BOX issues Area Forecast Discussion (AFD) at Jun 11, 3:50 PM EDT723
FXUS61 KBOX 111950
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
350 PM EDT Tue Jun 11 2024
.SYNOPSIS...
Partly to mostly cloudy conditions to continue tonight and into
Wednesday as well. While most areas are dry on Wednesday,
isolated to widely scattered showers are possible during the
afternoon hours in eastern Massachusetts and Rhode Island. High
pressure moving off the coast will allow warmer temperatures
for Thursday and humidity by Friday. An approaching cold front
will bring the risk for scattered showers and thunderstorms
Friday afternoon and evening. High pressure builds in for the
weekend bringing beautiful dry weather with pleasant
temperatures and low humidity.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
215 PM Update:
Satellite and observational analysis indicate models are
initializing the cold pool aloft associated with a broad upper
trough well this afternoon, with satellite showing partly to mostly
cloudy stratocumulus conditions. There could be a hit-or-miss shower
mainly in interior MA, CT and NW RI through sundown with PoP no
higher than 20% in any one area, but otherwise mostly cloudy and dry
weather should prevail. With the cloud cover, current temps are in
the upper 60s to lower 70s, on the cooler side for mid-June.
For tonight, any showers which developed should dissipate around
sundown. The main forecast challenge will be in regards to the
degree to which the existing cloud cover dissipates and how it would
impact low temps. Upper level trough responsible for the cloudiness
today slowly shifts eastward into much of interior VT/NH tonight, so
we're still under its influence, even into Wed. All else being
equal, around sundown into the evening we see decreasing cloud cover
toward mostly clear conditions, but the presence of the upper trough
as well as lingering lower level RH around suggests siding the
forecast toward a partial cloudiness look vs going fully clear.
Temps are likely to be very tough; any areas which see sustained
breaks could cool off pretty well with light winds and others which
see continued or persistent cloudiness trend on the milder side.
Thus a pretty wide range of lows mainly in the 50s, but lower 50s in
the terrain and where skies can clear out, and upper 50s
elsewhere.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
215 PM Update:
Wednesday:
Although the upper-level low over New England is expected to pull
away from the Northeast later in the day, the forecast for Wed is
essentially similar to today. Residual cyclonic flow aloft and a
modifying cold pool should again support clouds filling back in with
a partial to mostly cloudy look, and that should also keep
temperatures from reaching into widespread low 80s as today's NBM is
advertising. At least a lighter westerly flow could bring highs
closer to the upper 70s in western MA and much of northern CT
though, with highs in the lower to mid 70s for eastern/northeast MA
and much of RI.
Latest guidance seems a bit more bullish on isolated to scattered
shower chances Wed than today, as the east coast sea breeze
generates a mesoscale convergence zone in eastern MA/RI with the
lighter westerly flow across the interior. Dewpoints are also a
touch higher too over the coastal plain, and while the NAM's
dewpoints still look a few degrees too high, values in the mid 50s
seem reasonable enough to yield surface based CAPEs of around 500
J/kg or less; phrased as isolated to scattered showers with 20-40%
PoP though as BUFKIT soundings from even the bullish NAM indicate
the layer of instability doesn't reach into the -10C isothermal
layer for lightning. 12z HREF 1-hourly thunder probs are also
zero, with low probs confined to northern ME/NH closer to where
the upper low is progged. The risk for scattered showers should
be limited to just the MA/RI coastal plain around or within a
few miles either side of I-495; westerly non-convergent flow
further inland into CT and western MA should result in mainly
dry weather there. QPF amts likely no higher than a few
hundredths of an inch in any one area, so a few showers to dodge
but nothing too significant.
Wednesday Night:
Cloud cover with scattered light showers should dissipate shortly
after sundown towards mostly clear skies for the overnight.
Temperatures warm a bit aloft and that should help offset
radiational cooling to an extent with lows in the 50s, to low 60s in
the urban areas. With clear skies and light winds, there's an
outside chance at patchy radiational fog, with somewhat better
chances of development where showers developed during the daytime
hrs.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Highlights:
* Increasing heat and humidity Thursday into Friday. A cold front
brings showers and thunderstorms on Friday afternoon and evening
with drier and more comfortable conditions for Father's Day
Weekend.
* There is potential for significant warm-up next week as
highlighted by a moderate risk for excessive heat.
Thursday...
Looking at a sunny and warm day ahead with surface high pressure is
off shore and shortwave ridging aloft. Southwest flow ushers in warm
temperature aloft, 925mb temperatures are in the neighborhood of
+19C to +23C, yielding highs between 85-90 degrees. Southwest wind
keep coastal Rhode Island, south coast of Massachusetts, Cape Cod,
and the islands slightly cooler in the 70s. While it is not overly
humid, it will be noticeable as dewpoints creep into the upper 50s
and low 60s, highest near the coast and lowest in the interior.
