Lexington Weather

Lexington, Massachusetts, USA

51°F

10/6/2024 2:27am

Lexington Conditions: Clear
Temperature: 50.7°F / 10.4°C
Dew Point: 44.1°F
Relative Humidity: 78%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 30.11 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 302345
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
745 PM EDT Mon Sep 30 2024

.SYNOPSIS...
High pressure will bring dry conditions for most of the week, 
with only a slight chance of light rain midweek and again on 
Saturday. Temperatures will be seasonable through the first 
half of the week, then warm slightly above normal for the 
second half before cooling down over the upcoming weekend.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
730 pm update...

minor noise level tweaks to the forecast for tonight based on
latest guidance. As with the previous shift, there remains
questions about how much low stratus develops along the coast
and pushes inland late tonight. Currently a small patch of
stratus offshore, but with cirrus moving into the region, its
going to be hard to see how those low clouds evolve over the
next 6 hours. Models the last few days have been a bit agressive
in developing the nocturnal stratus, but on the flip side,
dewpoints are 2-3F higher than this time yesterday which points
to a little more moisture to work with. Low confidence in the
fog and drizzle aspect as well. Winds a few hundred feet above
the surface will be 10-13kt, which suggests some mixing will
occur near the surface -- so it's more a stratus than fog
situation. That said, it is also fog season near
rivers/lakes/ponds, so patchy surface based fog will probably
still form as well. Keep in mind that the long rambles about 
fog and stratus by a meteorologist means that most people will
just describe the weather tonight as quiet. 


Highlights:

* Pleasant afternoon with a mixture of sun and clouds. 

* Marine stratus returns overnight with patchy fog and drizzle 
  early tomorrow morning. 

Little weather concerns this evening thanks to surface high 
pressure, 1019mb, situated nearby Georges Bank. East to 
northeast flow kept much of eastern coastal Massachusetts cooler
with afternoon highs in the mid to upper 60s. Although, away 
from the influence of the on shore flow, highs warmed into the 
low and middle 70s across the Connecticut River Valley. No 
significant deviation from the previous forecast with respect to
tonight into Tuesday morning, marine stratus likely redevelops 
late this evening and overspreads the region through the predawn
hours. Though, do have lower confidence in the areal coverage 
of the marine stratus. BUFKIT soundings show a saturated layer 
near the surface which may lead to pockets of light drizzle. 
Given the added cloud cover, temperatures will remain near or 
slightly above normal tonight, low and mid-50s.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Highlights:

* Patchy morning fog with drizzle gives way to a mixture of 
  clouds and sunshine.

* Seasonable high temperatures away from the influence of 
  cooler on shore winds in eastern Massachusetts. 

High pressure near Georges Bank becomes absorbed by a separate 
area of higher pressure at the mouth of the St. Lawrence River. 
And as a result, the flow remains light out of the 
east/northeast. A gloomy start with patchy fog and drizzle 
during the morning commute. It will take some time for the 
marine stratus to erode, potentially as late as the late 
morning. HREF does show once the low clouds erode there are 
still fair amount of mid and high clouds remaining. That said, 
global attempt to bring in drier air aloft, which could result 
in a mixture of clouds and sunshine. Nevertheless, should have 
more in the way of sky cover than what we experienced Monday 
afternoon. As for Tuesday night, similar conditions anticipated,
return of lower clouds and patchy fog. 

Cooler again for Tuesday, highs in the middle and upper 60s 
across eastern Massachusetts and Rhode Island, while northern 
Connecticut and western Massachusetts reach the upper 60s and 
low 70s.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Key Points:

* Generally dry and mild. Possibly a few light showers Saturday.

