BOX issues Area Forecast Discussion (AFD) at Dec 13, 6:40 PM EST344
FXUS61 KBOX 132340
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
640 PM EST Fri Dec 13 2024
.SYNOPSIS...
Strong high pressure building in from the west will result in dry
but cold weather with below normal temperatures through the weekend.
Shift to a more unsettled weather pattern Monday into next week with
periods of precipitation possible. Temperatures trend above normal
through mid-week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
150 PM Update:
Ridge of high pressure is in place this afternoon over Southern
New England today and will continue to govern our weather into
tonight. Although some WNW gusts to 25 mph have developed in
central and eastern MA, these gusts should become more isolated
and ease by sundown to a lighter WNW wind for tonight. Clear
skies and lighter WNW winds should lead to good radiational
cooling and incorporated some of the colder MET MOS guidance for
lows. Lows forecast down in the mid teens for most, with upper
teens to low 20s for the urban areas and out over the Outer
Cape.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Key Messages...
* Sunny & cold Sat with highs mainly between 30 and 35, with
some ocean effect clouds over the Mid and Outer Cape.
Details...
Chilly and dry Saturday and Saturday night is expected, as the
center of a 1046+ mb high moves into northern New England. This
is one of the strongest high pressure areas that you'll ever see
in New England, and will bring with it very dry air and mostly
clear skies. The exception is over the Mid to Outer Cape where
ocean effect stratocumulus is expected to develop and
advance/fill in westward into the Mid-Cape. Wind trajectories
become a bit less favorable for ocean effect cloudiness Saturday
evening resulting in steadily decreasing ocean effect cloudiness
for the evening and overnight. Highs mainly in the upper 20s to
mid 30s, with lows under ideal radiational cooling in the teens
to low 20s.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Key Messages:
* Cold and dry weather on Sunday with vast high pressure over the
northeast.
* Weak system brings quick hitting light snow or rain to parts of
southern New England, perhaps a few pockets of freezing rain at
the onset, but confidence remains low with that part of the
forecast.
* More robust system brings wetting rain late Monday night into
Tuesday, and perhaps again late week.
The extended features a roller-coaster of weather, from dry and cold,
to mild and wet, even a few snowflakes mixed in for good measure.
Starting off, mid-level ridging and an impressive surface high
pressure, forecast near 1045mb, will round out the weekend, leading
to sunshine and likely below normal afternoon temperatures on
Sunday. 925mb temperatures -5C and -8C, these values are between the
25th and 10th percentile of climo, lending to highs in the mid-30s.
Mid-level ridging and the strong surface high pressure system will
shift east and off shore heading into late Sunday though Monday. Sky
cover fills in late Sunday with WAA at 850mb and the approach of a
modest mid-level shortwave. PWATs do increase to on average 2/3rd of
an inch, which doesn't sound like a lot, although for this time of
year the median is little more than 1/3rd of an inch. At the onset
there should remain enough cold air from the departing high pressure
system to allow for snow showers before a over to rain.
In between, there are low probabilites of freezing rain as the
warmer air advects aloft, given lower confidence in this, did omit
it from the weather grids, but will have to be watched as this
period becomes covered by the higher resolution guidance.
More interesting, will be Monday night into Tuesday as a mid-level
trough and shortwave arrives, leading to mild temperatures and our
next chance for wetting rains. While the trough isn't as robust as
the one earlier this week, it does have a modest LLJ of 50-60 knots
that will help transport higher PWATs of around an inch, greater
than the 90th percentile. Anticipate this will bring widespread
rain across the region, as for how much, too soon to say. But there
are moderate to high probabilites, between 60% and 75%, of greater
than half an inch by Tuesday evening. While not out of the question,
there are low probabilities, between 20% and 30% of greater than an
inch. The LLJ ushers in warmer temperatures, likely in the mid 50s,
but do have low probabilities we could warm above 60F, mainly across
CT, RI, and southeast MA. As for wind, there are no concerns for
major wind, though southwest winds will remain breezy, albeit below
advisory criteria.
Cooler and drier conditions mid week as high pressure and near zonal
flow returns, it will be short-lived. Thursday into Friday does look
unsettled, but there are areas of disagreement among the global
models on whether a deep through or cutoff low pressure system
reaches our area, nevertheless, it would appear either system would
bring unsettled conditions to the region to round out the week.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update:
Tonight: High confidence.
VFR. WNW winds 5-11 kts. Ocean effect clouds just offshore of
the Cape.
Saturday and Saturday Night: High confidence.
VFR conditions. SCT-BKN 025-035 bases(ocean-effect clouds) shift
over the Outer to Mid Cape from 16z Sat through Sunday,
possibly impacting HYA and ACK. NW winds 5-10 kt, turning to
light N Sat evening/overnight.
KBOS TAF...High Confidence in TAF.
KBDL TAF...High Confidence in TAF.
Outlook /Sunday through Wednesday/...
Sunday: VFR.
Sunday Night: Mainly VFR, with local MVFR possible. Slight
chance SN.
Monday: Mainly VFR, with local IFR possible. Chance RA, chance
SN.
Monday Night: Mainly VFR, with areas IFR possible. Breezy. RA
likely.
Tuesday: Mainly VFR, with local IFR possible. Breezy. RA.
Tuesday Night: VFR. Breezy.
Wednesday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Saturday Night: High confidence.
We continue to have marginal SCA conditions over the outer
waters due to WNW gusts 20-25 kt and seas around 5 ft. Gusts
should be gradually easing and seas lowering into tonight, and
though the SCA was continued, it could be cancelled early
pending trends.
Otherwise, generally tranquil conditions for mariners with seas
becoming 4 ft or less and NW to N winds around 15-20 kt. Dry
weather is expected under strong high pressure.
Outlook /Sunday through Wednesday/...
Sunday through Sunday Night: Winds less than 25 kt.
Monday: Winds less than 25 kt. Slight chance of rain.
Monday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain.
Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas. Rain likely.
Tuesday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain.
Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ250-
254>256.
&&
$$
SYNOPSIS...Loconto/Dooley
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...Dooley
AVIATION...Loconto/Dooley/Mensch
MARINE...Loconto/Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Dec 13, 6:40 PM EST----------------
If I'm using your data in a way that is against your terms please email the team at "threatweb@pupswoof117.com"! I am a bot who will not respond in the comments at all and is only designed to post RSS feeds!
