BOX issues Area Forecast Discussion (AFD) at Mar 12, 3:39 PM EDT
852
FXUS61 KBOX 121939
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
339 PM EDT Wed Mar 12 2025
.SYNOPSIS...
Seasonably cool through Thursday, with a period of light
rain/snow showers possible tonight. Trending milder Friday,
especially away from the south coast. By this weekend, 60s are
expected Sunday, along with windy conditions. A period of heavy rain
along with the potentially strong to damaging southerly wind gusts
are possible Sunday night into Monday. Drier weather returns by
Tuesday, with relatively mild temperatures.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
330 PM update...
Key Messages: seasonably cold with spotty light rain showers
transitioning to light snow showers.
Tranquil/dry late afternoon along with seasonable temperatures and a
modest N-NE breeze. For this evening, roughly 00z-06z, watching
current band of light snow/rain over Lake Ontario, mainly aloft and
not reaching the ground given dew pts in the single digits and teens
across western NY. This light precip is upstream of northern stream
energy moving across the northern lakes. This will yield increasing
clouds tonight over SNE. Deep layer moisture is lacking, so just
expecting light rain showers transitioning to light snow
showers/flurries tonight across MA/CT/RI. Although, some of this
will evaporate before reaching the ground, given our antecedent
conditions, with dew pts in the single digits across northern MA,
teens elsewhere. Hence, some areas will remain dry with no impacts
overnight for any locations, just some spotty light rain showers
transitioning to light spotty snow showers. Seasonably cold tonight
with lows in the upper 20s to lower 30s. N-NE winds 5-10 mph inland,
10-15 mph and more easterly along the coast.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
330 PM update...
Thursday...
Key Messages: Dry, seasonably cool with a mix of sun & clouds
Northern stream energy exits New England, with rising heights and
dry confluent flow over SNE. Hence, dry weather Thursday for
MA/RI/CT. Should be enough subsidence to support at least partial
sunshine at times. 1025 mb maritime high nosing southeast over SNE,
provides shallow cool air and a subsidence inversion to limit highs
Thu to the 40s. Which is seasonable for mid March. However,
it will feel cooler at the coast, given onshore winds.
Thursday night...
Key Messages: Dry & seasonable weather continues.
Weak wave of low pressure tracks south of SNE, with NE flow possibly
bringing low clouds into SE MA and RI. Otherwise, dry weather
prevails and seasonable cold, with lows in the upper 20s to lower
30s.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
330 PM update...
Key Messages
* Warming trend for the weekend w/ cooler conditions along south-
facing coastlines
* Unseasonably mild weekend with winds picking up Sunday
* Heavy rain with strong to damaging winds possible Sunday night
into Monday
* Calmer conditions next week w/ areas of minor flooding from
snowmelt and Sunday's rainfall
Details...
Pattern becomes more amplified by Friday as a strong upper level
trough digs over the Plains. Ahead of it, mid-level ridging builds
over the region. Surface temperatures warm underneath the ridge
except for the Cape and Islands where an onshore flow likely caps
temperatures in the lower to mid 40s. Highs in the interior will
likely sit in 50s, with temperatures closer to 60F possible in the
CT Valley. Overnight, lows are expected to be in the 40s and upper
30s due to continued cloud cover and onshore winds.
All eyes turn to strong upper level trough as it digs through the
plains this weekend, amplifying the upper level flow across the
eastern US. Meridional flow will help usher in unseasonably mild
temperatures and more moisture. Ensembles continue to indicate high
probabilities of temperatures over 60F by Sunday, especially over
the urban centers. Highs Saturday and for the rest of the region
Sunday will likely sit in the mid to upper 50s, with dew points in
the 40s Saturday and getting into the 50s Sunday.
