BOX issues Area Forecast Discussion (AFD) at Apr 9, 7:02 AM EDT580
FXUS61 KBOX 091102
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
702 AM EDT Wed Apr 9 2025
.SYNOPSIS...
Dry weather with decreasing northwest breezes are expected
today, along with below normal temperatures for early April.
Another chilly night is in store tonight with weak high pressure
in place. Increasing clouds Thursday but with generally dry
weather. Another prolonged cloudy period with onshore breezes
and several rounds of precipitation is expected for late in the
week into the weekend. This will be highlighted by a soaking,
wind- driven rain for Friday night and Saturday, with additional
rains possible for Sunday. We dry out and warm back up to above
normal temperatures early next week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Key Messages:
* Chilly start, and though temperatures rebound some under
full sun, another day with below-average temperatures.
* Breezes begin to ease into the afternoon.
Details:
For early-April standards, it's a chilly start to Wed morning across
Southern New England! A continued NW breeze being driven by low
pressure over Nova Scotia and a weak ridge of high pressure over the
OH Valley is helping to produce wind chills in the teens to the mid
20s. Although the gusts have trended downward during the overnight,
still have gusts in some areas around 25-30 mph. Though some colder
air stratocumulus cloudiness was still dotting portions of interior
Southern New England, most areas have trended to mostly clear sky
conditions.
Dry weather and a well-mixed atmosphere driven by full sun and cold
air aloft will be the case today. NW breezes will continue through
late morning; there may even be a little bit of a second bump-up in
wind speeds during the mid-morning hours. As high pressure over the
OH Valley begins to slide ESE through the Delmarva Peninsula through
this afternoon, it will result in a slackening pressure gradient for
the 2nd half of the day. Look for decreasing gust speeds into the
afternoon with a slight windshift to W. Besides the gusts, dewpoints
also will drop into the single digits as drier air aloft (PWATs
around 0.15-0.2") mixes to the surface. After the rather chilly
start, highs rebound into the 40s, with low 40s higher terrain and
mid to upper 40s lower elevations and cities. All in all not a bad
day, if still a bit breezy with cooler than normal temps.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Key Messages:
* Another rather chilly night tonight, although cloud cover
increases toward daybreak.
* Increasing cloudiness to overcast Thurs, with cooler onshore
breezes. Outside chance at light showers late-day in western New
England but better chances Thurs evening.
Details:
High pressure just offshore the mid-Atlantic to shift ENE towards
the 40N/70W benchmark area toward midnight and on towards
Georges Bank by daybreak. This will extend a weak sfc ridge
north of it into Southern New England. With the anomalously cold
& very dry airmass in place and clear skies/light winds, temps
should really fall quickly after sundown to values in the 20s.
Toward dabyreak, we start to see an increasing coverage of mid-
level cloud cover in response to 500 mb height falls and an
approaching sfc warm front. But that cloudiness shouldn't really
impact low temps that much.
Warm advection pattern then develops into Thursday with high
pressure near Georges Bank/south of Nova Scotia. This will allow for
at least a modest onshore flow and allow for the drier airmass to
modify. Will also see increased cloud cover carrying over from the
overnight period. Couple forecast aspects which are a little less
certain. One is on high temps, which will be influenced by how
quickly the aforementioned cloud cover comes in and the cooler
onshore flow. Ended up undercutting NBM temps by a few degrees into
the upper 40s to low 50s (NBM was showing rather widespread mid
50s), with the cooler readings near the coasts and in the terrain.
If cloud cover is slower to advance east then NBM temps could be
closer to correct. The next is on PoPs as some models continue to
show some QPF into western MA and portions of CT late in the day;
I'm not sure the drier airmass will have modified by then, and seems
to be a slower-eastward trend in the last day or so of model
guidance, so I capped PoPs here at no better than slight chance.
Thinking generally dry for the majority of the day.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Key Messages:
* Dreary, cloudy and unsettled late week into the weekend, with
onshore breezes and several periods of rain. Cooler than normal
highs and near/above normal lows.
* Periods of precip possible Thurs night (light, if any), Fri night
to most Sat (probable soaking, wind-driven rain), and another
possible period of rain Sunday for eastern coast.
* Brief warmup early next week before turning unsettled again Tue?
Details:
Thursday Night through the Weekend:
00z guidance remains consistent in its continued advertisement of a
slow-evolving, cloudy and dreary late week into the weekend, with
several periods of precipitation and onshore flow. This is in
response to a deep upper level trough which digs into the
southern/central Appalachians for late in the workweek and closes
off into an upper level low as we move into the weekend. A couple
low pressure areas coming up on the eastern periphery of the upper
trough over the Atlantic Seaboard will serve as foci for rain
chances (some higher elevation wet snows possible early in this
period). In addition, antecedent high pressure over the Canadian
Maritimes remains more or less in place into at least the early part
of the weekend, and the combo will help drive a rather prolonged
period of onshore E/NE flow, looking most enhanced Fri night into
Sat. Overall, in a period with lots of cloud cover and onshore
breezes, expect a narrower diurnal temperature range in this period,
with cooler than normal highs and near to slightly above normal
lows.
