BOX issues Area Forecast Discussion (AFD) at Oct 10, 7:38 PM EDT288
FXUS61 KBOX 102338
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
738 PM EDT Thu Oct 10 2024
.SYNOPSIS...
A warming trend arrives Friday into Saturday as high pressure
builds south of New England. Mostly sunny but blustery Saturday
with seasonably mild high temperatures. A strong Fall frontal
system then affects Southern New England for Sunday and into
Monday, which will bring a couple periods of steadier rains and
cooler than normal temperatures. Drying out by Tuesday. Fall-
like blustery conditions and below normal temperatures are
favored for Tuesday and Wednesday, and highs could be some 10
degrees colder than normal.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
735 PM Update:
Still dealing with some stratocumulus cloudiness especially around
northern Worcester County and the Berkshires, but most areas
have gone mostly clear. NW winds are still around 10 mph with
current temps in the lower to mid 50s as the winds have slowed
stronger cooling rates. There may be some slackening to the NW
winds but we still expect enough of a NW wind to keep temps from
really bottoming out, with scattered cloud cover in northern MA
gradually diminishing in coverage as we move into the late-
evening/midnight hours.
Previous discussion:
After a breezy afternoon winds will diminish as we go into the
overnight hours with high pressure settling to our south and west.
This placement continues to keep SNE beneath that NW flow and the
gradient doesn't slacken totally given the high's placement to our
west. This should keep winds from the NW tonight and prevent the
boundary layer from decoupling. Thus, while it will be chilly again
tonight, lows should remain in the upper 30s to near 40 for most, in
the low to mid 40s along the coast. The locations at most risk of
any patchy frost (low probability) are outside of the frost/freeze
program window so no headlines are planned.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Rising mid level heights (at least initially) and surface high
pressure building to our southwest will make for a quiet and
pleasant end to the work week with plenty of sun and lighter winds.
It will be noticeably warmer on Friday (5+ degrees warmer) thanks to
a warming airmass overhead (850mb temps from 0C today to 7C Friday).
This will also keep us from seeing the diurnal clouds we're seeing
today. Overnight the ridge is suppressed a bit as a trough of low
pressure passes to our north, but the only notable change
should be some mid/high clouds. Low temperatures will be quite a
bit warmer than the rest of the week, in the upper 40s and low
50s.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Highlights:
* Pick of the holiday weekend is Saturday with seasonably mild
temps, although a brief period of NW breezes is likely.
* Pretty strong Fall frontal system brings a period of steady rains
Sunday into Monday, though may turn more intermittent Sunday
evening. While significant impacts are not expected, cloudy and
rainy conditions generally govern.
* Generally dry Tue and Wed, but blustery conditions with below
normal temps. Highs may struggle to reach the mid 50s by midweek.
Saturday through Saturday Night:
Saturday is without question the pick of the holiday weekend, with
partly to mostly sunny skies after passage of a dry cold front
during the Sat AM hrs. That will bring a period of NW breezes (gusts
up to 25 mph) as 925-850 mb temps cool in the post-frontal
environment. Weak high pressure then moves in for later in the day
and then offshore during the evening/overnight. Slackening NW winds
as high pressure settles in by later in the day/early evening, then
turn ENE in response to a pretty robust frontal system that is
expected to affect our area for Sun/Mon (more on that to follow
below...). That will also bring increased cloud cover toward early
Sun AM, but mostly clear skies should generally prevail for Sat
night. Seasonably mild highs in the 60s to a few low 70s over SE New
England and the CT Valley given NW downsloped winds, with lows upper
30s to mid 40s.
Sunday into Monday:
Unfortunately the remainder of the holiday period is looking
unsettled and rainy, as a potent midlevel shortwave trough amplifies
and moves through the Gt Lakes and Northeast states Sunday into
Monday. This feature is expected to drive a strengthening surface
low near the northern mid-Atlantic or western NY region on Sunday,
which then moves ENE through interior northern New England into
Monday. There are uncertainties regarding the exact surface low
track and initial placement of a west-to-east warm frontal boundary
that is expected to lie somewhere across Southern New England, and
those will need to be ironed out a bit more as we get into the
higher resolution guidance windows. That said, while this timeframe
is likely to feature far from ideal weather, significant weather-
related impacts are not expected.
