596
FXUS61 KBOX 040033
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
833 PM EDT Thu Apr 3 2025

.SYNOPSIS...
A few Light rain showers are possible this evening with the
passage of a weak cold front. More light rain likely overnight
near the south coast as this cold front stalls. Drying and
clearing trend for Friday with mild daytime temperatures.
Turning unsettled this weekend with rain chances both of the
days along with below normal temperatures on Saturday to
slightly above normal on Sunday. Though there is some
uncertainty with how warm it may become Sunday. Drying out
Monday, but cooler temperatures return for the week ahead with
unsettled conditions Tuesday and perhaps late next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Last several runs of the HRRR have been bullish on the idea of
another round of showers as a weak cold front works its way east
across southern New England. Just started to see these showers
developing over eastern NY state. Expecting this trend to continue,
so used a time-lagged ensemble of the HRRR to tweak rainfall
chances overnight with this package. Also expecting another
round of showers toward the south coast. These showers were over
eastern PA.

Not much push to this front, so thinking it will take most of
the overnight hours to finally get offshore. Until this happens,
rather humid conditions with lower clouds and patchy drizzle
persist across southeast MA. Latest observations showed some
breaks in the low clouds north and west of I-95 in MA, RI and
CT. Expecting some lower clouds with the showers later tonight
just ahead of the cold front.

Brought temperatures back in line with observed trends.

Previous Discussion...

A weak cold front drops south through southern New England this
evening, bringing more scattered light showers and possibly a
rumble or two of thunder near the south coast, where residual
instability remains. The front wont make it much further than
the south coast before stalling as a weak low-pressure system
rides along it overnight. This will likely bring another round
of light rain to the areas, mainly along the south coast but as
far north as the MA Pike. Despite the cold fronts passage, we
wont see much clearing or cooling. Low to mid-level clouds will
stick around all night and help hold overnight lows in the upper
40s to low 50s.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Dry northerly air pushes out any remaining showers by mid-Friday
morning, with clearing skies from north to south. With 850mb
temperatures still around +8C, high temperatures will be able to
jump back into the low to mid-60s, with low 70s possible in
eastern MA. Winds remain from the NW Friday at 10-20mph.

Rising heights Friday night will keep things dry, but expect
increasing mid- to upper-level cloud cover ahead of the next
shortwave. Calm winds overnight will help radiational cooling
bring lows into the upper 30s to low 40s.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Key Messages:

* Less than ideal conditions this weekend with rain chances and
  a cooler feel due to a backdoor cold front.

* Cooler and unsettled conditions persist into early next week.

Saturday through Sunday Night: Anticipate broad area of high
pressure to build across southwestern Quebec, anticyclonic flow
brings a backdoor cold front and ushers cooler marine air as
result of the northeast to east flow. 925mb temperatures
decrease Saturday to +/-1C, resulting in afternoon highs from
the middle to upper 40s. The surface high shifts to the east and
the warm front lifts north which shifts wind direction to
southwest, advecting warmer and more moisture into southern New
England by Sunday. A forecast challenge on Sunday, how far north
does the warm sector reach? The trailing cold front is not too
far removed. Deterministic guidance, have the warm sector mostly
suppressed to the south, with limited warmer air aloft moving
out before early afternoon, limiting heating potential for the
afternoon. Appears to be the theme amongst the deterministic
guidance, cooler than 00z run and moving the warm sector out
quicker too. Spread in temperatures are shown easily on DESI,
viewing the 10th and 90th percentile of the NBM, has a spread of
20 degrees for almost the entire region, the exception is Cape
Cod and the Islands where the spread is much less, less than 7
degrees. As result did deviate from the warmer NBM solution by
blending in the cooler CONSMOS guidance, resulting highs are
middle 50s to near 60F. As for precipitation this weekend, PWATs
range between 1.3" and 1.5" which is 2-3 standard deviations
above normal. Rain arrives late Saturday morning into early
afternoon, from west to east. Expect precipitation to persist
through Sunday as the associated low- pressure system traverses
the region Saturday night through Sunday evening. During this
time frame, cannot rule out rumbles of thunder, SREF has fairly
low probabilities of MUCAPE exceeding 250J/kg at 30% across
southwestern New England. As the cold front exits Sunday night
into early Monday morning, enough cold air advects in behind the
front and may change the rain to a sleet/snow mix in the higher
terrain of northern and western Massachusetts.


