BOX issues Area Forecast Discussion (AFD) at Jul 3, 1:36 PM EDT991
FXUS61 KBOX 031736
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
136 PM EDT Wed Jul 3 2024
.SYNOPSIS...
High pressure brings dry weather and seasonably warm
temperatures today. Cloud cover increases later tonight and
especially on Independence Day, with scattered showers to dodge
for the holiday along with rising humidity levels. Very warm
weather with increasing humidity this weekend and into early
next week. Saturday will have the highest humidity levels.
While there is a risk of rain and thunderstorms throughout the
weekend and early next week, it won't rain continuously. There
will be significant dry periods, with Saturday into Saturday
night having the greatest chance for heavier rains.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
9 AM update...
High pres across SNE will shift to the south this afternoon with
S-SW flow developing. Other than some high clouds expect mostly
sunny skies with seasonably warm temps. Highs will reach low-
mid 80s, but cooler along the south coast due to southerly
winds. A brief sea-breeze is expected to develop along the
eastern MA coast but winds should turn southerly by mid-late
afternoon. Dewpoints in the 50s today keeps humidity levels in
the comfortable range.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
332 AM Update:
Tonight:
Upper level ridge flattens/weakens later tonight in response to
broad cyclonic flow/height falls moving into the Northeast states
into the early morning hrs. While most of the first part of the
night should see mostly clear to partly cloudy skies (high clouds),
increasing cloud cover overspreads for the overnight hours from NW
to SE associated with a significant surge in deep moisture (e.g.
PWAT values increasing to around 1.5-1.8"). Dewpoints then start to
rise into the lower to mid 60s for the overnight; that should offer
development of patchy fog over the southern waters, then expanding
slightly landward into the RI/MA South Coast. These are trends
indicated both in BUFKIT sounding profiles but also on some of the
LAMP MOS progs. With southerly winds increasing a bit, its northward
coverage probably will be pretty limited to the immediate coast. So,
turning a little more humid tonight but the increase in clouds also
will allow for lows to run some 10 degrees warmer than tonight, in
the mid to upper 60s.
Independence Day:
A weak frontal system approaching from the west, associated with a
surge in deep moisture, will slowly sag its way southward through
Southern New England during the holiday. This spells increased cloud
cover, although BUFKIT profiles showing several layers of saturation
indicate cloud cover could be more of a multi-layered look (mix of
low and mid clouds). The sagging boundary would ordinarily serve as
a focus for showers, and while there is quite a bit of deep moisture
around with PWATs nearly 2", there is hardly any instability to
speak of (less than 200 J/kg of MUCAPE). Couldn't really rule out a
shower anywhere or anytime, so I opted to phrase it in the zone
forecast as scattered showers vs chance shower phrasing. Despite the
semantics, it is generally dry most of the time, but I couldn't
say no to a shower to dodge. Although temperatures probably
will be slower to rise amid cloud cover (highs upper 70s to mid
80), it gets quite humid as dewpoints reach into the upper 60s.
Will have southerly breezes around 10-15 mph too.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Highlights:
* Few showers possible on Friday, otherwise dry, warm and muggy.
* Humidity becomes oppressive for Saturday along with the potential
for heavier rains and thunderstorms.
* Unsettled period continues Sunday though early next week,
although there will be dry periods, and continued heat and muggy
conditions.
Thursday Night and Friday:
Signals marine stratus and fog could develop along the south coast
and the adjacent waters of Rhode Island and Massachusetts as BUFKIT
forecast soundings have the lowest thousand feet saturated. Not out
of the question it may lead to pockets of drizzle and as well as
areas of patchy fog. Will say, there is low confidence in how
widespread fog could become, but felt it was worth mentioning due to
the numerous recreational boaters on the water for the Independence
Day holiday. If this were to develop, think it would occur overnight
into the predawn hours of Friday.
Heading into Friday, there are subtle height rises along with weak
shortwave energy traversing through the zonal mid-level regime. The
best forcing remains to our northwest, over the Great Lakes, though
bouts of shortwave energy does break off and travel east because of
the near zonal mid-level pattern. Given a moisture rich atmosphere,
PWATS are 1.5" to 1.8", and 2.0" plus along the southern coast a few
showers cannot be ruled out. Timing out the is difficult, will have
to utilize the high-res guidance to sort it out. With anomolously
high PWATs, dew points are elevated, it is the type of humidity you
can feel. Dew points climb into the low 70s and is accompanied by
highs in the low to middle 80s.
