Lexington Weather

Lexington, Massachusetts, USA

56°F

6/9/2023 8:01pm

Lexington Conditions: Clear
Temperature: 56.1°F / 13.4°C
Dew Point: 54.5°F
Relative Humidity: 94%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.67 in Steady
Visibility: 10 miles
Rain Today: 0.22 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 081753
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
153 PM EDT Thu Jun 8 2023

.SYNOPSIS...

Similar conditions expected today, Friday and Saturday, not a 
washout, but scattered afternoon showers each day, perhaps most 
numerous Friday. Temperatures will continue to run slightly 
cooler than normal. There will also be some near ground level 
smoke at times, as a result of the ongoing Canadian wildfires. A
brief pattern change occurs Sunday and possibly lingering into 
Monday, bringing drier and warmer conditions to the region. Then
the next frontal system may bring widespread rain to the region
around Tuesday.

&&

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

925 AM Update...

* Rather Cloudy/Cool Today with scattered showers with bulk of
  any sunshine confined to the south coast, Cape & Islands

Persistent closed upper level low pressure system will continue
to spin today along the northern New England/Quebec border. Some
additional shortwave energy rotating southward from this main
upper level low will result in forcing for ascent. The result 
will be scattered showers...especially this afternoon during max
heating. Perhaps we muster a few hundred J/KG of MUCape...but 
thinking if we do see any thunder it would be rather isolated. 
Therefore...kept the current forecast with just scattered 
showers. An abundance of clouds with cyclonic flow will keep 
highs mainly in the 60s. The exception to this will be areas 
near the south coast, Cape/Islands where they are just far 
enough removed from the upper level low. This will keep most of 
the showers to their north and also allow for some 
sunshine...especially during the first part of the day.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
345 AM update...

* Showers may become more widespread Friday

Tonight...

Any diurnal early evening scattered showers diminish with or shortly 
after sunset. Given cold pool aloft, light winds and decreasing 
diurnal clouds, another chilly night. Lows 45-50 with low 50s along 
the coast, including the city of Boston. Normal low, 52-57. 

Friday...

Vertically stacked low remains over northern New England, but some 
short wave energy dives into the backside of the trough and backs 
the mid level flow to more SW over New England. This results in more 
cyclonic flow aloft and greater moisture & instability advection 
into SNE. PWATs rising to near 1 inch and surface dew pts climb into 
the 50s. This combined with steep mid level lapse rates will provide 
sufficient instability for scattered showers and and isolated 
thunderstorms. Given the increased instability coupled with weak 
forcing for ascent, showers could be more widespread Friday than 
Thursday. Cold pool aloft (-21C at 500 mb) limits highs to the mid 
and upper 60s Friday, perhaps a few 70 deg readings in the CT River 
Valley. Winds light and variable except locally onshore.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...

345 AM update...

Highlights

* Warmer this weekend with more showers on Saturday and drier 
  weather on Sunday

* Unsettled weather returns early next week as a new area of low-
  pressure moves over The Northeast

Saturday

The upper low that's been sitting over The Northeast this week will 
finally lift out and fill during the first half of this weekend. 
This will allow warmer air to advect in from the west as a mid-level 
ridge builds east. Despite the upper-low ejecting away from the 
region, cold air aloft will continue to support steep lapse rates 
through the column. Additionally, there will remain sufficient 
moisture in the column to support more diurnal showers and 
thunderstorms on Saturday afternoon. With 925 hPa temps warming to 
12 to 13 Celsius on Saturday, we're currently expecting surface 
temperatures to top out in the low to mid 70s. This combined with 
steep lapse rates will support modest diurnal instability with CAPE 
values getting as high 500 J/Kg across southeastern MA and RI. Wind 
fields are forecast to be very week, thus no organized severe 
convection is a concern at this point. Nonetheless, a few isolated 
to scattered thunderstorms capable of producing small hail will be 
possible on Saturday afternoon. 

Sunday

Sunday looks to be the pick of the weekend as a mid-level ridge 
building in from the west will result in the lowest precipitation 
chances we've experienced since last week. A drier low-level air 
mass will support sunshine for most of the day, but we may see 
increasing cloudiness during the mid to late afternoon hours as a 
new system approaches from The Great Lakes. 925 hPa temps climbing 
to 15 Celsius should support highs in the upper 70s to low 80s 
across southern New England Sunday afternoon.

