Lexington Weather

Lexington, Massachusetts, USA

45°F
9/19/2020 8:30am 
  • Lexington Conditions: Clear
  • Temperature: 45.0°F / 7.2°CWarmer 2.0°F than last hour.
  • Dew Point: 36.5°FIncreased 1.3°Fsince last hour.
  • Relative Humidity: 72%Decreased 2.0% since last hour.
  • Wind: Wind from WNW WNW 1 mph, 10-min avg: 1 mph, gust: 2 mph
  • Barometer: 30.26 inRising 0.03  inHg/hr Rising Slowly
  • Visibility: 10 miles
  • Rain Today: 0.00 in
  •   
Southeast Middlesex County - Special Weather Statement
 - SEE ALL NEARBY ALERTS -

Area Forecast Discussion
for Boston, MA

        
000
FXUS61 KBOX 191127
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
727 AM EDT Sat Sep 19 2020

.SYNOPSIS...
Unseasonably cool and dry conditions persist into early next 
week. Hurricane Teddy will lift north and pass well east of our
region Monday into Tuesday before moving into the Canadian
Maritimes. The only impacts for southern New England will be 
high surf and pockets of minor coastal flooding/beach erosion, 
but dry weather will persist. Temperatures moderate to near or 
above normal level for the middle and end of next week. The 
other main story will be the continuation of prolonged dry 
weather through most if not the entire week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

725 AM Update...

* Chilly day despite plentiful sunshine.

* High Surf Advisory posted for most coastlines through Monday. 

After a chilly night with first frost of the season for some, 
an unseasonably cool day is in store. It will be less windy 
than on Friday though, as surface high pressure moves overhead. 
850mb temperatures fall to between -1C and +1C, which will only 
support highs mainly in the lower to middle 60s despite 
plentiful sunshine.

&&

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

Tonight:

* Freeze headlines likely needed for the East Slopes of the 
  Berkshires tonight. Frost headlines elsewhere away from the 
  immediate coast. 

Surface high pressure moving overhead combined with dew points 
falling into the 20s will make for the coldest night of the season 
so far. A combination of a very dry air mass (PWATs less than 0.25 
inches) and winds decoupling will allow temperatures to fall into 
the upper 20s to low 30s for the usual cold spots and mid to upper 
30s elsewhere except for 40s on the immediate coast. Record minimum 
daily lows could be challenged. See the Climate section for more 
details. Note that it will remain breezy along the coast throughout 
the night due to pressure difference between a 1035mb high over 
Quebec and Hurricane Teddy approaching Bermuda. 

Sunday:

* Chilly day with many locations not getting out of the 50s on the 
  last full day of astronomical summer. 

As surface flow turns northeast, the large temperature difference 
between the top of the boundary layer (+2C at 925mb) and the SST 
(around +18C near Massachusetts Bay) will help with vertical mixing 
and development of ocean-effect clouds over parts of Eastern MA and 
RI. How far inland the clouds spill inland remains to be refined but 
we have high confidence in widespread highs in the mid to upper 50s, 
which are more typical for late October! In other words, a real shot 
of fall for the last full day of astronomical summer. Normal highs 
for mid September are in the low to mid 70s. See the Climate section 
for the record minimum highs that could be challenged.

&&

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

Highlights...

* Hurricane Teddy passes well to our east Mon into Tue limiting
  impacts to high surf & minor coastal flooding/beach erosion

* Below normal temperatures to start off the week moderate to 
  near or above normal levels by the middle to end of the week

* Prolonged period of dry weather will continue through at most
  if not all of next week

Details...

Monday and Tuesday...

The main focus Mon into Tue will be Hurricane Teddy that will
pass well east of southern New England. Model consensus
continues to favor the track too far east to bring any rainfall
to southern New England. Low risk that a few showers briefly
back onto the coast, but even if this were to any rainfall would
be light and short-lived. Strong high pressure centered over
northern New England will bring persistent gusty NNE winds 
along the coast and especially the Cape/Islands. The result will
be continued high surf and pockets of minor coastal 
flooding/beach erosion during the times of high tide through
Tuesday. Please see that specific section for more details.

We probably will be dealing with more frost/freeze conditions in
the normally coolest outlying locations Sun night. High temps on
Mon will be mainly be in the lower to middle 60s, but parts of
the immediate coast may struggle to reach 60. High temperatures
should modify into the middle to upper 60s by Tue.

Wednesday through Friday...

Hurricane Teddy will have lifted into the Canadian Maritimes by
the middle of next week. The result will be more of a westerly
flow of air aloft and at the surface, allowing for moderating
temperatures. Highs should be well into the 70s and perhaps near
or above 80 in some locations Thu and Fri depending on the
timing of our next cold front. 

Besides temps moderating to near or above normal thresholds over
this time, the main story will be the continuation of prolonged
dry weather. Perhaps a few brief showers sometime Thu night/Fri
with a cold front, but even if that occurs instability/forcing 
appears quite limited so any rainfall would probably be short-
live and rather light.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

12Z TAF Update...

