BOX issues Area Forecast Discussion (AFD) at Sep 4, 3:38 PM EDT831
FXUS61 KBOX 041938
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
338 PM EDT Wed Sep 4 2024
.SYNOPSIS...
Dry weather prevails through Thursday accompanied by seasonably
warm days and cool nights. Coastal low pressure near Bermuda
moves northward Friday and passes to our east on Saturday. This
will bring a period of increased cloud cover, as well as
building up waves bringing the potential for rip currents on
east-facing beaches Friday and Saturday. A cold frontal passage
Saturday evening brings better chances for rains, but no
washouts are currently expected. Drier and seasonable weather
for Sunday into early next week, with cooler nighttime lows.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Highlights:
* Beautiful afternoon with seasonably warm conditions, cooling off
tonight with below normal highs in the upper 40s and 50s.
1030mb high pressure is anchored over the northeast and has allowed
for spectacular conditions today with seasonable highs in the upper
70s and lower 80s. Making it feel all the better are dewpoints that
are in the upper 40s and lower 50s. Clear skies this afternoon will
continue overnight and in combination with fairly light winds, will
have efficient radiational cooling. CONSMOS does well during these
situations and utilized this guidance source for tonight's minimum
temperatures - many spots away from the coast or any urban influence
should fall between the upper 40s and lower 50s, while coastal towns
are in the middle 50s. Do think the urban centers will retain a bit
of today's warmth, warmest spot is likely Boston with a low of 60F.
With efficient radiational cooling we run the possibility of fog to
develop. Do think if fog were to develop overnight it would occur in
river valley locations, mainly for western MA. That said, still a
possibility areas east in locations that have depressions/hallows.
At this time, do not think it will be widespread, but will be
monitored by subsequent shifts.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Highlights:
* Thursday afternoon features more sunshine and seasonably warm
temperatures, clouds increase late in the day with lower stratus,
drizzle, and fog possible by Friday morning.
Thursday: Any morning fog quickly disperses with clear skies above
and climbing temperatures. High pressure slowly drifts to the east
throughout the day but continues to provide enough subsidence to
allow for another sun filled day. Clouds begin to increase from the
southeast late in the day, but should not impact the overall feel
for the day. Expect seasonable highs in the middle to upper 70s with
dewpoints in the upper 40s and lower 50s.
Thursday Night: Mainly dry night, though low level moisture advects
in from an approaching low pressure system which leads to increase
cloud cover, likely stratus given BUFKIT profile soundings. The
soundings show the lowest couple hundred feet are saturated and the
lapse rate are neutral, which leads us to believe there will be
areas of drizzle into the early hours of Friday morning. Have noted
this in the WX Grids mainly after 06z. With the increase dewpoints
and cloud cover the lows Thursday night will be warmer in the middle
50s to lower 60s. And with the increase dewpoints, areas of patchy
fog are also possible.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Highlights:
* Partly to mostly cloudy Fri into Sat, although best chance for
rain showers is with a cold frontal passage around Sat night.
* Increasing waves Fri and Sat may bring a risk for rip currents or
building surf and could need rip current/surf headlines.
* Drier and seasonable weather Sun into early next week, with cool
nighttime lows.
Details:
Friday through Saturday Night:
A pretty complicated weather pattern evolution in this period,
although not likely to lead to necessarily impactful weather.
Slow-moving coastal low pressure near Bermuda will begin to progress
northeastward Fri into Fri night, with initial west-east oriented
sfc high pressure weakening and shifting northwestward into the
interior Northeast. This will draw shallow moisture off the ocean
landward and bring a continued risk for stratus and also some patchy
drizzle at times during the first part of Fri. The bigger
uncertainty specific to Fri is how persistent this low cloud deck
holds on; some afternoon heating/mixing allows for some breaks in
cloud cover, and there are some solutions which advertise mostly
clear skies Fri aftn. However presence of subsidence inversion
keeping shallow moisture suggests keeping at least partly cloudy
skies (a mix of clouds and sun?) for the second half of the day. We
should see another surge in low level RH leading to increased cloud
cover for the evening and overnight.
