Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 172340
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
740 PM EDT Sun Oct 17 2021

.SYNOPSIS...

Blustery and cool weather continues Monday and Tuesday. Dry 
weather generally persists Wednesday into Thursday with 
unseasonably mild temperatures returning. A cold front may bring
a few brief showers Thursday night and/or Friday, but a washout
is not expected. Behind the cold front; a rather cool airmass 
with below normal temperatures will move into the region for 
next weekend.

&&

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

735 PM Update:

Isolated diurnally driven showers across the interior were
dissipating early this evening with the loss of daytime heating.
We still can not rule out a brief spot shower or two overnight,
but generally expect dry weather with scattered clouds at times.
Previous forecast captures this well.

Low pressure over Nova Scotia and high pressure centered over the 
Ohio River valley has southern New England beneath a region of deep 
northwest flow. Deep northwest flow pattern will continue to 
advect cooler air over the region tonight. Overnight low 
temperatures will be chilly but seasonable for this time of 
year. We probably won't see any significant radiational cooling
as the elevated wind speeds will likely produce just enough 
mechanical mixing overnight. Additionally some moisture 
streaming in from The Great Lakes region will support areas of 
scattered clouds. Expecting low temperatures in the low-mid 40s
across the interior with temperatures staying a bit warmer 
along the coast in the middle 40s - to the lower 50s.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...

Short Term 

* Breezy northwest winds Monday
* Seasonable high/low temperatures

Monday

Deep northwest flow pattern continues with surface high pressure 
nosing in from the south west tomorrow afternoon. CAA aloft brings 
temperatures at 850 hPa below 0. Thus, diurnal mixing to 850 hPa 
tomorrow afternoon will only support high temperatures in the mid-
upper 50s for much of southern New England. Deep mixing will also 
support another day with west/northwest wind gusts up to 20 knots. 
Steep low-level lapse rates in the afternoon will again support the 
development of diurnal cu/stratocu and possibly an isolated 
instability shower or two.

Monday Night

Little change in the forecast between tonight and Monday night. 
Biggest difference will be attributed to the cooler air mass 
overhead. Low temperatures will fall into the low 40s for many areas 
and perhaps even the upper 30s for the low-lying areas out west. 
Otherwise continue to expect persistent winds out of the northwest 
and mostly clear skies.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...

Highlights...

* Dry/seasonable Tue but it will be breezy
* Unseasonably mild temps return Wed & Thu with dry weather
* A few showers possible Thu night and/or Fri but not a washout
* Cool/Below normal temps next weekend & watching offshore wave

Details...

Tuesday...

Upper trough/cold pool aloft begins to lift northeast and move away 
from the region. This should allow more sunshine than Monday and 
temps probably a degree or two higher. Expect high temps Tue 
generally in the 60 to 65 degree range. However, modest northwest 
LLJ coupled with lots of sunshine will result in good mixing. This 
will result in a rather breezy day with NW winds of 20-30 mph and 
perhaps a few gusts up to 35 mph.

Wednesday and Thursday...

High pressure to our south moves off the coast as a cold front 
approaches from the west. This will allow a return SW flow of milder 
temperatures back into southern New England. High temperatures 
should recover back into the upper 60s and lower 70s on Wed. The 
mildest day of the week looks to be Thursday as 850T moderate to 
between +10C and +12C. Highs probably will be able to reach into the 
lower to middle 70s in many locales on Thursday if enough solar 
insolation is realized.

Thursday night and Friday...

An approaching cold front will bring the potential for a few showers 
sometime Thursday night and/or Friday. Timing currently favors the 
greatest risk for some showers Thu night and Fri may end up mainly 
dry. This is certainly subject to change. Regardless, it does not 
look like a washout though as the deeper forcing/moisture will 
remain across northern New England. High probably are mainly in the 
60s on Friday.

Next Weekend...

EPS/GEFS guidance are in good agreement in developing northeast 
trough next weekend with below normal height fields.  It remains to 
be seen exactly how cool temperatures will get next weekend, but 
thinking high temperatures may remain in the 50s for one or both 
days next weekend. Low temps should be down into the 30s/40s 
depending on the amount of cloud cover. As for precipitation 
chances, most of the guidance favors the majority of the weekend 
ending up dry. That being said, an offshore wave of low pressure 
will need to be watched. A few members have it tracking close enough 
to the coast to result in a period of rain. Still to early to say 
much more at this point, but the greatest risk appears to be near 
the southeast New England coast at this point.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...

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

00z TAF Update:

Tonight...High confidence. VFR. W/NW wind 5-10 kt. 

Monday...High confidence. VFR with broken cigs 5-6k ft 
developing. Spot shower possible. NW gusts to 20-25 kt.

Monday Night...High confidence.
VFR. Northwest gusts 15-20 knots

KBOS Terminal...High confidence in trends.

KBDL Terminal...High confidence in trends.

Outlook /Tuesday through Friday/...

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

Wednesday through Thursday: VFR. Breezy. 

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

Friday: Mainly VFR, with local MVFR possible. Breezy.

&&

.MARINE...

Forecaster Confidence Levels.

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

Marine

Northwest flow pattern will support gusty winds over the marine 
waters into early next week. As a result SCY remains in effect 
through tomorrow afternoon. By Monday night, a low-level jet moving 
over the coastal waters will bring increasing wind speeds with gusts 
over the southern waters approaching 30 knots. Gale watch is in 
effect for Tuesday as gusts may to rise to 34 knots by Tuesday 
afternoon.

Seas generally range from 1-3 feet in the 
near-shore zones and 4-5 feet for the outer waters.

Outlook /Tuesday through Friday/...

Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Seas up to 5 ft. 

Tuesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Local rough seas. 

Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 25 kt. Seas locally approaching 5 ft. 

Wednesday Night: Winds less than 25 kt. 

Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. 

Thursday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Seas up to 5 ft. Chance of rain
showers. 

Friday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Local rough seas. Slight chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Gale Watch from Tuesday morning through Tuesday evening for 
     ANZ232-233-235-237-254>256.
     Small Craft Advisory until 2 PM EDT Monday for ANZ255-256.

&&

$$
SYNOPSIS...RM/Frank
NEAR TERM...Frank/RM
SHORT TERM...RM
LONG TERM...Frank
AVIATION...RM/Frank
MARINE...RM/Frank