Next Week

After a nice taste of summer weather on Sunday we'll return to 
another wet/unsettled pattern early next week. Low-level wind fields 
will turn south ahead of a robust upper-level low that will bring 
the region its next opportunity for substantial rainfall. Southerly 
flow will bring increasing moisture and cloud cover on Monday as 
well as the opportunity for some diurnal showers and thunderstorms. 
At this point guidance is not insistent on forcing strong enough to 
support a wash out on Monday, but Tuesday is a different story.

As the upper-low advances further east Monday into Tuesday, 
continued southerly flow is forecast to support PWATs rising to near 
1.5 inches across southern New England. As the surface low and 
associated cold front push through the region during the day 
Tuesday, southern New England should experience a more widespread 
rainfall event. Guidance suggests this would be followed up by more 
rainfall on Wednesday as a secondary area of low-pressure moves over 
The Northeast. Details are vague at the 7 day time range, but the 
signal is for a wet/unsettled first half of next week. Despite the 
wet/unsettled pattern, there is also a strong signal that more 
seasonable temperatures will prevail next week with daily high/low 
temps in upper 70s/low 60s respectively.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...

Forecaster Confidence Levels:

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

18z TAF Update...

Through Tonight...High Confidence.

Mainly VFR outside briefly lower conditions possible in any 
scattered showers into the first part of the evening. We will 
need to watch for some lower ceilings possibly working into 
mainly northern MA toward daybreak. We may also see some haze 
tonight near the south coast from the lingering wildfire smoke 
that has been impacting our region the last several days. 
Light/Calm winds.

Friday...Moderate Confidence.

A period of generally MVFR ceilings will be possible Friday
morning mainly across northern MA. We will also need to watch
for some lower vsbys from haze near the south coast Friday from
the lingering wildfire smoke. Otherwise...VFR outside briefly
lower conditions in the expected scattered showers and a few 
t-storms that are expected to develop by Friday afternoon. Light
NE winds except SE towards the Cape & Islands.

Friday night...Moderate Confidence.

The scattered showers and a few t-storms should wind down Friday
evening. It does appear that MVFR-IFR ceilings/vsbys may 
develop across the region Friday night as a result of the 
cooling boundary layer and lingering low level moisture. Areal 
extent/coverage of these potential low clouds and fog patches is
somewhat uncertain...but greatest risk will be across central 
and eastern sections of our region. Winds will be light/calm.

KBOS Terminal...High Confidence in TAF. Main concern will be a
period of MVFR ceilings that are possible Friday morning and
perhaps a few t-storms within the vicinity of the terminal 
Friday afternoon/early evening.

KBDL Terminal...High confidence in TAF. Main concern will be the
potential for a few t-storms within the vicinity of the terminal
Friday afternoon/early evening.

Outlook /Friday Night through Monday/...

Friday Night: Mainly VFR, with local MVFR possible. Chance
SHRA.

Saturday: Mainly VFR, with local MVFR possible. Chance SHRA,
isolated TSRA.

Saturday Night through Sunday: VFR. 

Sunday Night: VFR. Slight chance SHRA.

Monday: VFR. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

345 AM update...

Weak low pressure over Maine remains nearly stationary through 
Friday. Scattered showers and patchy fog will reduce vsby at times. 

Outlook /Friday Night through Monday/...

Friday Night through Saturday: Winds less than 25 kt. Chance of
rain showers. 

Saturday Night through 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.

&&

.FIRE WEATHER...
345 AM update...

Latest model simulations have the smoke conditions improving 
somewhat Thursday, with highest concentrations of smoke along and 
near the south coast. Nonetheless, Air Quality Alerts remain posted 
for western MA, and all of CT/RI.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Air Quality Alert until midnight EDT tonight for CTZ002>004.
MA...Air Quality Alert until midnight EDT tonight for MAZ002-003-
     008>011.
RI...Air Quality Alert until midnight EDT tonight for RIZ001>008.
MARINE...None.

&&

$$
SYNOPSIS...Nocera/RM
NEAR TERM...Frank
SHORT TERM...Nocera
LONG TERM...RM
AVIATION...Frank/RM
MARINE...Nocera/RM
FIRE WEATHER...