River Flood Warning 11, NWS Boston/Norton, MA

Area Forecast Discussion
National Weather Service Boston/Norton MA
643 AM EDT Sat May 10 2025

.SYNOPSIS...
Low clouds and scattered showers this morning will give away to
clearing skies this afternoon. High-pressure returns for
Sunday, keeping skies clear with temperatures warming back to
near 70F. Mainly dry and mild for the first half of the week, then
an unsettled pattern develops during mid to late week with a
chance of showers at times along with increasing humidity, but
dry periods as well.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Upper-level short wave moves offshore today with gradual clearing
conditions this afternoon into the evening.  Before that, however,
low cloud cover and lingering showers will still be around this
morning, especially in eastern MA.  As the surface low stacked
beneath the shortwave moves offshore, winds will flip around to the
NW and become gusty to 25-35mph this afternoon.  With low clouds and
NW winds tomorrow, high temperatures are unlikely to top 70F,
staying in the low to mid-60s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
WNW flow continues overnight overnight as a weak cold front
approaches from the north.  Winds become less gusty overnight and
may even decouple from the BL in low-lying areas.  With clear skies
and less wind, overnight temperatures will range from the low 40s to
the low 50s.

Sunday is shaping up to be the pick of the weekend as rising heights
and high pressure builds in.  Mid-level flow turns more westerly and
850temps begin to warm Sunday.  With sunny skies under subsidence
aloft, high temperatures will rise into the upper 60s to low 70s.
Still a bit breezy, as surface winds remain NW at 10-20mph.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Key Points:

* Dry and warmer Monday and Tuesday with above normal temps
  continuing through the week

* Unsettled pattern with increasing humidity developing Wed to Fri
  with chance of showers at times but a washout not expected.

Details...

Sunday night into Tuesday...

High pres builds into New Eng Sun night with clear skies and light
winds leading to excellent radiational cooling conditions. It will
be a chilly night with potential for lows to drop into the mid 30s
with a touch of frost in the colder radiators, with low-mid 40s
elsewhere.

The high pres over New Eng will slide offshore Mon and Tue as mid
level ridge builds into the region. Dry weather both days with most
sunshine on Monday then we may some increasing mid-high clouds Tue
from the SW. Warming temps aloft will result in above normal temps
into the 70s, but SW flow should keep temps in the 60s along the
south coast.

Wednesday through Friday:

As we head into the mid to late week period the mid level ridge
breaks down as slow moving upper trough approaches from the Ohio
valley. Not expecting any periods of strong forcing but a plume of
higher PWATs approaching 1.5 inches and weakness in the mid level
flow should bring a risk of showers at times. Specific details and
timing is uncertain but not expecting any washouts and there should
be dry periods as well. GEFS and EPS ensembles indicating moderate
to high probs of highs in the 70s, and GEFS even showing some lower
probs of 80+ Thu and Fri, but this is low confidence given
uncertainty in extent of cloud cover and timing of any showers. A
persistent onshore flow will bring increasing humidity as dewpoints
eventually climb into the 60s.

&&

.AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

12z TAF Update:

Today: High Confidence.

IFR conditions improving to MVFR from west to east this morning.
Rain will end from south to north this morning, with lingering
showers along the east coast through about 17z. Winds
transition to NW today with gusts 20-25 kts. Conditions improve
toward VFR generally from west to east in the mid morning to
early afternoon.

Saturday night: High Confidence.

VFR. W winds 5-10 kts.

Sunday: High Confidence

VFR. NW winds gusting 15-20 knots

KBOS TAF...High confidence.

IFR/MVFR this morning with off and on rain showers through
about 17z. MVFR/VFR after 17z today with westerly winds gusting
to 25 knots.

KBDL TAF...High confidence.

MVFR/VFR this morning, improving to VFR my late morning. WNW
Winds gust up to 25 knots this afternoon.

Outlook /Sunday Night through Wednesday/...

Sunday Night: VFR.

Monday: VFR. Breezy.

Monday Night through Tuesday: VFR.

Tuesday Night: Mainly VFR, with local MVFR possible.

Wednesday: Mainly VFR, with local IFR possible. Slight chance
SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Saturday and Saturday night: High Confidence.

W winds 15-25 kts with gusts to 30 kts on the outer southern
waters during the afternoon. Winds diminish overnight. Seas 2-5
ft during the day, diminishing to 2-4 ft by Saturday night.

Sunday: High Confidence.

NW winds at 10-10 knots. Seas continue to diminish to 1-3 feet.

Outlook /Sunday Night through Wednesday/...

Sunday Night through Tuesday Night: Winds less than 25 kt.

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 11 AM this morning to 8 PM EDT this
     evening for ANZ230-231-236-251.
     Small Craft Advisory until 8 PM EDT this evening for
     ANZ232>235-237.
     Small Craft Advisory until 11 PM EDT this evening for ANZ250-
     254>256.

&&

SYNOPSIS...KJC/KP
NEAR TERM...KP
SHORT TERM...KP
LONG TERM...KJC
AVIATION...KP
MARINE...KJC/KP