12z global guidance is in line with what they have been showing the 
last few days, namely deep layer ridging across the northeast all 
the way into the weekend (500mb heights forecast to rise to about 
585 dm, which is about 1.5 standard deviations above normal for this 
time of year). So the "big bubble, no trouble" theorm can be 
applied.  850mb temperatures start out around 7-8C and are progged 
to rise to around 11-12C by Friday. Thus a warming trend is expected 
for late this week. Stuck with NBM guidance for temperatures, so 
have highs in the upper 60s rising to mid/upper 70s for Friday. It's 
possible a few towns in the CT River Valley top out over 80F. Models 
indicate an upper trough will move through on Saturday, but trends 
have been to make it weaker with each successive run. Very little in 
the way of dynamics or moisture to work with, so if we do see any 
rain, it will be light. Stuck with the model blend output from the 
NBM and painted in PoPs only in the 20-25% range. With the slight 
weakening of the ridge due to the trough and some extra clouds, 
temperatures for the weekend will fall back to more near normal 
levels.  Model guidance has much more of a spread for early next 
week. Euro and Canadian indicate a fairly robust trough swinging 
through Monday/Tuesday, while the GFS is much more muted and faster. 
Kept with NBM PoPs on the order of 20%, but this is subject to much 
change.

One additional item to watch will be newly minted TS Kirk way out in 
the Atlantic. Although it will stay very far away and not directly 
affect us, it may end up generating a fairly sizeable long period 
(14-17 second) swell that could reach the coast late in the weekend. 
If this happens, we could see rough surf, rip currents, and perhaps 
some minor beach erosion. However, it's lots of conjecture at this 
point.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:

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

00Z Update. 

Tonight...Moderate confidence. 

Much of the forecast guidance available indicates that low
stratus will form just offshore and spread inland after 05z.
Some of that guidance also suggests visibilities will drop into
the IFR category in many areas as well. Think the guidance is
too agressive, however satellite does show some patchy stratus
lurking offshore and given continued E/NE wind flow, we can't
totally discount stratus forming. Have maintained a similar set
of trends to the 18z TAFs, with MVFR ceilings developing after
04-06z across the east, with perhaps a brief period just before
daybreak for BDL and BAF. Some spotty IFR ceilings are possible
as well. Slightly better odds for visibilities to drop below 3SM
across the Cape and even ORH (given it's higher elevation and
potential to be more in the clouds).  

Tomorrow...Moderate confidence.

MVFR stratus deck should lift and break up by mid morning with
VFR conditions by the afternoon, except towards Cape/Islands,
where MVFR should persist. 

Tuesday Night...Low confidence. 

MVFR with localized IFR possible. Light east to northeast 
winds. 

BOS TAF...Moderate Confidence in TAF. Highest probability for
IFR ceilings to develop is after 05z. Not expecting any
reduction in visibility. Ceilings should rise to MVFR mid-
morning and then become VFR by early afternoon. Steady NE
surface winds, so that means a small chance that ceilings stay
MVFR later into the day.  

BDL TAF...Moderate Confidence in TAF, primarily due to
uncertainty if MVFR ceilings develop in the area very late
tonight/early Tuesday morning. If it does occur, clouds should
break up by late morning, resulting in VFR conditions for
tomorrow afternoon. 


Outlook /Wednesday through Saturday/...

Wednesday through Friday Night: VFR. 

Saturday: VFR. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Tuesday Night...High confidence. 

Seas and winds remain below S.C.A throughout the period due to 
surface high pressure over the coastal waters. Marine stratus 
and patchy fog and/or drizzle tonight and again Tuesday night. 
Quiet weather conditions on Tuesday with east to northeast winds
15 to 20 knots and seas 3 to 4 foot. 

Outlook /Wednesday through Saturday/... 

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

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

Friday through Friday Night: Winds less than 25 kt. 

Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers.

&&

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

&&

$$

SYNOPSIS...Dooley/Nash
NEAR TERM...Dooley/Nash
SHORT TERM...Dooley
LONG TERM...Nash
AVIATION...Dooley/Hrencecin/Nash
MARINE...Dooley/Nash