BOX issues Area Forecast Discussion (AFD) at Jul 21, 7:23 PM EDT285
FXUS61 KBOX 212323
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
723 PM EDT Sun Jul 21 2024
.SYNOPSIS...
Seasonable and dry to end the weekend, although a rogue shower
or thunderstorm remains possible through this evening. The
weather pattern turns more active again next week with
increasing humidity and periods of wet weather with heavy rain
possible.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
7PM Update
Updated PoPs to reflect isolated shower that has popped up over
western MA. Expect this to fizzle out over the next hour or two
as daytime instability wanes. Otherwise no changes needed with
thsi update.
Previous Discussion
3PM
Highlights:
* Wonderful afternoon and evening across southern New England with a
low threat of a brief shower/rumble of thunder.
A weak cold front moves from north to south this afternoon with the
potential for a hit or miss shower or thunderstorm. Any thunderstorm
would be sub-severe with the greatest threat being lightning. There
are a few showers already developing across portions of northern New
York and coastal Maine. As the front dives south, cannot rule out a
shower or two to develop off the terrain of northern Massachusetts.
No need to go cancel any outdoor plans, just be mindful there is the
potential to have a brief shower or rumble of thunder generally
between now and early evening, with any showers quickly dissipating
after sunset.
Clear skies overnight and light winds leads to radiational cooling
and did lean on the cooler CONSMOS guidance. Away from the ocean and
influence of warm urban centers, temperatures should fall into the
mid and upper 50s. While urban locations remain a bit of the warmth
with lows in the mid 60s.
And it is not out of the question prone radiators develop patchy
fog, especially in the hallow and river valleys.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Update: 3PM
Highlights:
* Monday is mostly dry, along with increasing humidity, spot shower
or two possible during the afternoon with highs in the low to
middle 80s.
* Better chance for widespread rain overnight, along with mild
temperatures.
Monday: A fairly nice start to the week with sun and warm conditions
along with increasing humidity, followed by increasing rain chances
late day, but especially overnight. Surface high pressure is to the
north with the aforementioned cold front becoming quasi-stationary,
draped across southern New England by Monday morning. By late day
the front drifts north towards northern New England as a weak warm
front. Will be difficult to get wide spread shower activity tomorrow
afternoon as there is mid-level shortwave ridging. Though a rouge
shower or thunderstorm during the afternoon remains possible. With
the front pushing north, increasing dew points along with south flow
allows for a warm and somewhat muggy day, dew points return to the
mid 60s with highs in the low to middle 80s.
Monday Night: Our next rain maker arrives overnight as a plume of
higher PWATs advects into southern New England. A mid-level vortmax
and weak low pressure moving off the Mid Atlantic coast taps into
the moisture plume to produce widespread rain into the early hours
of Tuesday. There is some spread in how much rain we could get with
HREF showing heavies rain falling over the southern waters, but
worth monitoring because this area has a 10% probability of 3 inches
of rainfall in three hours. Fairly mild temperatures overnight given
the WAA and cloud cover, lows are in the mid 60s to low 70s.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Update: 3PM
Tuesday through Thursday
An active period of weather across southern New England begins on
Tuesday when the first of three disturbances will progress across
the region triggering scattered showers with embedded thunder.
Southern New England will be transitioning to a tropical like
environment on Tuesday as deep southwest flow advects a plume of
rich moisture into the Northeast. Precipitable water in the column
rises to 1.75 to 2 inches which is close to 2 standard deviations
above normal. At the surface, oppressive humidity will settle in as
surface dewpoints rise into the low to mid 70s. Extensive cloud
cover and rainfall will limit high temperatures to the upper 70s to
low 80s, thus high heat indices won't be a concern. On Tuesday
morning a subtle short-wave/meso-low is forecast to be in the
vicinity of southern New England, and with the plenty of moisture in
place we do expect a period of scattered showers with embedded
thunder. Given the surplus of moisture in place, any showers/storms
that develop will have the potential to produce some heavy
downpours. For this reason, southern New England is in a marginal
risk for excessive rainfall/flash flooding on Tuesday. Most of the
action looks to take place early in the day. By the afternoon,
latest suite of model guidance is supporting some height rises into
the afternoon/evening that could support a brief period of dry
weather before the next round of showers/storms on Wednesday.
