Old Res Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 171803
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
103 PM EST Tue Feb 17 2026

.WHAT HAS CHANGED...
Winter Weather Advisories issued for western and central 
Massachusetts Wednesday afternoon and evening. 

There is increasing confidence in the risk of snow and
freezing rain Friday into Saturday. 

Still watching a potential winter storm Sunday into Monday.
At the very least we may see potential coastal flooding along 
the eastern Massachusetts coast as well as marine impacts on the
coastal waters.

&&

.KEY MESSAGES...

- Travel impacts from accumulating snow Wednesday afternoon and
  evening. 

- A system on Friday/Friday night will bring a mix of snow,
  freezing rain, and rain to southern New England while
  scattered snow showers linger into Saturday. 

- Watching a potential winter storm Sunday into Monday.

&&

.DISCUSSION...
KEY MESSAGE 1...Travel impacts from accumulating snow Wednesday 
afternoon and evening. 

Still a challenging forecast regarding precipitation type and where 
a narrow band of snow sets up, but we have more confidence that much 
of western and central MA will see 2-4" of snow Wednesday afternoon 
and evening, where we are issuing Winter Weather Advisories. 

That said, confidence is a bit lower farther east, including the 
Boston and Providence areas, since temperatures initially may be too 
warm to allow snow to accumulate, so we think 1-3" totals are more 
likely in these areas. It's possible we will need to extend the 
Advisories into these areas with the Wednesday early morning 
forecast if things trend a bit colder.

12z HRRR and HREF closely match our thinking, but we are still wary 
of the "colder" 12z 3km NAM which would bring slightly higher totals 
than what we have now, or even 12z GFS which has the axis farther 
south into CT, RI, and SE MA. On the flip side, 12z RRFS is much 
warmer and would mean much less of an impact, but that seems to be 
the outlier. Trying to pinpoint banding in these setups is always 
difficult!

A weak low will pass off the coast and maintain a cold N/NE flow 
across southern New England. Initially, the airmass is relatively 
"mild" but as the precipitation arrives around midday, in the form 
of either light rain or light snow, we expect to see wet bulb 
cooling with temperatures falling into the low to mid 30s. Exactly 
how quickly this takes place is still a question, but we are more 
confident that the higher elevations of western and central MA will 
begin as snow. In the lower elevations including closer to the 
coast, even if it does change to snow quickly, the snowfall rates 
will be light and with marginal temperatures it will be tough to get 
accumulations right away. However as we approach late afternoon and 
especially evening, that's when most of the accumulation will occur 
(or if we see any briefly heavier snowfall).  now will taper off 
before midnight as low exits offshore. 


Key Message 2...A system on Friday/Friday night will bring a mix of 
snow, freezing rain, and rain to southern New England while 
scattered snow showers linger into Saturday. 

The active pattern continues late week into the weekend as, after 
brief ridging and surface high pressure on Thursday another 
vertically stacked shortwave/surface low moves out of the Great 
Lakes and over New England Friday night into Saturday. Temperature 
profiles will be complex and need to be honed in as we get closer 
(better, high-resolution data) but it looks to be a mixed 
precipitation event as a warm front lifts north providing lift from 
warm advection as well as some decent frontogenesis in the 
700mb/850mb level. Model soundings show a period of strong omega in 
the DGZ on the front end (Friday) which could allow for some decent 
snowfall rates especially further north. Closer to the south coast 
marginal temps may lead to a mostly rain event while a mid level 
warm nose also introduced the likelihood of freezing rain for parts 
of the interior. Another factor to consider is a secondary low that 
forms and deepens offshore. Looking at it from a probabilistic 
perspective, ensemble guidance presently shows a 15-40% chance of 4+ 
inches of snow through Saturday along and south of the MA Pike with 
a 40-55% chance to the north. This, with the potential for several 
hundredths of an inch of freezing rain. The bulk of the precip looks 
to fall before sunrise on Saturday but scattered snow showers 
continue during the day.


KEY MESSAGE 3...Watching a potential winter storm Sunday into Monday.

Guidance continues to show a potentially significant winter storm 
developing off the East Coast Sunday into Monday, but as usual at 
this time range, we are seeing a large spread in possible storm 
tracks with anything from an offshore pass to a direct hit on 
southern New England.

