266
FXUS61 KBOX 052324
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
624 PM EST Wed Feb 5 2025

.SYNOPSIS...
A fast moving low pressure system will bring a mixture of snow,
ice and rain on Thursday with slippery travel expected. Dry
and windy weather follows Friday with diminishing wind but
colder temperatures Friday night into Saturday. A snowstorm appears
likely later Saturday night into Sunday morning with perhaps some
mixing for some locations during the end of the storm especially
near the south coast. Dry but cold weather returns Sunday night and
Monday. The active weather pattern may continue next week depending
on the track of a couple low pressure systems in the Tuesday through
Thursday time frame.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Key Messages:

* Cool night with temperatures in the single digits to teens


Quiet night expected ahead of our next system. High pressure
shifts to the east, but dry conditions should prevail through
early Thursday morning. High clouds move in from the southwest
around/after midnight. Despite some cloud cover, it will be a
cooler night overall with temperatures dropping into the upper
single digits across interior MA and teens elsewhere.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Key Messages...

* Snow arrives between 6-10 AM Thu and then changes to ice/rain
  in the afternoon
* 1-4" of snow/sleet, with a light glaze of ice possible
* Temperatures unlikely to break freezing Thu afternoon across
  much of central and western MA


Main story for Thursday will be a low pressure system tracking
across SE Massachusetts bringing snow to start with a change
over to a wintry mix of toward the afternoon.

Plenty of cold air to start early Thursday morning given a
rather cool night. As the system approaches, snow increases from
southwest to southwest to northeast in the 6 to 10 AM timeframe.
Model soundings show some positive omega aligned in the DGZ for
a few hours within the arrival of the snow. This should
support moderate snow rates and visibilities as low as a 1/2
mile for a brief time. This will cause minor impacts to travel
as it does fall within the typical commute window.

As we head into late morning, we arrive at our main forecast
challenge...precipitation type. Southerly flow and warm air
slowly advects in from the south late morning. Where it get
complicated is the uncertainty in how quickly this warm air
moves in and how it impacts the thermal profiles into the
afternoon. These factors will influence our precipitation type.
As warmer air moves northward, snow transitions to a wintry mix.
We will likely start seeing this transitions in our more
southern areas (CT, RI, SE MA) late morning to early afternoon,
slowly making its way north early afternoon. This will include
what we call a "mixed bag" of precipitation types. Model
soundings support a change over to sleet at first in areas with
temperatures profiles showing the colder air staying intact in
a shallow layer at the surface. As warm air continues to scour
this out, precipitation transitions to freezing rain to rain by
late afternoon. The transitions to each precip type likely won`t
be uniform. Areas such as the Cape/Islands may have a quicker
period of sleet or freezing rain before switching to rain early
afternoon. By the evening, the system exits offshore with
precipitation moving out with it.

Winter Weather Advisories continue across most of southern New
England with a range of 1-4 inches of snow from the morning
snow and the threat for icing for the afternoon. Thinking the
threat of icing across the Cape and islands remains too low to
warrant an expansion of the advisory. Travelers should be
prepared for slippery travel on untreated surfaces Thursday and
a quick onset of snow in the commute timeframe (6 AM - 10 AM).

Thursday night, expect gradually improving conditions with
breezy westerly winds developing toward midnight. Temperatures
drop into the mid 20s to mid 30s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Key Messages...

* Dry/Windy Fri...Highs middle 30s-lower 40s with 35-50 mph gusts
* Remaining dry Sat with highs mainly lower to middle 30s
* Snowstorm likely later Sat night-Sun am with some mix possible
* Another winter weather event or two possible Tue through Thu

Details...

Friday...

Intensifying low pressure lifting north through the Canadian
Maritimes will combined with high pressure building eastward from
the Great Lakes. This will result in windy conditions across
southern New England. Bufkit soundings support northwest wind gusts
of 35-50 mph. Morning highs in the middle 30s to the lower 40s may
slowly fall during the afternoon as colder air works in from the
northwest. Wind Advisories may eventually be needed.

Friday night and Saturday...

High pressure over the eastern Great Lakes shifts east over our
region Fri night into Sat. This will allow winds to gradually
diminish with lows mainly in the teens to lower 20s with highs Sat
generally in the lower to middle 30s. While it will remain dry over
this time...we do expect some mid-high clouds to gradually
overspread the region from the west during the day Sat.

Saturday night and Sunday...

