Bristol, Connecticut 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

370
FXUS61 KBOX 241156
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
656 AM EST Tue Dec 24 2024

.SYNOPSIS...
A weak Clipper frontal system will bring a brief period of
steady light snow through the morning hours of Christmas Eve,
although only minor accumulations of up to an inch are
forecast. Otherwise, dry weather is expected from Christmas Day
through the weekend along with a slow warming trend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
345 AM Update:

Key Messages:

* Brief (couple-hour) period of steady light snow starting ~4-6
  AM western MA/CT and advancing eastward toward the coast by
  late morning. Snow may mix with rain near south coastal RI/MA.
  Many areas see accums up to an inch, though isolated/spot 2"
  amts are possible.

* Precip moves offshore by early afternoon - might clouds take
  some time to scour out?

It`s a mostly cloudy to overcast start for many in Southern New
England this Christmas Eve morning; other than over southeast
New England where stratus had developed in a low-level moist-
advective regime, most of Southern New England are seeing a
dense canopy of mid to high clouds. These conditions should hold
for another couple hours or so. A fast-moving Clipper low was
located near the northern shore of Lake Ontario per METARs, and
and is responsible for the cloudiness but also a brief period of
steady light snow in central and eastern NY, its eastward
extent now having advanced into the Albany NY metro area.
Although composite radar shows a rather large shield of precip,
observed visbys in the snow have not been much worse than a
mile. Current temps were in the mid 20s for most of Southern New
England, although the Cape and Islands were in the mid 30s.

Fast-moving Clipper low and its parent and shearing-out 500 mb
vort maxima remains forecast to move through Southern New
England during the first part of the day. Expect increasing
coverage of lower clouds with precipitation falling as light
snow into western MA/CT by around 4-6 AM, then steadily move
eastward into central MA/eastern CT/western RI around 5-7 AM,
and then further east into the remainder of eastern MA by 8-10
AM. With no substantial change in liquid-equivalent QPF, as well
as the rather shoddy-looking presentation on radar, even though
it is falling on a heavily-traveled Christmas Eve morning, I
really can`t see accumulations being enough to cause major
issues. The rather brief accumulation period should also keep
totals in most areas to around an inch for most areas (a festive
dusting), and is likely to mix with rain near the South Coast
given the above-freezing temps there. We should then see precip
move offshore by early this afternoon.

Where there are more questions on the forecast evolution is what
happens post-frontal, and in particular on sky cover and its
effect on temps. Typically in west flow events clearing tends to
be rapid and most models show clearing occurring quickly, but
observed satellite imagery shows a large expanse of post-frontal low
clouds that stretch from western New York all the way into
western North Dakota, as a rather strong subsidence inversion is
trapping lower level moisture. Cloud cover trends will need to
be monitored today but its net effect would be on temps. I opted
for a slower decrease in cloud cover into the latter part of
the afternoon, toward mostly clear conditions by sundown, with
highs in the lower 30s interior and mid/upper 30s coastal areas.
We will also see development of ocean effect clouds out over
the Cape and Islands later in the day.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
345 AM Update:

Key Messages:

Tonight:

Most areas will have already trended toward mostly clear skies
as we start to see strong ridge of high pressure nose into
Southern New England. Favorable conditions for ocean effect
stratocumulus with colder air over the milder SSTs and NNW wind
trajectories favor increasing coverage of clouds out over the
Cape and Islands and into a portion of South Shore. Temps likely
to bottom out in the teens to low 20s for most with better
radiational cooling anticipated. Near the eastern MA coast
where cloud cover and NW wind speeds increase with eastern
extent, lows stand to be quite a bit "warmer", in the mid/upper
20s with temps out over the Outer Cape around or just above
freezing. Despite the ocean effect cloudiness, should be dry for
tonight.

