Lexington Weather

Lexington, Massachusetts, USA

66°F

5/20/2024 3:51pm

Lexington Conditions: Clear
Temperature: 66.0°F / 18.9°C
Dew Point: 57.2°F
Relative Humidity: 73%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.98 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 170731
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
331 AM EDT Fri May 17 2024

.SYNOPSIS...

Mild across the interior today but increasing clouds and onshore 
winds will keep temperatures cool across eastern MA and RI. 
Seasonable with scattered showers on Saturday. We are then 
looking at a prolonged spell of dry weather with warming 
temperatures starting Sunday and continuing through Wednesday. 
High temperatures could approach the mid 80s by Tuesday and/or 
Wednesday in interior Southern New England, with temperatures in
the 70s near the coasts. Our next chance for rains doesn't 
appear until around Thursday. 
 

&&

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

3AM Update... 

Portions of far southern New England remain under the northern 
fringes of the stratus deck associated with low pressure well 
south of the region this morning which has allowed light rain 
showers to filter over the Cape and Islands over the last 
several hours. In contrast, the interior, mainly north of the 
Providence to Hartford line has been persistently clear, thus, 
radiation fog has been able to form in locations where dewpoints
have dropped below ~50F (Fitchburg, Orange, BAF Airfield). The 
expectation for today is that low pressure will continue to 
drift south as mid level ridging nudges in from the southwest, 
allowing for a period of sunshine this morning north and west of
the I-95 corridor. Areas that are able to capitalize on a few 
hours of sunshine will be able to mix to ~850mb where temps 
hover around 8C. 

Cloud cover and wind direction will have a significant influence on 
temperatures today, with 925mb jet holding strong over SE MA and RI, 
where winds will continue to gust to as high as 20kt this afternoon 
from the NE. So, while places in the Connecticut River Valley will 
warm quickly into the 70s, a significant temperature gradient will 
develop with areas east of approx. Worcester warming into the mid 
60s this morning before synoptic flow drops temperatures into the 
low 60s and 50s along the immediate coastline late this afternoon. 
This, "synoptic seabreeze" may extend as far inland as the I-495 
corridor prior to sunset. Onshore flow will also influence the 
development of afternoon cloudiness. 

&&

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

Weak shortwave will rotate around a low centered over northern 
Quebec/Ontario on Saturday as low pressure south of the region 
pivots ever so slightly north back towards SNE. The combined 
influence of the shortwave as well as some convergence from onshore 
flow will result in scattered shower activity very late tonight 
through the day on Saturday. Showers will be most widespread across 
eastern MA and RI but even so, not expecting a washout of a day. The 
NAM is the most bullish of guidance hinting at the potential for up 
to an inch and a half of rain to fall across far northeastern MA 
over the period ending 00Z Sunday, but a check of the 24 QPF HREF 
PMM paints a much more moderate solution with localized max QPF of 
around a half of an inch in Essex and northern Middlesex counties. 

The temperature forecast is proving to be quite tricky for Saturday, 
with the wetter, cloudier guidance, such as the NAM, really leaning 
into onshore flow to drive highs down into the mid to upper 50s 
region wide! In contrast to the NAM, most other guidance depicts 
widespread highs in the 60s away from the immediate coastline. Given 
the high level of uncertainty regarding temps tomorrow afternoon, 
relied heavily on "consensus" guidance to derive high temperatures. 
With widespread cloudiness, mixing will be limited, but should some 
portions of the CT River Valley be able to break out into brief 
period of sunshine, could see temps warm into the upper 60s in 
places like downtown Hartford and Windsor Locks.  


&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Highlights: 

* Significant warmup toward late-spring/early-summerlike 
  temperatures as we move into the early to midweek period. Likely 
  to see Tue and Wed reach into the lower to mid 80s inland! 

* Outside of diminishing spotty showers early Saturday evening, 
  mainly dry weather is expected with high pressure dominating.

Details:

Though we could still be dealing with hit or miss showers over 
eastern and northeast MA early Saturday evening, the forecast 
continues to trend more optimistically with decreasing cloudiness 
starting on Sunday. Expect cooler temps again near the coasts as 
onshore flow continues, with highs in the lower to mid 60s; while 
further inland, highs should push well into the 60s to the lower/mid 
70s. 