All of this uncertainty ties to how quickly a northern stream short 
wave can close off as it tracks through the Great Lakes and toward 
the East Coast, which is dependent upon the strength of the upper 
ridge over the North Atlantic. A stronger ridge, as seen in latest 
GFS and Canadian runs, would help the low to close off more quickly 
and gain a negative tilt, allowing the coastal storm to track closer 
to southern New England with higher impacts. Conversely, a weaker 
ridge, as depicted by 12z ECMWF, would mean the upper low closes off 
later and maintains more of a positive tilt, keeping the coastal 
storm more out to sea. It's also interesting to note the AI versions 
of GFS and ECMWF, which have performed well this winter, are fairly 
similar and both bring low close enough to impact at least the South 
Coast, Cape Cod, and Islands.

Right now odds favor at least some impact to CT, RI, and SE MA if 
not more of the area, but keep in mind we are several days out and 
probably won't see any notable trends in guidance until Thursday at 
the earliest. So for now, expect to see the usual run-to-run 
variations in the deterministic models and some showing big hits. 
It's just way too soon to lock into any one model solution.

One thing that we are becoming more confident in is the potential 
for coastal flooding and marine impacts, even with a more offshore 
track. We are approaching higher astronomical tides Sunday and 
Monday and much of eastern MA coast could be vulnerable to at least 
minor coastal flooding and beach erosion. On the coastal waters, 
there is the potential for NE gale force winds and rough seas, given 
fact that much of the guidance is showing a potentially strong 
coastal storm. 

&&

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

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

18z TAFs: Moderate confidence (60%).

Light S/SW flow should promote widespread IFR ceilings as we
head through late afternoon given milder air on top of deep
snowpack in place. Fog should also form tonight with areas of
1/2SM or less near South Coast. Not confident enough to include
in TAFs but it's possible it may be needed at KORH/KPVD
especially.

Not looking for substantial improvement tonight or Wed morning
as lower level moisture remains locked in, probably no better
than MVFR. Light rain or light snow arrives around midday and
changes to light snow everywhere (except Cape Cod/Islands) by
late afternoon, ending Wed night with VFR conditions to follow.

KBOS Terminal...Moderate confidence in TAF. Main question is
whether or not IFR ceilings persist through tonight once they
develop or if we see improvement to VFR ahead of the rain/snow
Wed. Expectation is that low clouds will hang tough but we may
not lose IFR ceilings until Wed.

KBDL Terminal...Moderate confidence in TAF. Higher confidence
that IFR ceilings persist but main question is whether or not 
fog come in sooner?

Outlook /Thursday through Sunday/...

Thursday: VFR. 

Thursday Night: VFR. Slight chance SN.

Friday: Mainly VFR, with local IFR possible. Breezy. RA likely,
chance SN, FZRA, PL likely.

Friday Night: MVFR/IFR conditions possible. Breezy. SN likely,
FZRA.

Saturday: Mainly VFR, with local IFR possible. Chance SN,
chance RA.

Saturday Night: Mainly VFR, with local IFR possible. Slight
chance SN.

Sunday: Mainly VFR, with local IFR possible. Breezy. 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 the week.

Weak low pressure will pass offshore Wed. Leftover E swell will 
maintain 5 ft seas on outer waters where SCAs remain posted. 
Otherwise relatively light winds and flat seas expected.

Outlook /Thursday through Sunday/...

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

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

Friday: Winds less than 25 kt. Rain likely, chance of snow,
chance of freezing rain. 

Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Snow likely,
rain likely. Local visibility 1 to 3 nm.

Saturday: Winds less than 25 kt. Seas up to 5 ft. Chance of
snow, slight chance of rain. 

Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain, slight chance of snow.

Sunday: Low risk for Small Craft Advisory winds with local
gusts up to 30 kt. Areas of seas approaching 5 ft. Chance of
snow, slight chance of rain. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Winter Weather Advisory from 1 PM Wednesday to 4 AM EST 
     Thursday for MAZ002>004-008>012-026.
RI...None.
MARINE...Small Craft Advisory until 7 AM EST Thursday for ANZ250-
     254>256.

&&

$$

DISCUSSION...BW/JWD
AVIATION...JWD
MARINE...JWD