Old Res Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 252336
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
736 PM EDT Fri Apr 25 2025

.SYNOPSIS...
Increasing cloudiness and also rather mild for late April
tonight. Periods of rain, with embedded downpours develop
overnight and continue into at least the first part of Saturday.
Some breaks in the overcast in western New England could allow
for enough warming for a few afternoon thunderstorms. Then a
cold front ushers in a much cooler airmass Saturday night. 
Cloudy, cool, and blustery conditions on Sunday. Warmer and more
pleasant weather Monday through Wednesday. A cold front will 
bring more seasonable weather on Thursday and Friday.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
415 PM Update:

Key Messages: 

* Filtered high clouds turn overcast before midnight, with some 
  stratus along the south coast. Turning a touch humid (by late 
  April standards).

* Rain develops just after midnight and moves east into eastern 
  MA/RI overnight. Brief downpours possible.

* Lows in the 50s tonight, and a few western areas stay near 60.

Details:

Mostly sunny conditions (filtered thru a canopy of high clouds) has 
allowed for several areas to warm into the 70s with a few low 80s in 
the warmer CT Valley and parts of eastern MA. Although cooler temps 
due to increased south flow along the immediate southern coast 
(60s/low 70s) or eastern MA coastal seabreezes. Been one of the 
milder days seen to this point in 2025. However we're in a pretty 
changeable weather pattern with weak high pressure well to our 
southeast allowing a modest southerly flow to return northward, with 
some marine stratus east of the Delaware shore looking to fill in 
N/NE tonight along our southern coastline. Many areas should stay 
dry through at least the first half of the night, but cloud cover 
should stand to increase in most areas. 

The bigger disturbance responsible for our weather pattern though is 
a low pressure area now over central MI, which will spread a warm 
front through Southern New England during the second half of the 
night. This feature will bring a pretty robust surge in moisture 
levels (PWATs rise to 1.3-1.5" on SWly 850 mb jet of 45-50 kt), with 
some very meager elevated instability as we move into the 2nd half 
of the night and into early Saturday morning. Expect steady light to 
moderate rains spreading in from the Berkshires overnight and 
continue into central/eastern MA and RI toward the early overnight 
to pre dawn hrs (~3-6 AM); there certainly could be some downpours 
in some of this rain activity but we expect rain to be pretty 
welcomed in light of recent dry weather we've had. Wouldn't rule out 
a rumble of thunder too but this is more the exception. Rain should 
be ongoing across much of Southern New England by morning. 

Lows tonight should be quite mild for late-April, and it may feel 
more like a early summer evening with lows in the 50s, given rising 
dewpoints into the 50s as well and increased S winds. Some areas, 
especially western CT/MA, could stay above 60F.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
415 PM Update:

Key Messages: 

* Rain moves offshore, but eastern MA and RI may struggle to reach 
  the lower 60s with overcast likely stubborn.

* A few t-storms possible west of Worcester Sat afternoon, and a 
  couple could become strong if we can clear 

* Stark change in air mass toward cooler and breezy conditions 
  Saturday night.

Saturday: 

Although still rather mild and a touch on the humid side, all in all 
Saturday is looking to generally be a washout, especially through 
the morning hours as steady moderate rain with some embedded 
downpours gradually moves offshore. Rain should be tapering off 
around mid-morning in western MA and most of CT, and during the late 
morning to early afternoon in eastern MA and RI. Will be overcast 
with limited warming likely for as long as rain continues. 

Besides timing the rain offshore, the main forecast uncertainty 
revolves around the extent to which we can shake free of cloud cover 
even after the rain exits. This will affect not just the 
temperatures, but also on potential afternoon destabilization and 
possible afternoon thunderstorms. Am not especially optimistic on 
many breaks in overcast in eastern MA and RI, where conditions from 
a stability perspective proving to be quite stable. Temperatures 
here may struggle to get into the low 60s under assumption that 
cloud cover will temper opportunities for diurnal warming. 

Latest guidance has trended more optimistically on cloud clearing 
across the Berkshires, CT Valley and into Tolland and western 
portions of Worcester Counties during the afternoon. Some heating 
and the higher dewpoints in the 50s could produce enough instability 
to pop off scattered convective showers or thunderstorms along the 
cold front. There is quite a bit of variability on how much 
instability we could see, and with lapse rates being on the lower 
side, the convective setting would hinge greatly on how soon we can 
break out into some sunshine. HREF mean surface based CAPE shows an 
axis of around 500-1000 J/kg in the above-described corridor, with a 
maximum (worst-case/earlier-clearing outcome) around 1000-1500 J/kg. 
Scattered t-storms could develop or move east from eastern NY during 
the midafternoon, and we could need to watch a couple stronger 
cells. In fact, there is some updraft helicity tracks shown in HREF 
output given a favorable deep layer shear profile. But this is 
conditional on there being enough heating to destabilize the 
atmosphere - there may be little if any development at all if cloud 
clearing is delayed. Airmass would likely be far more stable further 
east one goes with little if any t-storm threat in eastern New 
England. We could see highs in western New England in the mid 60s to 
low 70s if we can scatter out of cloud cover.

