Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 040843
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
443 AM EDT Sat Apr 4 2020

.SYNOPSIS...

As the large ocean storm continues to move farther offshore,
diminishing wind and gradual improving conditions are expected
today. A weak weather system and front will bring a few
showers Sunday afternoon and night. High pressure will bring
mainly dry conditions and mild temperatures Monday into
Tuesday. Unsettled conditions will linger from the middle to
latter portion of the week as a few weak, fast moving weather
systems cross the region.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Showers confined to eastern MA within the axis of the low level
jet, with northern edge gradually pushing south as mid level
drying overspreads the region. Showers will slowly diminish but
but may linger into the morning, mainly across SE MA closest to
the departing low level jet which moves to the south.

Otherwise, mid level ridge builds south across New Eng as the
ocean storm moves offshore with very dry air above 700 mb. Some
sunshine expected to develop in the CT valley and western MA
this afternoon, but plenty of moisture below 850 mb will likely
keep lower clouds across much of the eastern half of SNE today.

Gusty NE winds 25-35 mph along the coast this morning will
diminish in the afternoon. High will range from low/mid 40s east
coastal MA to low/mid 50s CT valley where some sunshine expected
to develop.

See coastal flooding section below for details regarding
potential for minor coastal flooding along east coastal MA
during this morning`s high tide.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Tonight...

Weak high pres over the region tonight. But enough low level
moisture along with increasing mid level moisture moving in from
the west ahead of a shortwave will result in partly to mostly
cloudy skies. Lows will range through the 30s.

Sunday...

The mid level shortwave will move over the ridge and into the
New Eng Sun afternoon with the attendant weak cold front
approaching from the west. Lots of low and mid level moisture
present will result in mostly cloudy skies with a bit of
sunshine possible across SE New Eng. Bulk of the shortwave
energy will remain to the north where best chance of showers,
but can`t rule out a few showers spilling into interior MA and
western CT in the afternoon. Developing S/SW flow will bring
milder temps into SNE, with highs in the 50s to around 60 in
the CT valley, but holding in the 40s Cape/Islands.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...

Highlights...

* A weak disturbance and approaching cold front bring scattered
  light showers Sunday into Sunday night

* Expect dry and mild conditions Monday into Tuesday as high
  pressure pushes across

* Several weak weather systems will bring scattered
  precipitation at times from Wednesday into Friday

Details...

Sunday night...

As the mid level steering pattern becomes nearly zonal across
the northern tier states by Sunday night, will see a weak short
wave in this flow will push across. Will see scattered light
rain or showers move across with a fast moving, weak cold front
through the night. With the fast movement of this system, expect
very light QPF amounts.

The last of the precipitation should push offshore during the
pre dawn hours. SW winds will shift to W-NW, running at around 5
to 10 mph.

Monday through Tuesday...

A large high pres ridge, extending from eastern Canada
southwest to the Appalachians into the interior SE U.S., will
see dry conditions and light NW winds during the day Monday. The
NW flow will take over aloft as well, bringing a deep dry layer
across along with the subsidence thanks to the high pressure.

With nearly full sunshine for at least part of the day, along
with H925 temps rising to +5C to +7C and offshore winds, should
see surface temps reach the lower-mid 60s across the coastal
plain and into the CT valley. Readings will remain cooler along
the immediate coast and across the higher terrain.

The mid level ridge building from the western Great Lakes
northward across Hudson Bay to the Arctic Circle will keep dry
conditions and mild temperatures Monday night into Tuesday as H5
heights rise to around 550 to 555 dm. Skies will start off
partly cloudy Monday, but mid and high clouds will push across
the region overnight and will linger through Tuesday. Temps will
remain mild overnight, with lows ranging from 35 to 40, coolest
across the N central and W Mass hills.

Will start to see band of low level moisture push SE out of NW
Canada into the Great Lakes and mid Atlc states during Tuesday,
but the high pressure ridge across Quebec into the northeast
will keep dry conditions in place. Light westerly winds will
also bring mild temps, though a tad cooler with the high clouds
streaming across. Highs will mainly be in the 50s, though could
touch 60 in some spots across interior E Mass as well as the CT
valley on Tuesday.