As mentioned, looking at several chances for precip; only Fri looks
to offer a relatively "drier" period, between these waves of precip.
The first such period looks to be on Thurs night/overnight period as
a weak warm front lifts through. While temps are cool enough in the
higher elevations to begin as a wet snow/rain mix, QPF looks sparse
and there is some guidance that's entirely dry. Wouldn't expect too
much QPF with this initial wave. Quite the opposite as we move into
Fri night into Sat, as low pressure slowly up the coast. This period
of steadier light to at times moderate rains also looks to be
accompanied by enhanced ENE flow, with potential for gale-force
gusts over some of our waters. Reasonably high enough confidence in
a period of wind-driven rains, although it doesn't look as though
this combo would equate to adverse impact, just an annoyance as we
move into another unsettled weekend. Another possible break in
precip Sat night before another potential round of rains near the
eastern coast as low pressure either passes close to Southern New
England or far enough offshore. The exact track of this low for late
Sat night/Sun is still uncertain with varied placement in the
NWP/ensembles. So in a nutshell, Fri night thru most of Sat looks to
be the soggiest.
It's also a rather long-duration period of onshore flow affecting
our eastern coastlines. Did look at coastal flooding potential since
we'll have this prolonged E/NE flow over several high tidal cycles,
but astro tides are still on the low side (slotting in around
9.35-9.45 ft MLLW at BOS Harbor) and that should limit any
potential.
Early Next Week:
The slow-moving upper trough finally moves offshore by early next
week, and we could stand to warm up at least briefly ahead of
another rather potent frontal system per ECMWF/GFS solutions. After
a longer period of cooler than normal highs, we could stand to warm
up briefly into early next week.
&&
.AVIATION /11Z WEDNESDAY THROUGH SUNDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12z TAF Update:
Today and Tonight: High confidence.
Continued VFR. Could be a second period/bump-up in WNW gusts to
20-25 kt during the morning, before easing into the afternoon
while shifting to W/WSW late in the day to around 10 kt. Winds
continue to ease into tonight and become light W/NW by
daybreak, along with an increase in VFR midlevel clouds.
Thursday: High confidence.
VFR for most of the day, though clouds increase from W to E and
could see some MVFR bases work into BAF/BDL late in the day.
Light winds early, but will become E/SE and increase to 5-10 kt.
BOS TAF...High confidence in TAF. WNW gusts to 25 kt continuing
thru the morning, but gusts decrease ~16-18z while becoming
W/WSW late in the day.
BDL TAF...High confidence in TAF.
Outlook /Thursday Night through Sunday/...
Thursday Night: Mainly VFR, with local IFR possible. Chance RA.
Friday: Mainly VFR, with local IFR possible. Breezy. Slight
chance RA.
Friday Night: MVFR/IFR conditions possible. Windy with areas of
gusts up to 30 kt. Chance RA.
Saturday: Mainly MVFR, with areas IFR possible. Windy with
gusts up to 30 kt. RA.
Saturday Night: MVFR/IFR conditions possible. Breezy. RA
likely.
Sunday: MVFR/IFR conditions possible. Breezy. Chance RA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
230 AM Update:
Previous Gale Warnings have now been downshifted to Small Craft
Advisories, which run thru noon on most nearshore areas/bays and
a couple hours later for the outer waters. We expect a continued
period of WNW gusts 25-30 kt on the waters through at least the
morning hours, but it is possible the SCAs could end sooner.
Areas of rough seas early today will be decreasing thru the day
to 4 ft or less on all waters by late-aftn.
Light winds and continued decreasing seas to 2-3 ft expected
tonight. Winds become ESE around 10-15 kt on Thursday. Dry
weather expected through Thursday.
Outlook /Thursday Night through Sunday/...
Thursday Night: Winds less than 25 kt. Slight chance of rain.
Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain.
Friday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas. Chance of rain.
Saturday: Strong winds with local gusts up to 30 kt. Rough seas
up to 9 ft. Rain.
Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 8 ft. Rain likely.
Sunday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Rain likely.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until noon EDT today for ANZ230>237-251.
Small Craft Advisory until 2 PM EDT this afternoon for ANZ250-
254>256.
&&
$$
SYNOPSIS...Loconto
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...Loconto
AVIATION...Loconto/BW
MARINE...Loconto
Source:
BOX issues Area Forecast Discussion (AFD) at Apr 9, 7:02 AM EDT----------------
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