Old Res Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 201834
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
134 PM EST Fri Feb 20 2026

.WHAT HAS CHANGED...
Winter Weather Advisories remain in effect from 10 AM today to 
7 AM Saturday due to accumulating snow and ice, leading to 
slippery road conditions.

Increasing confidence in seeing impacts from the Sunday/Monday 
coastal storm on the South Coast, Cape Cod, and the Islands with
dangerous marine conditions on the coastal waters. Winter Storm
Watches issued for the South Coast, Cape Cod, and the Islands. 
High Wind Watches issued for Cape Cod and the Islands. Storm 
Watches for all coastal waters except Boston Harbor where a 
Gale Watch has been issued. Coastal Flood Watch issued for the 
eastern Massachusetts coast.

&&

.KEY MESSAGES...

- Winter Weather Advisories remain in effect through 7AM
  Saturday for interior southern New England as a winter storm 
  with a mix of rain, snow, sleet, and freezing rain is 
  currently overspreading New England. Expecting mostly rain for
  areas southeast of I-95. All locations will see a change back
  to snow tonight with light accumulations possible. Slippery 
  road conditions are expected.

- Light snow showers continue Saturday with little additional 
  accumulation expected.

- Coastal storm likely impacts the South Coast, Cape Cod, and 
  the Islands but we still cannot rule out a more widespread 
  impact across the rest of southern New England.

&&

.DISCUSSION...
KEY MESSAGE 1...Winter Weather Advisories remain in effect 
through 7AM Saturday for interior southern New England as a 
winter storm with a mix of rain, snow, sleet, and freezing rain 
is currently overspreading New England. Expecting mostly rain 
for areas southeast of I-95. All locations will see a change 
back to snow tonight with light accumulations possible. Slippery
road conditions are expected.

A low pressure system continues to move northeast through the 
Great Lakes while another low has formed off the DelMarVa coast.
The warm front ahead of the Great Lakes low is driving the mix 
of precipitation currently pushing through southern New England,
with a warmer airmass keeping temperatures warm enough for rain
to present as the predominant p-type (with some snow starting 
to mix in across the higher elevations). The latest suite of 
guidance is indicating a warm nose pushing all the way up to the
Mass Pike, with global guidance nudging it as far north as 
northern MA. Areas north of the warm nose will likely remain 
solely as snow while areas under the nose will see a mix of 
p-types... likely sleet, rain, and snow. Patchy freezing rain is
possible in the interior higher elevations, but confidence is 
low on exactly how far east it could spread.

Winter Weather Advisories remain in effect through 7AM Saturday
for interior southern New England, with the greatest 
accumulations of wet snow expected (3-5" with spot 6" amounts 
along the NH border) near and north of the Mass Pike and into 
the Merrimack Valley/North Shore. Areas along and south of the 
Mass Pike into Northern Connecticut and northwest Rhode Island 
are more likely to see minor wet snow of a coating to 3" as well
as possible ice accretion up to 0.2".

Later tonight, expecting any mixed precip to fully transition 
to snow, with only minor accumulations expected. While totals 
will be light (1-2 inches) the timing of the transition will not
be ideal for the evening commute and will likely result in 
slick travel. Opted to not go with an advisory as confidence in 
snowfall and sleet totals over 2 inches remains low. 

Generally expecting a mostly rain event SE of I-95 with a 
period of light snow this afternoon/tonight. In these areas, a 
coating to a half inch of snow is possible mainly on grassy 
surfaces or side streets. 

KEY MESSAGE 2...Light snow showers continue Saturday with 
little additional accumulation expected.

Light snow showers are expected to continue through mid-morning
Saturday as an inverted trough remains stagnant over New 
England. However, the dendritic growth zone will dry out 
throughout the morning, leading to poor snow growth potential. 
Expecting very minor accumulations, if any, Saturday morning, 
with the North Coast/Cape Ann likely to see highest additional 
totals of up to 1".

