Waltham, Massachusetts 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

612
FXUS61 KBOX 251902
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
302 PM EDT Sat Apr 25 2026

.WHAT HAS CHANGED...
The track of the coastal low to the south of southern New England
looks to remain offshore, so chances for rain have been kept towards
the south coast for Sunday.

&&

.KEY MESSAGES...

- Cloudy with some light rain showers out towards CT and
  western MA this evening, then into southern RI and along the
  south coast tonight.

- Showers may linger towards the Cape and Islands tomorrow, but
  otherwise, cloudy and cool.

- Dry conditions early next week with temperatures around or
  slightly below normal. Trending unsettled and cooler mid to
  late- week with periods of rain, especially Thursday.

&&

.DISCUSSION...
KEY MESSAGE 1...Cloudy with some light rain showers out towards
CT and western MA this evening, then into southern RI and along
the south coast tonight.

High pressure remains affixed over New England into tonight as a low
pressure in the Mid Atlantic will continue progressing eastward.
Rain showers associated with this low are already under way in parts
of SW CT and NY, which will continue east through the rest of this
afternoon into tonight. Showers will very likely impact the Hartford
area and far western MA within the next couple of hours. These are
expected to spread into southern RI tonight and to the Cape and
Islands. Elsewhere, significant dry air will limit the chance for
rain showers.

Cool air aloft (925 around 2C) and persistent cloud cover will help
keep lows in the upper 30s across southern New England tonight.
Given these temperatures, the risk for any mixed precipitation in
any of theses overnight showers out in CT is very low to zero. A few
wet snowflakes in the highest terrain could mix with rain later
tonight, but confidence is very low in that occurring (plus, these
would have no impact).


KEY MESSAGE 2...Showers may linger towards the Cape and Islands
tomorrow, but otherwise, cloudy and cool.

Guidance has become clearer with regards to the track of this
coastal low pressure. The 12z NAM moved back towards the solution
the global guidance and other high res models were indicating, which
was more of an offshore track that would limit any risk for showers
for Sunday to the south coast, Cape Cod, and the Islands. High
pressure remains fixed over New England through Sunday, helping keep
the low off to our south. Onshore flow will continue, as well as
more overcast conditions. This will keep highs for Sunday in the 50s
with low 60s possible in the river valleys. As the low should remain
further offshore, stronger wind gusts should also remain well
offshore.

For Sunday night, cloud cover may start to clear out west as the low
continues pulling offshore, but clouds would be lingering over
eastern MA heading into Monday morning. Onshore flow continues
and lows likely fall in the upper 30s to low 40s.

KEY MESSAGE 3...Dry conditions early next week with normal to
slightly below normal temperatures. Trending unsettled and cooler
mid to late-week with periods of rain, especially Thursday.

High pressure moves back into the region as surface low pressure
pulls further offshore Monday. This will bring a period of dry
conditions to start the week. Temperatures hover between normal to
slightly below normal Monday/Tuesday with highs in the upper 50s to
low 60s. The warmest temperatures will likely be found in the CT
valley. Temperatures along the eastern coastal areas stay in the low
to mid 50s reinforced by onshore flow.

Ensemble guidance shows a general consensus with a transition
to a more unsettled pattern mid to late-week as an upper trough
approaches from the north and east. Scattered showers are
possible Wednesday as a piece of shortwave energy swings
onshore, with the showers most favored along the coastal
areas/east. The highest chances for more widespread showers/rain
should be Thursday as a more consistent plume of above normal
moisture arrives ahead of the approaching trough. Confidence
lowers in the details with differences among model guidance with
the evolution of the mid-level pattern and speed of the trough.
Some solutions close off a 500 mb low and favor a slower exit
of the system which could bring higher rain totals and showers
lingering through the day Friday. For now, we can expect the
highest probability of seeing widespread rain on
Thursday/Thursday night with lingering showers possible on
Friday. Not seeing any signal for excessive rainfall or flash
flooding concerns at this time.

The trough and cold front push through by the start of the weekend
with ensembles signaling at a below normal airmass settling across
southern New England. This could another weekend of slightly cooler
than normal temperatures.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

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

Rest of Today and Tonight: High confidence.

VFR. Satellite showing increasing mid to high level clouds this
afternoon which should continue. Ceilings start to lower to
lower-end VFR/MVFR levels near BDL around 20-23z with rain
showers. VFR visibility for most. Rain showers and MVFR ceilings
then expand southeast to near PVD overnight. SE winds this
afternoon will persist into the evening, remaining below 10 kt.
They then will shift SSW for some before going light and
variable in some areas to calm. Rain showers are a possibility
towards the Cape and Islands heading into Sunday morning.

Sunday and Sunday Night: High confidence.

BKN/OVC VFR for most, with NE winds 5-10 kt. Lowest
ceilings (MVFR) and stronger NE winds around 10-15 kt for the
Cape and Islands, to go along with periods of showers as low
pressure passes to our south. Chances for showers may linger
through Sunday night towards ACK.

KBOS Terminal...High confidence in TAF. Winds overnight may
periodically go calm.

KBDL Terminal...High confidence in TAF.

Outlook /Monday through Thursday/...

Monday through Tuesday: VFR. Breezy.

Tuesday Night: VFR. Slight chance SHRA.

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

Wednesday Night: Mainly VFR, with local MVFR possible. SHRA
likely.

Thursday: Mainly VFR, with local IFR possible. Breezy. SHRA
likely.

&&

.MARINE...
Forecaster Confidence Levels...

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

Tonight: High confidence.

Winds and seas are below SCA criteria through tonight, with E/SE
winds around 10-15 kt and seas 3 ft or less. Winds over the
eastern waters may be more W, though will remain light. Dry
weather today, although a risk for showers on the southern
waters tonight.

Sunday and Sunday Night: Moderate confidence.

Coastal low pressure passes over the southern waters Sunday into
Sunday night. Expect increasing northeast winds to around
20-25 kt well offshore and building seas, which could warrant
SCAs on the southern waters towards Monday if the low pressure
passes closer to Southern New England`s waters. NE winds around
10 kt northeast waters. Rain showers over the southern waters,
but mainly dry eastern waters.

Outlook /Monday through Thursday/...

Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft. Slight chance of rain
showers.

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

Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas.

Tuesday Night: Winds less than 25 kt. Areas of rough seas.
Slight chance of rain showers.

Wednesday through Wednesday Night: Winds less than 25 kt. Areas
of rough seas. Chance of rain showers.

Thursday: Winds less than 25 kt. Areas of rough seas. Rain
showers likely.

&&

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

&&

$$

DISCUSSION...Hrencecin
AVIATION...Hrencecin/Mensch
MARINE...Hrencecin/Mensch