Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 241927
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
327 PM EDT Thu Sep 24 2026

.WHAT HAS CHANGED...

High Wind Warning issued along the coast with a Wind Advisory issued 
for many locations further inland. Storm Warnings issued for all 
waters. Coastal Flood Watches for the eastern Massachusetts, Cape 
and Islands extended through Sunday. 

&&

.KEY MESSAGES...

- Strong/long duration Nor'easter will bring strong to damaging
  wind gusts, coastal flooding/beach erosion, and periods of
  heavy rain late Fri through the weekend. Power outages are a
  concern particularly along the coast with fully leafed trees. 

&&

.DISCUSSION...

KEY MESSAGE 1...Strong/long duration Nor'easter will bring strong to 
damaging wind gusts, coastal flooding/beach erosion, and periods of 
heavy rain  late Fri through the weekend. Power outages are a 
concern  particularly along the coast with fully leafed trees.  

An early season/long duration Nor'easter will bring a variety of 
impactful weather to southern New England later Fri right through 
the weekend. While there remains some uncertainty on the exact track 
and where the worst of the impacts are felt...confidence is 
relatively high that this will be an impactful storm for our region. 

There are several moving parts that our ideal for a strong early 
season Nor'easter. The high pressure over Quebec and the offshore 
low pressure system are both indicated to be outside the EPS/GEFS 
models climatology. This will result in a strong persistent NE 
gradient of wind beginning Fri and continuing into Sunday. While 
there remain track differences...the low pressure system initially 
backs westward to a position somewhere south of Long Island before 
eventually lifting NE and gradually weakening through early next 
week. This is the reason that this storm will be of such long 
duration. The easterly LLJ is also shown to be outside the models 
climatology. This will not only result in the forcing for bands of 
rain moving across the region...But several impacts that we will 
break down below.

1) Strong to Damaging Wind Gusts... 

The biggest concern with the strong NE winds are that they will be 
of both long duration and also coupled with heavy rain/fully leafed 
trees. This will exacerbate the risk for tree damage and power 
outages than if this same storm were occurring a few months later. 
The strongest of the winds will be along the coast...where we expect 
NE wind gust of 45 to 60 mph. It is also possible a few spots see 
winds reach 65-70 mph across the Islands...but that will be 
dependent on the track. Regardless...whether or not places hit 
specific high wind criteria is less important that the long duration 
combined with the fully leafed trees. Given that factor...we opted 
to go with High Wind Warnings along the coast. Further inland...we 
are expecting NE wind gusts of 30 to 45 mph but a few gusts near 50 
mph are possible in heavier bands of rain. Again...given the fully 
leafed trees combined with long duration of the event opted to issue 
a Wind Advisory. The wind and tree damage/power outage risk will be 
the biggest impact for most people. 

2) Beach Erosion/Coastal Flooding...

The other big issue with this storm will be the expected beach 
erosion/coastal flooding issues over multiple high tide cycles. 
While this will not be a storm under-going rapid bombogenesis...but 
the persistence of these strong NE winds and high seas offshore are 
concerning. A storm surge on the order of 1 to 2 feet and perhaps 
briefly near 2.5 feet are expected late Fri right through the 
weekend along east face ocean exposed beaches. We extended the 
Coastal Flood Watch in these locations through Sunday. This along 
with 15 to 25 foot seas offshore will result in pockets of minor 
coastal flooding/beach erosion during each high tide cycle late Fri 
through the weekend and a few pockets of low end moderate coastal 
flooding are also possible. Astronomical high tides are increasing 
through the weekend...so even as winds eventually start to slowly 
diminish these issues will be a concern. Given this event will 
impact multiple high tide cycles...the water may struggle to drain 
out after each high tide. Heavy rainfall may also exacerbate these 
issues a well. Overall...the biggest impact from this system may be 
in regards to beach erosion given such a long duration event. 

While NE winds will result in less coastal flood impacts on the 
south coast...high seas just offshore and swell may result in some 
splashover/minor coastal flooding in these locations as well. This 
is something we will need to watch.

3) Heavy Rain and Timing...

Lastly...periods of heavy rain will be impacting the region at times 
later Fri into the weekend. This is one area where there remains 
some significant differences on how quickly the rain shield 
overspreads the region from southeast to the northwest. The GFS/RGEM 
are on the faster side with rain ovespreading most of the region 
later Fri into Fri night. Meanwhile...the ECMWF/NAM struggle to 
bring steady rain into much of the interior until Sat. We blended 
the differences for now...but once the rain arrives will basically 
continue through the weekend and even into Mon. Rainfall totals of 1-
4" are possible with the highest amounts most likely near the coast. 
We opted not to issue a Flood Watch given some of the model guidance 
takes the heaviest rain south of our region and given the fact that 
its over a long duration.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...

