BOX issues Area Forecast Discussion (AFD) at Jan 11, 1:15 PM EST678
FXUS61 KBOX 111815
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
115 PM EST Sat Jan 11 2025
.SYNOPSIS...
A more significant storm passes well to our south today, leaving
southern New England with just a period of light snow showers
expected through the day. Dry and seasonable weather returns Sunday
through Tuesday before colder conditions return to our region late
Tuesday through Thursday.
&&
.NEAR TERM /UNTIL 7 PM THIS EVENING/...
915 AM Update:
Key Messages...
* Steadiest snows thru midafternoon along the North Shore, with
2-3" local 4" totals possible. Best chance of shovelable snow
here, although impacts should be minimal to minor.
* Although snow shuts off for RI and southeast MA/Cape Cod most
of today, another round of additional, steadier light snow to
break out late this afternoon and tonight.
* Snow tapers off in Northern CT, central and western MA by
midday.
Update to make some adjustments to the snow forecast thru
midnight following observations and expected near-term trends.
Greatest increase mainly into the MA North Shore, with 2-3" and
isolated/spot 4" totals are forecast, associated with a steadier
snowband driven by a mid-level deformation axis as upper low to
our northwest. South of this area into much of Northern CT, the
South Coast, southeast MA and Cape the Islands, a dryslot seen
on WV imagery moving through the -12 to -18C snow crystal growth
layer has really sapped snowflake production to more of an
intermittent snow shower or flurry. Snow has also started to
decrease into central and western MA as well. Expect these
trends to continue thru at least the early to midafternoon
hours, with the steadiest snows falling at light to perhaps
locally moderate intensities toward northeast MA.
The steadier snowband over the North Shore eventually collapses
south/southeast thru the Greater Boston area and into South
Shore, Cape Cod and the Islands. The exact timing when this
occurs is still a bit unclear but our current thinking between
4-7 PM with steadier light snows then resuming/breaking out for
these areas. The western extent of snow is also a little
uncertain but could extend as far southwest as far eastern RI
(I-95/PVD corridor). This led to a minor uptick in snow accums
along Route 3 in MA and into portions of Barnstable County late
this afternoon, but not much more than an inch of additional
snow for these areas with up to 2" for these locations in
eastern MA.
Previous discussion:
Regional radar shows light returns already overspreading southern
New England early this morning even as it has yet to materialize at
the surface just yet. There is a fair amount of dry low level air
yet to saturate, with dewpoint depressions of 10-20 degrees. All
told the front edge of appreciable snowfall is expected to move into
western CT/MA around 4-6am, eastern MA by 6-8am. This as the
southern stream shortwave and stronger system passes to our south,
failing to fully phase with the northern stream energy that is
bringing us today's snow. Given lack of deep moisture (PWATs <0.4")
and bufkit soundings showing minimal omega (lift) in the DGZ we
don't expect today's snowfall to be heavy or amount to high impact
accumulations for most. On the whole we expect over the course of
the day to see snow totals on the order of a half inch to 2 inches.
The maximum where closer to 2 inches is more likely would be over
eastern MA, especially Essex county where snow may add up to 3+
inches by the time it wraps up after 8pm tonight. Snow is expected
to be light and fluffy in nature given the cold atmosphere and high
snow-to-liquid ratios (~15:1). Snow tapers off from west to east in
the afternoon, but won't fully exit eastern MA until closer to 7-
9pm. This evening winds will once again begin to pick up overnight
as the pressure gradient increases between the low offshore and high
pressure ridge over the southeast U.S. Expect wind gusts 20-25 mph.
&&
.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Key Messages...
* Dry and sunny with light winds.
Sunday kicks off a period of dry and calm weather as high pressure
builds in from the south. Expect temps to begin a slight moderating
trend as winds begin to turn out of the W and SW; this means highs
in the mid to upper 30s.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Monday
A mid-level ridge and associated high pressure will support a sunny
and relatively mild day in southern New England on Monday. 925 hPa
temps rise to near -5 Celsius with modest low-level warm advection.
This should support high temps in the upper 30s/low 40sF at the
surface during the afternoon. Dry conditions continue into Monday
with seasonable low temps in the upper teens across northwest MA to
the low to mid 20s over the coastal plain by Tuesday morning.
Tuesday through Thursday
A cold front crosses the region Monday night into Tuesday beginning
a new pattern of mainly cold dry weather. 925 hPa temps dip back
down to the -10 to -15 Celsius range between Tuesday and Thursday
which will result in chilly afternoon temps in the upper 20s/low 30s
and frigid overnight low temps in the low to mid teens. While dry
northwest flow will limit precipitation chances during this time
frame, there may be a shot for some ocean effect snow showers along
the east coast on Wednesday as a weak area of low-pressure moves
through The Gulf of Maine. Latest ensembles means only support a
dusting of snow along the east coast, but there may be an
opportunity for an inch or more of snow on the outer Cape. We'll
have more details as we get into early next week.
