Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 092300
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
700 PM EDT Fri Jun 9 2023

.SYNOPSIS...
Showers and scattered thunderstorms wind down this evening.
Milder temperatures begin to return Saturday with the main
threat for diurnally driven showers confined to eastern New
England. A warming trend Sunday with a low risk for a few 
afternoon showers in the interior, then the weather pattern 
turns unsettled again for much of the upcoming week with the 
risk of showers each day. Temperatures will be seasonable for 
much of next week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
7 PM update...

Scattered showers and isolated t-storms continuing this evening,
although activity has diminished somewhat. SBCAPES down to 
250-500 J/kg, but cold pool aloft will help to sustain a few 
showers and possibly a t-storm for another few hours into the 
evening before winding down. Otherwise, generally dry weather 
prevails for the remainder of the night other than perhaps a 
brief spot shower. Low temps should bottom out mainly in the 
upper 40s to the lower 50s...but will need to watch for some 
patchy ground fog in the typically prone locations forming 
especially in areas that receive a modest amount of rain.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Highlights...

* Turning milder Saturday away from the coast with highs 70-75

* Scattered diurnally driven showers Sat and perhaps an isolated
  t-storm mainly confined to mainly the eastern half of MA/RI 

Details...

Saturday...

The upper trough axis will finally begin to shift east of the
region on Saturday. This will allow milder mid level temps to
spread eastward and also result in partial sunshine especially
across parts of interior southern New England. Weak pressure
gradient will promote sea breezes along much of the immediate
coast...holding high temps in the 60s in those locales. 
However...the rest of the region should see some partial 
sunshine with highs recovering into the 70 to 75 degree range. 
In fact...the lower CT River Valley will likely see highs more 
in the middle 70s. 

The cold pool aloft will be shifting east as well. This will 
keep much of western MA/CT dry on Saturday except perhaps for a 
spot shower. However...steep mid level lapse rates will persist 
across the eastern half of the region especially over eastern 
MA. Therefore...we do expect scattered diurnally driven showers 
to develop across central/eastern MA & RI on Saturday. Areal 
coverage will not be as widespread as today...so some of these 
locations should stay dry. We might have enough marginal 
instability for an isolated t-storm or two across eastern New 
England...but that is about it and not expecting a repeat of
today.

Saturday night...

Upper trough continues to move east and away from the region as
a mid level ridge axis approaches. This will result in
dry/tranquil weather Saturday night. Low temps will bottom out
mainly in the upper 40s to the middle 50s. Light/Calm winds may
promote patchy ground fog late in the typically prone
locations...but not expecting anything widespread.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Highlights...

* Mainly dry and warmer Sunday. Low risk for afternoon shower 
  interior

* Unsettled weather pattern returns for much of next week with 
  chance of showers each day. Seasonable temps

Sunday...

Weak ridging aloft develops across New Eng ahead of upper low 
dropping south into the Gt Lakes. This will bring partly to mostly 
sunny skies although some increase in clouds is expected during the 
afternoon. Marginal instability develops with a few hundred J/kg of 
CAPE which could lead to a shower in the interior in the afternoon, 
but given lack of forcing much of the region will be dry. It will be 
a warmer day as 850 mb temps rise to 12-13C. This will support highs 
in the upper 70s and lower 80s, but afternoon sea-breezes will keep 
coastal locations a bit cooler. 

Monday through Friday...

Unsettled pattern returns as anomalous upper low across the Gt Lakes 
gradually moves east across New Eng through midweek before lifting 
out. But additional shortwave energy will be rotating southward from 
Canada with trough reloading late in the week. This will result in 
an extended period of unsettled weather with the risk of showers 
each day. The challenge will be the timing of wet weather. A period 
of widespread showers and a few t-storms is expected sometime Monday 
into Tuesday as anomalous PWAT plume advects northward ahead of 
frontal system approaching from the west. However, there is 
considerable uncertainty with the exact timing. GFS focuses the rain 
mostly on Monday then drying out Mon night/Tue while ECWMF brings 
the rain in Mon night into Tue. We leaned toward NBM PoPs which 
brings highest PoPs late Mon into early Tue. 

Some drying is expected behind this system Tue night, then 
additional shower activity and possible thunder Wed as upper low and 
cold pool moves into the region. Remains somewhat unsettled Thu/Fri 
as multiple shortwaves will be rotating through the mean trough, 
although a drier pattern with less coverage of showers and not a 
washout. 

Despite the unsettled pattern, temps should average near normal for 
much of the upcoming week, and possibly above normal for a few of 
the days as GEFS/EPS ensembles show high probs of 850T above 10C and 
low probs of max temps of 80+. Coolest day expected to be Wed as 
upper low/trough axis moves overhead.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels:

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

00z TAF Update...

Tonight...Moderate Confidence.

Scattered showers and isolated t-storms diminish this evening 
with the loss of daytime heating. Otherwise...VFR outside of 
localized patchy ground fog that may develop in some spots 
overnight. Remnant smoke from the Canadian Wildfires may 
continue to flirt with the Cape and Islands a times...resulting 
in perhaps some marginal MVFR vsbys. There also may be a period 
of low clouds/fog that develop near the coast after midnight but
that remains uncertain. Light/Calm Wind.

Saturday...High Confidence.

Mainly VFR after any low clouds/fog patches burn off by mid-late
morning. Brief localized lower conditions are also possible in 
the afternoon...mainly across eastern MA in scattered showers 
and perhaps an isolated t-storm or two. Light NW winds except 
for sea breezes developing along portions of the immediate 
coast.

Saturday night...High Confidence.

Mainly VFR outside any localized patchy ground fog that may
develop in the typically prone locations toward daybreak. Light
SW Winds

KBOS Terminal...Moderate Confidence in TAF. A brief period of
MVFR cigs possible until about 01Z, otherwise VFR through the 
period. 

KBDL Terminal...Moderate Confidence in TAF. a brief showers
possible until 02z, otherwise VFR through the period. 

Outlook /Sunday through Wednesday/...

Sunday: VFR. 

Sunday Night: VFR. Slight chance SHRA.

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

Monday Night: Mainly MVFR, with areas IFR possible. Breezy.
SHRA likely, isolated TSRA.

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

Tuesday Night: VFR. Chance SHRA.

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

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight through Saturday night...High Confidence.

Weak pressure gradient will keep winds/seas below small craft
advisory thresholds through Saturday night. Main concern is for
a few nearshore thunderstorms early this evening...but the bulk
of those storms will dissipate as they approach the waters. The
only other issue will be some reduced vsbys mainly near and
south of the Cape/Islands tonight from the remnant smoke from 
the Canadian Wildfires and perhaps some fog late.

Outlook /Sunday through Wednesday/...

Sunday: Winds less than 25 kt. 

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

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

Monday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Rain showers likely, isolated thunderstorms. 

Tuesday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain
showers. 

Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers. 

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Air Quality Alert until midnight EDT tonight for MAZ020>024.
RI...None.
MARINE...None.

&&

$$
SYNOPSIS...KJC/Frank
NEAR TERM...KJC/Frank
SHORT TERM...Frank
LONG TERM...KJC
AVIATION...KJC/Frank
MARINE...KJC/Frank