684
FXUS61 KBOX 121438
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
938 AM EST Wed Feb 12 2025

.SYNOPSIS...

Quiet today with perhaps some light snow showers/flurries across
central and eastern Massachusetts. Another system moves across
southern New England Wednesday night through Thursday, with
light snow to start, transitioning to a wintry mix and then to
rain Thursday morning. Dry weather returns Friday into early
Saturday before yet another system brings a round of wintry
precipitation this weekend, probably starting as snow before
changing to rain near the coast and a wintry mix inland.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

Key Messages...

* Rather Cloudy with afternoon highs lower to middle 30s
* A few ocean effect snow flurries/light snow showers possible

Previous forecast is on track. Large high pressure over Quebec
will shift further east as the day wears along. This will result
in light N winds gradually becoming more NE/ENE and rather
cloudy skies. Temps at the top of the mixed layer on the order
of -11C/-12C along with onshore flow may allow some light ocean
effect snow showers/flurries develop across central and eastern
MA develop. Not expecting much of an impact or travel issues
from this activity. High temps will mainly be in the lower to
middle 30s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Key Messages...

* A messy storm system will bring first snow then a mix of sleet and
  freezing rain followed by rain overnight into Thursday morning.

Tonight a mid level trough digging into the Great Lakes will track a
surface low pressure center to our northwest over upstate New York.
A secondary low forms along the frontal boundary off the mid-
Atlantic coast and deepens as it passes over southern New England.
These features will be the main drivers of a messy winter system
bringing a burst of snow followed by a wintry mix and eventually
rain. That secondary low along with the high to the northeast will
provide a good setup for some cold air damming which will help to
keep some of those subfreezing temperatures in the interior even as
other locations rise above freezing.

Low level WAA on SE flow will overrun the colder air producing
widespread snow between 8 PM and midnight. Soundings show dry air
and little omega in the DGZ which will limit accumulations, but a
coating (south) to 3 inches (high terrain) is possible before a warm
nose pushes in around 850 mb. Further inland, generally northwest of
the I-95 corridor, this will lead to a switch to sleet then several
hours of freezing rain. Further south and east a flip from snow
straight to rain is more likely. Given the timing around the morning
commute, this could make for some hazardous roads, mainly in the
interior where freezing rain is a concern. A Winter Weather Advisory
remains in effect.

The dry slot soon overspreads SNE by mid afternoon bringing an end
to precipitation. With the passing of the low winds shift to the
W/NW and the boundary layer becomes much more well mixed. This will
make for a gusty afternoon as we tap into a 30-40 kt LLJ; expect
gusts 20-30 mph and potentially higher overnight.

&&

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

* Travel impacts likely this weekend, especially across interior
  where snow probably changes to a mix or even rain for a time. Less
  of an impact near coast where change to all rain is more likely.

* Minor snow accumulation possible late Sunday night into Monday
  morning.

* Dry and cold weather follows early next week.

Details:


Thursday Night - Friday:

Colder and dry Thursday night with high pressure and a cooler
airmass building in. Despite the favorable conditions for a chillier
night with the cool airmass and decreasing cloud cover, lows should
be moderated by breezy post-frontal winds. Temperatures fall into
the upper teens to low 20s across the interior and low to mid 20s
closer to the coastline. Surface high pressure stays in the place
for Friday with weak ridging aloft. With a below normal airmass
aloft, this will keep highs in the upper 20s to low 30s. A low level
jet positions across the region and with cold air advection
supplying the lapse rates to mix higher NW winds down to the
surface. The ECMWF EFI highlights windier than normal conditions,
but not necessarily high impact winds. The usual windy spots
(Berkshires and Worcester Hills) could see gusts 35-45 mph and up to
35 mph elsewhere. Wind decrease late afternoon to early evening.

Weekend:

The pattern becomes active again for the weekend as a southern
stream shortwave trough ejects northward ahead of a deep upper level
trough. Ensemble means track a surface low lifting NE across the
region by the end of the weekend. Plenty of support for
precipitation with this system with a plume of above normal moisture
with precipitable water values 300% of normal paired with synoptic
ascent. This provides a solid signal for widespread precipitation.
However, things get more complex with regards to the details like
precip type. More details below.