Today: High confidence.

VFR conditions. N winds 10 to 15 kts for interior terminals 
with gusts 15 to 20 kts. NNE winds 10 to 20 kts with gusts up 
to 30 knots for the southeast New England coast and perhaps
near 35 knots for ACK.

Tonight: High confidence.

VFR conditions. Light N winds across the interior, but gusts of
N-NE wind gusts of 20 to 25 knots will persist across the Cape
and Islands.

Sunday: High confidence.

VFR conditions for mos interior terminals. MVFR to low VFR 
conditions develop after 15z due to development of ocean-effect 
clouds for the Cape terminals, and possibly as far north as BOS and 
as far west as PVD. N winds turning NE at 5 to 10 kts for interior 
terminals and NE winds 15 to 20 kts with gusts up 25 to 35 kts for 
coastal terminals. 

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF. 
 

Outlook /Sunday Night through Wednesday/... 

Sunday Night: VFR. Windy with local gusts up to 30 kt along the
southeast New England coast.

Monday through Tuesday: VFR. Windy with gusts up to 35 kt across
the southeast New England coast.


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

Wednesday: VFR. Breezy.

&&

.MARINE...
Gale Warnings continue through this afternoon for the waters of Cape 
Cod and the Islands. Small Craft Advisories continue for all other 
waters for the entire weekend due to gusty NNE winds of up to 30 kts 
and rough seas of 6 to 10 ft. There could be a brief period late 
tonight and early Sunday when conditions drop below Small Craft 
criteria as post TC Sally departs and Hurricane Teddy moves north 
but expect rough seas and gusty winds for much of the weekend. 

Outlook /Sunday Night through Wednesday/...

* Distant Hurricane Teddy may still bring dangerously high seas
  and Gale Force Wind Gusts Mon into Tue

The main concern will be Hurricane Teddy passing well east of
our waters Mon into Tue. Nonetheless, very high seas on the
order of 12 to 17 feet will likely develop across our eastern
waters along with a period of Northerly Gale Force Wind gusts.

&&

.FIRE WEATHER...
* A Special Weather Statement is in effect for elevated fire weather 
  potential this weekend. 

With minimum RH falling to between 20 to 35 percent for many 
locations away from the immediate coast, as well as gusty northerly 
winds, there will be elevated fire weather potential today. The 
potential is exacerbated by the prolonged dry weather across 
southern New England.

&&

.TIDES/COASTAL FLOODING...
Large high pressure over eastern Canada/northern New England 
will generate gusty NE winds and rough seas across our waters
this weekend. 

This high pressure system will then combined with Hurricane
Teddy passing well east of our region Monday and Tuesday. The
end result will be for continued gusty N-NE winds and offshore
seas building to between 12 and 17 feet across our eastern
waters.

Given this setup we have issued a High Surf Advisory through
Monday for ocean exposed beaches. This will likely need to be
extended into Tuesday with later forecasts. High surf/Dangerous
rip currents are anticipated.

In addition, we are in a period of high astronomical tides into
early next week generally between 11.6 and 11.8 MLLW in Boston.
This coupled with persistent gusty NE winds and high seas will
lead to pockets of minor coastal flooding/beach erosion. We
opted to issue a Coastal Flood Statement for today/s midday high
tide mainly for some minor splash over along the eastern MA
coast. We think Sun and especially Mon/Tue have a greater risk 
for pockets of minor coastal flooding/beach erosion during the 
high tide cycle given very high sea offshore. We could see a 0.5
to 1.5 feet of storm surge with a low risk for up to 2 feet on 
Tue depending on the timing of the strongest winds. Coastal 
Flood Advisories will likely be needed, but fortunately 
significant coastal flooding is not expected.

&&

.CLIMATE...

Daily record minimum highs could be challenged on Saturday, Sep 19 
and Sunday, Sep 20. 

Sep 19:

BOS 49F (1938) 
BDL 57F (1981) 
ORH 54F (1987) 
PVD 57F (1913)

Sep 20:

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

Daily record minimum lows could also be challenged on Sunday, Sep 
20. 

BOS 42F (1979) 
BDL 30F (1979) 
ORH 29F (1941) 
PVD 38F (1979)

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Surf Advisory until 8 PM EDT Monday for MAZ007-019-020-
     022>024. RI...High Surf Advisory until 8 PM EDT Monday for RIZ006>008.
MARINE...Gale Warning until 4 PM EDT this afternoon for ANZ232-254-255.
     Small Craft Advisory until 8 PM EDT Sunday for ANZ231-233>235-
     237-250-251-256.

&&

$$
SYNOPSIS...Chai/Frank
NEAR TERM...Frank/Chai
SHORT TERM...Chai
LONG TERM...Frank
AVIATION...Chai/Frank
MARINE...Chai/Frank
FIRE WEATHER...Chai
TIDES/COASTAL FLOODING...Frank
CLIMATE...Chai
      

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