Friday...
As advertised, a cold front passage with the associated near-neutral
shortwave trough pushes across the northeast during Friday afternoon
and evening. Ahead of the front, robust southwest flow will increase
our temperatures and especially the humidity. Temperatures aloft are
very similar to Thursday, thus expecting another day with highs
between 85-90 degrees. Though the main difference are the higher
dewpoints, with PWATs surging to either side of 1.7 inch, dewpoints
are largely in the mid 60s. Combination of the heat and humidity
will fuel storms during the afternoon. Depending on which guidance
source, there is roughly 800 to 1200 J/km of SB CAPE. In addition,
modest jet dynamics provide roughly 40 knots of 0-6km shear. Leading
to a few storms during the afternoon, but will largely depends on
the timing of the frontal passage. In addition, high PWATs may lead
to locally heavy downpours, which may cause nuisance flooding, as
highlighted by the Marginal Risk for Excessive Rainfall Outlook.
Father's Day Weekend...
Drying out and falling humidity this coming weekend, a nice reprieve
from the humidity, as surface high pressure moves down from Canada.
PWATs drop in most cases below 0.3 inch on Saturday and 0.5 inch on
Sunday. That said, we are looking at mainly clear skies both days
with highs in the upper 70s to low 80s, and dewpoints in the 40s to
low 50s. With clear skies and potential for light winds on Saturday
night, there is the possibility for radiational cooling, which could
lead to a cooler than normal start on Sunday, Father's Day. Early
risers or golfers could be greeted by temperatures in the upper 40s
across the interior.
Next Week...
Dry weather continues into early next week as surface high pressure
sits along the east coast. Though the bigger talking point is the
potential well above normal temperatures... not only during the day
but also overnight. This is highlighted by the moderate risk for
excessive heat mid to late next week.
&&
.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18z TAF Update: High confidence.
Through 00z Tuesday: BKN-OVC VFR bases. A spot shower possible
mainly in interior CT/MA through sundown but coverage is too
sparse for a TAF mention and wouldn't result in restrictions.
Light mainly W/NW winds, with seabreezes near the coasts.
Tonight: VFR continues with some SCT-BKN 040-060 bases around.
Winds light to calm, with eastern MA seabreezes turning onshore
by 00-01z and then beginning a clockwise turn to light WNW by
the pre-dawn Wed hrs. Radiational fog potential tonight viewed
as unlikely with more clouds cover around.
Wednesday: Mainly VFR, though SCT-OVC stratocu bases could
approach borderline MVFR levels at times. While the interior
airports should be dry, a lower to moderate (20-40%) chance at
a shower for BED, PVD and BOS during the aftn hours. Light W/WSW
winds in the interior, with seabreezes developing by 14-16z.
KBOS TAF...High confidence in TAF. BKN-OVC VFR bases this
afternoon, trending SCT tonight. Outside shot at a -SHRA thru 22z
but too unlikely to mention in TAF. Sea breeze kicks out
between 01z-03z with winds coming around to light WNW by pre-
dawn. Somewhat better chance at -SHRA or VCSH on Wed, with sea-
breezes starting around 15z.
KBDL TAF...High confidence in TAF. SCT-OVC VFR bases this aftn,
trending SCT tonight. Isolated shower possible but too unlikely
to mention in TAF. VFR bases return on Wed. Light W winds.
Outlook /Thursday through Sunday/...
Wednesday Night: VFR.
Thursday through Thursday Night: VFR. Breezy.
Friday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA, isolated TSRA.
Friday Night: Mainly VFR, with local MVFR possible. Chance
SHRA, isolated TSRA.
Saturday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
215 PM Update:
Winds and seas/waves to remain below small craft advisory
levels through this portion of the marine forecast period. Light
mainly southerly winds around 10 kt or less should be the rule
tonight through Wednesday night, though could turn easterly
nearest the shoreline with seabreezes. Seas mainly 3 ft or less,
with 1-2 ft seas near shore.
There could be a hit or miss shower Wed aftn near the
coastlines. Could see fog develop Wed evening over the outer
waters.
Outlook /Thursday through Sunday/...
Wednesday Night through Thursday: Winds less than 25 kt.
Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.
Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain
showers, isolated thunderstorms.
Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Rain showers likely, isolated thunderstorms.
Saturday: Winds less than 25 kt. Areas of seas approaching
5 ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Loconto/Dooley
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...Dooley
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Jun 11, 3:50 PM EDT----------------
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