Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 141837
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
237 PM EDT Tue Apr 14 2026

.WHAT HAS CHANGED...
No significant changes, the forecast remains on track.

&&

.KEY MESSAGES...

- Scattered late day and evening showers and thunderstorms with
  a low risk of severe weather. 

- Summerlike warmth continues Wednesday away from the coast, 
  but backdoor front will bring cooler temps to portions of 
  eastern MA. Another round of scattered afternoon and evening 
  showers and thunderstorms with a low risk for severe weather. 

- Temperatures trend milder western MA/CT and cooler in eastern
  MA/RI Thurs-Sat, with periods of showers/t-storms mainly
  focused on Fri.

- Strong cold frontal passage Sunday ushers in cooler 
  temperatures for early next week. 

&&

.DISCUSSION...
KEY MESSAGE 1...Scattered late day and evening showers and 
thunderstorms with a low risk of severe weather. 

Latest hi-res guidance has delayed onset of scattered convection 
moving into SNE to late in the day and this evening. We still have 
height rises into early afternoon then weak height falls developing 
late today and this evening as a weak shortwave passes to the north. 
There are favorable mid level lapse rates approaching 7 C/km and 
there is sufficient 0-6km shear for storm organization. However, 
instability is marginal with MLCAPES generally 500-1000 J/kg and 
with potential convection delayed into the evening instability will 
be diminishing. Also forcing for ascent is marginal as well. So 
while there are some conflicting signals for severe weather, if 
robust convection can get going to the north and west later this 
afternoon favorable deep layer shear should be enough to support a 
few strong to severe storms with the timing mainly from 5-10 pm 
across northern and western MA where HREF is showing some updraft 
helicity tracks. Strong to damaging wind gusts will be the primary 
threat but can't rule out some hail given steep mid level lapse 
rates and favorable deep layer shear.  

KEY MESSAGE 2...Summerlike warmth likely to continue Wednesday away 
from the coast, but backdoor front will bring cooler temps to 
portions of eastern MA. Another round of scattered afternoon and 
evening showers and thunderstorms with a low risk for severe 
weather. 

Backdoor front expected to slip southward into NE MA Wed morning and 
eventually move through rest of eastern MA by late afternoon but 
timing is uncertain. 925 mb temps 20-21C south and west of the 
boundary which will result in temps reaching low-mid 80s, especially 
across CT and portions of central/W MA which will remain on the warm 
side of the boundary. Meanwhile, temps will likely fall into the 50s 
in NE MA with temp forecast uncertainty highest across interior E 
and SE MA which will be close to the boundary. It is possible temps 
here warm well into the 70s and possibly lower 80s before the front 
moves through then falling sharply by late afternoon but this will 
depend on the timing of the front. 

Another round of scattered showers and thunderstorms expected Wed 
afternoon into the evening as another low amplitude shortwave 
approaches. Environment is fairly similar to today with MLCAPES 500-
1000 J/kg although mid level lapse rates are less favorable. 0-6 km 
shear is up to 40 kt which is quite favorable for storm 
organization. Hi-res CAMs do show varying areal coverage of 
convection developing into the afternoon in the interior then 
eventually becoming focused near the south coast during Wed night. 
CSU machine learning probs and Nadocast showing low risk for severe 
across the interior so can't rule out a few strong to severe storms 
again with damaging wind the primary threat. HREF severe wind probs 
are a bit lower tomorrow and focused across CT. 

KEY MESSAGE 3...Temperatures trend milder western MA/CT and 
cooler in eastern MA/RI Thurs-Sat, with periods of 
showers/t-storms mainly focused on Fri.

Challenging temperature and rain chances forecast Thurs and Fri as 
unseasonably warm temperature profiles aloft are met with quasi-
zonal mid-level flow with several hard-to-time impulses (some 
convectively-influenced) moving through the WSW flow. There is also 
the potential for a backdoor frontal boundary to bring significantly 
cooler temperatures to at least eastern and northeast MA, but 
potentially as far westward as central MA and RI. 

Ended up keeping a rather generic/broad-brush to PoPs, with lesser 
chances on Thurs and most of the day could be dry. Better chances 
could exist on Fri with NWP showing a stronger/more-coherent 
shortwave disturbance moving in. 

