Old Res Weather

Lexington, Massachusetts, USA

35°F

2/16/2025 7:17pm

Lexington Conditions: Few Clouds
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: 10 miles
Rain Today: 0.01 in
UV Index: $VPuv None

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 262144
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
544 PM EDT Sun Jul 26 2026

.WHAT HAS CHANGED...
Refined shower chances and flash flood potential through the
upcoming week.

&&

.KEY MESSAGES...

- Low-impact weather through Monday night. A few thunderstorms
  are possible Monday afternoon across western portions of
  southern New England.

- Temperatures on the lower end of seasonable as chances for
  prolonged rainfall return through Wed (possibly into Thurs).
  Monitoring for increasing chances of localized heavy rainfall
  and potentially flash flooding.

&&

.DISCUSSION...
KEY MESSAGE 1...Low-impact weather through Monday night. A few 
thunderstorms are possible Monday afternoon across western portions 
of southern New England.

A weak area of low pressure continues to spin southeast of 
Nantucket, maintaining low clouds and occasional light precipitation 
across the outer Cape and Islands. While not the best beach day 
there, a High Risk for rip currents continues through this evening 
for east-facing beaches of Cape Cod and Nantucket. Elsewhere, most 
of southern New England enjoys sunshine and comfortable conditions. 
The remainder of today through tonight will be relatively quiet. 
Lingering low-level moisture from northeasterly flow combined with 
light winds and mostly clear skies overnight may allow for patchy 
fog to develop in the typical low-lying and river valley locations 
of eastern Massachusetts. Overnight lows fall into the 50s inland 
and the lower 60s along the immediate coast, which is seasonably 
cool for late July.

Monday will feature seasonable temperatures, with highs in the lower 
to middle 80s inland and upper 70s along the coast. A shortwave 
trough dropping into the Northeast, along with an embedded 850-700mb 
disturbance, will provide enough forcing for isolated to scattered 
showers and thunderstorms during the mid to late afternoon, 
primarily west of the Connecticut River Valley. PWATs increase to 
around 1.3 inches, near to slightly above climatological normals but 
not especially anomalous. While a few thunderstorms may produce 
locally heavy downpours, rainfall amounts should generally remain 
modest, with isolated localized totals approaching one-half inch. 
Flash flooding is not anticipated, as 3-hour flash flood guidance 
remains around 2.5 to 3.0 inches. Instability increases to around 
800-1200 J/kg Monday afternoon, but weak deep-layer shear (generally 
less than 30 kt) should limit storm organization. As a result, 
convection is expected to remain isolated and pulse-like, with many 
locations remaining dry. The highest PoPs therefore remain focused 
west of the Connecticut River. CSU machine-learning guidance also 
keeps the better severe-weather signal west of eastern New York. 
While severe weather appears unlikely, the primary hazards with any 
storms will be cloud-to-ground lightning and brief, locally heavy 
rainfall.

Monday night, any lingering convection will diminish during the 
evening. Southwesterly flow aloft then increases moisture, with 
PWATs climbing toward 1.5 inches. Low clouds become more widespread 
overnight, and scattered light showers may begin to develop ahead of 
a more unsettled pattern on Tuesday. Overnight temperatures remain 
mild, holding in the 60s.

KEY MESSAGE 2...Temperatures on the lower end of seasonable as 
chances for prolonged rainfall return through Wed (possibly into
Thurs). Monitoring for increasing chances of localized heavy 
rainfall and potentially flash flooding.

Guidance continues to hone in on a low pressure system pushing 
into New England by Wednesday, but a mid-level trough 
accompanied by several embedded shortwaves will brings chances 
for prolonged rainfall later Tuesday into Wednesday... possibly 
lingering into Thursday. There continues to be a strong signal 
for PWATs 120-170 percent of normal to advect into the region by
Tuesday, with deterministic guidance on the extreme high end of
that range. The ECMWF and it's ensemble continue to be the most
aggressive of the guidance suite. Not only is it favoring a 
slower progression of the low as well as favoring more of the 
near-shore/coastal track, but it's also indicating the low could
deepen much further than the GFS or CMC ensembles are 
indicating. Soundings continue to exhibit the textbook 
environment for efficient rain processes with deep warm cloud 
depths aligned with instability and slower mid-level wind 
speeds, which would create an environment for training storms. 
ECMWF ensemble probabilities show 50-80% chance for 1.0"+/24 
hours Tue into Wed across southern New England and 10-30% for 
2.0"+/24 hours across the CT River Valley, and the deterministic
ECMWF mirrors those locations with around 2.0"/24 hours as 
well. Combined with the enhanced forcing of the low, the higher 
PWATs and potential for training, the threats for localized 
heavy rainfall and potentially flash flooding are continuing to 
be monitored. Unfortunately, there still remains some 
uncertainty in the guidance regarding where exactly the low 
could track, with the Canadian and GFS (and their ensembles) 
indicating the low moving further south near NYC and/or off our 
southern waters. Another large question that remains is where 
the heaviest rain bands will set up given the timeframe is still
too far out to utilize the hi-res guidance.

