BOX issues Area Forecast Discussion (AFD) at Aug 16, 2:18 PM EDT988
FXUS61 KBOX 161818
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
218 PM EDT Sat Aug 16 2025
.SYNOPSIS...
Heat and humidity briefly returns Sunday along with the risk for a
few showers and thunderstorms during the afternoon and evening as a
cold front crosses the region. Cooler/below normal temperatures
follow for much of the upcoming work week with comfortable humidity.
Dry weather dominates next week...but some wet weather is possible
in the late Tuesday through Thursday time frame. In addition...Major
Hurricane Erin will bring dangerous rip currents and high surf to
ocean exposed beaches by mid to late week.
&&
.NEAR TERM /THROUGH TONIGHT/...
Key Messages:
* Gorgeous afternoon, rouge shower possible in far western areas,
and a mild and muggy night ahead.
Right on cue, diurnal cu bubbled up across southern New England. Not
much to complain about this afternoon with seasonable temperatures
in the lower to middle 80s, though dewpoints are split. The 1pm
observations show the eastern half of the region is enjoying lower
dewpoints in the upper 50s to lower 60s, while the western half is
more humid with dewpoints in the upper 60s.
Weak forcing in southern New York and northeastern Pennsylvania have
allowed for diurnally driven pop up showers. A rouge shower could
move into western Massachusetts and Connecticut, bringing a brief
period of rain and a rumble of thunder. These diminish as we lose
the daylight and dry conditions overnight.
A shifting of the wind to the S/SSW will usher in higher dewpoints
this evening and overnight, leading to areas of stratus and patchy
fog across portions of Connecticut, Rhode Island, and southeastern
Massachusetts. Have lower confidence with how far inland these
clouds reach, but think areas south of I-90 have more clouds than
clear skies, which will lead to a mild and muggy night in the middle
and upper 60s, where there area less clouds, lows fall into the low
60s.
&&
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
Key Messages:
* Briefly hot and humid, a cold front brings sct'd showers and
storms later in the afternoon and early evening.
* Cooler and less humid conditions post cold front.
Areas of stratus or fog eventually erodes, but could take as late
10am or 11am. Otherwise mixture of sun and clouds, building warmth,
and humid conditions for Sunday. Luckily it only lasts for one day,
a cold front brings cooler and less humid air to the region for next
week.
First, southwest flow brings in warmer air mass with temperatures
aloft at 850mb at +16C to +18C, with proper mixing, should have
highs in the upper 80s to lower 90s. Dewpoints are on the rise too
with values in the upper 60s to lower 70s. This will result in heat
indices 2-3 degrees warmer than the actual high temperature.
The aforementioned cold front moves across southern New England from
northwest to southeast during late afternoon and early evening. This
is associated with a mid-level trough and shortwave. Mean MUCAPE are
between 800-1200 J/kg, and DCAPE values ~700 J/kg, a limiting factor
are mid-level lapse rates, which are around ~6C/km. SPC did include
all of southern New England in a marginal risk for severe weather,
with the primary threat of damaging wind gusts. Given the higher
PWATs ~2" localized flash flooding in urban areas or due to poor
drainage is possible. Less of a flooding threat elsewhere as it's
been fairly dry.
Sunday night into Monday morning brings in a noticeably cooler and
less humid air mass. This will set the stage for a very comfortable
week ahead.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
Key Messages...
* Cooler next week with highs in the 70s through at least Thu,
warming up into the 80s toward the weekend.
* Mostly dry with a low probability window for rain showers between
late Tue and Thu.
* Hurricane Erin brings dangerous surf and rip currents mid/late
week.
