Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 150546
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
146 AM EDT Sat Aug 15 2020

.SYNOPSIS...
A touch of fall arrives this weekend with temperatures only in
the 70s and a gusty northeast wind, as high pressure builds
across the Canadian Maritimes and low pressure tracks south of
New England. Low pressure may bring a few light showers to
eastern MA and RI, especially Saturday and Saturday night.
Another low will likely track too far south of New England
Sunday for much if any rain to occur here in southern New
England. Temperatures should recover to seasonable levels by
Tuesday and persist at those levels into Thursday with mainly
dry weather.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...

140 AM Update:

No major changes to the forecast as previous forecast remains on
track on a relatively quiet night of weather.

PREVIOUS DISCUSSION...

1020 PM Update:

A beautiful evening is in progress with comfortable temperatures
and humidity. Overnight temperatures fall into the low to mid
60s away from the immediate coast. The second half of the night
will feature increasing low to mid-level clouds associated with
an uptick in northeast flow for Eastern MA and RI. Winds could
gust over 25 mph by daybreak along the Eastern MA coast.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/...
*** Touch of fall this weekend with highs only in the 70s and
 accompanied by a gusty northeast wind especially Saturday ***

*** High Surf Advisories remain in effect for most eastern MA
 beaches on Saturday ***

Saturday:

Rex block pattern supports chilly 1025 mb high pressure over the
maritimes while low pressure tracks southeast of the 40N/70W
benchmark. Robust low level northeast jet up to 30 kt at 925 mb
will yield G35 mph at times per model soundings across eastern
MA and RI. Not your typical mid August day for southern New
England with broken to overcast strato-cu clouds and spotty
light showers/drizzle from this low level jet. Temps will only
rise into the 70s but will feel cooler given the gusty NE winds
especially in coastal eastern MA with wind off the ocean. Hence
a touch of fall tomorrow so get those sweatshirts ready.

Airmass modifies westward (925 mb temps only +13C to +14C in
eastern MA) with highs closer to 80 in Hartford and Springfield
along with more breaks of sunshine.

The strong onshore winds combined with the long fetch associated
with NE winds will result in building seas of 5-10 ft. This will
yield rough surf and strong rips especially along the eastern MA
coastline from the MA/NH border thru Cape Cod and Nantucket.
Thus high surf advisories remain in effect.

Saturday night:

Low pres over Georges Bank exits out to sea and Maritime high
begins to build over southern New England. With low level jet
easing may see a slight decreasing trend in clouds and
drizzle/showers as the night progresses. Cool temps with lows in
the upper 50s and lower 60s along with winds easing with time.

&&

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

* Early taste of fall Sunday/Monday with highs in the 70s. Isolated
  chance for showers with an easterly wind flow.

* Strong rip currents and large waves at the beach.

* Seasonable summer conditions return mid next week with highs in
  the 80s and mainly dry conditions.

Sunday...

Second half of the weekend remains rather tricky. Models
indicate a secondary low pressure system will move off the
coast of the mid Atlantic and travel south of southern New
England late Sunday morning. Majority of models do keep the
center far enough south and that would continue our dry stretch
of weather. But, the 12z GFS brings the low further north, which
would provide southern Rhode Island, southeast Massachusetts,
the Cape and Island with a chance for showers. PWAT values
generally aren`t overly impressive, but modest around 1.25" and
1.50" for Sunday afternoon.

Additionally, temperatures are expected to remain below average. A
northeast to easterly wind will suppress afternoon temperatures
in the low and middle 70s. Coolest locations will be near the
eastern shore of Massachusetts, the Cape and Island.

Finally, the `High Surf Advisory` might need to be extended from
Saturday into Sunday for the eastern shore of Massachusetts, Cape
Cod, and the Islands.

Monday through Tuesday...

For the most part a mainly dry and once again cool day. The onshore
flow will allow temperature to remain in the 70s for the majority of
us. Coastal Massachusetts and Rhode Island are in the low to
middle 70s with the CT Valley reaching the low 80s.

A cold front will move from west to east across southern New England
early in the day on Tuesday which brings in the chance for morning
showers and a drier/warmer afternoon. The wind direction
transitions from an easterly [off the water flow] to a westerly
flow. This will help bounce temperatures back into the low 80s.

Wednesday through Friday...

A quiet stretch of quiet and mainly dry weather with an area of high
pressure moves into place. Temperatures will bounce back to the
low and middle 80s to round out the week. Outside of a handful
afternoon pop up showers we will remain dry yet again.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

0530z TAF Update:

Rest of tonight: High confidence in trends, moderate on timing.

VFR for most terminals except ACK through 10z, with NE winds
5-10 kt. Timing of MVFR stratus with localized IFR should become
more widespread eastern MA/RI by 12z. Have high confidence in
trend but only moderate on timing as it could differ by a couple
of hours. As stratus gets going, look for NE winds to increase,
gusting up to 20 kt for Cape and Island terminals by 12z.

Saturday: Moderate confidence.

Eastern MA/RI terminals should see deterioration to IFR to MVFR
ceilings by late morning. Interior MA/CT terminals should
remain mostly VFR. Slight chance for showers across eastern MA
but main concern is strong NE winds 15-20 kt, with up to 25 kt
winds and 30 kt gusts possible on the outer-Cape and Nantucket
terminal.

Saturday night: moderate confidence.

NE winds slowly ease but MVFR/IFR persist over eastern MA with
MVFR-VFR elsewhere. Spotty light rain showers possible eastern
MA.

KBOS Terminal...High confidence in TAF. Stratus possible as soon
as 09z, more likely around/after 11z.

KBDL Terminal...High confidence in TAF.

Outlook /Sunday Night through Wednesday/...

Sunday through Sunday Night: Mainly MVFR, with local IFR
possible. Breezy. Chance SHRA.

Monday: Mainly MVFR, with areas VFR possible. Breezy. Chance
SHRA.

Monday Night: Mainly VFR, with areas MVFR possible. Breezy.
Chance SHRA.

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

&&

.MARINE...
Tonight...light NE winds this evening increasing 15-25 kt by
daybreak as low pressure tracks southeast of the 40N/70W
benchmark. Dry weather and good vsby.

Saturday...NE winds 20-30 kt as low pressure tracks across
southeast Georges Bank. Low clouds, scattered showers/drizzle
may limit vsby at times. Long NE fetch will build seas up to 10
ft. Dangerous wind and seas for small recreational boaters.

Saturday night...Georges Bank low exits out to sea with winds
and seas slowly easing. Evening drizzle/scattered showers
diminish overnight.

Outlook /Sunday Night through Wednesday/...

Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Areas of rough seas. Chance of rain showers.

Sunday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas. Chance of rain showers.

Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Chance of rain showers.

Monday Night: Winds less than 25 kt. Areas of rough seas.
Chance of rain showers.

Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Surf Advisory from 8 AM this morning to 8 PM EDT this
     evening for MAZ007-019-022>024.
RI...High Surf Advisory from 8 AM this morning to 8 PM EDT this
     evening for RIZ008.
MARINE...Small Craft Advisory until 8 AM EDT Sunday for ANZ231>235-237-
     250-251-254>256.
     Small Craft Advisory from 7 AM this morning to 10 PM EDT this
     evening for ANZ230-236.

&&

$$
SYNOPSIS...Nocera/Loconto/Gaucher
NEAR TERM...Nocera/Loconto/Chai
SHORT TERM...Nocera
LONG TERM...Loconto/Gaucher
AVIATION...Nocera/Loconto/Chai
MARINE...Nocera/Loconto


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