For Sat and into Sat night...the main uncertainty here revolves
around the timing of an approaching cold frontal passage. This cold
front is in association with a pretty strong cold-core upper low
expected to be over the Gt Lakes/western NY region. The timing of
this frontal passage is in some question, and the speed at which the
departing coastal low from Fri/Fri night exits into Atlantic Canada
will influence the timing and how progressive this frontal passage
would be for Sat/Sat night. Some breaks in early-day overcast is
expected Sat, but will then increase as the cold front nears our
western areas later Sat, then spread eastward with mainly showers
for Sat night. There could be a rumble or two of thunder embedded
given the strength of the upper level forcing, but think this would
be an exception vs the rule. This evolution is agreed upon in the
GFS and Canadian GEM, and while the 00z ECMWF was slowest, its 12z
run now shares similar timing. Tried to focus Chance level PoP for
Sat night, although significant QPF is not expected with this
frontal passage.
One concern in this period is the potential for rip currents on east-
facing beaches for Fri and especially into Sat. The slow-moving
coastal low and elongated fetch north of it will build up waves
starting Fri and by Sat, offshore wave heights around 7-9 ft at 9-11
sec period are forecast. We'll need marine headlines for most waters
this weekend, but also need to consider rip current and/or surf
headlines for east-facing beaches given expected wave heights and
that we are now in the post-Labor Day period where beaches tend to
become less staffed by lifeguards. RipRisk forecast for Sat is in
the High range.
Sunday into Early Next Week:
Cold front should have moved offshore early Sun AM, leading to
building high pressure and deep cyclonic flow aloft. This should
bring dry weather, full sun and strong diurnal temperature ranges to
Southern New England. Temps in this period are generally seasonable,
although good radiational cooling conditions could bring cooler than
normal nighttime lows, especially in the locales which typically
radiate well (NW MA, eastern CT, the I-495 corridor etc).
&&
.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18z TAF Update:
Today through Thursday...High confidence.
VFR, except patchy late night fog in the CT valley. Wind
becoming south 5 to 10 knots this afternoon with sea-breezes
along the coast. Light to calm wind tonight, then East to
Southeast wind 5 to 12 knots Thursday.
Thursday Night... Moderate confidence.
VFR, becoming MVFR with localized IFR. Mainly dry, through there
could be areas of light rain or drizzle mainly across eastern
MA. East winds 10 to 15 knots along the coast, light and
variable across the interior.
KBOS TAF...High confidence in TAF.
VFR with sea-breeze through 00z, becoming south/southwest
overnight, will have another sea-breeze develop on Thursday
around 15z.
KBDL TAF...High confidence in TAF.
VFR with light south winds for the afternoon and then light and
variable tonight. East/southeast winds Thursday 5 to 8 knots.
Outlook /Friday through Monday/...
Friday: Mainly VFR, with local MVFR possible. Breezy. Slight
chance DZ.
Friday Night: Mainly VFR, with local IFR possible.
Saturday: Mainly VFR, with local MVFR possible. Slight chance
SHRA.
Saturday Night: Mainly VFR, with local MVFR possible. Chance
SHRA.
Sunday: VFR. Slight chance SHRA.
Sunday Night through Monday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today through Thursday Night... High confidence.
Vast area of high pressure will provide tranquil boating conditions
this evening into Thursday, featuring east to southeast winds 10 to
15 knots and seas generally 1-3 feet with the southern most outer
waters approaching 4 ft. Thursday night into Friday morning increase
stratus and drizzle may lead to some visibility restrictions. Seas
increase Thursday night into Friday morning 3-5 feet, which could
prompt a Small Craft Advisory. Conditions are marginal and decided
to hold off on issuing the advisory, but future updates may include
it.
Outlook /Friday through Monday/...
Friday: Winds less than 25 kt. Local rough seas. Slight chance
of drizzle.
Friday Night through Saturday: Winds less than 25 kt. Areas of
rough seas.
Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers.
Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers.
Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft.
Monday: Winds less than 25 kt. Seas locally approaching 5 ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Loconto/Dooley
NEAR TERM...Dooley
SHORT TERM...Dooley
LONG TERM...Loconto
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Sep 4, 3:38 PM EDT----------------
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!