Forecaster Confidence Levels...

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

Through Tonight...High confidence. 

VFR, outside of areas of MVFR cigs over portions of southeast
MA, especially towards ACK and the Cape today into tonight. NE 
winds of 10 to 20 kt with gusts of 20 to 30 kt, strongest 
towards the southeast New England coast. Gusts near 40 kt for 
Nantucket.

Friday...High confidence. 

VFR most of the day, with MVFR cigs moving in from the
southeast, impacting ACK as early as 16z and FMH/HYA by 26/00z.
Lowered cigs come following -RA/RA moving in throughout the day
from SE to NW. Strong NE winds, 15-25 kts with gusts 30-45 kts,
strongest over southeast MA terminals.

Friday Night...High confidence in trends. Moderate confidence in
timing.

MVFR further overspreads the region from SE to NW. Local IFR
possible towards the Cape and islands.late.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Sunday Night through Tuesday/...

Saturday: Mainly MVFR, with local IFR possible. Strong winds
with gusts up to 55 kt. RA.

Saturday Night: MVFR/IFR conditions possible. Strong winds with
gusts up to 50 kt. RA.

Sunday: MVFR/IFR conditions possible. Strong winds with gusts
up to 45 kt. RA.

Sunday Night: Mainly VFR, with local IFR possible. Windy with
gusts up to 35 kt. SHRA, slight chance TSRA.

Monday: Mainly VFR, with local MVFR possible. Windy with local
gusts up to 30 kt. SHRA likely, slight chance TSRA.

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

Tuesday: Mainly VFR, with local MVFR possible. 

&&

.MARINE...

Forecaster Confidence Levels...

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

Tonight through the Weekend...High confidence.

* Dangerous conditions for Mariners Fri into the weekend with NE 
  wind gusts of 45 to 60 knots and seas offshore of 15-25 feet.

An early season Nor'easter will combined with high pressure over 
Quebec to result in strong NE wind gusts of 45-60 knots and seas 
offshore building to between 15 and 25 feet late Fri into the
weekend. Storm Warnings have been issued for all waters. This 
is a dangerous storm for mariners with the worst conditions 
later Fri into Sun. Mariners should consider returning to port 
as soon as possible. NE winds will persist Mon too...so although
conditions will improve this process will be quite slow. 


Outlook /Sunday Night through Tuesday/...

Saturday: Moderate risk for storm force winds with gusts up to
60 kt. Rough seas up to 25 ft. Rain. 

Saturday Night: Low risk for storm force winds with gusts up to
50 kt. Rough seas up to 22 ft. Rain. 

Sunday: Moderate risk for gale force winds with gusts up to
45 kt. Rough seas up to 14 ft. Rain. 

Sunday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 14 ft. Rain showers likely,
slight chance of thunderstorms. 

Monday: Low risk for Small Craft Advisory winds with local
gusts up to 30 kt. Rough seas up to 10 ft. Chance of rain
showers. 

Monday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers. 

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Wind Advisory from noon Friday to 2 AM EDT Sunday for 
     CTZ002>004.
MA...Wind Advisory from noon Friday to 2 AM EDT Sunday for MAZ004-
     011-026.
     Wind Advisory from 8 AM Friday to 2 AM EDT Sunday for MAZ005-
     006-012>014-017-018.
     High Surf Advisory from 5 AM Friday to 8 PM EDT Sunday for 
     MAZ007-015-016-019-022>024.
     High Wind Warning from 8 AM Friday to 2 AM EDT Sunday for 
     MAZ007-015-016-019>024.
     Coastal Flood Watch from Friday afternoon through Sunday 
     evening for MAZ007-015-016-019-022>024.
RI...Wind Advisory from 8 AM Friday to 2 AM EDT Sunday for RIZ001.
     High Wind Warning from 8 AM Friday to 2 AM EDT Sunday for 
     RIZ002>008.
MARINE...Storm Warning from 2 PM Friday to 8 PM EDT Saturday for ANZ230-
     236.
     Storm Warning from 8 AM Friday to 8 PM EDT Saturday for ANZ231-
     254-281.
     Storm Warning from 2 AM Friday to 8 PM EDT Saturday for 
     ANZ232>235-237-255-256-282-283.
     Storm Warning from 11 AM Friday to 8 PM EDT Saturday for 
     ANZ250-251-280.

&&

$$

DISCUSSION...Frank
AVIATION...Belk
MARINE...Frank