601
FXUS61 KBOX 120521
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
121 AM EDT Mon May 12 2025

.SYNOPSIS...
High pressure remains in control through Tuesday. The threat
for scattered showers will increase for the second half of the
week...but not expecting a washout with plenty of dry weather
mixed in too. It will also turn a bit humid by late in the week.

&&

.NEAR TERM /THROUGH TODAY/...
Key Point:

* Frost Advisory for interior Massachusetts this morning

* Sunny dry conditions to start the week

High pressure remains in control today with a mid-level ridge
aloft limiting any substantial cloud cover for a second straight
afternoon. Expecting a very pleasant spring day with high temps
in the upper 60s to low 70s. The pressure gradient strengthens
this afternoon in response short-wave energy traversing over
northern Maine. This will support steady southwest winds this
afternoon from 10-15 mph with some gusts from 20-25 mph
expected. Overall a quiet start to the week.


&&

.SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/...

Tonight and Tomorrow

Key Messages

* Continued dry conditions tonight and tomorrow

* Warm and sunny across the interior on Tuesday. Cooler along
  the east coast

Tonight

Little change in the overall synoptic pattern tonight. An
upper-level ridge aloft continues to support quiet weather.
Low-level west/southwest flow allows some moisture to trickle
into southern New England which should support increasing
cloudiness overnight. Nonetheless, only expecting FEW to SCT
coverage at most. Should have fairly efficient cooling
overnight which will allow most locations in southern New
England to experience low temps in the upper 40s/low 50s by
Tuesday morning. This is close to the climatological normal for
mid-May.

Tomorrow

A surface Anti-cyclone builds east over The Gulf of Maine
tomorrow. This will support east/southeasterly winds in southern
New England for much of the day. While high pressure will
continue to support more sun than clouds Tuesday afternoon,
cooler onshore flow will have the east coastal areas
feeling significantly cooler than the interior. High temps near
the coast in the low to mid 60s. Inland, expect high
temperatures to gradually increase from the upper 60s/low 70s
along I-95 to the mid to upper 70s in the CT River Valley.
Clouds increase from southwest to northeast tomorrow as well as
a blocked cut-off low over The Mid-Atlantic States slowly
traverses Northeast.


&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Key Messages...

* Scattered showers at times along with increasing humidity, but
  plenty of dry periods as well

* Greatest risk for a few t-storms appears to be Fri and Sat

* Seasonable temps Wed-Thu, then above normal Fri thru Sun

Details...

Tuesday night into Thursday...

Upper level ridge axis is forecast to break down as Ohio Valley
trough deamplifies and slowly approaches New Eng through Thu sending
multiple shortwaves into the region. This combined with plume of
PWATs around 1.5 inches will result in scattered showers at times,
although given weak forcing and lack of instability not expecting a
washout with dry periods. Initially, any showers Tue night into Wed
should be mostly confined to central/western MA and northern CT with
drier air likely holding on across eastern MA. Then shower risk
expected to expand across rest of SNE Wed night and Thu. Near
seasonable temps Wed and Thu, upper 60s and low 70s, with increasing
humidity as dewpoints climb into the 60s Thu.

Friday through Sunday...

Weak upper trough axis slides east of New Eng by Fri, then pattern
will be governed by an upper low from western Lakes to SE Canada
with multiple shortwaves moving into the region within the SW flow
aloft. Pattern will remain unsettled but rather low confidence on
timing of any shortwaves. There will a continued risk of showers and
perhaps some convection/thunder threat Fri and Sat as instability is
forecast to increase, but this will all depend on favorable timing
of shortwaves with diurnal heating. Above normal temps expected with
moderate humidity levels.

&&

.AVIATION /05Z MONDAY THROUGH FRIDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

06Z TAF Update...

Through 12Z...High Confidence.

VFR. NW winds diminishing and becoming light/calm.

Monday...High Confidence.

VFR. S winds Mon morning become SW by early-mid afternoon with
gusts on the order of 20 to 25 knots.

Monday Night...High Confidence.

Increasing clouds from the southwest to northeast, through dry,
with VFR CIGs. Southwest winds diminish, becoming northerly
between 5 to 8 knots.

Tuesday...High Confidence

VFR. Winds becoming east/southeasterly from 5 to 10 knots.

KBOS TAF...High Confidence in TAF

KBDL TAF...High Confidence in TAF.

Outlook /Tuesday Night through Friday/...

Tuesday Night: Mainly VFR, with local MVFR possible.

Wednesday: Mainly VFR, with areas MVFR possible. Slight chance
SHRA.

Wednesday Night: MVFR/IFR conditions possible. Chance SHRA.

Thursday: Mainly VFR, with areas IFR possible. Chance SHRA,
isolated TSRA.

Thursday Night: Mainly VFR, with areas IFR possible.

Friday: Mainly VFR, with local MVFR possible. Chance SHRA,
isolated TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Tuesday...High Confidence.

High pressure will support relatively calm conditions over the
coastal waters between today and Tuesday. Southwest winds may
flirt with SCY criteria over the east coastal waters this
afternoon with 20-25 knot gusts possible, though generally
expect sub-SCY criteria gusts. Seas should remain 4 feet or less
over the outer marine zones today followed by 0-2 foot seas
tonight into Tuesday.

Outlook /Tuesday Night through Friday/...

Tuesday Night: Winds less than 25 kt.

Wednesday: Winds less than 25 kt. Slight chance of rain
showers.

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

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

Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Frost Advisory until 6 AM EDT early this morning for MAZ002-
     003-008-010.
RI...None.
MARINE...None.

&&

$$

SYNOPSIS...KJC/RM
NEAR TERM...RM
SHORT TERM...Dooley/RM
LONG TERM...KJC
AVIATION...KJC/RM
MARINE...KJC/RM