BOX issues Area Forecast Discussion (AFD) at May 19, 7:02 AM EDT
886
FXUS61 KBOX 191102
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
702 AM EDT Mon May 19 2025
.SYNOPSIS...
Unseasonably cool temperatures are expected for much of the
workweek, with temperatures running some 10 to 20 degrees below
normal by midweek. Mix of sun and clouds, cool and quite breezy
today. Chilly night expected tonight as northwest breezes
continue. Cloud cover increases again on Tuesday as onshore flow
develops. Unsettled weather returns once again in the second
half of the week into the weekend. Cooler than normal high
temperatures will prevail before starting to recover heading
into the weekend.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
300 AM Update:
Key Messages:
* Partly to mostly cloudy and quite breezy. Northwest gusts
25-35 mph.
* Highs 50s to near 60 northern/northeast MA to the mid 60s for
CT and RI.
Details:
Our weather pattern early this morning continues to be governed
by a pronounced upper level low pressure area, seen on morning
water vapor imagery circulating near the Bay of Fundy.
Maritime-polar origin moisture continues to be advected around
its circulation into Southern New England. When combined with a
rather cool airmass, it's led to stratocumulus cloudiness of
varying extent. A tightening northwest gradient was also leading
to rather breezy northwest winds with speeds around 10-15 mph
with gusts 20-30 mph. So it's led us to a partly to mostly
cloudy, breezy and somewhat cooler morning compared to where
we've been of late. Temps early this morning range around the
upper 40s to the mid/upper 50s.
With a rather blocky mid/upper flow pattern over the North
Atlantic, that upper level low will not move much through the
day and could even retrograde a bit. Essentially today will
feature a continuation of conditions from the overnight...with
more cloud cover north and east and generally lesser amts of
clouds south and west. Although there could be periodic, hit-
or-miss light rain showers, the vast majority of the time ends
up being dry. Other than the cooler temperatures for this time
of year, it will also be quite breezy as mixing gets going to a
little better degree than Sunday. Northwest gusts could punch up
to around 30-35 mph, which should tend to ease somewhat into
the early evening. Although CT and RI have the best shot at
reaching into the mid 60s, northern and northeast MA could
really struggle to reach 60 degrees.
So all told, a partly to mostly cloudy day with northerly
breezes and temps some 10 degrees colder than late-May climo,
with the winds making it feel cooler.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
300 AM Update:
Key Messages:
* Unseasonably cool and continued breezy tonight. Lows in the
low to mid 40s, with wind chills near the freezing mark in
interior Southern New England.
* Periods of sun early Tue, then onshore flow and lower
cloudiness moves in from the Gulf of Maine by afternoon.
Could be some drizzle or light rain at times in the lower
clouds. Unseasonably cool, with highs in the mid 50s coastal
MA to the upper 50s to mid 60s elsewhere.
Details:
Tonight:
Upper low near the Maritimes slowly meanders ESE into Nova
Scotia. This should translate to a bit less cloud cover with
more east and less west. With 925 mb temps dropping to 0 to +2C,
a continued NW breeze and some radiational cooling allowing for
air temps to fall into the low to mid 40s, tonight should be
rather cold to the point where we could see wind chills get to
near the freezing mark in interior Southern New England!
Hopefully you haven't put away your jackets or sweatshirts just
yet - and honestly, we're looking at an unseasonably cool week,
so it might be a good idea to keep them at the ready as we move
into the rest of the workweek.
Tuesday:
Surface ridge of high pressure over NY will begin to nose into
Southern New England on Tue, allowing for easing NW breezes.
Though we should see some limited amt of sunshine early, we get
into a moist onshore flow during the day on Tue as moisture from
that pesky upper level low returns back landward. This will lead
to increased NE breezes and an increase in shallow RH/lower
clouds, greatest coverage in the eastern half of Southern New
England. Moisture is pretty shallow but the depth of it does
increase a bit by afternoon, with drier air atop it. So we
could see either some off-and-on periods of drizzle too near the
immediate coast as the low cloud deck comes in. But the
majority of the time should end up dry. CT Valley probably has
the best shot at seeing the mid 60s, but getting into the low
60s elsewhere could be a tall ask, and the eastern MA coast
could struggle to even get to the mid 50s. For context, our
typical nighttime lows for this time of year run around the
upper 40s to low 50s.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Key Messages:
* Cooling trend continues through the week, with Wednesday and
Thursday the coolest days
* Another system will likely bring rain and gusty winds to southern
New England in the latter part of the week. Track and timing are
still in flux, though.
Details...
