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 021909
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
309 PM EDT Sat May 2 2026

.WHAT HAS CHANGED...
No significant changes.

&&

.KEY MESSAGES...

- Light rain continues this afternoon. More widespread rain
  arrives for the Cape and Islands tonight into the early
  morning hours Sunday.

- Drying trend Monday into Tuesday with warmer temperatures and
  breezy to gusty southwest winds. 

- Cold front brings a chance of showers and thunderstorms late
  Tuesday, followed by an unsettled and cooler pattern mid to  
  late week. 

&&

.DISCUSSION...
KEY MESSAGE 1...Light rain continues this afternoon. More widespread 
rain arrives for the Cape and Islands tonight into the early morning 
hours Sunday.

A mid level trough digging into the Mid Atlantic this evening and 
overnight continues to send a plume of moisture ahead of it on SW 
flow. This moisture together with a surface boundary and favorable 
placement beneath a 120kt upper jet will continue to produce light 
to moderate rain showers over much of the region, though it will be 
exiting east through the afternoon and evening. Attention then turns 
to the more widespread soaking expected to accompany a sub 1000mb 
coastal low lifting north but remaining offshore overnight. This 
will bring a soaking rain, mainly confined to Cape Cod and the 
islands. That being said, wrap around moisture will likely bring 
widely scattered showers to much of eastern MA on Sunday morning. By 
mid to late morning Sunday drier air will have moved in the at the 
surface and upper levels for most of SNE; however, a layer of 
moisture at 850 mb together with lingering cyclonic flow aloft will 
lead to widespread diurnal clouds so don't expect skies to clear 
fully even as the mid/high clouds from the overnight system exit. 
Temperature-wise, not much change in the mid levels and we're 
looking at near persistence if not a few degrees warmer than 
Saturday owing to the breaks of sun. Finally, better mixing behind 
the system will lead to some breezy winds Sunday afternoon with a 
weak LLJ overhead, but damaging winds are not expected. 

KEY MESSAGE 2...Drying trend Monday into Tuesday with warmer 
temperatures and breezy to gusty southwest winds. 

Low pressure lifts into the Canadian Maritimes Monday while high 
pressure builds to our south over the southwestern Atlantic. Aloft, 
quasi-zonal flow dominates much of the CONUS, though a developing 
Rex block over the Pacific Northwest may influence the pattern later 
in the forecast period. For sensible weather, expect mainly dry 
conditions with increasing sunshine and a warming trend. Southwest 
flow will advect milder air into the region, with 850mb temperatures 
rising from around +4C to +6C Monday to +12C to +14C Tuesday. 
Forecast soundings support a well-mixed boundary layer, expecting 
highs in the mid 60s to lower 70s Monday and upper 70s to low 80s 
Tuesday. The pressure gradient tightens through the period, 
resulting in breezy conditions Monday with southwest gusts 20-30 
mph, increasing to 25-35 mph Tuesday. Given recent dry conditions, 
gusty winds, and relatively low humidity (min RH 25-35% Monday and 
30-40% Tuesday away from marine influence), elevated fire weather 
concerns are possible. Coordination with state fire weather partners 
is ongoing, and headlines may be needed early next week. 

KEY MESSAGE 3...Cold front brings a chance of showers and 
thunderstorms late Tuesday, followed by an unsettled and cooler 
pattern mid to late week. 

Cold front approaches late Tuesday, though timing remains uncertain. 
With highs climbing well above normal, guidance suggest a few hundred 
J/kg of CAPE, which may support scattered convective showers and 
thunderstorms. Current CSU-ML guidance indicates low-end (~5%) 
severe probabilities But this will need to be monitored give a 
strengthening low-level jet in the vicinity. The front may be slow to 
clear the region, sagging south of southern New England Wednesday 
with lingering showers and possible thunderstorms.  

Looking ahead, the pattern becomes more active as mid-level ridge 
develops across western CONUS, replacing the Rex blocking, and a 
trough across the eastern CONUS. This will support multiple 
shortwaves and surface lows moving through the flow, resulting in 
periodic chances for showers Thursday into Friday. Timing details 
remain uncertain at this range. Late week bears watching, as 
guidance suggests a stronger system could impact the region Thursday 
night into Friday, accompanied by a robust southerly low-level jet. 
This may bring a period of heavier rainfall and gusty winds. While 
details remain uncertain this far out, the potential exists for 
impactful conditions including hazardous marine weather. 
Astronomical tides appear relatively low late week, which should 
limit coastal flood potential unless a stronger system materializes. 

Behind the front, cooler temperatures return with highs generally in 
the upper 50s to lower 60s Wednesday and beyond. 

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

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

18Z Update

This afternoon: Moderate confidence in TAF. 

- SHRA continues through early evening for BOS while RA continues
 for the south coast and southeast MA. S winds SE/ESE 5-10 kts.

Tonight: Moderate confidence. 

VFR outside of the Cape and island terminals as a system
offshore brings low clouds and RA to those sites. Can't rule 
out a passing shower for BOS, but more likely mid Sunday 
morning. Winds come around to NW 5-10 kts.

Sunday: High confidence. 

MVFR, at least for east terminals early Sunday AM. For BOS this
is likely a short window of lowered ceilings and scattered
showers. Improving to VFR mid to late morning and closer to 
early afternoon for Cape/Island terminals. VFR for west/central 
terminals. NW winds 8-12 kts with a few gusts to 20 kts. 

Sunday night: High confidence. 

VFR. W winds 5-10 kts become lighter SW through the night. 

KBOS Terminal...High confidence in TAF. 

KBDL Terminal...High confidence in TAF.

Outlook /Sunday Night through Thursday/...

Sunday Night: VFR. 

Monday through Tuesday: VFR. Breezy. 

Tuesday Night: VFR. Windy with gusts up to 30 kt. Slight chance
SHRA.

Wednesday: VFR. Windy with gusts up to 30 kt. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Overall high confidence.

S winds become NW tonight, turning NW and becoming 10-20 kts
with some gusts to 25kts Sunday. Rain begins to increase on the
southern waters later tonight into Sunday.

Seas also increase Sunday morning, and a small craft advisory 
is in effect for the outer waters for seas of 4-6 ft. 

Outlook /Sunday Night through Thursday/...

Sunday Night: Winds less than 25 kt. Local rough seas. 

Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft. 

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

Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. 

Tuesday Night: Strong winds with gusts up to 35 kt. Local rough
seas. 

Wednesday: Strong winds with gusts up to 35 kt. Seas up to
5 ft. Chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 11 AM Sunday to 2 PM EDT Monday for 
     ANZ250-254>256.

&&

$$

DISCUSSION...BW/Dooley
AVIATION...BW/Dooley
MARINE...BW/Dooley