Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 150543
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
143 AM EDT Mon Jun 15 2026

.WHAT HAS CHANGED...
No significant changes.

&&

.KEY MESSAGES...

- Showers and thunderstorms expected to move through tonight, 
  some of which could produce severe wind gusts.

- Drier and slightly cooler following tonight's front.

- High astronomical tides and up to one-foot of storm surge 
  could cause minor coastal flooding for the evening high tides 
  tonight, Monday night and Tuesday night.

- Near seasonable temperatures and dry conditions followed by
  more unsettled weather at the end of the work week.

&&

.DISCUSSION...
KEY MESSAGE 1...Showers and thunderstorms expected to move through 
tonight, some of which could produce severe wind gusts.

A cold front associated with low pressure currently centered over 
part of MI and southern ON will continue pushing to the east and 
north this afternoon, moving through southern New England tonight. 
This will be the main driver for chances of showers and 
thunderstorms, primarily after 7 PM. Though, the chance for a stray 
shower or two ahead of the main system arriving around 6 PM at the 
earliest towards western MA and CT is nonzero. Storms are expected 
to move in between 7-11 PM tonight, and a Slight risk (level 2 out 
of 5) for severe weather exists over western MA into CT, primarily 
for an elevated severe wind risk. CAMs indicate an elevated 
convection setup with a strengthening wind field and good 
forcing from the approaching front. Despite the lack of 
instability overnight and forecast soundings indicating a slight
inversion in the lower levels, the forcing from the front may 
be enough to erode that inversion and tap into the stronger 
wind field aloft. RAP, NAM, and NAMNEST soundings indicate a 
little after midnight that effective bulk shear values may 
increase to around 30-40 knots. With the general evolution of 
these storms, CAMs have come into more agreement regarding them 
forming along a line ahead of/along the cold front (and we are
currently seeing that occur west of the region). However, the 
risk should die down around and after 4 AM. Weaker storms could 
persist then through around 7 AM.

Some spread still exists across the guidance regarding rainfall
totals. Generally, the higher rainfall totals should be mostly 
in northern New England with part of far NW MA included, where 
around half an inch is possible. The majority region can expect 
totals ranging between 0.20-0.35" of rain and the mesoscale- 
influenced low pressure developing would be tracking more just 
off the coast of Maine. This is the feature to watch with
limiting rainfall totals. PWAT values are mainly forecast 
around 1.5-1.8" with pockets of 2.00"+ creeping north into RI, 
SE MA, and the Cape and Islands. Considering the convective 
nature of these showers/storms, locally higher rainfall totals 
elsewhere are not out of the question.

KEY MESSAGE 2...Drier and slightly cooler following tonight's front.

In the wake of tonight's cold front, temperatures fall to a more 
seasonable level. Highs for Monday are forecast to be in the upper 
70s to low 80s across southern New England with dewpoints in the 
50s. 925 mb temperatures fall to around 15C from around 20-25C, with 
the exception of parts of eastern MA where 925 mb temps around 20C 
return for Monday afternoon. High pressure starts to build in as
a surface ridge develops. Lows in the interior tomorrow night 
may fall to the low 50s with mid/upper 50s into the coastal 
plain. Winds go light to calm with clearer skies, lending some 
favorability to a possible radiational cooling setup.

KEY MESSAGE 3...High astronomical tides and up to one-foot of storm 
surge could cause minor coastal flooding for the evening high tides 
tonight, Monday night and Tuesday night.

Astronomical tides will be building to their highest level on 
Monday, peaking around 12.0 ft at Boston Harbor Monday evening, but 
remaining elevated into Tuesday night. Storm surge observations 
along the tidal gages shows about 0.7 to just over a foot of 
storm surge, and the storm surge forecast data from P-ETSS and 
Stevens Institute indicate storm surge values of around one half
to a foot of storm surge. 

With hardly any wave action, forecast total water level should be 
pretty similar to recent days. Coastal Flood Statements now have 
been extended for the southern and eastern coasts for very minor 
tidal flooding into Tuesday night. We may be able to get away with a 
Coastal Flood Statement vs an Advisory for Nantucket for the Tuesday 
evening high tide, but will give later shifts an opportunity to 
reassess that. The evening high tide cycles tonight, Monday night 
and Tuesday night are the periods we are most concerned for, as 
those high tide magnitudes are higher.  

