Old Res Weather

Lexington, Massachusetts, USA

35°F

2/16/2025 7:17pm

Lexington Conditions: Mist, Overcast
Temperature: 35.1°F / 1.7°C
Dew Point: 32.4°F
Relative Humidity: 90%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.00 in Falling Slowly
Visibility: 1¾ miles
Rain Today: 0.01 in
UV Index: $VPuv None

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 181123
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
723 AM EDT Tue Aug 18 2026

.WHAT HAS CHANGED...

No significant changes.

&&

.KEY MESSAGES...

- Gradual clearing today with a low chance of showers in parts of
  the interior. Drier into Wednesday.

- Generally becoming unsettled once again towards the second 
  half of the week into the start of next week.

&&

.DISCUSSION...

KEY MESSAGE 1...Gradual clearing today with a low chance of 
showers in parts of the interior. Drier into Wednesday.

Low pressure continues to pull off to the east and northeast today, 
which will allow for slow clearing, developing from west to 
east. Onshore flow persists as this low pulls further away from 
the region, which will likely keep temperatures near the coasts 
slightly cooler in the 70s. The rest of southern New England 
may reach the low 80s, as that's where clouds should scatter 
out sooner. With the clearer conditions inland, it will also be 
less humid as winds shift more northwest. A spot shower or two 
cannot be entirely ruled out across much of central MA into RI, 
CT this afternoon. Tonight should be calm with patchy fog 
possible and lows in the 60s.

Zonal flow persists aloft into Wednesday as an upper level low 
tracks well to our north across the Hudson Bay. Some guidance does 
indicate some shortwave energy moving within the flow across the 
region later Wed into Thu which could lead to a spot shower or two, 
however the more favorable parameters remain to our north and west.

KEY MESSAGE 2...Generally becoming unsettled once again towards
the second half of the week into the start of next week.

A stronger shortwave within the flow aloft makes its way east 
heading into Thursday, bringing with it more favorable dynamics and 
moisture for showers. Discrepancies still remain regarding the 
wave's track across the ensemble and deterministic guidance, with 
the GEFS continuing to show higher probabilities for 24 hour 
rainfall of 0.1"+ extending into CT, SE MA, and RI while the ECMWF 
and Canadian ensembles continue to favor a more southern track. 
NAEFS guidance, notably, keeps the more anomalous moisture off to 
our south and east, though PWAT values reaching to around 1.5" are 
not out of the question.

Under the post-frontal airmass Friday with high pressure overhead, 
conditions will be drier overall. Temperatures will likely be in the 
low 80s and down to the mid 70s, particularly along the coasts where 
onshore winds will keep it slightly cooler. Conditions become 
unsettled once more, though, as we keep an eye on a deepening trough 
digging into the Great Lakes region towards the weekend period. 
Shortwaves moving along the boundary that may stall just off the 
east coast could bring chances for showers. Thunderstorms could be a 
possibility depending on if these waves could take advantage of 
daytime heat. More details will become apparent as we approach this 
timeframe.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...

Forecaster Confidence Levels...

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

12z TAF Update...

Today and tonight...Moderate confidence in trends with low
confidence in timing especially near the coast.

Low end MVFR-IFR with localized LIFR conditions early this
morning should gradually improve today. Gradual improvement
should occur from west to east through the afternoon with most
locations eventually improving to VFR. However...timing remains
uncertain especially on the coast. In fact...given onshore flow
we can not rule out low clouds/fog bank flirting with coastal 
sections through the afternoon and never fully departing. 

Regardless...low clouds and fog patches should return sometime 
tonight in some locations from east to west given the cooling 
boundary layer and dewpoints remaining into the 60s. Timing and 
westward extend of the low cloud/fog bank remains uncertain 
though...but areas near the coastal plain will likely be 
impacted. Low end MVFR-IFR conditions expected to redevelop 
along with the potential for some LIFR conditions too. 

Winds will generally be light to calm through
tonight...generally 10 knots or less but with onshore flow along
the coast.

Wednesday...High confidence.

Drier westerly flow of air should allow for low clouds/fog
patches that do develop overnight to burn off much quicker then
today. Most locations should be VFR by mid-late Wed morning. 
WSW winds of 5-10 knots

KBOS Terminal...Low confidence in TAF.

We are leaning to the the LIFR conditions early this morning 
gradually improving and eventually reaching MVFR-VFR levels by 
mid-afternoon. However...that is not a guarantee given onshore 
flow and dewpoints in the 60s. It is possible that low clouds 
and a fog bank flirt with the terminal through the afternoon. 

KBDL Terminal...Moderate confidence in TAF.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: VFR. 

Thursday: VFR. Slight chance SHRA, slight chance TSRA.

Thursday Night through Friday Night: VFR. Slight chance SHRA.

Saturday: VFR. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Wednesday Night...Moderate confidence.

Low pressure continues to shift farther off to the east. Seas
diminish more to 2-4 ft across the coastal and nearshore waters.
Ocean waters off to the east may take longer to drop off as they
may get to around 5-6 ft heading into tonight. By Wednesday,
seas fall to 2-3 ft across all waters. Winds through this period
remain generally under 15 kt outside of occasional gusts in the
afternoons. More N winds shift W, then S tonight, then more SW
by Wednesday night.

A higher rip current risk is expected for east-facing
beaches where a Rip Current Statement is in effect from 8 AM 
this morning through 8 PM tonight.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Winds less than 25 kt. 

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

Thursday Night: Winds less than 25 kt. Chance of rain showers,
slight chance of thunderstorms. 

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents through this evening for MAZ007-015-016-
     019-022-024.
RI...None.
MARINE...None.

&&

$$

DISCUSSION...Hrencecin
AVIATION...Frank
MARINE...Hrencecin