Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 301137
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
737 AM EDT Sat May 30 2026

.WHAT HAS CHANGED...
Upgraded the Wind Advisory to a High Wind Warning for Cape Cod and 
Nantucket. Expanded the Wind Advisory to include all of Eastern 
Massachusetts and Rhode Island.

&&

.KEY MESSAGES...

- Low pressure system brings rain and strong to damaging to portions 
  of southern New England today.  

- Cooler than normal temperatures early next week with hit-or-
  miss shower/thundershower chances during the daytime hours 
  Monday and Tuesday. 

- Monitoring possible offshore low development around midweek,
  which could pass far enough south to allow for warming
  temperatures, or lead to a continuation of cooler than normal
  temperatures and possible rains with a closer pass.

&&

.DISCUSSION...
KEY MESSAGE 1...Low pressure system brings rain and strong to 
damaging to portions of southern New England today.

The forecast remains on track for a deep trough of anomalously cold 
air and an associated strong low-pressure system to impact the 
region today. While this system will bring widespread showers and 
isolated storms, the primary concern is strong, potentially damaging 
winds. 

Model guidance has remained consistent regarding this wind threat. 
As a deepening low rotates offshore, a 45-60 kt LLJ at 925 mb will 
sweep across eastern portions of southern New England. Model 
guidance signals distinct pressure rises on the west side of the 
exiting low. Analyzing from a vertical profile perspective, model 
soundings show how close the 45 kt+ winds are to the surface. With 
steep lapse rates, these are good indicators for a good portion of 
the winds are favored to be mixed down to the surface. A good 
portion of high-res guidance and the ECMWF and its ensemble show a 
signal for strong to damaging gusts. The NAM/GFS have leaned on the 
lower end with gusts. Inland areas can expect widespread gusts 35-45 
mph. HREF means support potential for gusts 45-55 mph near the coast 
as the LLJ passes overhead. This seems reasonable given that the 
strongest core of the LLJ passes through east southern New England. 
The upper percentiles of the HREF even suggest a low probability for 
isolated 60 mph gusts across the Cape and Islands. Winds will ramp 
up from north to south, increasing after 7 AM for northern locations 
and peaking for the south coast and Cape and Islands in the 
afternoon.The current Wind Advisories and High Wind Warnings are 
currently on track based on latest guidance. 

As the system tracks offshore, it will bring another batch of 
precipitation through the region today. Following a brief lull early 
this AM, showers will spread southward after 6 AM, likely not 
reaching the Cape until the early afternoon. Very marginal 
instability may support a few embedded brief downpours and isolated 
thunderstorms. Rain will gradually decrease from west to east mid-
afternoon into the evening as the low pulls away.
Ensembles indicate rain totals between 0.20" and 1.2" is the more 
likely range with the higher end totals favored for northeast MA. 

In tandem with the strong wind signal, this deep trough is pulling 
down an anomalously cold airmass that will linger all day, keeping 
afternoon highs on the chilly side for end of May.
Highs likely stay in the upper 40s and low 50s. Given the timing of 
the cold air and precipitation, higher resolution guidance, 
particularly the NAM, suggests some snowflakes mixing in at the 
higher elevations. It has backed off a little in recent runs, likely 
due to timing of the steadier precip rates (need that for efficient 
dynamic cooling). However, it still highlights the north MA border 
for a trace of light snow. All that said, we could still see a few 
flakes mix in for the higher elevations of the interior this AM if 
the timing is right with the higher risk for the high elevations of 
the northern MA border. No travel impacts expected.  

KEY MESSAGE 2...Cooler than normal temperatures early next week
with hit-or-miss shower/thundershower chances during the 
daytime hours Monday and Tuesday. 

Ensemble means continue to point to 500 mb troughing governing 
Southern New England's weather late this weekend into a good portion 
of next week, in a slow-evolving, blocky 500 mb pattern. There are a 
couple of upper level lows that will be moving into and/or 
meandering around Southern New England.

The first of these closed upper lows settles in Sunday night and 
into Monday, before moving offshore into Tuesday. Really not much 
change in terms of sensible weather each day, with diurnally-driven, 
hit-or-mostly-miss showers or low-topped thundershowers popping up 
with the cool pocket of air aloft associated with the closed low. 
This type of showery pattern also means no one area can be 
guaranteed to be rain-free, but there will be several dry periods in 
between. Temperatures trend slightly cooler than early-June normals, 
with values in the mid 60s to mid 70s with comfortable humidity 
levels. Climatological normals run around the mid/upper 70s for 
highs.

