Old Res Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 271906
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
306 PM EDT Sun Sep 27 2026

.WHAT HAS CHANGED...
All wind advisories have expired. Coastal flood 

&&

.KEY MESSAGES...

- Windswept rain with minor coastal flooding/beach erosion
  continue into Monday. Localized urban and street flooding
  possible. 

- Minor coastal flooding continues through Monday evening.

- Marked improvement Tuesday, followed by mainly dry and warmer
  weather through Friday. Forecast confidence decreases next 
  weekend.

&&

.DISCUSSION...

KEY MESSAGE 1...Windswept rain with minor coastal flooding/beach erosion
continue into Monday. Localized urban and street flooding 
possible. 

Latest analysis of our Nor'easter has the low pressure center 
shifting into the NJ coastline. Viewing from satellite imagery, its 
general circulation is visible as it rotates, pivoting a band of 
convective-type clouds across portions of the Northeast, especially 
near its center. Over southern New England there are hints of 
convective type clouds which translate to the surface as pockets of 
moderate to heavy rainfall rates in east/central MA. The banded 
nature of this system has resulted in areas in central CT on the 
drier side today while other areas in eastern MA have been recieving 
rain much of the day. 

Expect banded showers/rain to continue tonight and through Monday as 
the low pressure center weakens and slowly retrogrades back east 
toward southern New England. High-resolution guidance continues to 
indicate the potential for pockets of higher rain rates shifting 
across portions of RI, central/eastern MA, and CT. As the low exits 
to the northeast Monday night, rain will taper off. Some showers are 
possible through early Tuesday morning, mainly in east MA as there 
is some wrap around moisture behind the low. We've seen plenty of 
rain already, with a range of 2-6 inches across Rhode Island, 
southeast MA, and portions of central/east MA. We should likely see 
another 0.50 to 2.0" through early Tuesday morning. Urban poor 
drainage flooding will continue to be possible with additional
rain, especially in the areas that have already recieved a 
larger amount of rain (east/southeast). We opted to keep the 
Flood Watch going given the continued prolonged rainfall and as 
we see river levels rising to action level and a few even to 
minor flood stage. 

The 925mb LLJ oriented across southern New Engand will continue to 
slowly weaken tonight and Monday resulting in gradually decreasing 
gusts. Gusty NE/E winds will continue with gusts 25-35 mph and in 
the 20-30 mph range Monday. 


KEY MESSAGE 2...Minor coastal flooding continues through Monday
evening.

The persistent NE onshore flow combined with increasing 
astronomical tides and some wave action will lead to a continued
risk for minor coastal flooding along multiple high-tidal 
cycles tonight, Monday and Monday night. Tidal gage observations
indicate that observed storm surge values have been running 
about a quarter to one-half foot higher than forecast values; 
despite this, many tidal sites on the eastern coast have only 
reached into the minor flood stage range. Given those trends and
that surge values are forecast to only slowly decrease - around
1.25 to 1.4 inches tonight, then slowly around a foot on Monday
and a foot or less into Monday evening. Because of this, we 
opted to issue a Coastal Flood Advisory for the east coast and a
Coastal Flood Statement with lesser impacts along the southern 
coast. The Monday daytime high tides (morning along the south 
coast, early afternoon for the eastern MA coast) have the 
highest astro tides, so that tide cycle has the best shot at 
seeing minor inundation on shoreline roads. 


KEY MESSAGE 3...Marked improvement Tuesday, followed by mainly 
dry and warmer weather through Friday. Forecast confidence 
decreases next weekend.

The weekend's long-duration nor'easter exits east-northeast as the 
mid-level flow becomes less amplified and blocking diminishes. 
Through the remainder of the week, the mid-level flow becomes fairly 
zonal with a few weaker impulses passing through during the mid to 
late week. These may bring a low probability of a light shower or 
two, but otherwise mainly dry weather is expected. Expect marked 
improvement Tuesday as the decaying nor'easter exits the region and 
winds shift to the northwest. This northwest flow will advect lower 
PWATs into southern New England, bringing any lingering early 
morning showers to an end. While PWATs remain somewhat elevated into 
the afternoon, there is little forcing to support additional 
precipitation. Thus, clouds may hang tough through much of the 
afternoon before some breaks develop later in the day. Northwest 
flow will also keep temperatures a few degrees below climatological 
normals, though it will be noticeably warmer than this past weekend. 
Highs Tuesday reach the upper 60s to around 70 degrees.