Next Weekend
Surface high pressure builds in from the west on Friday supporting
moderating temperatures. This will begin a southwest flow pattern
that will result in mild temperatures in the low to perhaps mid 40s
next weekend. This flow pattern may also be accompanied by periods
of snow or rain, but details are vague at this time. At this point,
we can say with moderate confidence that next weekend should feature
mild/unsettled weather. Stay tuned for further details.
&&
.AVIATION /18Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18z TAF Update:
Rest of the Afternoon (thru 00z Sun): High confidence in trends
though moderate confidence in timing.
Mix of VFR to IFR across Southern New England, though lowest
conditions in periods of steady light snow. Earliest improvement
(20z-23z) toward VFR for interior New England airports. Further
east, a steadier light to moderate snowband now over the North
Shore is expected to shift southward through east coastal MA
toward Cape Cod thru 23z which could briefly bring visbys to
1/2SM, and portions of this band could make it into PVD at times
but this is still uncertain. Toward 23z-00z, snow should be
mostly confined to South Shore and the Cape, with conditions
improving to BKN/OVC VFR elsewhere. Northerly winds around 5 kt
or less becomes NW and increases to 5-10 kt late this afternoon.
Tonight: High confidence.
Residual MVFR/brief IFR visby -SHSN over the Cape and Islands
ends by 04z. VFR then anticipated, but MVFR ocean effect
cloudiness remains over Hyannis and Nantucket. NW winds around
10 kt, with gusts 18-20 kt coastal MA.
Sunday and Sunday Night: High confidence.
VFR for most, though SCT-OVC MVFR/VFR ocean-effect cloudiness
continues to periodically impact Hyannis and Nantucket until NW
flow weakens early/mid-afternoon. VFR for all airports by mid-
afternoon, though midlevel cloud canopy spreads eastward for Sun
night. NW winds around 5-10 kt with gusts 18-20 kt Cape and
Islands, though decreases and shifts to WNW/W by late afternoon
Sun and then becomes light SW Sun night.
KBOS TAF...High confidence in TAF/trends but moderate on
timing. IFR visby snow with brief intervals LIFR thru ~22z,
then with steady improvement to VFR with gradual cloud clearing.
N winds become NW and increase to around 10 kt as snow ends.
KBDL TAF...High confidence in TAF. Intermittent, MVFR snow
showers shuld come to an end by 20z, with conditions improving
to VFR as clouds scatter out. N winds around 5-10 kt.
Outlook /Sunday Night through Wednesday/...
Sunday Night through Monday: VFR.
Monday Night through Tuesday: VFR. Breezy.
Tuesday Night: VFR. Breezy. Slight chance SN.
Wednesday: 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.
Seas 1-3 ft. Winds becoming N 5-10 kt. Winds and seas increase
after 7pm with gusts up to 25 kts and seas 3-5 ft for the outer
waters. Small Craft Advisories in effect for outer waters.
Sunday...High confidence.
Seas 3-5 ft. Winds 10-15 kts.
Outlook /Sunday Night through Wednesday/...
Sunday Night: Winds less than 25 kt.
Monday: Winds less than 25 kt. Seas locally approaching 5 ft.
Monday Night: Winds less than 25 kt. Areas of seas approaching
5 ft.
Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of snow.
Tuesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Areas of rough seas. Chance of snow,
chance of freezing spray. Local visibility 1 to 3 nm.
Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Slight chance of snow.
&&
.TIDES/COASTAL FLOODING...
Just issued a coastal flood statement for this morning's high
tide (around 10 AM, then until midday) for ACK & MVY. Just
minor/nuisance minor coastal flooding expected. It's a
combination high astro tides and weak pressure falls (inducing
some storm surge, currently about 1.3 ft at ACK tide gauge)
from coastal low off NC coast beginning to intensify, as it
tracks ENE south of New England. The statement is only for MVY
and ACK, given this location is closest to the influence of the
pressure falls. Again, just minor/nuisance coastal flooding
expected. Parking lots and shoreline roads that typically flood
in these marginal situations, will likely take on some water
this morning.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 10 PM this evening to 3 PM EST
Sunday for ANZ250-256.
Small Craft Advisory from 10 PM this evening to 7 PM EST
Sunday for ANZ254-255.
&&
$$
SYNOPSIS...BW/RM
NEAR TERM...Loconto/BW
SHORT TERM...BW
LONG TERM...RM
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley
TIDES/COASTAL FLOODING...
Source:
BOX issues Area Forecast Discussion (AFD) at Jan 11, 1:15 PM EST----------------
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