Lexington Weather

Lexington, Massachusetts, USA

53°F
10/17/2021 8:22pm 
  • Lexington Conditions: Clear
  • Temperature: 53.4°F / 11.9°C
  • Dew Point: 47.7°F
  • Relative Humidity: 81%
  • Wind: Wind from W W Calm, 10-min avg: 1 mph, gust: 4 mph
  • Barometer: 29.66 in Steady
  • Visibility: 10 miles
  • Rain Today: 0.35 in
  •   

Area Forecast Discussion
for Boston, MA

        
000
FXUS61 KBOX 111122
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
722 AM EDT Mon Oct 11 2021

.SYNOPSIS...

High pressure remains in control into late this week with warmer 
than normal temperatures. Widespread precipitation chances return to 
the forecast for either Saturday or Sunday, but timing is uncertain 
at this time.

&&

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

7 AM Update...

Main change in the latest update was to increase sky cover in
the immediate near term. Have fairly widespread stratus in place
over much of southern New England. Anticipate these clouds will
scatter out later this morning and into the early afternoon.
Leaned toward the latest RAP guidance which has a decent handle
on the current situation per 950 hPa RH. Rest of the forecast
looks good and remains on track.

Discussion from 4 AM...

* Mainly dry and quiet weather today with a mix of sun and
  clouds.
* Rip current statement issued for eastern MA beaches. 

Low pressure system tracking well to our southeast will continue
to pull away, leaving us with a mainly dry forecast for Columbus
Day. While we can't rule out a sprinkle or stray shower, strong
high pressure to our north will help suppress precip chances.
Expect clouds to hang around for much of the morning due to a
combination of onshore flow and a moist low level. But we 
should improve to a mix of sun and clouds by the afternoon hours
along with diminishing winds. With mixing up to 900mb and 925mb
temps +10 to +13C, expect highs in the upper 60s to low 70s. 

In addition, a Rip Current Statement has been issued for the
eastern MA coast due to persistent easterly swells. With beaches
being unguarded this time of the year, people should exercise
caution if going out into the waters.

&&

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

Tonight...

With high pressure building in as well as decreasing clouds and
winds, it should be a decent night for radiational cooling.
Leaned towards the MOS guidance for overnight lows. Expect lows
to fall into the mid 40s to low 60s, except for mid 50s in the 
urban centers and near the coast.


Tuesday...

High pressure moves overhead with winds turning to the southeast
and south. Expect more sun than clouds and with 925mb
temperatures +13 to +15C, expect highs in the low to mid 70s.
These forecast highs are about 10 degrees warmer than the
climatological normals for the second week of October.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...

Highlights

* Above normal temperatures with quiet weather through much of the 
  week. Cannot rule out a few isolated showers across the interior 
  on Wednesday, but the next opportunity for widespread rain showers 
  is this weekend. 

Tuesday night through Friday...

Ridge axis will be situated over New England into Quebec Tuesday 
night. A trough will lift across the Great Lakes. The ridge will 
build offshore and into Nova Scotia by late Wednesday, while the 
deamplifying trough lifts into northern New England/southern Quebec. 
Another ridge builds in from the Great Lakes on Thursday and over 
the region on Friday. The trough lifts offshore Wednesday night into 
early Thursday. High pressure generally in place over the region 
through this period, though on Wednesday into early Thursday a weak 
surface trough swings through. High pressure builds back in on 
Thursday and Friday. 

Not anticipating any major concerns through this timeframe. High 
pressure generally in control through the period bringing dry and 
quiet weather. Above normal temperatures are expected with a gradual 
upward trend with southerly/westerly flow. Will have 925 hPa temps 
on Wednesday increasing to 14-17 degrees Celsius. For 
Thursday/Friday will have W/NW flow keeping 15-18 degree Celsius air 
overhead at 925 hPa. For all day time highs during this period went 
with a blend of the NBM 75th percentile and 90th percentile of 
guidance to bump up highs. High temperatures ranging from the upper 
60s to mid 70s for most days. Not out of the question there could be 
some upper 70 degree readings late in the week depending on cloud 
cover. Low temps generally in the 50s, but did lower temperatures 
for Tuesday night into early Wednesday to the 10th percentile of 
guidance. Expecting a strong radiational cooling night with clear 
skies and light winds. Should see lows in the mid to upper 40s in 
the typical strong radiator spots, elsewhere readings will be in the 
50s.