Wednesday/Christmas Day:

1030+ mb high pressure over much of NY will continue to ridge
into Southern New England, with continued NWly winds strongest
near eastern MA. Essentially similar large-scale pattern to
tonight, with clear skies/more sun away from the Cape and
Islands. For the Cape and Islands, it looks to be a cloudy and
rather breezy Christmas Day with not much change between
overnight minimum temps to the highs. Late in the day as a
shortwave trough digs into the Canadian maritimes, it could be
enough to support some ocean effect rain or snow showers. It is
still unclear how far west this activity may progress but kept a
mention of isolated snow or rain showers (temperature-
dependent) for the Cape and Islands. Highs again mainly in the
30s, with lower 30s for most, trending toward mid to upper 30s
across the Outer Cape.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Updated: 4:00 AM

Key Messages

* High pressure will support quiet weather across southern New
  England through at least Saturday

* Temperatures on the uptick with above normal temperatures settling
  in by Friday

* Precipitation chances increase late weekend/early next week

Wednesday night through Saturday

A quasi-stationary surface high pressure system will support quiet
weather across southern New England Wednesday night through at least
Saturday. No significant weather to speak of during this time frame,
but we do expect temperatures to climb to near to above normal
levels as we approach the weekend. High temps on Thursday in the mid
to upper 30s with gradually increase to the low to mid 40s by
Saturday. Overnight low temps will be closer to normal ranging from
the low to mid teens across the interior and mid to upper 20s closer
to the coast.

Sunday and Monday

As surface high pressure finally slides east of the region during
the second half of the weekend, short-wave energy approaching from
the Midwest will introduce the next opportunity for substantial
precipitation in southern New England. There is some uncertainty
with respect to how quickly the aforementioned upper-level ridge
will break down. This will determine how quickly the short-wave
approaching from the west will reach the region. Most ensemble
members support a later arrival, which would allow for a dry/quiet
day on Sunday and higher rain chances on Monday. Given the warmer
temperatures expected to be in place ahead of the event, we would
not anticipate a significant snowfall event, but rather rain, or
perhaps freezing rain depending on surface temperatures at the time
rainfall arrives. Overall, a lot of uncertainty with this system at
7 days out, but we will have new details as we progress toward the
weekend. Until then, stay tuned....

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:

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

12z TAF Update:

Today: Moderate confidence.

VFR to deteriorate to MVFR cigs and MVFR-IFR visby -SN
developing 12-16z west to east, tapering off late morning in the
west to early afternoon eastern airports. Clearing to VFR
anticipated after snow ends but it may take until midafternoon
before improvement occurs. SW winds under 10 kt to start, then
shifting to W at similar speeds by early afternoon before
becoming NW late.

Tonight and Wednesday: High confidence.

VFR, although ocean effect stratocumulus with MVFR bases develop
tonight for Hyannis and Nantucket; similar conditions prevail
into Wednesday, although could see some ocean effect flurries or
rain showers develop after 18z. NW winds 5-15 kt, tending
stronger toward the east coast.

KBOS TAF...Moderate confidence in TAF. Light snow should develop
by 13z with categories becoming MVFR with MVFR/IFR vsby thru
16-17z. Coatings possible but runways should be mostly dry.
Improvement to VFR anticipated but may be delayed until close to
20z. SW winds around 10 kt shift to W and then NW by late in
the day, which continue into Wed.

KBDL TAF...Moderate confidence in TAF. Ongoing MVFR/IFR snow
moves east by 15z; while improvement is expected once snow ends,
it may take longer for clouds to lift/scatter out. S winds shift
to W around 10 kt then become N 5-10 kt tonight and overnight.

Outlook /Wednesday Night through Saturday/...

VFR.

&&

.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.

Updated: 4:00 AM

Overall high confidence.

SW winds contiinue to increase early this morning but gusts are
expected to remain around 15-20 kt, highest over the northeast
waters. A clipper system may spread light snow that could reduce
visby to 3 SM over the northern waters late this morning, with
temperatures warm enough for rain over the southern waters.

Winds then shift to WNW later this afternoon and NW while
increasing to around 20-25 kt tonight over the eastern waters,
with seas building to 4-6 ft. Have issued a small craft advisory
for the eastern outer waters through Wednesday/Christmas Day.
It is possible that the SCA may need to be extended into part of
Wednesday night, although winds will have decreased and seas
should be slowly decreasing as well. Bands of ocean effect snow
showers Christmas Day near Cape Cod as well.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Isolated rain showers.

Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain.

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

Friday through Friday Night: Winds less than 25 kt. Seas
locally approaching 5 ft.

Saturday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 11 PM this evening to 7 PM EST
     Wednesday for ANZ250-254.

&&

$$

SYNOPSIS...Loconto/RM
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...RM
AVIATION...Loconto/RM
MARINE...Loconto/RM