High pressure dominates much next week moving from southern Quebec
on Monday toward the northern Atlantic by mid/late week. This keeps
a lid on most precipitation while directing cooler and less humid
air into the region on N/NE low level flow. 925 mb temps drop from
24C on Sunday to 12-14C through much of next week. This leads to
high temperatures below normal, in the low to mid 70s for most
through Thursday. Meanwhile, dewpoints start off the week in the 40s
and 50s meaning no high humidity to speak of, though dewpoints may
creep up into the 60s briefly on Wednesday before drier air is once
again pulled in behind the exiting tropical system. While dry
weather is more than likely, we continue to monitor the low
probability that a mid level shortwave and stalled front with its
associated plume of moisture could lead to more widespread rain well
north of Erin mid week. At this time the EPS ensemble is the only
guidance showing anything of note, but something to watch. Speaking
of Erin, the NHC continues to indicate what the guidance has been
showing, that Hurricane Erin will turn north then northeast, being
steered out to sea and precluding any direct impact to SNE. The
exception would be the energy that it sends north in the form of
large swell/wave heights, especially along our south facing, ocean
exposed beaches by mid week. This will also mean dangerous rip
currents become more likely Wed/Thu.
&&
.AVIATION /18Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through 00z... High Confidence.
VFR. A low chance, less than 30% of -SHRA across interior southern
New England this afternoon. Light wind, sea-breeze for coastal sites
with winds 8-12 knots, inland sites have winds less than 8 knots.
Tonight... Moderate Confidence.
Wind shift to the S to SSW, ushering in a more humid airmass and
lowering ceilings across the southern New England. Flight category
falls from VFR to MVFR, potential IFR due to low stratus and fog.
Sunday and Sunday Night... Moderate Confidence.
Any MVFR/IFR early Sunday morning improves to VFR by 15z. Cold front
Sunday afternoon will bring sct'd shower or thunderstorm mid to late
afternoon, which may briefly lower categories. SW to W winds 10-15
knots, turning to the N/NE overnight at 10 knots.
KBOS terminal...High Confidence through 08z, moderate there after.
VFR, ENE to ESE wind this afternoon. After 00z, wind becomes S and
less than 8 knots. Have somewhat lower confidence after 08z due to
the potential for lower ceilings. Opt to include a FEW020 after 08z
as to hint towards the potential. Heading into Sunday, VFR, breezy
SSW to SW winds 10-12 knots. A cold front brings -SHRA and -TSRA
late in the afternoon, included a PROB30 as a result.
KBDL terminal...High Confidence.
Outlook /Monday through Wednesday/...
Sunday Night: Mainly VFR, with local IFR possible. Breezy.
Scattered SHRA, isolated TSRA.
Monday: VFR. Breezy.
Monday Night through Tuesday: VFR.
Tuesday Night: VFR. Chance SHRA.
Wednesday: VFR. Breezy. Chance SHRA, slight chance TSRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Sunday Night... High Confidence.
Surface high pressure shifts east tonight, this is ahead of an
approaching cold front Sunday later afternoon. Storms possible late
Sunday evening, followed by drying conditions overnight. Light south
wind continues through tonight, but increasing speeds ahead of the
cold front. Conditions are below Small Craft Advisory. Post cold
front, gusty N to NNE wind will likely produce gusts to advisory
criteria across the northeast waters by Sunday night. Seas through
tonight are less than 2 feet. Seas building to 3 and 4 feet Sunday
afternoon.
Outlook /Monday through Wednesday/...
Sunday Night: Low risk for Small Craft Advisory winds with
local gusts up to 30 kt. Seas locally approaching 5 ft.
Scattered rain showers, isolated thunderstorms, patchy fog.
Local visibility 1 to 3 nm.
Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft.
Monday Night: Winds less than 25 kt. Seas up to 5 ft.
Tuesday: Winds less than 25 kt. Local rough seas.
Tuesday Night: Winds less than 25 kt. Areas of rough seas.
Slight chance of rain showers.
Wednesday: Winds less than 25 kt. Areas of rough seas. Chance
of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...BW/Dooley
NEAR TERM...Dooley
SHORT TERM...Dooley
LONG TERM...BW
AVIATION...BW/Dooley
MARINE...BW/Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Aug 16, 2:18 PM EDT----------------
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