Did an isolated shower mention on Wednesday as a surface trough 
swings through. The risk of a shower is highest across western 
portions of the CWA. Think that most areas will be dry, but could 
see an isolated shower or two across parts of the interior. This 
coincides with a moisture surge of PWATs approaching 1 inch. 
Uncertain if there will be enough mid level moisture in place. This 
also still matches up well with the highest probabilities of 
EPS/GEFS measurable precipitation. 

Saturday through Sunday...

Ridge axis builds offshore and a trough lifts in from the 
Mississippi River Valley on Saturday or Sunday. A deep low should be 
situated to the northwest of the region, which will slide a warm and 
cold front through New England. This far out timing and intensity is 
uncertain due to model differences, but this brings a shot for more 
widespread precipitation. 

Pretty good agreement in a trough lifting into and through the 
region, but the specific details are uncertain at this time. Due to 
this have just kept the NBM guidance which keeps slight chance to 
chances of precipitation. Still looks like above normal temps 
persist into Saturday, but will depend on how quickly/when the cold 
front moves through. Think there could potentially be some rumbles 
of thunder given K index values increasing to around 30 and a few 
hundred J/kg of MUCAPE, but have held off from including a thunder 
mention in the latest forecast.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...

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

Today...High confidence in trends, moderate in timing.

Starting off with a mix of LIFR to MVFR with stratus and patchy
fog. Should see any fog burn this morning, but ceilings may take
a bit to lift/scatter out. Gradual improvement is expected and
should eventually become VFR late this morning or early
afternoon. Winds generally out of the NE/ENE at 5-10 kts. Gusts
of 20-25 kts along and south of the south coast.

Tonight...High confidence in trends, moderate in timing. 

VFR for most especially earlier in the evening. May see some
LIFR to MVFR fog developing. Have hinted at for the majority of
terminals with low cloud bases and some visby reduction. Winds
light and variable and generally less than 5 kts.

Tuesday...High confidence. 

Any patchy fog burns off quickly and conditions improve to VFR.
Light winds out of the southeast/south generally less than 5
kts.

KBOS Terminal...High confidence in TAF. 

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Thursday: VFR. 

Thursday Night: VFR. Slight chance SHRA.

Friday: VFR. 

&&

.MARINE...

Forecaster Confidence Levels.

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

Small Craft Advisories remain in effect overnight for the southern 
and southeastern coastal waters for gusts up to 25 knots and seas 
over 5 foot. SCA are expected to extend to the northeastern waters 
Monday morning. A coastal low pressure system will weaken as it 
moves northeast off of the Mid-Atlantic states and will bring 
periods of rain.

Outlook /Tuesday Night through Friday/...

Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Patchy fog. 

Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. 

Wednesday: Winds less than 25 kt. Seas locally approaching
5 ft. 

Wednesday Night through Friday: Winds less than 25 kt. 

&&

.TIDES/COASTAL FLOODING...

Issued a Coastal Flood Statement for this afternoon's high tide
cycle across eastern MA coast. Any impacts will be restricted to
very marginal and localized splashovers. Nonetheless, given that
it is a public holiday and the continued nice stretch of
weather, decided to hoist a statement for awareness purposes.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Rip Current Risk through this evening for MAZ007-019-
     022>024.
RI...High Rip Current Risk through this evening for RIZ008.
MARINE...Small Craft Advisory until 2 AM EDT Tuesday for ANZ235-237.
     Small Craft Advisory until 8 AM EDT Tuesday for ANZ250.
     Small Craft Advisory until 11 AM EDT Tuesday for ANZ254.
     Small Craft Advisory until 2 PM EDT Tuesday for ANZ255-256.

&&

$$
SYNOPSIS...BL/Chai
NEAR TERM...BL/Chai
SHORT TERM...Chai
LONG TERM...BL
AVIATION...BL/Chai
MARINE...BL/Chai
TIDES/COASTAL FLOODING...
      

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