NWS Forecaster Discussion
BOX
Area Forecast Discussion National Weather Service Boston/Norton MA.
412
FXUS61 KBOX 271950
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
250 PM EST Tue Jan 27 2026
.WHAT HAS CHANGED...
No significant changes. Confidence remains high on well below normal
temperatures this week with another surge of Arctic air Thursday
night into Friday. Low confidence on potential impactful winter
storm Sunday.
&&
.KEY MESSAGES...
- Mainly dry with well below normal temperatures this week, and
potentially hazardous wind chills Thursday night into Friday.
- Monitoring a possible late-weekend coastal storm. Uncertainty
remains large in the track.
&&
.DISCUSSION...
KEY MESSAGE 1...Mainly dry with well below normal temperatures
this week, and potentially hazardous wind chills Thursday night
into Friday.
Fairly active northern stream through the end of the week as a
series of moisture starved shortwaves move through the region. A
few snow showers will be possible through the early evening with a
shortwave passage, then we have another shortwave moving through Wed
night with a low risk for a few flurries. In between the 2
shortwaves a period of shortwave ridging will provide mostly sunny
skies on Wednesday.
Arctic air will remain entrenched across the region this week with
850 mb temps -15C to -20C. Highs through Thu will be in the teens
to lower 20s with lows mostly in the single numbers, while overnight
and morning wind chills will be below zero. A third shortwave will
drop down Thu night into Fri bringing a reinforcing shot of arctic
air Thu night through Fri night. In fact we may see widespread below
zero temps late Fri night and early Sat. The potential exists for
dangerously cold wind chills which will likely require cold weather
headlines from Thu night and Fri night.
KEY MESSAGE 2...Monitoring a possible late-weekend coastal
storm. Uncertainty remains large in the track.
We continue to monitor the potential for a coastal storm late next
weekend. Deterministic and ensemble has remained generally
consistent and agreeable with development of a coastal storm off of
the East Coast this upcoming weekend. Despite this consistent signal
for a coastal storm over the past runs, there is plenty of
uncertainty. Very normal this far out.
There is good consensus for an amplified ridge setting up over
western CONUS/Canada, helping a trough dig southward from Canada
later in the week. Where model solutions start to diverge is with
degree of amplification of the trough and whether the 500mb low
closes off. This is present in the WPC Cluster Analysis with half of
the grand ensemble with a closed 500mb low. Within that guidance,
there are solutions that favor a closed low shifting across the Ohio
Valley, potentially shifting as south as the Georgia/Carolinas
before it tracks back northward. This amplified trough and possible
low will keep cold air locked in across the northeast through the
weekend. Surface coastal low development has been consistent across
guidance, but with solutions even showing deep surface low
development(sub-990mb) off the East Coast. The ingredients are there
for deep low development, with cold air in place interacting with a
warm/moist air with air-sea interactions helping to enhance. As
expected, given the uncertainty in the details of the pattern, there
is large variance in the track of the surface low evidence across
ensemble guidance. Some solutions track around the 40N/70W
benchmark, but there is still spread with how close to shore the low
tracks with a chunk of solutions showing an offshore pass. This will
heavily influence the amounts and impacts with this potential storm.
Cluster analysis also signals at differences in the amplification of
the ridge to the east (offshore) which may influence the low track.
This may likely be a more complex detail as the strength of this
ridge could depend on the small-scale details/thermodynamics of the
system as it evolves. Another thing to keep monitoring...
Plenty to be said on the pattern, low tracks, model QPF with large
amounts of variance, but what prompts the close monitoring are the
solutions that indicate an impactful storm. Glancing the upper
percentiles of ensemble guidance, aside from the fact the spread is
large between them, the 75th/90th percentiles (worst case scenarios
of the ensemble suite) indicate potential for an impactful snow
storm. The Probabilistic WSSI indicates probabilites 20-50% for
moderate winter storm impacts with the highest probabilities
for eastern and southeast MA. This realistically displays
potential for a storm while leveraging the large amount of
uncertainty in the track, amounts with the storm. Snow would not
only the the concern in the case of a strong coastal low
pressure (strong winds, coastal flooding). Ensembles indicate
moderate probabilities for gusts greater than 40 mph across the
waters and southeast coastal areas.
We are 5-6 days out still, so there is plenty of uncertainty and we
expect to see continued spread and changes from run to run over the
next few days. The important thing is to not stay locked in on a
solution, especially this far out. This is best seen from a
view, leveraging the full range of possibilities. As we go
through the week, ensembles should begin to converge on more
likely solutions/scenarios which will be messaged accordingly
alongside the other potential (lower probability) scenarios.
&&
.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18Z TAFs: High confidence.
Mainly VFR through Wed night. BKN-OVC cigs 4-6k ft developing
through early evening with a risk of a few snow showers with
brief MVFR vsbys, then clearing. A period of W gusts to 20-30 kt
developing late afternoon and evening, with potential gusts to
35 kt at ACK, diminishing overnight. W wind 10-15 kt Wed.
KBOS Terminal...High Confidence in TAF.
KBDL Terminal...High Confidence in TAF.
Outlook /Thursday through Sunday/...
Thursday through Friday Night: VFR. Breezy.
Saturday: VFR.
Saturday Night: Mainly VFR, with local MVFR possible. Strong
winds with local gusts up to 40 kt. Chance SN.
Sunday: Mainly VFR, with local IFR possible. Strong winds with
gusts up to 45 kt. Chance SN.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Another surge of gusty W winds late this afternoon into tonight
with the passage of a shortwave. Gusts to 25-35 kt likely with
strongest gusts on southern waters where Gale warnings are in
effect. SCAs in effect elsewhere. Winds diminish late tonight
through Wed.
Freezing spray advisory expanded to much of the nearshore
waters for a period of moderate freezing spray tonight into Wed
morning. Another round of widespread moderate to perhaps heavy
freezing spray is possible Thu night into Fri.
Outlook /Thursday through Sunday/...
Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft. Freezing spray, slight chance of snow showers.
Thursday Night through Friday: Moderate risk for Small Craft
Advisory winds with gusts up to 25 kt. Local rough seas.
Freezing spray.
Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Freezing spray.
Saturday: Winds less than 25 kt. Slight chance of snow.
Saturday Night: Moderate risk for gale force winds with gusts
up to 45 kt. Areas of rough seas. Chance of snow, chance of
freezing spray. Local visibility 1 nm or less.
Sunday: gale force winds with gusts up to 45 kt. Rough seas up
to 15 ft. Snow likely, chance of rain. Visibility 1 nm or less.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 4 AM EST Wednesday for ANZ230.
Freezing Spray Advisory until 10 AM EST Wednesday for
ANZ231>235-237-251-254-255.
Small Craft Advisory until 7 AM EST Wednesday for ANZ231-251.
Small Craft Advisory until 7 AM EST Wednesday for ANZ232>235-
237.
Small Craft Advisory until 4 AM EST Wednesday for ANZ236.
Small Craft Advisory until 10 AM EST Wednesday for ANZ250.
Gale Warning until 1 AM EST Wednesday for ANZ254>256.
&&
$$
DISCUSSION...KJC/Mensch
AVIATION...KJC
MARINE...KJC