Otherwise, high temperatures are expected to remain on the 
lower end of seasonable, even dipping to slightly below normal 
at times given 850mb temperatures hovering around +12C to +14C 
through mid- week.

&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

18z TAF Update:

This Afternoon & Tonight...High confidence, except moderate 
confidence across Cape Cod and the Islands.

Mainly VFR conditions with ENE to NE winds, becoming light and 
variable or northerly overnight. The exception is across Cape Cod 
and the Islands, where a distant offshore low continues to advect 
MVFR stratus and reduced visibilities into the region. There remains 
a low to moderate potential for this stratus to expand north and 
northwest toward KPVD and KOWD after 08z before retreating back 
toward the coast around sunrise.

Monday...High confidence, except moderate confidence across Cape Cod 
and the Islands.

Predominantly VFR. Areas of MVFR stratus may linger across Cape Cod 
and the Islands through around 15z before improving to VFR by 18z. E 
to ESE winds remain below 10 kt. A weak front approaches western 
southern New England after 18z, bringing a slight chance of isolated 
showers or thunderstorms to western terminals, including KBDL. 
Confidence remains too low to include in the current TAF package, 
though later forecasts may need to introduce VCSH or VCTS if 
confidence increases.

Monday Night...Moderate confidence.

VFR conditions at the start of the period should gradually 
deteriorate to MVFR, with localized IFR/LIFR ceilings developing 
overnight. Confidence in the timing of these restrictions remains 
lower. Scattered showers are also possible overnight, with more 
widespread precipitation expected by Tuesday. Light S winds.

KBOS Terminal...High confidence.

KBDL Terminal...High confidence.

Outlook /Tuesday through Friday/...

Tuesday: Mainly VFR, with areas MVFR possible. Breezy. Chance
SHRA, slight chance TSRA, patchy BR.

Tuesday Night: Mainly MVFR, with local IFR possible. Breezy.
SHRA likely, slight chance TSRA, patchy BR.

Wednesday: Mainly MVFR, with areas IFR possible. Breezy. SHRA,
slight chance TSRA, patchy BR.

Wednesday Night: Mainly VFR, with areas MVFR possible. Breezy.
SHRA likely, chance TSRA.

Thursday: VFR. Breezy. Chance SHRA, slight chance TSRA.

Thursday Night: VFR. Chance SHRA, slight chance TSRA.

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

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Tuesday...High confidence.

Light winds and seas 1-4 ft through Monday. Increasing winds 
and seas for Sunday; however, below SCA. NE winds 10-15 kts 
with gusts to 20 kts. Light NE to SE winds Monday. 

Seas increase late Tuesday into Wednesday with SCA conditions 
becoming more likely from winds and increased seas. 

Increased risk for rip currents today with the greatest risk 
for the east-facing beaches/coastline.

Outlook /Tuesday through Friday/...

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

Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers, slight chance of thunderstorms,
patchy fog. 

Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Seas up to 5 ft. Rain showers likely, slight
chance of thunderstorms, patchy fog. 

Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Rain showers likely, slight
chance of thunderstorms. 

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

Thursday Night: Winds less than 25 kt. Areas of rough seas.
Slight chance of rain showers, slight chance of thunderstorms. 

Friday: Winds less than 25 kt. Seas up to 5 ft. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents until 8 PM EDT this evening for MAZ022-
     024.
RI...None.
MARINE...None.

&&

$$

DISCUSSION...Dooley/McMinn
AVIATION...Dooley/McMinn
MARINE...Dooley/McMinn