This is a low-ceiling/low-impact coastal flooding scenario, with 
splashover or at worst minor coastal flooding in the usual 
vulnerable shoreline roads (including but not limited to Easy Street 
in Nantucket and Morrissey Blvd in Boston). However we'll carry 
these headlines for more awareness, given that there are more 
visitors to Southern New England who may not be as familiar with 
coastal/tidal flooding. 

KEY MESSAGE 4...Near seasonable temperatures and dry conditions
followed by more unsettled weather at the end of the work week.

After the surface ridge starts to weaken its grip on the area 
Wednesday, southwesterly flow returns. A weak disturbance may bring 
some lighter precip to the west Wednesday followed by a stronger 
system and attendant frontal boundary Thursday. Some varied timing 
disagreements between the global guidance and the GFS ensembles show 
better chances on Wednesday than the EC but overall still pretty 
low. 

The front expected to clear the coast Friday bringing and end to the 
shower and storm activity for southern New England bringing a return 
to dry conditions for next weekend with temperatures slightly above 
normal and very comfortable dewpoints in the upper 40s and 50s.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

06z TAF Update...

Overnight: Moderate confidence.

Areas of MVFR to IFR possible with incoming SHRA and TSRA 
associated with a passing cold front. Expecting bulk of the 
showers and storms to pass through 04-08z for BDL and 07-11z 
elsewhere. Winds prevailing out of the south from 10-15 kt 
sustained, shifting NW in the wake of the front. Have added LLWS
overnight prior to the cold frontal passage for all but inland 
terminals to account for 35-40kt flow at 2-3 thousand feet.

Monday: High confidence.

Conditions improve to VFR behind the front as NW flow develops.
Generally NW winds decreasing to near 10 kts throughout the 
day.

Monday Night: High Confidence.

VFR. NW winds 5-10 kts. Few lingering high level clouds 
possible over Cape/Islands.

KBOS Terminal...Moderate confidence in trends. Moderate 
confidence in timing. Have inserted a TEMPO group for thunder 
overnight as confidence is increasing.

KBDL Terminal...High confidence in trends. Moderate confidence 
in timing. Threat of thunder approaching right around 06z still 
looks good.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Wednesday: VFR. 

Wednesday Night: VFR. Slight chance SHRA.

Thursday: VFR. Windy with local gusts up to 30 kt. Chance SHRA,
slight chance TSRA.

Thursday Night: VFR. Windy with local gusts up to 30 kt. Chance
SHRA.

Juneteenth: VFR. Breezy. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Monday....High confidence.

Seas remain 4-5 ft across the southern waters, but drop to 2-4 
ft across the northern waters. Likewise, wind gusts remain 
around 20 kts across the southern waters and drop to near 10 kts
across the northern waters.

Monday Night...High confidence.

Localized parts of the southern outer waters early Monday night
may see seas to 5 ft before settling to 2-4 ft overall heading 
into Tuesday morning. Winds remain NW, sustained between 10-15 
kt with not much in the way of wind gusts.

Tuesday...High confidence.

Seas generally 2-4 ft. NW winds turning SW with some gusts up 
to 20 kts possible.

Outlook /Tuesday Night through Friday/...

Tuesday Night: Winds less than 25 kt. 

Wednesday through Wednesday Night: Winds less than 25 kt.
Slight chance of rain showers. 

Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Local rough seas. Slight chance of rain
showers. 

Thursday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Rough seas up to 8 ft. Chance of rain
showers. 

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Coastal Flood Advisory until 2 AM EDT Tuesday for MAZ024.
RI...None.
MARINE...Small Craft Advisory until 2 AM EDT early this morning for 
     ANZ230-236.
     Small Craft Advisory until 8 AM EDT this morning for 
     ANZ231>235-237-250-251-254>256.

&&

$$

DISCUSSION...McMinn
AVIATION...McMinn
MARINE...McMinn