Following northwest flow ushered in by the backside of the low over
the Maritimes, winds will shift to the northeast heading into
Tuesday night. Some spotty showers are also possible Tuesday night,
but not much -- if any -- rain is expected to accumulate. Cool
temperatures aloft will linger through the week. The result of this
cooler air that's been advected in: highs on Wednesday may not even
reach 60 in some parts of the region and will sink lower into the
low 50s Thursday before we begin to see temperatures closer to
normal values Friday.
A surface low is expected to move up along the east coast towards
southern New England. This late spring Nor'Easter could bring
periods of heavy rainfall and gusty winds starting sometime in the
early hours of Thursday through Friday, with the chance of scattered
showers lingering through Saturday. Ensembles are starting to agree
on the low passing to the southeast Thursday afternoon/evening, then
reaching the Maritimes by Saturday night/early Sunday morning. There
is still significant variance in its track though. The GEM tracks
its center right over SE MA, while the GFS and ECMWF track it to the
southeast of Nantucket (though the GFS keeps it further offshore).
This uncertainty is also seen in the different ensembles' 24 hour
QPF values, however, there is starting to be some agreement in
higher totals being towards eastern MA. These higher totals, though,
still range from 0.40" to a little over an inch over 24 hours. If
the storm remains closer to the coast, we can expect more rain and
gustier winds. Both decrease if the low tracks further offshore.
The overall consensus is that the end of this week will be unsettled
and cool with continued broad cyclonic flow and cooler temperatures
aloft. Scattered showers may linger over the region Saturday before
possible clearing heading into Sunday as the upper level low sitting
over the region begins its exit. Colder nights in the back end of
the week will linger, but highs heading into the weekend will begin
to improve to more seasonable levels.
&&
.AVIATION /11Z MONDAY THROUGH FRIDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12z TAF Update:
Today through Tonight: High confidence.
A continuation of SCT-OVC mainly VFR but with periodic MVFR
ceilings. Hit or miss -SHRA possible too but too isolated for a
taf mention. Better chance at MVFR ceilings in northern MA. NW
winds increase to 15-18 kt with gusts 25-35 kt late- morning to
mid- afternoon, then gusts around 20-25 kt as we approach
23-00z, easing further into the overnight.
Tuesday: High confidence overall, but some uncertainty on
timing.
Mainly VFR ceilings, though we will have to watch for periods
of MVFR ceilings mainly for east coastal MA and perhaps into RI
during the 2nd half of the day as winds become NE. N winds
lighten and become NE/ENE in eastern MA and RI, and while this
could happen as soon as 15z, it becomes more likely in the
afternoon.
KBOS TAF...High Confidence in TAF.
KBDL TAF...High Confidence in TAF.
Outlook /Tuesday Night through Friday/...
Tuesday Night: Mainly VFR, with areas MVFR possible. Slight
chance SHRA.
Wednesday: MVFR/IFR conditions possible. Chance SHRA.
Wednesday Night: MVFR/IFR conditions possible. Breezy. SHRA
likely.
Thursday: Mainly MVFR, with areas IFR possible. Windy with
gusts up to 35 kt. SHRA, isolated TSRA.
Thursday Night: MVFR/IFR conditions possible. Windy with areas
of gusts up to 35 kt. SHRA likely.
Friday: Mainly VFR, with areas MVFR possible. Breezy. Chance
SHRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today through Tuesday: High confidence.
An anomalously strong upper level low near Nova Scotia will
continue to drive NW breezes through tonight. NW gusts continue
to range between 25-30 kt, and will continue to be the case
today, with a slower decrease in NW gusts to around 20 kt. Small
craft advisories reamin posted on all waters.
We should see more N/NE winds develop on Tuesday around 15-20 kt,
which could be accompanied by periods of drizzle or light rain
showers but not enough to restrict visibility.
Outlook /Tuesday Night through Friday/...
Tuesday Night through Wednesday: Winds less than 25 kt. Areas
of seas approaching 5 ft. Slight chance of rain showers.
Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers.
Thursday: Moderate risk for gale force winds with gusts up to
35 kt. Rough seas up to 13 ft. Rain showers, isolated
thunderstorms.
Thursday Night: Low risk for gale force winds with gusts up to
35 kt. Rough seas up to 13 ft. Chance of rain showers.
Friday: Winds less than 25 kt. Areas of rough seas. Chance of
rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ230-
236.
Small Craft Advisory until 5 AM EDT Tuesday for ANZ231>235-237-
250-251-254>256.
&&
$$
SYNOPSIS...Loconto/Hrencecin
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...Hrencecin
AVIATION...Loconto/Hrencecin
MARINE...Loconto/Hrencecin
Source: BOX issues Area Forecast Discussion (AFD) at May 19, 7:02 AM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202505191102-KBOX-FXUS61-AFDBOX)
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