KEY MESSAGE 3...Monitoring possible offshore low development 
around midweek, which could pass far enough south to allow for 
warming temperatures, or lead to a continuation of cooler than 
normal temperatures and possible rains with a closer pass.

More uncertainty during the mid to latter part of the upcoming 
workweek with regard to the next surge of vort energy diving 
southward from the Canadian Maritimes. This feature digs south/south-
southwest to a position generally south of 40N/70W into a wound-up, 
closed mid/upper circulation and associated surface low. The 
placement of this cyclone, when it begins to exit further offshore 
and if we see any rainy conditions associated with its 
north/northeast passage are all unclear at this time. Besides just 
rain chances, this feature's location will also dictate temperatures 
as some of the further-offshore/drier solutions bring in shortwave 
ridging aloft north of it extending into New England, with potential 
for drier weather and a considerable warmup in temps for at least 
interior Southern New England. On the other hand, a closer pass to 
Southern New England would bring cooler than normal temperatures and 
perhaps some light rains. We offered to not make many changes to NBM 
at this point and let trends dictate subsequent adjustments to the 
forecast.

&&

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

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

12z TAF Update...

No major changes from the previous update.

Today: Moderate confidence.

Mainly MVFR ceilings. IFR is possible for the east terminals,
though it should be off and on. Rain spreading south from 
northern MA; more persistent rains from ORH east. Low chance for
a few embedded thunderstorms though lower confidence on 
location. 

NE winds increase significantly to 18-25 kt, with gusts 30-45 
kt, strongest in eastern MA. Will take until early afternoon 
(17-20z) for strong NE winds and moderate rain to develop 
towards the Cape and Islands. 

N-NE wind gusts and rain decrease generally from west to east
after 20Z with ceilings trending VFR as well. BOS should start
seeing improvements around 22Z and 00-04Z for the Cape and 
Islands.

Tonight: High confidence. 

MVFR with moderate rain and NE winds 15-25 kt / gusts 35-40 kt 
Cape and Islands early, but conditions improve to widespread VFR
by 04z Sunday. Winds shift to N/NW and decrease significantly 
to around 5-10 kt, occurring soonest in northern MA.

KBOS...Moderate confidence in TAF. Steady moderate rain with
periods of MVFR visby and MVFR-IFR ceilings develops between 
now and 13z, with strong NE winds increasing to 20-25 kt 
sustained/gusts to 45 kt most of Sat.

KBDL...Moderate confidence in TAF. Light rain arrives 13-15Z with
MVFR ceilings and N winds gusting to 30-35 kt most of Sat.
Rain/winds decrease after 20Z with improving ceilings.

Outlook /Sunday through Wednesday/...

Sunday: VFR. Slight chance SHRA.

Sunday Night: VFR. Chance SHRA.

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

Monday Night: VFR. 

Tuesday: VFR. Chance SHRA, slight chance TSRA.

Tuesday Night: VFR. Slight chance SHRA.

Wednesday: VFR. Breezy. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

*Dangerous Marine Conditions Expected Today into Early Tonight*

A powerful storm system is expected to bringing strong northeast 
winds, rough seas, and moderate rain to the waters today. 

NE winds increase this morning across the northern waters, 
eventually increasing across the southern water this afternoon. 
Winds 30-35 kts with frequent gusts 45-50 kts. Offshore seas build 
to around 12-14 ft, with 5-8 ft nearshore. NE winds come around to 
northerly this evening into the Gale force range, decreasing further 
tonight. Storm Warnings for most of the waters, with the exception 
of Boston Harbor and Narragansett Bay where there are Gales. 

High winds and built up seas will bring high surf to the surf zones 
today along the east facing beaches. If you are venturing out to the 
beach, stay a safe distance for jetties. 

Outlook /Sunday through Wednesday/...

Sunday: Winds less than 25 kt. Local rough seas. Chance of rain
showers. 

Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers. 

Monday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers. 

Monday Night through Tuesday: Winds less than 25 kt. 

Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers. 

Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 25 kt. Local rough seas. Slight chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Wind Advisory until 8 PM EDT this evening for MAZ004>007-
     012>021-023-026.
     High Wind Warning until 8 PM EDT this evening for MAZ022-024.
RI...Wind Advisory until 8 PM EDT this evening for RIZ001>008.
MARINE...Gale Warning until 8 PM EDT this evening for ANZ230-236.
     Storm Warning until 8 PM EDT this evening for ANZ231>235-237-
     250-251-254>256-280>283.

&&

$$

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