Lexington Weather

Lexington, Massachusetts, USA

66°F

5/20/2024 2:26pm

Lexington Conditions: Few Clouds
Temperature: 66.4°F / 19.1°C
Dew Point: 57.0°F
Relative Humidity: 72%
Wind: SW 4 mph, 10-min avg: 1 mph, gust: 7 mph
Barometer: 29.99 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 180716
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
316 AM EDT Sat May 18 2024

.SYNOPSIS...

Unsettled and cool today with scattered showers. Chance for
improvement on Sunday as high pressure begins to nudge in from
the southwest. Early summerlike temperatures expected Monday through
Wednesday, with the warmest days expected to be Tuesday and 
Wednesday. A cold front around Thursday offers the next chance 
at showers or thunderstorms, with temperatures then cooling to 
more seasonable levels by late in the week.

&&

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

Today we remain under the influence of pesky mid level low to 
our south that has brought unsettled conditions to southern New 
England for the last several days. With low to our south, weak 
shortwave lifts from the Great Lakes into northern Maine by late
this evening. 

Given southern New England is "sandwiched" between the shortwave and 
the low, we'll have a few chances for showers today; actually, the 
first chance for showers is already underway with light 
precipitation backing in across the Cape and Islands, thanks to 
persistent ENE. Showers will become more widespread after 15Z today 
as PWATs surge to >1.0", aided by a weak 925mb jet of 20-30kt draped 
over eastern MA. General thinking is showers are possible in any 
location, but will be more widespread east of the Worcester metro 
area. In fact, the CT River Valley may "luck out" with a primarily 
dry day as weak high pressure attempts to nudge in from the 
southwest. While it will a dreary and rather chilly day, with little 
to no diurnal swing in temps from current obs (in the 50s and 
low 60s, west), QPF will be minimal, with HREF ensemble mean 
QPF around 0.1" across Middlesex and Essex Counties. Should high
pressure be able to scatter out a few breaks of sunshine across
western MA, could see temps warm briefly into the mid to upper 
60s in places like Hartford and Springfield. 

&&

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

Pattern of persistence carries through this evening with little 
change in the synoptic setup through early tomorrow morning. 
Shortwave passing to our Northwest may renew shower activity 
between 00-06Z tonight. Widely scattered shower activity across 
the eastern half of the CWA will become increasingly sparse 
after the midnight hour, giving way to a more drizzle-stratus 
dominated environment by early morning. Temps will pretty much 
remain stagnant overnight given no change in the pattern with 
low sin the 50s.

While Sunday previously looked to be a much nicer day for southern 
New England, there are indications that the influence of onshore 
flow will persist through the better part of the day across eastern 
MA and RI, though conditions should improve across CT and western MA 
as weak high pressure is able to take better hold over the region. 
Fortunately, pesky mid level low tracks seaward, which will allow 
rain chances to decrease significantly by sunrise. As has been the 
case with many days this Spring, it's likely Sunday is another case 
of the "haves and have nots", as the CT River Valley breaks out into 
sunshine and temperatures warm into the low 70s while strong onshore 
flow pins stratus across eastern MA and much of RI where temps 
struggle to climb out of the 50s along the immediate coast. It's 
probably safe to say those in the Boston to Providence corridor are 
ready to shake this gloomy pattern, but fear not, the long term AFD 
highlights a significant pattern chance by mid week!

&&

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

Highlights: 

* Warming temperatures under partly to mostly sunny weather through 
  midweek, with the warmest days likely on Tuesday and Wednesday. 
  Could have our first 80 degree day in Boston Tuesday and/or 
  Wednesday, with 3 days of lower-mid 80s in Hartford.

* Our next chance for rains is around later Wednesday night or 
  Thursday with showers or thundershowers associated with a cold 
  front. 

* Cooling to more seasonable levels for late-week.

Details: 

While the general theme of a substantial warming trend to 
temperatures for the early to midweek period is still valid, today's 
00z guidance indicated more potential for continued cloud cover on 
Monday with higher RH in the 1000-850 mb layer, especially for 
eastern and southeast New England. Ended up bringing highs down from 
NBM by a couple degrees for Monday on the basis of this cloud cover, 
though the temperature forecast has obvious sensitivities to how 
long clouds linger/scatter out, and that is still a bit unclear. 
Kept highs in the mid 50s to mid 60s for the coasts and the coastal 
plain, but still think highs soar into the mid to upper 70s from 
central MA/eastern CT westward with less cloud cover. 

