Area Forecast Discussion
National Weather Service Boston/Norton MA
426 AM EDT Sun Sep 20 2020

.SYNOPSIS...
Cooler than normal and dry weather persists into early next 
week. Hurricane Teddy will pass nearly 400 miles east of our 
coastline on Tuesday as it heads north into the Canadian 
Maritimes. While we will remain dry, it will bring a period of 
windy conditions along the coast, especially Cape Cod and 
Nantucket. Minor coastal flooding and some beach erosion may 
also occur during the Tuesday afternoon high tide. Otherwise, 
the prolonged period of dry weather continues right through the 
upcoming week. Temperatures will moderate to above normal levels
by Wednesday and that will continue for the rest of the week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
415 AM update...

* Freeze Warnings and Frost Advisories continue for much of
  southern New England until 8 AM this morning. 
* Near record cold temperatures this afternoon...
* Freeze/Frost Advisories will likely be needed again for 
  tonight...
* Some splashover possible along the MA east coast at high tide

Strong high pressure over southern Quebec/northern New York/and
northern New England will provide a mainly sunny but chilly day
today here in southern New England. Just some mid and high level
cloudiness floating through as an upper level trough moves
through. A few ocean-effect stratocumulus clouds formed
overnight and were affecting portions of Cape Cod and the islands.
These should move south and/or dissipate by mid morning.

Winds will be from the north to northeast and become rather gusty
...from 15 to 25 mph along the east and southeast coast of MA. 
Gusts from 25-30 mph are possible over Nantucket. It will be
quite chilly today, with 850 mb temps of only 0C to -1C. The
record low maximum temperature for Boston is 58 degrees set back
in 1960...and this could be matched or broken. Highs will 
generally be in the mid to upper 50s, but anticipate lower 60s
in the CT River valley, Merrimack valley, RI, and the islands.

The astronomical tide is forecast to be 11.7 ft MLLW at Boston
this afternoon, which is high, but a surge of only 0.3 ft is
anticipated. This may cause some splashover at the usual places,
but felt that it would not be widespread or significant enough 
to warrant a Coastal Flood Statement.

A High Surf Advisory is in effect along the MA and RI coasts.

There remains an elevated fire weather potential due to the
persistent dry weather and somewhat gusty winds, especially in
southeastern areas.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Tonight and Monday...

High pressure over northern New England tonight retreats
westward into New York State Monday. The result is more of the
same weather. Dry, mainly clear conditions. That sets the stage
for good radiational cooling tonight. Additional freeze and
frost warnings will be needed again, in roughly the same region. 
We will assess which zones already received a freeze tonight
before issuing the warnings/advisories. We are forecasting lows
ranging from 30-33 in western MA...to the mid and upper 30s
elsewhere, except 40 to 45 in Boston, Providence, Cape Cod, and 
Nantucket. Monday will be a few degrees warmer...with highs
mainly from 60-65, but still a little below normal. Northeast
winds will be gusty again along the east and south coasts, with
up to 30 mph possible on Nantucket.

High Surf Advisory remains posted through the period.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...

Highlights...

* Hurricane Teddy passes well to our east Tue keeping us dry, but 
  bringing windy weather at the coast especially Cape/Nantucket

* Minor coastal flooding/beach erosion likely during the Tue 
  afternoon high tide along the eastern MA coast & Cape/Nantucket

* Above normal temperatures return Wed and persist through the end of 
  this week

* Prolonged dry weather continues with little if any rainfall 
  expected for the entire week

Details...

Monday night...

High pressure in control will result in one more chilly night across 
the region. Low temps will be down into the 30s to the lower 40s in 
many locations with frost again likely in the normally cooler 
outlying locations. Temperatures may begin to rise toward morning 
across the Cape/Islands as winds pick up given increasing 
pressure gradient from Hurricane Teddy.

Tuesday...

Hurricane Teddy will be passing nearly 400 miles east of our 
coastline on Tue as it heads towards the Canadian Maritimes. Teddy 
will pass too far to the east of southern New England to bring any 
rain. That being said, a high pressure system centered over northern 
New England combined with Teddy will result in a windy day along the 
coast. This is especially true across parts of the Cape/Nantucket, 
where a period of northerly wind gusts of 40 to 50 mph are possible. 
Elsewhere, it will not be as windy although still breezy with 20 to 
30 mph wind gusts likely. High temperatures should recover into the 
65 to 70 degree with plenty of sunshine.

High Surf along with minor coastal flooding/beach erosion are 
anticipated during the Tuesday afternoon high tide cycle. Please see 
our Tides/Coastal Flood Section for more information.

Wednesday through Saturday...

Hurricane Teddy will lift into the Canadian Maritimes on Wednesday. 
The result will be more of a milder westerly flow of air aloft and 
at the surface. The EPS/GEFS are in agreement in above normal 2 
meter temperature anomalies for the second half of the week. 
Therefore, we expect above normal temperatures to return Wednesday 
and persist through the end of the week. High temperatures should 
reach well into the 70s and depending on the amount of solar 
insolation/timing we could be 80+ for a day or two in some locations.