Monday though Thursday: Briefly drier conditions on Monday,
though the next system is not too far off as a low-pressure
system moves into northern New England from the Great Lakes
region for Tuesday. The exact positioning is uncertain as
guidance ranges from roughly Albany, NY to Montreal. The system
lacks moisture, PWATs fall from 0.4" to 0.2" during Tuesday
morning, but cold air aloft and marginal surface temperatures in
the higher elevations, AOA 1,000 FT, may lead to a snow/rain
mix, with spotty rain showers in the lower elevations. A quick
break on Wednesday is followed by another quick moving system
late next week. As for temperatures, trending slightly below
normal with highs in the 40s, but cooler across interior
southern New England in the mid 30s, this if for Monday thru
Wednesday, perhaps nearing the 50s Thursday. Lows in the 30s
Monday night, followed by lows in the 20s Tuesday night and
Wednesday night.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Tonight...Moderate Confidence.

IFR/LIFR in the early evening hours ahead of a cold front. This
cold front moves from north to south between 01-05z this
evening. There could be some light showers associated with the
cold front. CIGS will gradually rise back to MVFR/VFR levels
behind the cold front. Weak low pressure system traverses near
the south coast late overnight, which will bring light showers
and MVFR CIGS through about 06-12z. These showers should stay
mainly south of the MA pike.

Friday... High Confidence

VFR. West/northwest winds at 10 knots gusting 20 knots.

Friday Night... High Confidence

VFR. Light northerly winds under 10 knots.

BOS TAF...Moderate confidence.

Cold front could bring some light showers this evening between
02-04z with gradual improvement of CIGS to MVFR/VFR this
evening.

BDL TAF...Moderate confidence.

VFR CIGS this evening. A weak low will bring light rain
overnight with gradual clearing conditions by morning.

Outlook /Saturday through Tuesday/...

Saturday: Mainly MVFR, with local IFR possible. Breezy. SHRA,
chance FZRA.

Saturday Night: Mainly MVFR, with areas IFR possible. Breezy.
SHRA.

Sunday: Mainly MVFR, with local IFR possible. Breezy. Chance
SHRA.

Sunday Night: Mainly MVFR, with local IFR possible. SHRA
likely.

Monday: MVFR/IFR conditions possible. Slight chance SHRA.

Monday Night: Mainly MVFR, with local IFR possible. Slight
chance SHRA, slight chance SHSN.

Tuesday: Breezy. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight through Friday night...High confidence.

Gusty SW winds at 20-30 knots continue this evening before
diminishing as a cold front approaches and stalls near the
southern waters. Light rain showers are possible overnight as a
weak low pressure systems moves from west to east tonight. Winds
shift NW at 10-15 knots late overnight and remain there for
Friday.

Seas this evening remain elevated around 4-8 feet, diminishing
to 3-6 feet by Friday morning. Seas drop to 2-4 feet by Friday
afternoon.

Outlook /Saturday through Tuesday/...

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

Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Rain showers.

Sunday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Chance of rain showers.

Sunday Night: Winds less than 25 kt. Areas of rough seas. Rain
showers.

Monday: Winds less than 25 kt. Local rough seas. Chance of rain
showers.

Monday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers.

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 10 PM EDT this evening for ANZ230.
     Small Craft Advisory until midnight EDT tonight for ANZ231-251.
     Small Craft Advisory until 5 AM EDT Friday for ANZ232>234.
     Small Craft Advisory until 11 AM EDT Friday for ANZ235-237.
     Small Craft Advisory until 1 AM EDT Friday for ANZ236.
     Small Craft Advisory until 8 AM EDT Friday for ANZ250.
     Small Craft Advisory until 8 PM EDT Friday for ANZ254>256.

&&

$$

SYNOPSIS...Dooley/KP
NEAR TERM...Belk/KP
SHORT TERM...KP
LONG TERM...Dooley
AVIATION...Belk/Dooley/KP
MARINE...Dooley/KP