For temps, modified NBM highs Fri and Sat to bring cooler temps (mid 
60s to low 70s) along the eastern MA coast to RI/central MA, but 
highs should end up well into the 70s to lower 80s in western MA/CT 
under SW winds. Highs are somewhat cooler on Fri with more cloud 
cover and periods of showers/t-storms, in the 60s to low 70s. By 
Sat, we become more entrenched in cooler onshore flow with highs in 
the 50s to mid 60s. The potential exists for large temperature busts 
given placement of the backdoor frontal boundary. 

KEY MESSAGE 4...Strong cold frontal passage Sunday ushers in 
cooler temperatures for early next week. 

Strong cold front moves in for the latter half of the weekend 
bringing a risk for showers and thunderstorms for Sunday. Passage of 
this front will usher in an unseasonably cool airmass (850 mb temps 
as low as -8C Mon). Expect cool temperatures more typical of 
early/mid March vs mid-April, with highs in the mid 40s to lower 
50s, but blustery conditions will make it feel quite a bit
cooler. 

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...

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

This Afternoon and Tonight...Moderate confidence in areal coverage 
of TSRA and timing. 

VFR. A cold front brings hit-and-miss thunderstorms to areas across 
western New England late this afternoon into the early evening. This 
could lead to brief MVFR ceilings and IFR visibilities. It bank of 
low stratus/fog develops off the east coast of MA, which should 
remain off shore the first half of the night, before inching on 
shore early Wednesday morning, here flight categories fall to MVFR. 

SW to S wind today, periodically gusty 15-20 knots. Wind speeds ease 
overnight, becoming calm in protected areas. 

Wednesday and Wednesday Night... Moderate Confidence.

Becoming VFR. A frontal boundary remains in the vicinity of SNE and 
have moderate confidence this remains across NE MA. North of the 
boundary MVFR with winds E to E. South of the boundary VFR and winds 
are SW. Showers and thunderstorms develop along the boundary between 
18z-00z. Overnight becoming IFR to MVFR across most of the region, 
the only area that could remain low-end VFR is be the lower CT River 
Valley and points SW. Light southwest wind. 

KBOS Terminal... Moderate confidence in TAF.

Have moderate confidence in the chance of TSRA and lower clouds 
Wednesday morning. Will have LLWS tonight between 02z-08z.

KBDL Terminal... Moderate confidence in TAF. 

Have moderate confidence in the timing and coverage of TSRA this 
afternoon/evening.

Outlook /Thursday through Sunday/...

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

Thursday Night: VFR. Chance SHRA.

Friday: VFR. Chance SHRA, slight chance TSRA.

Friday Night: Mainly VFR, with local MVFR possible. Chance
SHRA, slight chance TSRA.

Saturday: Mainly VFR, with areas MVFR possible. 

Saturday Night: Mainly VFR, with areas IFR possible. Slight
chance SHRA.

Sunday: Mainly VFR, with areas IFR possible. Breezy. Chance
SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

SCA for outer southern waters through tonight for marginal 
seas. S- SW winds will gust to 20+ kt at times, shifting to E 
over NE MA waters during Wed with SW flow persisting over 
southern waters. Variable winds Wed night less than 20 kt,
mostly N-NE over NE MA waters and SW over southern waters. Late
night and early morning fog possible.

Outlook /Thursday through Sunday/...

Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers. 

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

Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers. 

Friday Night: Winds less than 25 kt. Slight chance of rain
showers, slight chance of thunderstorms. 

Saturday through Saturday Night: Winds less than 25 kt. 

Sunday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers. 

&&

.CLIMATE...
Upcoming record highs:

Tue 4/14
Boston 83 in 2023
Hartford 96 in 2023
Providence 87 in 2023
Worcester 90 in 2023

Wed 4/15
Boston 82 in 1896
Hartford 88 in 1941
Providence 82 in 1938
Worcester 85 in 1941

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 4 PM EDT this afternoon for ANZ254.
     Small Craft Advisory until 8 AM EDT Wednesday for ANZ255-256.

&&

$$

DISCUSSION...KJC/Loconto
AVIATION...Dooley
MARINE...KJC
CLIMATE...Nocera