The other main story will be the continued prolonged stretch of dry 
weather. Little if any rain is expected this entire week. We may see 
a few brief showers Thu night/Fri with a weak cold front, but 
moisture/instability is lacking. Therefore, any rainfall we see 
would be short-lived and light.

&&

.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

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

0815Z update...

Today...High confidence.

VFR. A few clouds around 4000-6000 ft through mid morning over
Cape Cod and the islands. NNE winds gusting to 20-25 kt along
the coast, with up to 30 kt gusts possible over outer Cape Cod
and Nantucket.

Tonight and Monday...High confidence.

VFR with clear skies and light winds across the interior. Will
remain gusty across Cape Cod and the Islands, with winds out of
the NE with speeds of 15-20 kts and gusts of 25-30 kts.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF. 
 
Outlook /Monday Night through Thursday/... 

Monday Night: VFR. Windy with local gusts up to 30 kt. 

Tuesday: VFR. Strong winds with gusts up to 45 kt. 

Tuesday Night: VFR. Strong winds with areas of gusts up to
45 kt. 

Wednesday through Thursday: VFR. Breezy. 

&&

.MARINE...
415 AM update...

*Small Craft Advisories continue through Monday night...

A very rough period is in store for the marine community.
Mariners should pay close attention to the forecast.
Rough seas from 5 to 9 ft will persist on NE winds today, which
will gust up to 20-30 kt today, highest in southeastern waters.
By tonight, seas build to 8 to 10 ft over the outer waters.
The seas will be 5 to 6 ft at the entrance to Boston Harbor and
at the entrance to Narragansett Bay. The same is true for
Monday, with slightly higher seas...up to 10 to 12 ft southeast
of Nantucket. Seas will then build further, as mentioned below.

Outlook /Monday Night through Thursday/...

* Distant Hurricane Teddy will bring dangerously high seas & strong 
  northerly wind gusts across our eastern MA coastal waters Tue

Hurricane Teddy will be passing nearly 400 miles east of our 
coastline on Tue. Nonetheless, very high seas on the order of 12 to 
18 feet will likely develop across our eastern waters along with a 
period of Northerly Gale Force Wind gusts of 35 to 45 knots. There 
is even a low probability for 50 knot gusts east of the Provincetown 
to Nantucket areas. We continue with a Marine Weather Statement to 
highlight this concern for Mariners, especially those headed east 
into the open Atlantic.

Winds and seas diminish Wed with further improvement on Thu as a 
ridge of high pressure builds south of the waters.

&&

.FIRE WEATHER...
We continue with the special weather statement today at the request 
of our fire weather partners. The unusually prolonged stretch of dry 
weather continues and minimum RH values will drop to between 25 and 
35 percent across much of the region this afternoon. It will be a 
bit gusty near the coastline too.

While Monday may have similar conditions as today, there are 
even greater fire weather concerns on Tue. Distant Hurricane 
Teddy should generate 20 to 30 mph wind gusts over most areas
but up to 40 to 50 mph for Cape Cod and Nantucket. Something we
will have to watch, with low afternoon RH values.

&&

.TIDES/COASTAL FLOODING...
High astronomical MLLW tides of 11.7 ft this afternoon and 11.6 feet 
on Monday afternoon may result in some nuisance splashover/beach 
erosion along the eastern MA coast given gusty NE winds.

There is more concern on Tuesday as distant Hurricane Teddy results 
in some pressure falls and the potential for northerly wind 
gusts of 40 to 50 mph across the Cape/Nantucket. This combined 
with highs seas offshore may result in pockets of minor coastal 
flooding along the eastern MA coast. This is especially true on 
the north facing coastline across Cape Cod Bay and Nantucket 
Sound given the wind trajectory and the potential for a 1-2 foot
storm surge. While we are not expecting a significant coastal 
flood event, inundation on vulnerable shoreline roadways may 
occur within a few hours of the high tide along with beach 
erosion. This will likely require the eventual need for a 
Coastal Flood Advisory for Tuesday.

&&

.CLIMATE...
Sun, Sep 20...Current record daily coldest high temperatures 
and year.

BOS 58F (1960) 
BDL 58F (1982) 
ORH 53F (1987) 
PVD 56F (1972)

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Frost Advisory until 8 AM EDT this morning for CTZ002>004.
MA...High Surf Advisory until 8 PM EDT Tuesday for MAZ007-019-020-
     022>024.
     Frost Advisory until 8 AM EDT this morning for MAZ005-006-012-
     013-017-018-026.
     Freeze Warning until 8 AM EDT this morning for MAZ002>004-
     008>011.
RI...High Surf Advisory until 8 PM EDT Tuesday for RIZ006>008.
     Frost Advisory until 8 AM EDT this morning for RIZ001.
MARINE...Small Craft Advisory until 6 AM EDT Tuesday for ANZ231>235-237-
     250-251-254>256.

&&