KEY MESSAGE 3...Coastal storm likely impacts the South Coast, 
Cape Cod, and the Islands but we still cannot rule out a more 
widespread impact across the rest of southern New England.

Still seeing differences among deterministic models and 
ensembles regarding track of the Sunday/Monday coastal storm but
those differences have begun to decrease a bit over past 24 
hours. Storm track, whether it passes southeast of 40/70 
benchmark or makes a closer pass, is highly dependent upon 
strength of downstream 500 mb ridge, which ultimately affects 
how deep and orientation of upper trough moving off East Coast.

12z GFS remains the strong outlier when compared to other 
models and brings coastal storm right over 40/70 benchmark, 
which if it verifies, would bring widespread heavy snow and 
strong winds to much of SNE. We're also still seeing a very 
large spread in GFS ensemble members and Canadian/ECMWF 
ensembles as well, so forecast confidence in any particular 
solution is not very high. GFS solution is not completely 
supported by other guidance but we have noted more of a NW 
trend; consensus is for a weaker downstream ridge which results 
in a slightly farther offshore pass but still brings heavy snow 
and strong winds to Cape Cod and the Islands and South Coast. 
This would also bring accumulating snow to much of SNE, but not 
the extreme amounts as seen on some model snow maps that have 
been making the rounds these past few days. 

Since we are most confident on 6"+ totals on Cape Cod and the 
South Coast, we will issue a Winter Storm Watch for these areas.
We considered also including more of RI and SE MA given recent 
trend but decided to hold off for now given spread in ensemble 
members. Keep in mind if we see continue to see a NW trend in 
guidance, the Watch will likewise need to be expanded to include
more of SNE, at least into more or RI and eastern MA including 
Providence and Boston. We're just not quite ready to buy into 
that just yet.

Onset of the snow looks to be Sunday night, with the peak of 
the snowfall rates later Sunday night into Monday, before snow 
tapers off Monday evening. It's possible dry air at onset could 
cause snow to hold off until Monday, something depicted toward 
end of 12km NAM run, so it's also not out of the question that 
the bulk of the snow could fall during the day Monday.

In addition to the snow, there is increasing confidence in 
seeing widespread 50-60 mph gusts on Cape Cod and the Islands 
and most of the coastal waters. Even with a more offshore track,
coastal storm should deepen rapidly down into 970-mb range, 
producing a wide envelope of high winds as well as moisture on 
the cold conveyer belt. High Wind Watches have been issued for 
Cape Cod and the Islands, with Storm Watches for the coastal 
waters. This will be a dangerous storm for mariners with 
potential for at least 25 foot seas offshore.

Finally, high astronomical tides Monday into Tuesday brings the
potential for minor to moderate coastal flooding along eastern 
MA coast, depending upon timing of highest surge. Surge guidance
and pattern recognition suggests a 3 foot surge around high 
tide early Monday morning and again early Tuesday morning, which
could bring the water level to over 6 feet in Nantucket Harbor 
and to 13.5 feet in Boston, although wave impacts along the 
coastline would result in greater impacts (likely Moderate) as 
well as coastal erosion. Keep in mind large pressure falls would
also add to the water level, so even a more offshore track 
could still result in significant coastal flooding.

&&

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

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

18Z TAF Update: Moderate confidence due to uncertainty in 
precip type and timing of lowest conditions.

Precip continues to move east with Ptype starting as snow then 
turning to sleet/freezing rain/rain. Freezing rain is most 
likely in western portions of western MA and CT with sleet/snow 
more likely in eastern MA. Rain/sleet most likely in RI and SE 
MA with rain most likely over the Cape and Islands. Mixed precip
will continue through about 00z-03z tonight before switching 
back to snow/snow showers as the system exits. The only area not
anticipated to switch back to snow is the South Coast and 
Cape/Islands. 

CIGS are quickly dropping to IFR/LIFR across the region, within
30 mins of precip starting. CIGS remain IFR/LIFR overnight even
as precip begins to taper off.