Saturday Night: 

Cold front then rushes offshore during the evening to overnight 
hours. Strong cold and dry advection will usher in a much cooler 
airmass to Southern New England, with increased westerly breezes and 
drier air/lower dewpoints. Quite a change in airmass: our 925 mb 
temps tumble from around +14-16C Saturday afternoon to around 0C! 
Strength of the upper level low and cooler air aloft suggests 
the evening could still be fairly cloudy in western New England.
Lows to fall into the 40s with westerly breezes around 10-15 
mph.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Long Term

 * Cool and blustery conditions on Sunday 

 * Warming trend Monday through Wednesday 

 * Closer to normal temps Thursday and Friday with unsettled weather 
   possible Friday

Unfortunately, after a rainy Saturday, the weather on Sunday may be 
just as unpleasant, with cloudy, cool, and blustery conditions. With 
the 500mb closed trough and cold pool over the region, cyclonic 
vorticity and diurnal heating will likely lead to light popcorn 
showers, especially north of the MA Pike.  High temps Sunday wont 
top 60, staying in the mid to upper 50s.  With CAA and a tight 
pressure gradient, blustery north winds could make it feel like the 
40s outside.  The CAA and diurnal heating will promote mixing to 
around 850mb, where winds increase from 30mph to 60mph towards 
sunset.  Not sure if the 60mph winds aloft will arrive in time 
before the sunsets and the nocturnal inversion sets in, but wind 
headlines may be needed for late in the day Sunday.  Gusts at the 
surface will likely reach the 35-45mph range, with the NBM showing 
low to moderate probs for 45-55mph in the high terrain.  

Just in time for the beginning of the work week, the nice 
spring/early summer weather returns with highs warming into the low 
70s on Monday and mid to upper 70s on Tuesday and Wednesday.  Less 
windy on Monday as a mid-level ridge axis passes over the region. 
Ridge axis moves east of the region Tuesday and Wednesday, allowing 
winds to turn southwesterly and become gusty again around 20-30mph. 
A cold front moves through sometime Wednesday afternoon or evening, 
but dry air may keep rain or thunderstorms from forming along this 
front.  Temperatures behind the cold front for Thursday and Friday 
will be more seasonable in the 60s to low 70s.  Unsettled weather is 
possible heading into Friday as guidance hints at another possible 
shortwave exiting the Great Lakes.

&&

.AVIATION /23Z FRIDAY THROUGH WEDNESDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

00Z TAF Update:

Tonight: Low confidence. 

Guidance is not handling current conditions well as low clouds
are not materializing even as warm southerly winds blow over 
the cold ocean waters. Hence confidence in the forecast 
overnight is low. Guidance has also slowed down the onset for 
precipitation, now reaching western MA/CT around 9-10z, and 
eastern MA/RI around 11-12z. 

Saturday: Moderate confidence. 

Widespread MVFR (with some IFR) in bands of steady moderate
rain, which begins to move offshore around 18-20z. By then, 
clouds scatter to VFR-MVFR (perhaps still some straggling IFR 
along the south coast). Possible SCT SHRA/TS near/west of ORH 
after 20z Sat, although development and strength of any TS 
would depend on how quickly we see any breaks in OVC. If we do 
see any storms, they would likely be weakening as they move east
of ORH. S/SW winds around 10-15 kt with occasional gusts to low
20s-kt range. 

Saturday Night: High confidence. 

Improvement toward SCT-BKN VFR with cold frontal passage, 
though some MVFR bases may develop overnight in western 
airports. Winds become W/WNW around 10-15 kt with gusts 25 kt 
(up to 30 kt high terrain).
 
KBOS TAF...High confidence in TAF thru 07z, then moderate to low.

VFR with E/SE winds continuing thru 03z before becoming S 
around 10 kt. Mainly MVFR bases with 3-6SM RA developing after 
10z Sat, possibly IFR at times. RA ends ~18-20z with slow 
improvement in cigs to borderline VFR levels. Another round of
showers and perhaps a rumble or two of thunder is possible late
afternoon to early evening

KBDL TAF...High confidence in TAF thru 05z, then moderate to low.

VFR with south winds around 10 kt. MVFR-possible IFR bases with
3-6SM RA developing after 09z, then tapering off around early 
to mid afternoon. Possible SCT SHRA/TS after 20z depending on 
how quickly improvement develops from AM rains. 

Outlook /Sunday through Wednesday/...

Sunday: Mainly VFR, with local MVFR possible. Strong winds with
gusts up to 40 kt. Slight chance SHRA.

Sunday Night: VFR. Strong winds with gusts up to 40 kt. Slight
chance SHRA.

Monday: VFR. Breezy. 

Monday Night: VFR. 

Tuesday: VFR. Breezy. 

Tuesday Night: VFR. Breezy. Slight chance SHRA.

Wednesday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels:

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

Southerly winds will be increasing to around 15-20 kt tonight, 
with seas building to 2-4 ft. Southerly flow then continues to
strengthen into the SCA range for Saturday, with winds 25-30 kt
and seas 4-7 ft. Rain and reduced visibilities expected until a
sharp frontal passage Saturday evening, bringing a windshift to
W/NW around 15-25 kt.

Outlook /Sunday through Wednesday/...

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

Sunday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Seas up to 5 ft. Slight chance of rain
showers. 

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

Monday Night: Winds less than 25 kt. 

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

Tuesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain
showers. 

Wednesday: Winds less than 25 kt. Local rough seas. Slight
chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 AM Saturday to 8 AM EDT Sunday for 
     ANZ231>237-250-254>256.

&&

$$

SYNOPSIS...Loconto/KP
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...KP
AVIATION...Loconto/KP
MARINE...Loconto/KP