A mid-level ridge builds across the southeastern CONUS this week, 
while surface high pressure settles south of the region Wednesday 
through Friday, leading to a stretch of quieter and warmer weather. 
Guidance hints at a weak northern-stream shortwave Wednesday night 
into early Thursday, followed by a secondary shortwave Thursday 
night into Friday. PWATs Wednesday night into Thursday remain below 
1.2 inches and do not align particularly well with the best forcing. 
Outside of a brief light shower, would anticipate more clouds than 
anything. PWATs increase to around 1.5 inches Thursday night with 
the passage of the secondary weak shortwave, when a few light 
showers could brush the region. No significant impacts are 
anticipated with either disturbance. Temperatures trend warmer 
through the middle and latter half of the week, though the latest 
guidance has trended somewhat cooler compared to previous runs. 
Highs generally return to the lower and middle 70s, with Thursday 
potentially the warmest day as temperatures reach the middle to 
upper 70s. No notable cold is expected overnight, with lows 
generally falling into the 50s.

Forecast confidence decreases next weekend due to considerable 
disagreement among the guidance. Interestingly, some solutions 
depict a setup somewhat similar to earlier this week, with another 
strong area of high pressure over eastern Canada and low pressure 
developing off the Carolinas. Other guidance instead settles the 
high over New England while low pressure develops across the Ohio 
River Valley and approaches the region late in the weekend or early 
the following week. Given these significantly different scenarios at 
this range, expect changes to the forecast as guidance comes into 
better agreement.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

18z TAF Update: 

Through 00z Monday: High confidence. 

IFR for most with wind-driven rain and mist, though MVFR/IFR at
BDL with lighter/intermittent rain. NE winds gusting to around
20-25 kt for the interior, but upwards of 30-35 kt for eastern
MA/RI. 

Tonight: Moderate confidence. 

IFR prevails with continued rain and enhanced NE winds. 
Ceilings could slip as low as LIFR tonight/overnight but 
confidence on if and when this happens is moderate. Gradual,
very slow easing trends to NE gusts in the 25-30 kt range,
strongest near the northeast coast.

Monday: Moderate confidence. 

Continued IFR, though optimism for MVFR ceilings by afternoon 
as rain begins to taper to more intermittent showers. NE winds 
around 10-15 kt with gusts in the low 20s kt range. 

Monday Night: Moderate confidence. 

Categories should trend to MVFR with stratus lingering around
but rain should be tapering off to drier conditions by early Tue
AM. NE to N winds around 10 kt.

KBOS Terminal...Moderate confidence in TAF. 

KBDL Terminal...Moderate confidence in TAF.

Outlook /Monday Night through Friday/...

Tuesday: MVFR/IFR conditions possible. Breezy. Patchy BR.

Tuesday Night: Mainly VFR, with areas MVFR possible. 

Wednesday: Mainly VFR, with local MVFR possible. 

Wednesday Night: VFR. 

Thursday: VFR. Breezy. 

Thursday Night: VFR. 

Friday: VFR. Breezy. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Monday...

The nor'easter will continue to weaken resulting in the
gradual weakening of winds/gusts through Monday. Winds will 
still gust 25-30 kts tonight and into Monday. This will allow
remaining Gale Warnings in the northern waters to expire this
evening and convert to SCAs. SCAs also continue for the southern
waters as well. Seas diminish to 6-10 ft tonight and 5-7 ft by 
Monday evening. Highest seas will linger across the northern
waters Monday. Lingering higher seas will keep Small Craft 
conditions around through Tuesday, especially for the outer 
waters. 

Outlook /Monday Night through Friday/...

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

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

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

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

Thursday: Winds less than 25 kt. 

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Flood Watch through late Monday night for MAZ004>007-012>024-
     026.
     Coastal Flood Advisory until midnight EDT Monday night for 
     MAZ007-015-016-019-022>024.
     High Surf Advisory until 2 AM EDT Monday for MAZ007-015-016-
     019-022>024.
RI...Flood Watch through late Monday night for RIZ001>008.
MARINE...Gale Warning until 9 PM EDT this evening for ANZ230-250-251-
     280.
     Small Craft Advisory until 2 PM EDT Monday for ANZ231.
     Small Craft Advisory until 8 AM EDT Monday for ANZ232>235-237.
     Small Craft Advisory until 8 PM EDT Monday for ANZ254>256.

&&

$$

DISCUSSION...Loconto/Dooley/Mensch
AVIATION...Loconto/Dooley
MARINE...Dooley/Mensch