The main story for the early to midweek portion of the forecast is a 
warming trend toward late-spring/early-summerlike temperatures 
accompanied by dry weather, as 500 mb heights rise over Southern New 
England. 850 mb temps will also be steadily rising to values around 
+11 to +13C by Tuesday, and around +12 to +14 C by Wednesday. Warmup 
begins in earnest on Monday, with highs reaching into the 70s with 
perhaps a spot 80 degree reading in the CT and Merrimack Valleys. 
Some concern for cooling seabreezes near the immediate coast and 
kept temps for both coasts in the mid 60s to around 70. Warmest days 
in the stretch look to be both Tuesday and Wednesday with high 
pressure to our south promoting a strengthening SW pressure 
gradient. Several days of antecedent dry weather would also tend to 
favor warmer temps. That would keep the sea breeze from making any 
landward inroads and allow for warm temperatures to make it all the 
way to the eastern coast with little resistance. Outside of Cape Cod 
where highs still only around the mid to upper 60s, temps on Tuesday 
and Wednesday should soar well into the 70s for most, with lower to 
mid 80s in the CT/Merrimack Valleys.  

This period is overall a dry one outside of spotty rain showers 
early Saturday evening. We may not see our next chance for rains 
until around Thursday as a cold front approaches from the west, but 
this is by no means set in stone. 
&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:

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

Through Today...High Confidence

Mainly VFR with some MVFR across the Cape and Islands associated
with patchy rain showers. Patchy fog will result in localized 
IFR across the interior through 13Z this morning. VFR will
prevail for much of the area after 13Z, though MVFR/marine
stratus likely to stick around for the Cape and Islands all day.
E/NE flow between 5-10kt with gusts to 20kt possible along the
immediate coastline. 

Friday Night... Moderate Confidence

VFR, away from the Cape and Islands where MVFR persists, to 
start before patchy fog development drives categories down to
locally IFR. Persistent E/NE flow.

Saturday... Moderate Confidence

VFR across the CT River Valley with MVFR for eastern MA RI
Saturday morning falling to MVFR/IFR during the afternoon as
showers develop mid day. Onshore flow will drive cigs to as low
as 003ft along the coast. Winds 5 to 15kt. 

KBOS TAF...Moderate Confidence

VFR today with onshore NE winds, gusting as high as 20kt for a
brief period this afternoon. Patchy fog across the interior
should remain clear of the terminal. MVFR develops overnight
tonight as stratus and fog redevelops given onshore flow.
Showers possible by early Saturday morning. 

KBDL TAF...High confidence in 
TAF.

Patchy fog this morning may briefly deteriorate VFR to IFR. VFR
through the day before fog redevelops tonight. Light E/NE winds
today, generally less than 10kt. 

Outlook /Saturday Night through Tuesday/...

Saturday Night: Mainly VFR, with local IFR possible. 

Sunday: Mainly VFR, with local MVFR possible. 

Sunday Night through Tuesday: VFR. 

&&

.MARINE...
Forecaster Confidence Levels:

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

3AM Update... Extended SCA for outer waters through 00-06Z
Sunday 

Today... High Confidence.

Any pockets of fog burning off by mid to late Fri AM. E/ENE 
winds 15-20 kt with 20-25 kt gusts. Seas remain elevated across
the outer waters, so the SCA remains.

Tonight...High confidence.

Winds remain out of the NE at 10-20 kts. Could see a return of
stratus/fog across the waters late. Visibilities of 1-4 SM with
the lowest across the eastern waters. Seas remain elevated so
have extended the SCA through the period.

Saturday... High Confidence

Scattered showers with persistent E/NE flow. Gusts to around
15kt. Seas gradually subsiding but remain above 5ft across the
outer waters, thus, extended SCA through Saturday evening. 

Outlook /Saturday Night through Tuesday/...

Saturday Night through Monday: Winds less than 25 kt. Seas up
to 5 ft. 

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 AM EDT Saturday for ANZ250-
     254>256.

&&

$$

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