Old Res Weather

Lexington, Massachusetts, USA

35°F

2/16/2025 7:17pm

Lexington Conditions: Overcast
Temperature: 35.1°F / 1.7°C
Dew Point: 32.4°F
Relative Humidity: 90%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.00 in Falling Slowly
Visibility: 10 miles
Rain Today: 0.01 in
UV Index: $VPuv None

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 280557
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
157 AM EDT Tue Apr 28 2026

.WHAT HAS CHANGED...
Increased rainfall amounts Wednesday night into Thursday.
Otherwise, no other significant changes were made to the
forecast. 

&&

.KEY MESSAGES...

- Pleasant weather continues today and tonight with the warmest 
temperatures inland and across the CT Valley. Much cooler conditions 
along the coast with highs in the upper 40s to lower 50s.

- Increasing chance for showers across coastal areas Wednesday. 
Better chance for a more widespread soaking rain Thursday.  

- Upper level low keeps things cooler and unsettled Friday into the 
weekend. 


&&

.DISCUSSION...

KEY MESSAGE 1... Pleasant weather continues today and tonight with 
the warmest temperatures inland and across the CT Valley. Much 
cooler conditions along the coast with highs in the upper 40s to 
lower 50s.

Ridge of high pressure crests overhead this afternoon through the 
overnight. This results in a mainly clear day outside of a few mid 
and high level clouds ahead of an area of low pressure that will 
pass well to the northwest of the CWA. Of greater consequence will 
be a fairly stiff onshore flow that will be 5-10 mph stronger than 
what we saw on Monday. The stronger onshore flow will likely help 
knock temps a few degrees lower than we've seen in recent days. 
Nonetheless...still expect highs to reach into the 60s in most 
locations away from the immediate coast. The mild spots will again 
be the CT Valley where high temps of 70+ seem likely. 
Meanwhile...onshore flow will hold high temps mainly in the 
lower to middle 50s along the immediate coast, Cape and Islands.


Mainly dry and cool again tonight with another night of decent 
radiational cooling. The magnitude of cooling will be less than 
previous nights with a mid and high level cloud deck building 
overhead. Lows will be in the 30s in many locations with lower 40s 
in most areas. High res guidance shows areas of low stratus, patchy 
showers, and drizzle mainly across SE MA and the islands late 
tonight. Still somewhat low (20-35%) POPs mainly contingent upon the 
orientation/location of an inverted trough extending from a distant 
coastal low.


KEY MESSAGE 2...Increasing chance for showers across coastal areas 
Wednesday. Better chance for a more widespread soaking rain 
Thursday. 

Most places remain dry for Wednesday as high pressure will be 
slow to move offshore. As a trough approaches from the west, 
Precipitable water (PWATs) increase to 0.5-1.0 inches. 
Therefore, expect cloudy skies for the day with continued NE 
flow. Highest chance of showers across eastern Mass and 
especially the Islands where high res guidance shows the 
inverted trough setting up and acting as a source of lift.

More broad synoptic-scale lift from an approaching shortwave brings 
an increasing chance for widespread light to perhaps moderate 
rainfall Wednesday night into Thursday morning. PWAT values rise to 
around 1.0-1.5", supportive of widespread showers/rain. Model 
guidance has come into better agreement with the idea of a secondary 
low developing offshore of the Cape Thursday. We are still 
monitoring the risk for coastal flooding but the  probability is 
still quite low at this point for the eastern coastal areas. For 
example, the Steven's Institute coastal flooding guidance does 
indicate a low probability (~5%) of near flood/splashover for east-
facing beaches. Thankfully, not looking at a significant chance for 
freshwater flooding as rainfall will be quick to move out Thursday 
afternoon. The 01z NBM mean 24 hour QPF has increased from a 
widespread 0.5-0.75" to 0.75-1.0". There is even a swath of mean 
QPF >1" across NE Massachusetts. 

KEY MESSAGE 3...Upper level low keeps things cooler and unsettled 
Friday into the weekend.

Weather pattern remains unsettled Friday through the weekend as a 
rex blocks keeps an upper level low above northern New England. This 
pattern will bring a much cooler airmass with 850mb temperature 
anomalies falling to 6-8C below normal. Non zero POPs continue 
through the weekend under a slow moving cold pool aloft (500mb temps 
falling to -20 to -30C). This will lead to some instability, so 
can't rule out a graupel within any showers. There are still 
model/ensemble members that indicate the potential for a coastal 
system to give a glancing blow to southern new england over the 
weekend. The trend with the 00z ensembles has been a solution much 
further to the east. The other scenario is a closer track with 
rain/gusty winds later Saturday into Sunday to portions of southern 
New England. Again, this is still low probability scenario 
right now being displayed by a small percentage of model 
solutions. This will continue to be monitored as confidence in 
the upper pattern and details increases as we get closer.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

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

06z TAF Update:

Today...High confidence. Low/mod for low clouds on 
Cape/Islands.

VFR for most. Confidence lower in the potential for periods of 
BKN low clouds near the Cape and Islands esp later in the day. 
E-NE winds 6-15 kts with the strongest near the coast. NE winds 
gust to between 20 and 25 knots across the Cape and especially 
Nantucket during the daylight hours. 

Tonight...High confidence. Moderate for ceilings. 

VFR for most. MVFR-IFR ceilings develop across Cape and Islands
potentially reaching the east coast and BOS after midnight.
Confidence in the inland extent of these conditions is low at
this time but could extend as far inland as BED. 

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Wednesday through Saturday/...

Wednesday: Mainly VFR, with local MVFR possible. Chance SHRA.

Wednesday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA.

Thursday: MVFR/IFR conditions possible. Breezy. SHRA.

Thursday Night: Mainly VFR, with local MVFR possible. Breezy.
Slight chance SHRA.

Friday: VFR. Breezy. 

Friday Night: VFR. 

Saturday: VFR. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Today through Wednesday..High confidence.

High pressure centered over the Canadian Maritimes with distant low 
pressure well southeast of the Benchmark continues NE flow through 
much of the week. This long fetch will generate 3 to 6 foot seas 
across the outer-waters...so current small craft headlines will 
persist through at least Thursday. 


Outlook /Wednesday night through Saturday/...

Wednesday: Winds less than 25 kt. Areas of rough seas. Chance
of rain showers, patchy fog. 

Wednesday Night: Winds less than 25 kt. Areas of rough seas.
Chance of rain showers. 

Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Rain showers, slight chance of
thunderstorms. 

Thursday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain showers. 

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 AM EDT Thursday for ANZ250.
     Small Craft Advisory until 8 AM EDT Thursday for ANZ254>256.

&&

$$

DISCUSSION...Mensch/FT
AVIATION...Mensch/FT
MARINE...Mensch/FT