
our thinking right now...but it will be cooler if backdoor front 
moves faster than current indications.

Tuesday and Wednesday...

High pressure over eastern Canada will allow for the backdoor cold 
front to have crossed the region and result in cooler temps Tue and 
Wed. Highs will probably be held in the 50s along portions of the 
coast and in the 60s further across the interior. A shortwave trough 
also may bring a period of showers to the region sometime later Tue 
into Wed...but specific timing remains uncertain. 

Thursday/Friday/Saturday...

Upper trough pushes east of the region late in the week...allowing 
for upper level ridging to build back into southern New England. 
This should allow highs to reach well into the 70s to perhaps even 
near 80 away from the immediate coast and any sea breezes. The upper 
level ridging should result in generally dry weather Thu/Fri...but a 
shortwave/cold front may bring an increasing chance for showers 
sometime Sat.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...

Forecast Confidence Levels:

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

00z TAF Update... 

Tonight...High Confidence

VFR conditions with increasing mid level cloudiness this
evening. MVFR ceilings develop after midnight with localized 
IFR conditions. Some scattered showers approaching from the 
west later this evening and especially after midnight. The 
showers will be more numerous across the interior...weakening as
the move east. That being said...a few brief showers may 
survive onto the coast after midnight. SSW generally 5 to 10 
knots. 

Sunday...High confidence. 

MVFR/IFR cigs early in the morning. 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. Scattered showers possible 
between 05Z and 09Z. MVFR develops behind diminishing showers 
for the better part of the morning. VFR redeveloping Sunday 
afternoon. 

KBDL TAF...High confidence in TAF. Scattered showers after
01Z/02Z...but MVFR conditions probably will not develop until
near or after midnight.

Outlook /Monday through Thursday/...

Monday: Mainly VFR, with local MVFR possible. Breezy. 

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

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

Tuesday Night: Mainly MVFR, with local IFR possible. Chance
SHRA.

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

Wednesday Night: Mainly MVFR, with areas VFR possible. Slight
chance SHRA.

Thursday: Mainly VFR, with local MVFR possible. 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... High confidence.

Generally tranquil boating conditions expected through Sunday
outside of a few rounds of widely scattered showers overnight
tonight and tomorrow evening. Onshore breeze across the eastern
waters will subside quickly this evening giving way to primarily
south/southwest winds for Sunday. Some patchy fog possible
Sunday night. 

Seas mainly 3ft or less all waters.

Outlook /Monday through Thursday/... 

Monday through Monday Night: Winds less than 25 kt. 

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

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

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

&&

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

&&

$$

SYNOPSIS...KS/Frank
NEAR TERM...Frank/KS
SHORT TERM...KS
LONG TERM...Frank
AVIATION...KS
MARINE...KS/Frank