BOX issues Area Forecast Discussion (AFD) at Sep 17, 2:10 AM EDT566
FXUS61 KBOX 170610
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
210 AM EDT Thu Sep 17 2026
.WHAT HAS CHANGED...
No significant changes to the forecast.
&&
.KEY MESSAGES...
- Increased humidity and warmer temperatures continue tomorrow.
- Scattered showers possible Thursday evening into Friday
morning.
- Rain chances return for the second half of the weekend. There
remains uncertainty in the details such as coverage, timing,
amounts.
&&
.DISCUSSION...
KEY MESSAGE 1...Increased humidity and warmer temperatures
continue tomorrow.
Warmer temperatures with increased humidity continue into
tomorrow as an anomalous moisture plume and higher 925 mb
temperatures advect into southern New England via SW flow.
Looking ahead into tonight, the increased moisture and winds
dropping off in the interior may favor the development of some
patchy fog, especially in the CT Valley. With 925 mb
temperatures reaching around 16-19C in the afternoon Thursday,
high temperatures in the low 80s are a possibility, especially
in the river valleys. These higher low level temperatures remain
over the region overnight as well with high pressure affixed
just to our south continuing SW flow; lows tonight will likely
only drop into 60s as opposed to the areas of 50s and 40s we've
seen the past few nights. PWATs up to 2.0" and dewpoints in the
upper 60s will make it feel more humid, too. Despite the
increased humidity, the region should remain dry for much of the
day tomorrow.
KEY MESSAGE 2...Scattered showers possible Thursday evening
into Friday morning. Dry during the day Friday.
A weak shortwave trough progresses eastward behind the plume of
moisture, which will aid in the development of scattered showers
across southern New England. As previously mentioned, latest
guidance has shown PWATs reaching ans even exceeding 2.0"
Thursday afternoon/evening. However, we are not anticipating
widespread downpours as guidance continues to track the stronger
forcing across northern parts of New England. Global models and
a number of the CAMs (with the exception of the NAM) are in
agreement that higher rainfall totals should generally remain to
our north, and ensemble probabilities also favor this outcome.
Totals across southern New England should primarily range
between 0.1" to 0.3" based on the more northern track of the
wave. The latest CAMs have still shown some elevated instability
Thursday night, so a low chance of some isolated downpours
cannot be completely ruled out. Totals could also increase
slightly if the wave were to end up tracking a little further
south, but the general consensus is that the greatest forcing
will remain to our north and we could generally expect a few
tenths of an inch.
Following this system, drier air pushes back in with NW flow,
which will aid in clearing skies through the day and bringing
temperatures back to a more seasonable range.
KEY MESSAGE 3... Rain chances return some time late Saturday
night into Monday morning. There remains uncertainty in the
details such as coverage, timing, amounts.
A high pressure should move across northern New England
Saturday, then over the North Atlantic Sunday. This should
clear the path for a low pressure to move from the lower Great
Lakes south of New England late some time late Saturday night
into Monday. This will likely be our next period of rainfall.
However, the timing is not yet finalized, especially with a high
pressure over the ocean. Would not be surprised if a slower
timing develops.
There is also a question about how much rainfall we can expect
across our region. High pressure over eastern Canada may nudge
far enough south to pus the ultimate storm track far enough
south where we could wind up dry Tuesday into Wednesday.
Assuming this occurs, total rainfall amounts could be limited to
a general 1-2 inches by Monday afternoon. Otherwise, with a
nearly stationary front close to the south coast of New England
could trigger some showers right into mid week.
&&
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06Z TAF Update...
Through 12Z...Moderate confidence.
VFR outside of areas of patchy fog, where MVFR/IFR visibilities
are possible. Mid-level cigs for most of the region with the
exception of ACK. SSW winds near 4-8 kts. Patchy fog is
possible in the valleys (BDL) and other prone areas ORH, BED. If
it does develop it will likely be between 08z and 12z, burning
off quickly after sunrise.
Thursday...Moderate confidence.
VFR with areas of MVFR developing in the early afternoon/late
morning hours. SSW winds at 5-10 kts. Exception is BOS where a
sea breeze moves in 13-15Z out of the SE to ESE through late
afternoon. Showers arrive in the afternoon hours from W to E,
with chances continuing to increase through the evening.
Showers are more likely to develop after 2 PM for the western
terminals and after 22Z for the more eastern terminals.
Thursday Night...Moderate confidence.
MVFR with areas of IFR with patchy fog. Showers continue to
move across the region from west to east, exiting the
Cape/Islands around 12Z. SW winds 5-10 kts, shifting to NW
06-12Z as front moves through.
KBOS Terminal...Moderate confidence in TAF.
Sea breeze develops 13-15Z with winds shifts SE then to ESE for
the afternoon. Winds shift back toward the S then SSW between
21-23Z. -SHRA more likely begin developing in the vicinity
after 21Z. The highest chances for seeing -SHRA between 01-07Z.
KBDL Terminal...Moderate confidence in TAF.
Outlook /Friday through Monday/...
Friday through Friday Night: VFR. Breezy.
Saturday: VFR.
Saturday Night: VFR. Chance SHRA.
Sunday: Mainly VFR, with areas MVFR possible. Breezy. SHRA
likely.
Sunday Night through Monday: VFR. Breezy. Chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through Thursday night...High confidence.
High pressure continues along with SW winds at 10-15 kt into
tomorrow. Gusts just under 20 kt are possible in the afternoon
and evening hours. Chances for showers over the waters increase
Thursday night, especially for northern parts of the eastern
waters. Seas remain at 2-3 ft, though areas of the southern
waters may approach 4 ft heading into Friday morning.
Outlook /Friday through Monday/...
Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers.
Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft.
Saturday: Winds less than 25 kt. Areas of seas approaching
5 ft.
Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Sunday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers.
Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers.
Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft. Chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
DISCUSSION...Belk/Hrencecin
AVIATION...Mensch
MARINE...Belk/Hrencecin
Source:
BOX issues Area Forecast Discussion (AFD) at Sep 17, 2:10 AM EDT----------------
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