After a period of drier weather Tuesday evening, another short-wave
approaches southern New England on Wednesday. This will be
accompanied by stronger shear and more instability, thus the
thunderstorm threat may be a bit more elevated. Overall synoptic
forcing and lapse rates are on the weak side, but given the tropical
environment and high values of shear/instability in place there may
be a low risk for a strong to severe storm or two. Details are vague
at this time range, but we'll have more details as we enter the
window of high resolution guidance in the next 24 to 36 hours.
Expect periods of heavy downpours on Wednesday with continued humid
conditions. While precip chances will exist for most of the day, the
latest model guidance supports slightly higher chances during the
afternoon hours.
The active period of weather next week wraps up on Thursday as a
cold front pushes through The Northeast and displaced the tropical
moisture with a much drier air mass characterized by PWATs around 1
inch. Much like Wednesday, precip chances will exist for most of the
day on THursday, but there is a chance for a few hours of dry
weather ahead of the approaching frontal boundary. The greatest risk
for showers and storms looks to be more in the afternoon/evening
time frame. CSU machine learning probs for excessive rainfall are 15
percent or greater for a good chunk of southern New England. This is
slightly higher than the implied 5 to 15 percent marginal risk that
WPC has southern New England currently in for Thursday. Plenty of
details to iron out before then, but to summarize, expect wet/muggy
conditions Tuesday through Thursday with daily chances for showers
and thunderstorms.
Friday into the Weekend
High pressure and an associated upper-level ridge build in behind
Thursday evenings frontal boundary. This will support drier/sunnier
conditions as we head into the weekend. Next week looks to be
slightly above normal temperature wise with a good chance for high
temperatures in the mid 80s to low 90s right through Sunday.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
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 and dry. Light north wind. Patchy radiational fog is
possible in prone locations as well as the potential for marine
fog for terminals on Cape Cod and Islands.
Monday... High Confidence.
VFR. Light and variable winds becoming S. A sea breeze ESE
winds developing along the east coast of Massachusetts.
Monday Night... Moderate Confidence.
VFR, becoming MVFR with localized IFR along with -SHRA and
-TSRA. S wind becomes SE less than 10 knots.
KBOS TAF... High Confidence in TAF. VFR through the TAF period a
sea breeze has developed and continues through 00z/02z, then
wind direction becomes SSW.
KBDL TAF... High confidence in TAF.
Outlook /Tuesday through Friday/...
Tuesday: MVFR/IFR conditions possible. Chance SHRA, isolated
TSRA.
Tuesday Night: Mainly VFR, with areas MVFR possible. Chance
SHRA, isolated TSRA.
Wednesday through Wednesday Night: Mainly VFR, with areas IFR
possible. Chance SHRA, isolated TSRA.
Thursday: Mainly VFR, with local MVFR possible. Chance SHRA,
isolated TSRA.
Thursday Night: VFR. Chance SHRA, isolated TSRA.
Friday: Chance SHRA, isolated TSRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Monday Night... High Confidence.
Dry conditions tonight and most of Monday, increasing chances of
rain Monday night as weak low pressure system exits the Mid
Atlantic coast and moves towards southern New England.
Rest of Sunday, periods of breezy conditions near shore from
the west/southwest for most waters. South wind for most waters
on Monday with wind speeds 10 to 15 knots, wind becomes more
southeast Monday night. Seas are between 2 and 3 feet.
Outlook /Tuesday through Friday/...
Tuesday: Winds less than 25 kt. Chance of rain showers,
isolated thunderstorms.
Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers.
Wednesday through Wednesday Night: Winds less than 25 kt. Seas
locally approaching 5 ft. Chance of rain showers, isolated
thunderstorms.
Thursday through Friday: Winds less than 25 kt. Areas of seas
approaching 5 ft. Chance of rain showers, isolated
thunderstorms.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Dooley/RM
NEAR TERM...Dooley
SHORT TERM...Dooley
LONG TERM...RM
AVIATION...Dooley/RM
MARINE...Dooley/RM
Source:
BOX issues Area Forecast Discussion (AFD) at Jul 21, 7:23 PM EDT----------------
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