Old Res Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 041842
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
242 PM EDT Sat Apr 4 2026

.WHAT HAS CHANGED...
Small craft advisories now in effect for all waters through Sunday. 
Best chance for widespread rains is during Sunday afternoon,
then a cooldown to temperatures into early next week.

&&

.KEY MESSAGES...

- Turning overcast with cool onshore breezes and perhaps some 
  drizzle thru midnight, then another round of scattered showers
  overnight into the pre-dawn hours.

- Still overcast most of Sunday but with modest warming; while 
  generally dry during the morning, widespread rains develop 
  during the afternoon with a cold front, clearing into the 
  waters by evening.

- Rain/snow showers possible Monday night into Tuesday morning,
  but otherwise dry and cool.

- Temperatures increase through the second half of next week 
  and conditions remain dry.

&&

.DISCUSSION...
KEY MESSAGE 1...Turning overcast with cool onshore breezes and 
perhaps some drizzle thru midnight, then another round of scattered 
showers overnight into the pre-dawn hours.

A backdoor cold front was working its way through central MA and 
eastern CT, bringing increasing marine cloudiness, much cooler air 
(40s to low 50s common) and a gusty ENE wind in the 25-35 mph range 
across eastern MA and RI. This backdoor front will continue to surge 
westward toward the spine of the Berkshires thru late afternoon. As 
the PBL continues to cool, expect cloudiness to continue to fill in 
and lower/thicken as we move into the mid evening hours. There could 
be some patchy drizzle around as the overcast stratus layer takes 
hold, but much of the time is dry. Will be rather cool and moist 
with temps in the mid 30s to low 40s by midnight, with E/ESE winds 
around 5-10 mph this evening (gusts to 20 mph near the coast). 

The lingering frontal boundary then begins to return northward as a 
warm front overnight, in response to strengthening 925-850 mb 
warm/moist advection on SWly 40-45 kt LLJ. Rising PWATs and lowering 
Showalter indices to around 0 units then should allow for a round of 
scattered showers to develop and move northward sometime thru the 11 
pm to 5 am timeframe. Wouldn't rule out a rumble of thunder given 
falling Showalter indices but this seems like the exception vs the 
rule. That will also bring with it slowly rising temperatures and 
dewpoints into the pre-dawn hours, although overcast conditions to 
continue. 

KEY MESSAGE 2...Still overcast most of Sunday but with modest 
warming; while generally dry during the morning, widespread rains 
develop during the afternoon with a cold front, clearing into the 
waters by evening.

We then get into a cloudy warm sector with SW winds around 10 mph (a 
bit stronger over the Cape and Islands). This cloud cover will be 
tough to shake free of as shallow moisture remains trapped 
underneath very mild 925-850 mb temps around +10C. Thus warming 
would be driven more through advective processes with very little to 
nil insolational heating. NBM high temps in the upper 50s to mid 60s 
seem optimistic and brought these down about 5 degrees into the 50s 
in most areas. 

Wouldn't rule out a hit or miss shower during the morning in the 
cloudy warm sector, but it looks as though the best chance for 
widespread showers is during Sunday afternoon as a cold front moves 
in from the west. A round of steady light to at times moderate 
showers, perhaps with a rumble or two of thunder as Showalter 
indices dip to -1, as the front gradually trudges east toward the 
eastern coastal waters by early evening. Additional/lingering rains 
should persist toward southeast MA, southern RI and the Cape and 
Islands thru midnight; but the majority of Southern New England to 
see decreasing cloudiness and falling dewpoints with westerly winds 
post-frontal. Rain amounts range from about a quarter to third of a 
inch, perhaps as much as a half-inch in steadier showers. Lows 
Sunday night in the 30s, with values in the 30-32F range in interior 
higher terrain as WNW winds pick up.  

KEY MESSAGE 3...Rain/snow showers possible Monday night into 
Tuesday morning, but otherwise dry and cool.

Following Sunday's cold front, colder and drier conditions take hold 
as surface high pressure starts to take hold and an upper level 
trough settles overhead. A shortwave may move through the region 
Monday night into Tuesday morning, which would interrupt this brief 
dry period with a mix of rain and snow showers. These are not 
expected to be very impactful to travel or roads as temperatures 
remain mostly in the 40s and upper 30s. Higher elevations may dip 
below freezing, but temperatures there will also improve quickly 
heading into Tuesday morning. Outside of the risk for showers that 
could linger through the day as the shortwave passes through, drier 
conditions can be expected as dewpoints fall into the 20s across the 
region (30s over the Cape and Islands). Tuesday night will be 
noticeably cooler as the trough sits overhead and 925 mb 
temperatures fall to -8C to -5C after being just at or below 0C 
Monday/Monday night. Winds remain mostly W and NW for the start of 
the week in the post-frontal airmass.

KEY MESSAGE 4...Temperatures increase through the second half 
of next week and conditions remain dry.