Tuesday night through Friday...

Confidence lowers during this timeframe with the continued
progressive mid level steering flow continues, with widening
model solution spread amongst the model members.

At this point, should see several weak systems cross the
region, bringing scattered showers at times. However, exact
timing and track of each wave as they cross the region still in
question. May see the first low pass close to or S of the region
sometime on Wed, while a second system may push across later
Thu into Friday. With clouds and the potential for precip each
day, should see temps run close to or a bit below seasonal
levels.

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

Through Today...Moderate confidence.
Widespread MVFR/IFR through the morning, then gradual
improvement in the afternoon with cigs lifting to VFR in the CT
valley. MVFR cigs lingering in eastern New Eng. Showers across
eastern and SE MA into the morning, then dry in the afternoon.
NE gusts 25-35 kt near the coast, diminishing in the afternoon.

Tonight and Sunday...High confidence.
Mix of MVFR/VFR cigs. Light winds tonight, becoming S/SW near 10
kt during Sun. Local sea breezes developing.

KBOS Terminal...Moderate confidence in TAF.

KBDL Terminal...Moderate confidence in TAF.

Outlook /Sunday Night through Wednesday/...

Sunday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA.

Monday: VFR. Breezy.

Monday Night through Tuesday: VFR.

Tuesday Night: Mainly VFR, with local MVFR possible. Breezy.
Slight chance SHRA.

Wednesday: Mainly VFR, with local IFR possible. Breezy. Chance
SHRA.

&&

.MARINE...

Today...
Winds will gradually diminish through the day as the low level
jet weakens and moves to the south. Winds will drop below gale
force from N to S this morning and below 20 kt by evening. Very
rough seas gradually subsiding.

Tonight...
Light winds but large easterly swell impacts the eastern MA
waters.

Sunday...
Winds turn southerly with speeds below 15 kt. Easterly swell and
rough seas continue over eastern MA waters.

Outlook /Sunday Night through Wednesday/...

Sunday Night: Winds less than 25 kt. Areas of rough seas.
Slight chance of rain showers.

Monday: Winds less than 25 kt. Local rough seas.

Monday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers.

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

Tuesday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers.

Wednesday: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers.

&&

.TIDES/COASTAL FLOODING...

Coastal Flood Advisories issued for east coastal MA and
Nantucket for the morning high tide today which occurs 830-930
AM. Current storm surge at low tide around 2.5 to 2.8 ft but the
surge expected to decrease to around 2 ft during high tide.
Expected storm tide at Boston will be around 12.2 ft (FS 12.5
ft), and around 5.5 ft at Nantucket (FS 5 ft).

Seas 14-17 ft still present over the eastern MA waters and
while they are diminishing, expect 12-15 ft seas at high tide.
These are long period waves with E/NE swell directed toward the
coast. The elevated storm tide combined with the wave energy
will be sufficient for areas of minor coastal flooding along
east coastal MA and Nantucket. Lower confidence for coastal
flooding along Cape Cod Bay as waves here around 6 ft which may
not be enough for much more than splash over.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Coastal Flood Advisory until 10 AM EDT this morning for MAZ007-
     015-016-019-022.
     Coastal Flood Advisory from 8 AM to 11 AM EDT this morning for
     MAZ024.
RI...None.
MARINE...Gale Warning until 10 AM EDT this morning for ANZ232-256.
     Gale Warning until 8 AM EDT this morning for ANZ231-233>235-
     237-250-251.
     Small Craft Advisory until 2 PM EDT this afternoon for ANZ230.
     Small Craft Advisory until 3 PM EDT this afternoon for ANZ236.
     Gale Warning until noon EDT today for ANZ254-255.

&&

$$
SYNOPSIS...KJC/EVT
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...EVT
AVIATION...KJC/EVT
MARINE...KJC/EVT
TIDES/COASTAL FLOODING...KJC


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