Warmest days look to be on Tuesday and Wednesday, with full 
sunshine, southwest breezes and continue dry weather. Relatively 
strong SW flow should keep sea breezes from making much of any 
intrusion landwards, so even sites such as Boston and the North and 
South Shore have a solid chance at reaching 80 degrees, having last 
occurred at Boston on October 28th of last year. Mid 80s inland seem 
reasonable on both days. Despite the breezes, both days should feel 
more reminiscent of early summer with dewpoint temps in the mid to 
upper 50s.  

Dry weather to prevail through Wednesday. Our next chance for 
showers or thundershowers isn't until a cold front arrives around 
Wednesday night or Thursday, but the timing and the strength of any 
thunderstorms are both uncertain. Latest guidance favors 
Thursday for frontal passage so favored the highest PoP around 
Thursday but only around 20-30 percent given the uncertainties 
in timing. Friday appears to be more entrenched in post-frontal 
colder air, with temps seemingly poised to return closer to 
late-May climatological levels. 


&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

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


Through Today...Moderate confidence.

VFR to MVFR early this morning gradually degrading to MVFR/IFR
with LIFR possible across the Cape and Islands by late morning.
Scattered rain showers, primarily from Worcester, east, at any
point today, with greatest chance for widespread shower activity
between 15-00Z. It is possible that portions of the CT River
Valley remain VFR all day with cigs around 040. NE Winds 5-15kt
with a few gusts to 20kt possible along the immediate eastern
coastline. 

Saturday Night...Moderate confidence.

Conditions remain consistently MVFR to LIFR from West to
Southeast, lowest on the Cape and Islands. Light showers and
drizzle continue through the first half of the evening. MVFR to
IFR conditions persist due to pesky onshore flow. Winds continue
to blow from the E/ENE gusting to around 10-15kt overnight. 

Sunday... Moderate Confidence

Conditions improve from west to east after sunrise from 
MVFR/IFR to VFR/MVFR. VFR possible for BOS-PVD line, SE after 
18Z, though MVFR to hang on across the Cape for the duration of 
the day. NE winds gusting 15 to perhaps 20kt once again. 


KBOS TAF...High confidence in TAF through 00Z. Moderate after
this time.

VFR degrading to MVFR after 10Z this morning as shower activity
increases. IFR this afternoon. NNE/NE flow 10-15kt with the
occasional gust to 20kt possible. Forecast of persistence, with
little change in conditions over the next 24 hours. 

KBDL TAF...High confidence in TAF. 

Generally VFR but will become borderline VFR/MVFR this
afternoon. Showers most likely stay east of the terminal but a
stray shower may impact the terminal this afternoon or early
evening. Winds NE 5-10kt with gusts to 15kt. 

Outlook /Sunday Night through Wednesday/...

Sunday Night through Monday: Mainly VFR, with local MVFR
possible. 

Monday Night through Tuesday Night: VFR. 

Wednesday: VFR. Breezy. 

&&

.MARINE...
Forecaster Confidence Levels:

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

Extended the SCA for the eastern outer waters through early
Monday morning for persistent seas. 

Saturday... High confidence.

Scattered light rain and drizzle across the waters. Will have
visibilities of 3-5 SM. Persistent 15-20 kts out of the NE with
gusts up to 20 kts. Seas 1-4 ft across the interior waters and
4-6 ft for the outer.

Saturday Night...Moderate confidence.

Scattered light rain and drizzle anticipated to persist. Will 
continue to see NE winds at 10-15 kts and gusts around 20 kts. 
Visibilities of 3-5 SM and seas 3-6 ft for the outer waters.

Sunday... High Confidence. 

Continued NE winds 10-15kt. Seas across the eastern outer
waters will remain above 5 feet through the period, but will 
fall below 5 ft elsewhere. Vsby reductions early Sunday morning 
should improve through the day. 

Outlook /Sunday Night through Wednesday/...

Sunday Night: Winds less than 25 kt. Seas up to 5 ft. 

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

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

Tuesday Night through Wednesday: Winds less than 25 kt. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 2 AM EDT Monday for ANZ250-254.
     Small Craft Advisory until 8 PM EDT this evening for ANZ255-
     256.

&&

$$

SYNOPSIS...Loconto/KS
NEAR TERM...KS
SHORT TERM...KS
LONG TERM...Loconto
AVIATION...KS
MARINE...Loconto/KS