Confidence increasing that a snowstorm will impact much of southern
New England later Sat night into Sun AM. We are still outside 84
hours in the model world...so certainly will see some changes going
forward. The current guidance though is in very good agreement in
the likelihood of a snowstorm later Sat night into Sun morning. We
have a low pressure system that tracks eastward from the Ohio Valley
with a modest high pressure system across Quebec. This low pressure
system looks to track to our south and appears to be associated with
a closed 850 mb low. This may potentially bring a period of strong
forcing along with a period of moderate to heavy snow possible.
There may also be some mixing during the latter half of the storm
depending on the track. We can say though that there is high
confidence in a plowable snowfall with this system...but it is too
early to given specific amounts. Later shifts may need to consider
Winter Storm Watches.

Given the fact that is event is still more than 3 days out...the
track is not set in stone. If the low pressure system trends
north...there may be more mixed precipitation especially south of
the MA turnpike with the heavier snow risk across northern MA. If
the low pressure system trends further south...mainly snow would be
expected across southern New England but with the higher amounts
south of the MA Turnpike and lower totals to the north.

Regardless...motorists traveling later Sat night into Sun morning
should be prepared for a snowstorm.

Sunday night and Monday...

A ridge of high pressure builds into the region Sun night and Mon.
This brings dry and cold weather to the region. Lows Sun night will
be in the single digits and teens with highs Mon mainly between 30
and 35.

Tuesday through Thursday...

We will have to watch the potential for the threat of another winter
weather event or two in the next Tue through Thu time frame. High
pressure in Quebec will provide at least seasonably cold air to
southern New England. We also will have to watch two potential low
pressure systems to our south. The first Tue into early Wed and
perhaps another one later Wed into Thu. The models are likely
struggling with which one of the low/s to put more weight into and
how far north they track. The guidance is split on the northern
extent of precipitation with both potential systems. Quite the ways
out...but the potential exists for more winter weather/snow next
week depending on how far north those low pressure systems track.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:

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

Tonight...High Confidence.

VFR. NW winds 10 to 15 knots today, becoming light/calm from
the SW tonight.

Thursday...Moderate Confidence.

Widespread IFR/LIFR conditions overspread the region from
southwest to northeast in the morning as snow arrives in the
11-14z timeframe. Precipitation type becomes more complex
generally starting 16-18z with a change to sleet/freezing rain,
and eventually some rain along the coastal plain. Generally
expect 1-4" of snow/sleet followed by a light glaze of ice
possible especially across the interior. Precipitation moves out
by 00z with gradually improving conditions.

KBOS TAF...High Confidence in TAF.

KBDL TAF...High Confidence in TAF.

Outlook /Friday through Monday/...

Friday: VFR. Strong winds with gusts up to 40 kt.

Friday Night: VFR. Windy with local gusts up to 30 kt.

Saturday: VFR. Breezy.

Saturday Night: Mainly IFR, with local MVFR possible. Breezy.
SN, FZRA likely.

Sunday: MVFR/IFR conditions possible. Windy with local gusts up
to 30 kt. Chance SN, chance FZRA.

Sunday Night through Monday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels:

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

Thursday...High Confidence.

Developing southerly LLJ will include SE winds gusts of 20 to
30 kt, so Small Craft Advisories will be in effect through
Friday.

Outlook /Friday through Monday/...

Friday: Moderate risk for gale force winds with gusts up to
35 kt. Areas of rough seas.

Friday Night: Moderate risk for Small Craft Advisory winds with
areas of gusts up to 30 kt. Local rough seas.

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

Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas locally approaching 5 ft. Snow, rain,
freezing rain likely. Visibility 1 to 3 nm.

Sunday: Low risk for gale force winds with gusts up to 30 kt.
Local rough seas. Chance of rain, chance of snow showers. Areas
of visibility 1 to 3 nm.

Sunday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Freezing spray.

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory from 7 AM to 7 PM EST Thursday for
     CTZ002>004.
MA...Winter Weather Advisory from 7 AM to 7 PM EST Thursday for
     MAZ002>021-026.
RI...Winter Weather Advisory from 7 AM to 7 PM EST Thursday for
     RIZ001>007.
MARINE...Small Craft Advisory from 9 AM Thursday to 6 AM EST Friday for
     ANZ230>237-250-251-254>256.
     Gale Warning from 6 AM to 8 PM EST Friday for ANZ230-236.
     Gale Watch from Friday morning through Friday evening for
     ANZ231>235-237-250-251-254>256.

&&

$$

SYNOPSIS...Frank/Mensch
NEAR TERM...Mensch
SHORT TERM...Mensch
LONG TERM...Frank
AVIATION...Frank/BW/Mensch
MARINE...Frank/Mensch