Lexington Weather

Lexington, Massachusetts, USA

53°F

10/17/2021 8:20pm

Lexington Conditions: Clear
Temperature: 53.4°F / 11.9°C
Dew Point: 47.7°F
Relative Humidity: 81%
Wind: SW 1 mph, 10-min avg: 1 mph, gust: 3 mph
Barometer: 29.66 in Steady
Visibility: 10 miles
Rain Today: 0.35 in

Area Forecast Discussion
for Boston, MA

        
000
FXUS61 KBOX 140008
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
808 PM EDT Wed Oct 13 2021

.SYNOPSIS...
High pressure remains in control through Friday with mainly dry 
weather and temperatures well above normal. A strong frontal system 
brings breezy conditions and periods of showers and possible thunder 
Saturday night into early Sunday. Turning more seasonable and 
blustery for Sunday into Monday, followed by a warming trend through 
midweek.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
No major changes to the forecast this evening. Mainly brought 
it back in line with observed trends. One problem will be the 
stratus across portions of CT and MA towards the Connecticut 
River. This stratus had been persistent for some time, but 
recently showed some erosion along the northern edge per 
observations at BDL. Only expecting this stratus to get more 
expansive as the night progresses and low level humidity 
increases. This will have a significant impact on temperatures, 
which could be quite lower should these clouds dissipate quicker
than currently thought.

Previous Discussion...

Ridging and dry air aloft (PWATs less than an inch) promoting mostly 
clear conditions across most of MA/RI and into eastern CT, along 
with warm temps in the 70s (77 at OWD & BOS!). However low clouds 
have been stubborn much of the day across western CT into southwest 
MA, although some breaks of sunshine did boost temps into the low 
70s in the Hartford area. Even along the coast, despite a light 
southerly wind, temps climbed into the upper 60s to lower 70s, 
courtesy of SSTs in the 60s minimizing seabreeze impact. 

Dry/tranquil conditions continue into this evening, although trends 
will be for increasing clouds as mid/upper trough approaches from 
the NW. Good deep layer moisture associated with this trough, as 
PWATs climb to 1.2-1.4 inches and K indices rising to about 30 units 
overnight. Although, deep layer moisture is lagging behind the 
forcing for ascent. Thus, given moisture and forcing are somewhat 
out of phase, along with the lack of instability, not expecting much 
more than an isolated shower/sprinkle overnight. Hence, most areas 
remain dry.

Not as cool as previous nights given increasing clouds, thus lows 
tonight in the 50s. Given dew pts remain somewhat high for mid Oct 
(50s vs 40s), patchy fog is likely.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
330 PM Update:

Thursday...

Decreasing clouds as mid/upper trough exits along with increasing NW 
flow aloft, slowly drying the column. Although with dew pts 55-60 
combined with some sunshine and weak cyclonic flow aloft, time 
sections indicate broken diurnal strato-cu and cu developing late 
morning into the afternoon. Some of the guidance also suggest a spot 
shower/sprinkle possible in eastern MA from seabreeze convergence. 
Although, most of the region and day remains dry. Another warm day 
with 925 mb temps +16C/+17C and NNW boundary layer winds, supporting 
highs in the low to mid 70s, with upper 70s possible if enough 
sunshine develops! Normal high this time of year is 60-65. It will 
feel warm too given dew pts will be 55-60. Hence, not much of a drop 
off shade vs sunny areas. 

Thursday night...

Decreasing diurnal clouds, light winds and dew pts 55-60 (well above 
avg for mid Oct) should yield at least patchy dense fog, if not more 
widespread. Mins will be in the 50s. Although, a weak backdoor cold 
front moving across eastern MA, shifting winds to NNE may provide 
slightly drier air and mixed boundary layer limiting fog formation. 
Thus, greater risk for dense fog may be farther inland.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Highlights...

* Dry weather with above normal temperatures through Friday.

* Cloudy, but breezy and mild Saturday. then a strong cold front
  passes through late Saturday and Saturday night. Gusty 
  enhanced showers, possible thunder with frontal passage with 
  wetting rains likely. Possible marine headlines.
  
* Blustery and less-above normal temperatures Sunday and Monday,
  with upslope clouds and possible light showers in the terrain.
  Possible first frost in northwest MA Monday night? 

* Dry weather continues through Wed with temperatures trending 
  above normal again.

High pressure dominates much of this time period, except for
a window Saturday afternoon into Saturday night when a cold 
front will move through our region. Latest guidance was in good 
agreement with the timing of this front. Instability looks to be
limited, but cannot dismiss the idea of a few thunderstorms due
to modest dynamics. Not looking like a widespread severe weather
day at this time. Another high pressure arrives behind this
front, and should lead to drier and cooler conditions through
mid week.

Temperature-wise, expecting above normal conditions through
Saturday. Once this cold front moves through, conditions trend
to near to slightly below normal through Tuesday. Thinking
temperatures swing back above normal toward the middle of next
week.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Low - less than 30 percent. 
Moderate - 30 to 60 percent. 
High - greater than 60 percent.

Overnight...moderate confidence, some uncertainty on areal
extent and duration of IFR in fog. 

MVFR/VFR with patchy IFR in fog across the hilly terrain of 
MA/CT. Other than a spot shower dry weather prevails. Light SW
winds. 

Thursday...High confidence.

Areas of MVFR/IFR possible early, otherwise VFR cigs. Light 
N/NW winds with localized sea breezes along eastern MA coast.
Spot shower possible in eastern MA along this seabreeze
boundary. 

Thursday night...moderate confidence, some uncertainty on
MVFR/IFR conditions northeast MA. 

VFR but possible MVFR in northeast MA in response to NNE winds. 

KBOS Terminal...High confidence in TAF. 

KBDL Terminal...High confidence in trends, lower on exact timing
and details. 

Outlook /Friday through Monday/...

Friday through Friday Night: Mainly VFR, with local MVFR
possible. 

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

Saturday Night: Mainly VFR, with areas MVFR possible. Breezy.
Chance SHRA, isolated TSRA.

Sunday: VFR. Breezy. Slight chance SHRA.

Sunday Night: VFR. Breezy. 

Monday: VFR. Breezy. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels.

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

330 PM Update: 

Tranquil boating conditions through Thursday night with light 
winds and seas as high pres in control. SW flow today/tonight 
shifting to NW Thu behind a weak trough, and then NNE in eastern
MA waters Thu night as a weak backdoor front moves across these
waters. 

Outlook /Friday through Monday/...

Friday through Friday Night: Winds less than 25 kt. 

Saturday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft. Chance of rain
showers. 

Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Rain showers likely,
isolated thunderstorms. 

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

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

Monday: Low risk for Small Craft Advisory winds with gusts up
to 20 kt. Areas of rough seas. Chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$
SYNOPSIS...Belk/Nocera
NEAR TERM...Belk/Nocera
SHORT TERM...Nocera
LONG TERM...Belk
AVIATION...Belk/Nocera
MARINE...Belk/Nocera