041
FXUS61 KBOX 161842
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
242 PM EDT Sat May 16 2026

.WHAT HAS CHANGED...
Only change was to increase probability of precipitation
overnight with some isolated showers.

&&

.KEY MESSAGES...

- Streak of well above normal temperatures Sunday through
  Wednesday. There is an increasing chance for record warm
  temperatures Tuesday and Wednesday. Isolated thunderstorms are
  possible Tuesday, some of which may be strong.

- Unseasonably warm Wednesday with scattered thunderstorms
  possible later in the day with some potentially strong to
  severe.

- Cooler, more seasonable temperatures late week.



&&

.DISCUSSION...
KEY MESSAGE 1...Streak of well above normal temperatures Sunday
through Wednesday. There is an increasing chance for record warm
temperatures Tuesday and Wednesday. Isolated thunderstorms are
possible Tuesday some of which may be strong.

Mainly dry and warmer for the rest of the day with high pressure
largely in control of the weather pattern. A few widely scattered
showers are possible overnight as a weakening batch of convection
makes its way through the region. Best chance will be across
portions of northern and central Massachusetts where forcing will be
a bit more concentrated.

High confidence continues in a pattern change to unseasonable warm
temperatures for the first half of next week and potentially
flirting with record highs on Tue/Wed. Strong Bermuda ridge pushes
500mb heights to 588-590 dm. GEFS/EPS ensembles show a 60-80 percent
chance of high temps of at least 90 across the CWA. This is a strong
signal considering we are still several days away from this event!

More significant warm up begins Sunday as southwest flow helps warm
temps into the middle 80s for much of the interior. Elsewhere, water
temps in the 50s will help keep temperatures about 10 to 15 degrees
cooler. High pressure to the N of the region shifts winds to the NE
on Monday resulting in slightly cooler temperatures, especially near
the coast. Highs Mon on the immediate coast probably in the upper
60s and 70s while 80+ risk will be confined to the interior. The
hottest days look to be Tue and/or Wed depending on the timing of a
cold front. 925T near +24C should result in the potential for high
temperatures to climb into the 90s away from any modified marine
influences. This may result in record high temperatures being
challenged at least in areas away from the south coast. Main factor
acting against realizing the widespread mid 90s advertised by the
NBM will be cloud cover extent. Should be a somewhat drier heat with
dewpoints in the lower 50s Tuesday.

Finally, guidance continues to show a chance for isolated strong to
sever thunderstorms Tuesday afternoon. There should be plenty of
instability for storms with the NBM showing a widespread 40-60%
chance of values exceeding 1000 J/kg Tuesday afternoon. The limiting
factor at this time is the lack of wind shear and forcing as a front
remains well to the west. Thus, at this time, the coverage of storms
remains in question.


KEY MESSAGE 2...Unseasonably warm Wednesday with scattered
thunderstorms possible later in the day with some potentially strong
to severe.

A low pressure system and attendant cold front is expected to track
across the northeast Wednesday into Thursday. Depending on the
timing of the cold front, we may see one last day of above normal
high temperatures in southern New England. This is supported by warm
925mb temperatures bumping up to 23-25C with enhancement from the
WAA ahead of the approaching system. There is high confidence for
temperatures 80F+ with ensembles indicating potential for highs
around 90 in the valleys inland. South coast and Cape and Islands
will stay in the 70s and low 80s from the southwesterly onshore
flow. Another early season hot day, so be sure to hydrate, take
breaks, and have a cool place to do so.

Ahead of the cold front, southwesterly flow aloft helps to advect in
Gulf moisture as instability builds ahead of the frontal system with
the ample heating. MLCAPE values appear on the marginal side,
although shear appear sufficient with the help of a jet. With the
added forcing of the front, this should support scattered
thunderstorms developing later in the day with potential for some
storms being strong to severe. Forecast soundings indicate a good
amount of dry air at the surface which may be a signal for strong
downdrafts (gusty winds) within any strong-severe storms. The
assorted ML guidance shows a signal with low probabilities for
severe at this time. We are still a ways out and details on the
timing of the front will need to be ironed out more before
confidence increases in the severe potential. Stay tuned.

KEY MESSAGE 3...Cooler, more seasonable temperatures late week.

A cold front will swing through by Thursday bringing in a cooler
airmass. This will bring in more seasonable/seasonably cool
temperatures late-week with mainly dry conditions and northerly
component flow.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

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

18Z TAF Update...High confidence

This Afternoon through Tomorrow...High Confidence

VFR conditions through tomorrow. Steady southwest winds around
10 knots today with some gusts of 20+ knots possible during the
mid- afternoon hours. Southwest winds should be strong enough to
fend off a sea- breeze. Steady west winds continue overnight
and become more west/northwest on Sunday. Areas of LLWS
overnight from BOS points SE.

KBOS...High confidence in TAF

KBDL...High confidence in TAF.

Outlook /Sunday Night through Thursday/...

Monday: VFR. Breezy.

Monday Night: VFR.

Tuesday through Tuesday Night: VFR. Breezy.

Wednesday through Wednesday Night: VFR. Breezy. Chance SHRA,
slight chance TSRA.

Thursday: VFR. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

SCAs remain in effect on most waters as easterly swell that
brings elevated seas in the 4-7 ft range tonight. Winds shift
W tonight into Sunday. Given the continued elevated seas and
increase in winds tomorrow, SCAs have been extended through
Sunday afternoon. Winds and seas are expected to remain
elevated then gradually fall as high pressure builds in.

Outlook /Sunday Night through Thursday/...

Monday through Monday Night: Winds less than 25 kt.

Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft.

Tuesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas.

Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Chance of
rain showers.

Wednesday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Chance of rain showers, slight chance of
thunderstorms.

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for
     ANZ231>234.
     Small Craft Advisory until 2 AM EDT Sunday for ANZ235-237-251.
     Small Craft Advisory until 2 PM EDT Sunday for ANZ250-254>256.

&&

$$

DISCUSSION...Mensch/FT
AVIATION...McMinn/FT
MARINE...FT