A band of steady light to perhaps at times moderate intensity rains
seems likely to occur along and north of a progged warm front, which
loose model consensus seems to point to an initial placement roughly
along the Mass Pike, but its location varies across the various
global models. Pretty good burst of warm advective lift should
support the potential for steady rains near and north of the warm
front, given an 850 mb SWly jet progged around 40 kt. The placement
of the warm front will be pretty critical both for where the best
QPF will be located (and there might not be much precip at all south
of the warm front), but it will also affect Sunday high temps. Could
be a struggle for areas north of the warm front to warm up, and
soundings at locations such as Fitchburg and Lawrence show a shallow
cooler air mass that doesn't really modify much, even as the warm
front lifts northward. Thus for temps on Sunday, I opted to deviate
from NBM which seems much too mild given the lack of mixing, toward
highs in the low to mid 50s along the Route 2 corridor and upper
50s/mid 60s along/south of the Mass Pike into CT-RI-SE MA. Regarding
PoPs, I sided toward the higher end of Likely to borderline
Categorical north of the Mass Pike, tapering to chance/low likely
levels for CT-RI-SE MA.
As the warm front lifts north later Sunday into Sunday night, still
looks unsettled but better rain chances then occur with the arrival
of a cold front which moves through later Sunday night and into
Monday. Here too, NBM-based high temps for Monday seem too warm
given cloud cover and rains to begin the day, and instead offered
readings in the mid 50s to lower/mid 60s. Monday also stands to be
breezy as strong cold advection develops post-cold front, with NW
gusts around 20-25 mph. More rapid clearing then takes place later
Monday and into Monday evening, setting the stage for a rather
chilly Fall night with lows in the mid 30s to lower to mid 40s and a
continued NW wind.
Tuesday through Wednesday Night:
Deep longwave trough sets up for Tue into Wed. An even cooler
airmass advects into Southern New England in this forecast period,
with GFS 925 mb temps falling to around 0C (!) by Tue night. While
dry weather should prevail, when it comes to temps, partly cloudy to
mostly sunny conditions probably won't be able to offset the cold
advection. Highs on Tue and Wed may only reach into the lower to mid
50s in the lower elevations, and in the mid 40s across the higher
terrain. This is about 10 degrees colder than mid-October
climatology (around upper 50s highs/around low 40s lows). It should
be pretty blustery as well.
&&
.AVIATION /23Z THURSDAY THROUGH TUESDAY/...
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. NW winds diminish to 5-10 kt tonight, but a bit stronger
Cape/Islands and immediate eastern MA coast.
Friday: High confidence.
VFR. WNW/NW winds 10-15 kts with gusts up to 20 kts.
Friday night: High confidence.
VFR. WSW winds 5-10 kts increasing and becoming WNW.
KBOS TAF...High confidence in TAF.
KBDL TAF...High confidence in TAF.
Outlook /Saturday through Tuesday/...
Saturday: VFR. Breezy.
Saturday Night: VFR.
Sunday: VFR. Chance RA.
Sunday Night: Mainly MVFR, with local IFR possible. Breezy. RA
likely.
Columbus Day: Mainly VFR, with local MVFR possible. Breezy.
Chance SHRA.
Monday Night through Tuesday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today through Friday night...High confidence.
Another surge of 25+ kt gusts expected into this evening for
the eastern MA waters assocd with the shortwave passage to the
east. Winds diminish late tonight into Fri but still expect
10-20 kt winds. Friday night winds up out of the WSW gusting
25-30 mph. Seas increase to 5-7 ft on the outer waters.
Outlook /Saturday through Tuesday/...
Saturday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas.
Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Sunday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain.
Sunday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas. Rain likely.
Columbus Day: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Chance of rain showers.
Monday Night: Winds less than 25 kt. Areas of rough seas.
Slight chance of rain showers.
Tuesday: 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 8 AM EDT Friday for ANZ250-254-255.
&&
$$
SYNOPSIS...Loconto/BW
NEAR TERM...Loconto/BW
SHORT TERM...BW
LONG TERM...Loconto/Mensch
AVIATION...Loconto/BW
MARINE...Loconto/BW
Source:
BOX issues Area Forecast Discussion (AFD) at Oct 10, 7:38 PM EDT----------------
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