Saturday: Moderate Confidence

CIGS gradually improve to MVFR/VFR late morning to early 
afternoon. Snow showers may linger into the afternoon esspically
across western MA/CT, although confidence in any snow that 
falls Saturday will be light, under a half inch. 

KBOS Terminal...Moderate confidence in TAF.

Snow should begin around 19z this afternoon and could become 
moderate briefly before becoming mixed with sleet after 22z. Not
anticipating ptype to switch to rain at this point. ptype 
should become all snow again this evening after 02z with snow 
lingering into Saturday morning. CIGS will quickly drop to 
IFR/LIFR as snow begins this afternoon and remain there into 
Saturday morning before becoming MVFR.

KBDL Terminal...Moderate confidence in TAF.

Light snow should become more of a mixed precip this afternoon 
with sleet and freezing rain possible. ptype switches back to 
snow later this evening before tapering off overnight. CIGS 
remaining IFR this evening, improving to MVFR later overnight.

Outlook /Sunday through Wednesday/...

Sunday: Mainly VFR, with areas MVFR possible. Breezy. Chance
SN.

Sunday Night: MVFR/IFR conditions possible. Windy with areas of
gusts up to 35 kt. Chance SN.

Monday: Mainly VFR, with local IFR possible. Strong winds with
areas of gusts up to 40 kt. Chance SN.

Monday Night: VFR. Windy with local gusts up to 35 kt. Slight
chance SN.

Tuesday: VFR. Breezy. 

Tuesday Night: VFR. 

Wednesday: Breezy. Chance RA, slight chance SN.

&&

.MARINE...
Forecaster Confidence Levels...

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

High confidence through the end of this week.

Low pressure passing SE of New England will bring increasing 
E/NE winds through this evening, before winds back to N/NW and 
diminish later tonight and Sat. Rough seas will linger awhile 
longer offshore, then the developing coastal low as outlined 
above is expected to bring dangerous marine conditions later 
Sunday night and into Monday night.

Outlook /Sunday through Wednesday/...

Sunday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of snow. 

Sunday Night: Strong winds with gusts up to 40 kt. Rough seas
up to 16 ft. Chance of snow. Local visibility 1 nm or less.

Monday: gale force winds with gusts up to 45 kt. Rough seas up
to 23 ft. Chance of snow. Areas of visibility 1 nm or less.

Monday Night: Low risk for gale force winds with gusts up to
40 kt. Rough seas up to 22 ft. Chance of snow. 

Tuesday: Winds less than 25 kt. Rough seas up to 13 ft. 

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory until 7 AM EST Saturday for CTZ002>004.
MA...Winter Weather Advisory until 7 AM EST Saturday for MAZ002>014-
     026.
     Coastal Flood Watch from Monday evening through Tuesday 
     morning for MAZ007-015-016-019-022>024.
     Winter Storm Watch from late Sunday night through Monday 
     evening for MAZ020>024.
     High Wind Watch from Monday morning through Monday evening for 
     MAZ022>024.
RI...Winter Weather Advisory until 7 AM EST Saturday for RIZ001-003.
     Winter Storm Watch from late Sunday night through Monday 
     evening for RIZ006>008.
     High Wind Watch from Monday morning through Monday evening for 
     RIZ008.
MARINE...Gale Watch from late Sunday night through Monday evening for 
     ANZ230.
     Storm Watch from Monday morning through Monday evening for 
     ANZ231.
     Storm Watch from late Sunday night through Monday evening for 
     ANZ232>234.
     Storm Watch from late Sunday night through Monday afternoon 
     for ANZ235-237.
     Storm Watch from Monday morning through Monday afternoon for 
     ANZ236.
     Small Craft Advisory from 7 AM to 1 PM EST Saturday for ANZ250-
     254>256.
     Storm Watch from Monday morning through Monday evening for 
     ANZ250-251.
     Storm Watch from late Sunday night through Monday evening for 
     ANZ254>256.

&&

$$

DISCUSSION...McMinn/JWD
AVIATION...KP
MARINE...JWD