High pressure moves into the Mid-Atlantic region during the second 
half of the week then shifts more offshore, which will aid in 
bringing back SW flow over southern New England and keep the region 
dry. Temperatures will improve as the week goes on and the upper 
level trough moves off to the east. Highs will likely end up back in 
the 50s and 60s. Some uncertainty remains, though, towards the end 
of the week as the GEFS hints at another backdoor front that could 
lead to cooler temperatures, particularly across eastern MA and RI. 
If that plays out, highs could struggle to hit 60F Friday afternoon. 
By comparison, the other ensembles do not have this feature and have 
highs in the mid to upper 60s. We should get more clarity as we get 
closer in time.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

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

18z TAF Update: 

Today: High confidence in TAF/trends but moderate on timing.

SCT-OVC VFR ceilings (low-VFR/MVFR range eastern MA/RI) as
backdoor cold front now moving thru central MA/CT brings a 
gusty windshift to ENE thru 20z toward the Berkshires. Gradual 
deterioration in ceilings likely into the remainder of the 
afternoon; ceilings could drop into MVFR range as soon as 20z 
from BOS/Cape airports to ORH/PVD, then continue to spread 
westward to BDL/Berkshires thru 00z. NE/E winds around 12-15 kt 
with gusts 20-23 kt, though trending E/ESE at BDL and PVD late.

Tonight: High confidence in TAF/trends but moderate on timing
any showers. 

MVFR to LIFR ceilings with E/ESE winds around 10-15 kt. Though
there could be patchy intervals of drizzle, scattered showers
develop ENE as backdoor front from today lifts northward as a
warm front. Uncertain on exact timing but best chance probably
not sooner than 03z continuing to about 10-11z. Winds to then 
turn from E/ESE 10-15 kt with occasional gusts 20-25 kt to SE-S 
around 10 kt.

Sunday: Moderate confidence. 

IFR/patchy LIFR early, but should trend toward IFR-MVFR cloud
bases by mid-morning to noontime. Possible mist and drizzle 
ahead of cold front, which brings widespread rain showers 
approx. 17-23z from west to east. A low chance for a rumble or
two of thunder but think SHRA predominates much of the time. SW
winds around 10-15 kt (upwards of 20 kt with gusts 25-28 kt Cape
and Islands), shifting to W/WNW and decreasing to under 10 kt
speeds upon frontal passage. 

Sunday Night: High confidence. 

Mainly VFR, possible VFR/MVFR ceilings western high terrain. NW
winds increase to 10-15 kt with gusts 25 kt. 

KBOS Terminal...High confidence in TAF/trends but moderate on
timing. E winds around 15-20 kt with area of SCT VFR/MVFR 
ceilings lingers most of today; deteriorating to MVFR ceilings
as soon as 20z, continuing to trend to MVFR-IFR ceilings this 
evening as winds become ESE. Psbl SHRA 05-10z Sun. 

KBDL Terminal...High confidence. VFR with north winds, trending
easterly late in the day with arrival of MVFR ceilings. Ceilings
continue to lower to MVFR/IFR range early tonight. Psbl SHRA
03-08z Sun.

Outlook /Sunday Night through Thursday/...

Monday: VFR. Windy with local gusts up to 30 kt. 

Monday Night: VFR. Chance SN, slight chance RA.

Tuesday: VFR. Breezy. Chance SHRA, chance SHSN.

Tuesday Night: Breezy. 

Wednesday through Wednesday Night: 

Thursday: Breezy. 

&&

.MARINE...
Forecaster Confidence Levels...

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

High confidence.

Given NE/E gusts are currently in very solid SCA to near-gale-
force range with the immediate passage of the backdoor front, 
and that SWly gusts for Sunday look to be more in the SCA range 
with strongly- inverted profiles, have hoisted SCAs for all 
waters starting now through 00z Monday (thus, gale watches on 
southern waters converted to SCAs). 

Expect gusts to be strongest thru Saturday afternoon at around 
25-30 kt (occasional gusts to 35 kt possible), then settle in 
around 25-30 kt range. Seas remain in the 3-5 ft range thru 
tonight, then increase more markedly as southerly winds increase
the fetch, building offshore to nearly 10 ft on southern 
waters. Winds Sunday night to shift to NW at sub-SCA levels 
briefly, but could gust to around SCA ranges late overnight 
Monday.

Low chance at mist/fog overnight, but better chance for rain
showers late Sunday afternoon to early Sunday evening.

Outlook /Sunday Night through Thursday/...

Monday: Winds less than 25 kt. Local rough seas. 

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

Tuesday: Winds less than 25 kt. Chance of rain showers. 

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

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

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT Sunday for ANZ230>237-250-
     251-254>256.

&&

$$

DISCUSSION...Loconto/Hrencecin
AVIATION...Loconto/Hrencecin
MARINE...Loconto/Hrencecin/Nash/Nocera