779
FXUS61 KBOX 051814
AFDBOX

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

.SYNOPSIS...
Windy conditions into this evening will usher in much colder
temperatures overnight into Wednesday as winds gradually
diminish. A fast moving low pressure system will bring a mixture
of snow, ice and rain on Thursday with slippery travel
expected. The active weather pattern continues with another
storm Saturday night into early Sunday bringing a wide variety
of wintry precipitation. We also will need to watch the
potential storm by late Tuesday and Wednesday of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Key Messages:

* Mostly sunny but colder

Mainly tweaks this morning. Some high level clouds should mostly
pass by our region by mid morning. Brought temperatures back in
line with observed trends.

Previous Discussion...

It`s all about a high pressure moving across southern New
England today. Plenty of sunshine with a gusty northwest wind,
which will keep high temperatures 10-15 degrees lower than
Tuesday. Gusty winds diminish after sunset.

&&

.SHORT TERM /THURSDAY/...
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

Still rather quiet tonight, but setting the stage for a quick-
moving low pressure Thursday. By morning, this high pressure
should be over the North Atlantic. The main result of that is
for winds to become southeast, pushing warmer air towards our
region. Despite that, northerly ageostrophic flow in the lowest
levels is expected to trap colder air across much of interior
southern New England. This becomes the forecast challenge over
the next 36 hours or so. What will the thermal profiles look
like? How quickly will they change?

Latest thinking is that sufficiently cold air remains in place
for the morning, leading to a light snowfall by New England
standards. Things get more complicated during the afternoon.
The SE flow should push enough warm air our way to transition
the snow to a wintry mix from south to north, eventually leading
to rain and freezing rain for a time before all precipitation
ends towards evening. Winter Weather Advisories continue across
most of southern New England. 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.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Key Messages:

* Windy but dry Friday with more seasonable temperatures

* Colder Saturday with another fast-moving storm that may bring
  accumulating snow and some ice Saturday night. May switch to
  rain for some.

* Dry and seasonably cold to start the week

Details...

A brief quiet period between Thursday`s system and the next one
moves in for Friday with high pressure making its way into
southern New England. Temperatures moderate a bit for Friday as
well before the cold air advection associated with the stronger
winds really kicks in ahead of a shortwave moving through New
England. 925 mb temperatures around -10C across southern New
England. Temperatures at 850 mb may also sit around -15C in this
airmass. Forecast soundings are still favoring deep mixing for
Friday, so the chance for wind advisory-level gusts remains.

For the weekend`s system, ensemble guidance is still quite far
apart in terms of accumulation amounts. However, the general
pattern expected is colder air already in place will encourage
initial precipitation to be snow. As warm air advects in from
the southwest, precipitation will likely switch over to more of
a mix, with some places further south fully switching to rain.
This may extend up into much of eastern MA, but the details of
ptype and where which ptype will fall still need to be ironed
out. The GEFS runs a bit lower compared to the ENS and Canadian
ensemble; GEFS QPF values primarily sit in the 0.4-0.5 inch
range over a 24 hour period through 00z Monday (7 PM Sunday),
the GEPS has values up to 0.8 inches in the CT Valley and RI
(0.65 inches is the general amount outside of those regions),
and the ECMWF ensemble has values mostly from half an inch to
0.6 inches. Needless to say the range is still broad in terms of
QPF. Similar situation for snow accumulations and ice. Across
all guidance, values for freezing rain/ice accumulations vary
significantly at this time, as is the same with snowfall
amounts. However, all ensembles have decent probs for 24 hour
accumulations of 3+ inches (50 to 100%): the GEFS has the
highest probs north of the Mass Pike while the GEPS is
especially aggressive across the CT Valley and eastern Worcester
county, even showing up to 50% probs for greater than 6 inches.
However, this is the only model showing this signal at this
time. Guidance appears to have the majority of this system out
of the area by Sunday morning, but it could linger through
Sunday night. Timing will be more refined in future updates.
Sunday`s highs expected to be milder due to the SW flow
associated with this system.

Following the weekend`s shortwave, dry conditions return to
start the week as high pressure returns for Monday. This may
be short- lived as another shortwave moves closer towards
midweek.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Forecast Confidence Levels:

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

Today and 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 /Thursday Night through Monday/...

Thursday Night: Mainly VFR, with local IFR possible. Windy with
local gusts up to 30 kt.

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.

Today and Tonight...High Confidence.

High pressure approaches the waters today, then crosses the
waters tonight. Winds subside this morning, but rough seas
should linger across the eastern outer coastal waters into this
afternoon.

Thursday...High Confidence.

Developing southerly LLJ will include SE winds gusts of 20 to
30 kt, so Small Craft Advisories will likely be needed once
again. Reduced visibility in a burst of snow and sleet during
the morning, to be followed by rain during the afternoon.

Outlook /Thursday Night through Monday/...

Thursday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas.

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...None.

&&

$$

SYNOPSIS...Belk/Hrencecin
NEAR TERM...Belk
SHORT TERM...Belk
LONG TERM...Hrencecin
AVIATION...Belk/Hrencecin/Mensch
MARINE...Belk/Hrencecin