Saturday:
Unsettled conditions heading into the upcoming weekend. Shortwave
energy ejects out of the Great Lakes for Saturday, and with several
hundred units of MUCAPE, convective showers are possible. The warm
cloud layer is from 12,000 feet to 15,000 feet, meaning there is the
potential for efficient rain makers, with PWATs near max of climo,
with forecast values as high as 2.0 to 2.5", daily climo max per the
sounding archive is around 2.05", with the max of all soundings
at 2.73" for CHH. Heavy rains are possible. WPC mentioned the
western CWA in day four excessive rainfall outlook, most of
Connecticut and central to western Massachusetts.
Saturday afternoon is warm and very muggy with dew points in the low
to potentially the mid 70s, down right tropical! Highs are between
the low and middle 80s.
Sunday through Tuesday:
Southern New England is still on the outer periphery of a mid-level
ridge that is anchored over Bermuda. Model guidance continues to
show bouts of shortwave energy riding the ridge, leading to a daily
chance for daily chances for convective showers. While the risk
continues into early next week, it won't rain continuously. There
will be significant dry periods as well.
Guidance continues to indicate warm and muggy conditions with highs
well into the 80s to 90 degrees and lows in the 60s to low 70s. High
PWATs linger as well, likely leading to dew points in the upper 60s
to 70 degrees.
&&
.AVIATION /18Z WEDNESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through 00z:
VFR. S wind 10-15 kt with gusts to 20 kt. Sea-breeze along
eastern MA coast kicks out 21-22z with wind shift to S.
Tonight: High confidence.
VFR cigs. Low risk of a shower 09-12z in the interior. SW wind
5-15 kt.
Thursday: High confidence.
Mainly VFR cigs, but patchy MVFR possible over higher
elevations. Isolated morning shower possible, then a few
showers or a t-storm possible in the afternoon in the interior.
SW wind 10-20 kt.
Thursday night: Moderate confidence.
Cigs gradually lowering to MVFR with IFR possible near the south
coast. A few evening showers possible, then scattered showers
and possibly a t-storm near the south coast after midnight.
KBOS TAF...High confidence in TAF. Sea-breeze kicks out 21-22z
with wind shift to S.
KBDL TAF...High confidence in TAF.
Outlook /Friday through Sunday/...
Friday: VFR. Chance SHRA.
Friday Night: Mainly VFR, with local IFR possible. Chance SHRA.
Saturday: MVFR/IFR conditions possible. Breezy. Chance SHRA,
isolated TSRA.
Saturday Night: Mainly VFR, with areas IFR possible. Breezy.
Chance SHRA, isolated TSRA.
Sunday: VFR. Breezy. Slight chance SHRA, isolated TSRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today through Thursday: High confidence.
Tranquil boating conditions expected today, with light southerly
winds around 10 kt and easterly seabreezes nearest the coast. SW
winds increase tonight to around 10-15 kt, although there will be a
risk for patchy fog overnight on the southern waters and southern
nearshore bays and harbors. Visbys could turn as low as one
quarter mile.
Winds then increase to around 15-20 kt on most waters for
Independence Day, although gusts near shore could get to near-SCA
levels during the daytime hrs. Scattered showers possible later in
the day but shouldn't restrict visby.
Seas through the period generally 3 ft or less on all waters.
Outlook /Thursday Night through Sunday/...
Thursday Night: Winds less than 25 kt. Isolated rain showers.
Local visibility 1 to 3 nm.
Friday: Winds less than 25 kt. Slight chance of rain showers.
Friday Night: Winds less than 25 kt. Chance of rain showers.
Saturday: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers, isolated thunderstorms.
Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain showers, isolated thunderstorms.
Sunday: 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...Loconto/Dooley
NEAR TERM...KJC
SHORT TERM...Loconto
LONG TERM...Dooley
AVIATION...KJC/Dooley
MARINE...Loconto/Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Jul 3, 1:36 PM EDT----------------
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