233
FXUS61 KBOX 281750
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
150 PM EDT Sun Jun 28 2026

.WHAT HAS CHANGED...
No significant changes.

&&

.KEY MESSAGES...

- Scattered showers this afternoon following morning fog.

- Warming trend takes hold, though could see dangerous heat
  Wednesday through Friday.

- Risk for showers and thunderstorms mid to late week.

&&

.DISCUSSION...
KEY MESSAGE 1...Scattered showers this afternoon following morning
fog.

Fog this morning that had been lurking over the waters and took hold
over much of the region this morning will likely stick around until
sunrise. Fog recedes, though cloudier skies will take a bit longer
to decrease. High pressure will start to take hold over the region,
keeping winds light. We do remain under some troughing aloft,
though, keeping the chance for some showers in play this afternoon.
The chance for scattered showers over southern New England makes a
return, yet the risk for these becoming thunderstorms remains low
- - much like yesterday. MLCAPE values will remain mostly below
500 J/kg and MUCAPE generally maxes out around 500 J/kg as well. So,
a rumble or two cannot be entirely ruled out, but is unlikely. Highs
today will be mostly in the 80s.

KEY MESSAGE 2...Warming trend takes hold, though could see dangerous
heat Wednesday through Friday.

A strong upper level ridge continues building in from the west to
start the week, which will be a key factor in this week`s heat.
Ensembles and deterministic guidance suites are in good agreement
that this ridge will continue into the Ohio Valley to start the work
week, then continuing further east into the northeast CONUS. The
signals for intense heat heading into the middle of the week have
not changed too much from the previous forecast: ensembles continue
to keep the highest probabilities of highs reaching and/or exceeding
100F over urban areas and the river valleys, especially on Thursday.
GEFS probabilities for Thursday afternoon range generally between 20-
40 percent with Canadian ensemble probabilities slightly higher at
30-60 percent. This ensemble is also highlighting the CT River
Valley more aggressively than other aforementioned areas, with some
spots in the range of 60-70 percent. The continued overall consensus
across the different guidance suite aids in increasing confidence in
the risk for this dangerous heat overall. Mean 850 mb temperatures
across the ensembles continue to reach 20-23C, and 925 mb
temperatures in the deterministic guidance continue to key in on 25C
temperatures and higher, even to 30C(!). This is all before dew
points and overall moisture are being taken into account. With
ambient temperatures possibly reaching 100F, heat indices could soar
into the triple digits, lending to a Major (3/4) level Heat Risk.
Urban areas, the Merrimack Valley, and the CT River Valley could see
Extreme (4/4) Heat Risk impacts, especially on Thursday.

Another issue with these high daytime temperatures is that not much
relief is expected overnight. NBM has low probabilities for
temperatures getting below 70F overnight between Wednesday and
Friday (generally at 20 percent and lower). The other ensembles are
equally pessimistic; GEFS, ECMWF ENS, and the Canadian ensemble all
have probabilities generally higher than 60 percent for temperatures
staying above 70F overnight.

KEY MESSAGE 3...Risk for showers and thunderstorms mid to late week.

As the ridge builds in heading into the middle of the week, a few
shortwaves may track along the eastern edge. Some showers and/or
thunderstorms associated with them may move through the region
Tuesday, briefly bringing a little bit of relief from the heat. Once
the ridge has built up into southern New England for Wednesday and
Thursday, chances for showers and storms drop significantly. Chances
increase for the end of the week as the ridge breaks down. More
refined details will come into the picture as we get closer to both
events.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

18Z TAF Update:

Through 00z Monday: Overall high confidence, but moderate near
the eastern MA coast.

Mainly VFR, though a couple things to monitor which could offer
at least brief restrictions. One is SCT slow-moving SHRA/possible
ISO TS mainly affecting BDL, ORH, PVD and perhaps BED 19-00z,
with brief MVFR visby restrictions if a direct hit. Coverage of
SHRA/TS decreases with sunset. The other is a
potential return of marine stratus and fog at IFR levels at
BOS, which were TEMPO`d in through 00z. Light winds, easterly
near the coast.

Tonight: High confidence in trends but moderate on timing.

VFR early, but we should see stratus/fog return at IFR-LIFR
levels for most airports, lowest categories Cape and Islands,
PVD and BOS. Exact onset timing is uncertain but the risk
increases after sundown, and especially after 02z. Light S/SW
winds, calm at times.

Monday: High confidence.

IFR-LIFR stratus and fog disperse 12-13z to VFR conditions
thereafter. Light winds, with seabreezes developing at BOS by
15z and PVD by 16-18z.

KBOS Terminal...Moderate confidence in TAF. Showed prevailing
VFR but with TEMPO IFR ceilings/visbys thru sundown to account
for stratus/fog over the water returning inland. Better chance
IFR-LIFR stratus after 02z Monday, dissipating by 12-13z Monday.
Seabreeze starting around 15z Monday.

KBDL Terminal...High confidence in TAF.

Outlook /Monday Night through Friday/...

Monday Night: VFR.

Tuesday: VFR. Breezy. Slight chance SHRA, slight chance TSRA.

Tuesday Night: VFR. Breezy. Chance SHRA, slight chance TSRA.

Wednesday through Thursday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Through Monday Night: High confidence.

Winds and seas remain below small craft advisory thresholds,
with light east/southeast winds through Monday night and seas 3
ft or less all waters. Winds near shore/port on Monday could
turn east around 10 kt due to sea/bay breezes. Main issue for
mariners tonight into Monday is fog and mist, which could reduce
visibility to less than 1 mile; it is less certain if mist/fog
develops again Monday evening.

Outlook /Monday Night through Friday/...

Monday Night through Tuesday: Winds less than 25 kt.

Tuesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Chance of
rain showers, slight chance of thunderstorms.

Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 25 kt. Seas up to 5 ft.

Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain
showers.

Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Extreme Heat Watch from Wednesday morning through Friday
     evening for CTZ002>004.
MA...Extreme Heat Watch from Wednesday morning through Friday
     evening for MAZ002>021-026.
RI...Extreme Heat Watch from Wednesday morning through Friday
     evening for RIZ001>007.
MARINE...None.

&&

$$

DISCUSSION...Hrencecin
AVIATION...Loconto/FT
MARINE...Loconto/FT