Old Res Weather

Lexington, Massachusetts, USA

35°F

2/16/2025 7:17pm

Lexington Conditions: Light rain, Mostly cloudy
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 231149
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
749 AM EDT Tue Jun 23 2026

.WHAT HAS CHANGED...
No changes to the forecast at this time.

&&

.KEY MESSAGES...

- Showers expected to continue today with some embedded thunder
  and heavier downpours possible.

- Drier through midweek. Turning mostly cloudy, humid and
  unsettled by late this week into the weekend. Though it won't
  be raining all the time, chances for showers/storms will exist
  on most days Fri- Sat, but severe weather potential looks very
  limited.

&&

.DISCUSSION...
KEY MESSAGE 1...Showers expected to continue today with some 
embedded thunder and heavier downpours possible.

Showers will continue to impact southern New England today as 
another wave tracks over the region. Latest mesoanalysis has an area 
of increased moisture transport at 925 mb from the S/SW, so showers 
moving into this area over RI and SE MA may intensify and produce 
higher rainfall rates, especially as any pockets of MUCAPE are 
encountered. Based on the latest guidance, a more south track for 
the next wave is favored with heavier, more widespread rain 
remaining mostly to the south of southern New England. The exception 
would be along the south coast and into the Cape and Islands where 
heavier showers remain possible. PWATs over this area heading into 
the afternoon hours are also forecast around 2.0-2.10". High-res 
guidance also has some MUCAPE over much of SE MA into the Cape and 
Islands through the afternoon, which would help produce periods of 
heavier downpours and some embedded thunder within any showers that 
develop. The RAP also has a burst of some elevated MUCAPE values 
over Cape Cod early this morning that could favor thunder there. 
With the showers we've seen overnight producing occasional lightning 
and heavier downpours in CT and now heading into RI, this is not out 
of the question. With regards to totals, thinking has not changed 
much as totals in the 1-2" range remain the main expectation with 
this system. Flash flooding is not a widespread concern considering 
the drought conditions we've been experiencing, but flashier areas 
including urban and poor drainage areas may see some flooding under 
any heavier rainfall rates. With persistent cloud cover today, highs 
will likely not climb higher than the 70s.

Rain should clear out of the region heading into tonight as the wave 
moves offshore, though showers may linger early tonight over the 
Cape and Islands. Winds shift NW and drier air makes its way into 
the region in the wake of the passing cold front, which will 
also aid in clearing remaining cloud cover heading into 
Wednesday. Lows tonight are expected to be in the upper 50s and 
low 60s. 
 

KEY MESSAGE 2...KEY MESSAGE 2...Drier through midweek. Turning mostly
cloudy, humid and unsettled by late this week into the weekend.
Though it won't be raining all the time, chances for showers/storms
will exist on most days Fri-Sat, but severe weather potential 
looks very limited.

After the cold front pulls away later tonight, we get into a drier 
weather pattern Wed onward thru the daytime hrs Thurs. 

Our weather pattern then turns more unsettled for late in the week 
into at least the early part of the weekend. Broadly-cyclonic, quasi-
zonal pattern with enhanced westerly 500 mb flow stretches from the 
Gt Lakes region to the Northeast states in this period. Salient 
large-scale features in this period by early Thurs night include one 
mid-level shortwave trough over the Gt Lakes region, another weaker 
500 mb disturbance near the central Plains, with an elongated, quasi-
stationary frontal boundary draping itself from the OH/mid-MS Valley 
eastward to the mid-Atlantic/southern New England vicinity. Zonal 
regimes like this one are typically prone to timing errors when it 
comes to precip/thunder chances and are also sensitive to daily
convective details which are unknown at this time horizon. 
Adding to that uncertainty is there are differences in the 
strength of the initial/lead Gt Lakes shortwave, which influence
whether or not better rain chances move in by Thurs night. GFS 
guidance is weaker/broader and thus more progressive with rain 
chances into New England by Thursday night, while the 
international guidance feature a stronger trough and is slower 
to move PoP in until Fri. 

I would rate confidence in the timing of rain/thunder chances later 
this week into the weekend as lower than average, given the above 
sources of uncertainty. Forecast carries a rather non-descript 
Chance PoP for most of this timeframe; it won't be 
raining/thundering the whole time, but ID'ing those periods is 
subject to the timing details become more in-focus. That said, an 
early estimate for rain/thunder chances is more centered into Fri 
aftn/Fri evening with the lead shortwave, then increasing again into 
at least the south coast to areas south of the Mass Pike Sat/Sat 
night as the central Plains shortwave moves through or just south of 
Southern New England. Although mid-level flow is seasonably strong, 
much of this period is mostly cloudy and rather humid, but also one 
with limited diurnal heating leading to weak instability. Indeed, 
NSSL machine-learning severe weather progs offer tempered severe 
weather probabilities on Fri. Wouldn't rule out a strong storm or 
two on Fri, but early lean is that the prospects of storms becoming 
severe seem limited. 

High pressure and dry weather return for the weekend.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

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

12Z Update

Moderate confidence at best. 

Widespread IFR conditions currently, with scattered showers and
an isolated TSRA currently pushing east across the Cape. With a
weak frontal boundary currently extending from NE Mass to SW
Connecticut drifting slowly south, this will keep the threat for
scattered showers and general IFR conditions going most of the
day. Various model guidance although they show that general
scenario for the day, differ on timing and location of the
showers. So went a little broadbrush with prevailing -SHRA at
many TAF sites with TEMPOs for when there might be a potential
for a little heavier showers. Any risk for TSRA from late
morning into early evening will be generally south of the
region, but can't rule it out across ACK.  

Expect any remaining -SHRA to have moved away from the region by
02z. Given the slow moving boundary and no real push of drier
air into the region, IFR/MVFR conditions will likely persist for
most of the night, but confidence is low on timing of seeing
improvement to VFR. However, once VFR sets in, it will remain in
place for all of Wednesday.

KBOS Terminal...Moderate Confidence. Expect a wind shift to NW
in the 14-15z timeframe, and then veering to NE by mid-afternoon 
although winds will stay less than 10kt the entire day. 
Scattered -SHRA expected at times through the day, but timing is
difficult to pinpoint. 

KBDL Terminal...Moderate confidence. Scattered -SHRA expected at
times through the day, but timing is difficult to pinpoint. 

Outlook /Wednesday Night through Saturday/...

Wednesday Night through Thursday: VFR. 

Thursday Night: Mainly VFR, with local MVFR possible. Chance
SHRA, slight chance TSRA.

Friday: Mainly VFR, with areas MVFR possible. Breezy. SHRA
likely, slight chance TSRA.

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

Saturday: VFR. 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 Wednesday...High confidence.

Rain and a few embedded storms continue before finally moving 
off to the east this evening. Moderate to heavy rainfall at 
times expected, resulting in poor visibility less than 1 mile at
times. Seas 2-4 ft with SW winds at 10-15 kt shifting NW in the
wake of a passing cold front this evening into tonight. Winds
then shift more SW for Wednesday, remaining around 10 kt.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. 

Thursday through Thursday Night: Winds less than 25 kt. 

Friday: Winds less than 25 kt. Slight chance of rain showers,
slight chance of thunderstorms. 

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

&&

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

&&

$$

DISCUSSION...Loconto/Hrencecin
AVIATION...Loconto/Hrencecin/Nash
MARINE...Loconto/Hrencecin