Overall, ensemble means and deterministic guidance show the general
pattern of a surface low tracking northeast Saturday into Sunday
with push of warm air aloft northward Saturday night. With plenty of
cold air ahead of the system, this overall favors a snow to wintry
mix/rain progression with this system. Details such as precip type
and change over timing are still uncertain due to model differences
in the track and timing of the surface features of the system.

Despite disparities between guidance, we should see minor
accumulations across northern CT and most of MA. Notable split
between ECMWF and GFS. The ECMWF ens has generally shown higher
probabilities for > 3" (40-70%) for interior MA while the GEFS
trends lower with probabilities less than 40% and confined to the
higher elevations of MA. This disagreement is likely from the
uncertainty in the timing of the warmer air. What we can take from
this right now is that areas north of the MA Pike have the highest
potential for Advisory level amounts while others it is less certain
due to the timing of the warm air and transition to mixed precip. By
mid-morning Sunday, warm air will be in full force changing things
to rain.

A cold airmass follows the system Sunday night into Monday and there
is a low chance (< 30%) that precip could change back over to light
snow for a period Sunday evening.

Early next week trends cool and dry with a trough and a surface high
pressure over the northeast.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:

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

12z TAF Update:

Today...High Confidence

MVFR cigs increase in coverage after 15z with E/NE winds,
gusting to 25kt along coast. We should also see scattered
flurries, mainly over eastern MA, but not confident enough in
timing and coverage to include in TAFs.

Tonight...Moderate Confidence.

Next round of precipitation arrives between 05 and 08Z from SW
to NE and should bring MVFR cigs/vsbys in light SN to CT and
western MA with less of a chance farther east. SN transitions to
FZRA and RA 09-11Z.

Thursday...High Confidence

IFR/LIFR with rain likely along the coast, wintry mix inland,
then all precip ending as rain by afternoon. Improvement to
MVFR/VFR toward 00z Fri.

KBOS TAF...High confidence. May see flurries during day but not
confident enough in timing to include. Looking ahead to
tonight/Thu, light snow likely starts after midnight (06z) and
quickly changes to rain around 09z with less than one inch of
snow accumulation before the changeover.

KBDL TAF...High confidence. Light snow begins around 04z and
changes to a FZRAPL mix 07z-10z, before changing to rain closer
to 13-14z. Snow accumulation around one inch with less than
0.10" of icing before the change to rain.

Outlook /Thursday Night through Sunday/...

Thursday Night: VFR. Windy with gusts up to 35 kt. Slight
chance FZRA.

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

Friday Night: VFR. Breezy.

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

Saturday Night: MVFR/IFR conditions possible. SN, RA.

Sunday: Breezy. RA, SN.

&&

.MARINE...
Forecaster Confidence Levels:

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

Weak wave of low pressure tracks south of 40N/70W 12z today,
then zips east out to sea. Tranquil conditions today, with NE
wind 10-15 kt. Then tonight, low pres approaches from the SW,
with NE winds 15-20G30KT across the MA/RI waters late tonight
into Thu AM. Low moves up the I95 corridor early Thu, then into
the Gulf of ME Thu afternoon, with wind shift from NE to WNW
late.

Outlook /Thursday Night through Sunday/...

Thursday Night: Strong winds with gusts up to 35 kt. Rough seas
up to 10 ft.

Friday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Rough seas up to 10 ft.

Friday Night: Winds less than 25 kt. Local rough seas.

Saturday: Winds less than 25 kt. Chance of rain, chance of
snow.

Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Rain.

Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Rough seas up to 12 ft. Rain.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory from 10 PM this evening to 10 AM EST
     Thursday for CTZ002>004.
MA...Winter Weather Advisory from 10 PM this evening to 10 AM EST
     Thursday for MAZ002>006-008>012-026.
RI...Winter Weather Advisory from 10 PM this evening to 10 AM EST
     Thursday for RIZ001.
MARINE...Small Craft Advisory from 7 PM this evening to 7 PM EST Friday
     for ANZ231>235-237-250-251-254>256.

&&

$$

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