BOX issues Area Forecast Discussion (AFD) at Jan 11, 3:15 PM EST157
FXUS61 KBOX 112015
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
315 PM EST Sat Jan 11 2025
.SYNOPSIS...
Steadier light snows with minor additional accumultion over
eastern Massachusetts shift southward toward Cape Cod early
tonight before trending drier overnight. Sunny, drier and
seasonable weather conditions for Sunday. A mild start to the
week, but temperatures trend colder than normal Tuesday through
Thursday, with some moderation in temperatures by late next
weekend. Potentially turning unsettled by next weekend.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
310 PM Update:
Key Messages:
* Most persistent snow thru late afternoon into eastern RI and much
of southeast MA, with local additional snow amts up to 2"
expected, mainly on grassy/colder surfaces.
* Steadier snow then shifts into Cape Cod tonight with coatings to
an inch of snow before tapering off by midnight.
* Possible spotty instances of black ice overnight?
Details:
While areas of light snow in interior Southern New England have
started to taper off, still have periods of mainly light snow
in portions of the MA/RI coastal plain, the North Shore and into
Cape Cod. Given the character of snow/depiction on local radar,
these bands of snow are from some synoptic-lift influence (mid-
level deformation axis along the North Shore and enhanced by
upward vertical motion from a 150-kt jetstreak located to our
south), as well as ocean-enhancement. Near-term model forecast
guidance has indicated a steadier light to moderate snowband,
which had dropped anywhere from 2-3 inches to locally up to 4
inches in the Merrimack Valley/North Shore, moving southward
thru late this afternoon but it seems as though that process is
already starting to take place with visbys improving at BVY and
snow beginning to fill back in into portions of RI and much of
southeast MA. An additional accumulation of up to an inch is
forecast into eastern RI and southeast MA as this band moves
towards the Cape and Islands early tonight, while snow begins to
taper off toward the north and west with little to no
additional accums expected. Impacts with this snow are
essentially minimal to minor, and area webcams show accumulation
mainly on grass and perhaps some colder secondary/side streets.
We continue to expect minimal to very minor impact as this band
pivots southeast and orients itself toward the bay side of Cape
Cod.
Moving into tonight, lighter snow with accums of a coating to
an inch, perhaps locally 2" near the Cape and Islands should
begin to shut off by late-evening/midnight. Clearing/improvement
is expected for the majority of Southern New England with
modest NW winds, though the Outer Cape will see an increase in
ocean-effect cloud cover. Not expecting widespread issues, but
with the upstream airmass not especially dry or windy and
pavement generally wet vs snow-covered, it is possible we could
see patchy slippery spots from black ice overnight. Lows mainly
in the mid teens to low 20s, with mid to upper 20s over the
Outer Cape and Islands given a little stronger winds and ocean
effect cloudiness.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
310 PM Update:
Key Messages:
* Sunny and seasonable for most of Southern New England, with ocean
effect cloudiness tapering off.
* Increasing mid to high clouds Sunday evening but dry weather.
Details:
Still will be contending with ocean effect cloudiness over the Mid
to Outer Cape, roughly from Hyannis eastward. But overall shaping up
to be a pretty tranquil, seasonable Sunday for much of Southern New
England with a good deal of sunshine and decreasing NW breezes. Even
the Mid/Outer Cape should see ocean effect cloudiness decrease/taper
off by the midafternoon as winds decrease and shift to a lighter
westerly less favorable direction. An increasing stream of high
clouds arrives late Sunday but we should still see a good amount of
sunshine with highs in the 30s for most of Southern New England.
For Sunday night, high pressure to our south will allow for a light
SWly return flow to develop. A mid-level warm front associated with
an Alberta Clipper low currently located as of Saturday afternoon
near northeast North Dakota will spread an increasing canopy of mid
to high clouds through a good portion of Southern New England Sunday
evening. Dry weather will still continue, but the timing of these
clouds during the evening/overnight could pose forecast challenges
regarding how low temperatures may get. I sided temps into the upper
teens to lower to mid 20s, although if cloud cover is less extensive
then temps could be quite a bit colder.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Key Messages:
* Mild start, then returning to cooler than normal for most of next
week.
* Little in the way of precipitation for the upcoming week, outside
of a few ocean effect snow showers Tuesday.
Monday and Tuesday: High pressure shifts east as the mid-level ridge
starts to flatten across the northeast. There is weak forcing
passing through on Monday, but with limited PWATs, roughly 0.2" to
0.3" an isolated upslope flurry or snow shower cannot be ruled out
for those along the east slope of the Berkshire, otherwise, it is a
mixture of sun and clouds with seasonable highs in the upper 30s to
40F. The high terrain of northern Worcester County and the Berkshire
it will be a tag cooler in the low 30s. Cold front moves through
overnight with little fanfare. Lows return to the upper teens and
low 20s with the urban core, like Boston in the upper 20s. Heading
into Tuesday some sun gives way to increasing clouds, a mid-level
low moves over northern New England late in the day. Weak surface
low pressure system to our east and building high to the southwest
will allow for gusty northwest winds and this ushers in a colder air
mass to the region. Steep low-level lapse rates over "warm" SST the
upper 30s and low 40s could result in ocean effect snow showers for
parts of the outer Cape and Islands. W/NW winds gusting 20 to 30
mph. High temperatures in the upper 20s to low 30s.
Wednesday to Friday: Weak mid-level ridging for both Wednesday and
Thursday is accompanied by surface high pressure building across the
Ohio River Valley. Below normal temperatures continue these days
with highs only in the upper 20s and low 30s across the coastal
plain. Nighttime lows in the low and middle teens. Dry weather is
anticipated as PWATs are less than 0.2" along with mainly clear
skies. Will see some clouds develop late Thursday afternoon ahead of
a modest shortwave and mid-level trough. Surface high pressure moves
to the south on Friday and mid-level ridging loft will usher in WAA
and increasing PWATs. Highs on Friday should rebound to the middle
and upper 30s.
Next Weekend: An early look towards next weekend features unsettled
conditions and slightly above normal temperatures. A weak warm front
approaches southern New England Saturday with spotty shower activity
ahead of the trailing cold front late next weekend.
&&
.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
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 /Monday through Thursday/...
Monday: VFR.
Monday Night through Wednesday Night: VFR. Breezy.
Thursday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High- greater than 60 percent.
310 PM Update:
Small Craft Advisories continue over the outer waters for
tonight into the first half of Sunday, as NW winds increase to
around 15-25 kt with seas 3-5 ft. More tranquil weather
conditions then develop for Sunday afternoon into the evening,
with westerly winds decreasing in speed and seas decreasing to
under 4 ft all waters.
Periods of light snow will continue to impact eastern nearshore
and offshore waters, with visibility reduced to one-half mile
in steadier bands of snow. Snow tapers off by midnight. Although
we expect dry weather and good visibilities expected into
Sunday, expect ocean effect clouds most of the day.
Outlook /Monday through Thursday/...
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. Seas up to 5 ft.
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.
Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 25 kt. Areas of rough seas. Chance of freezing spray.
Wednesday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of freezing spray.
Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
&&
.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...Loconto/Dooley
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...Dooley
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Jan 11, 3:15 PM EST----------------
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