By Sunday afternoon a narrow corridor of 60-80 kt 925 mb winds
overspread the CWA. BUFKIT soundings indicate an inversion near the
surface which would help cap the strongest gust potential. A good
rule of thumb in scenarios with a strong LLJ and inversion is to
take about 50% of the 925 mb wind speeds to get a reasonable
estimate for expected wind gusts. In this case, that would translate
to a period of 30-40 kt wind gusts between 18z Sunday and 06z Monday
morning. At this time, the area to watch for the strongest wind
gusts would be areas with higher terrain and along and east of the I-
95 corridor.
The other threat with the system is a period of heavy rain as the
shortwave energy finally reaches southern New England Sunday night.
The forecast NAEFS mean meridional wind forecast is at
climatological max Sunday into Sunday night. The anomalous southerly
flow should have no issue advection copious moisture into the
region. PWAT values are still forecast to reach 1" to 1.5", or about
3-4 standard deviations above normal for this time of year.
Combining these ingredients with the robust LLJ over the region will
result in the chance of heavy rain. Guidance currently has the
highest probabilities for this heavy rain across SE CT into RI and
SE MA. In these areas, the NBM has a 20-30 percent chance of 24-hour
rainfall totals exceeding 2". The swath of heaviest rainfall will
likely shift around as we get closer to the event, but there is good
agreement that the region will experience a soaking rain Sunday
night into Monday. While dry antecedent conditions will likely
prevent widespread flash flooding issues, snowmelt, and heavy
rainfall across northern New England may result in river rises along
larger rivers such as the Connecticut River. GEFS river ensemble
forecasts have a 30% chance of the CT river exceeding flood stage at
Deerfield MA. Higher chances further south w/ probabilities rising as
high as 70% at the CT river at Middle Haddam.
We dry out behind this system for Tuesday morning and winds shift
more to the WNW before mid to upper level ridging builds back in
during the day behind the shortwave. Highs will likely be in the 50s
across southern New England.
&&
.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18z update...
Thru 00z...VFR, dry weather and a modest N 10 kt inland, NE
10-15 kt along the coast. High forecast confidence.
Tonight...High confidence.
VFR cloud bases but a period of MVFR cigs roughly 03z-06z with a
band of rain showers/sprinkles transitioning to snow
showers/flurries later in the evening. Little if any
accumulation is expected. East winds 5-10 kt, except 15-20kt
with gusts up to 25 kt along the south coast and Cape Cod.
Thursday...High confidence.
Any lingering MVFR cigs in the morning, quickly give way to VFR
cloud bases. East winds 10-15 kt, gusts up to 20 kt along the
south coast and Cape Cod.
Thursday night...high confidence.
VFR cloud bases, dry weather and NE winds 10-15 kt, gusts up to
20 kt possible over the Cape. MVFR cigs may develop in the NE
flow over southeast MA into RI.
KBOS TAF...High Confidence in TAF. Low probability for a period
of MVFR cigs in -RA/SN 03z-06z tonight.
KBDL TAF...High Confidence in TAF. Low probability for a period
of MVFR cigs in -RA/SN 03z-06z tonight.
Outlook /Friday through Monday/...
Friday: Mainly VFR, with local MVFR possible.
Friday Night: Mainly VFR, with local IFR possible.
Saturday: Mainly VFR, with local IFR possible. Breezy. Slight
chance RA.
Saturday Night: Mainly VFR, with areas IFR possible. Breezy.
Chance RA.
Sunday: MVFR/IFR conditions possible. Windy with gusts up to
35 kt. Chance RA.
Sunday Night: Mainly MVFR, with areas IFR possible. Windy with
gusts up to 35 kt. RA.
Monday: Mainly VFR, with local IFR possible. Breezy. Chance RA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
330 PM update...
Through Thursday night...High confidence.
Tonight...high pressure moves across northern New England tonight,
providing, dry, tranquil weather along with modest E-NE winds.
Marginal SCA, up to 25 kt and 5 ft seas possible south and east of
Cape Cod and the islands.
Thursday...High pressure drifts into the maritimes, yielding dry,
tranquil weather for mid March, with modest NE winds. Marginal SCA,
up to 25 kt and 5 ft seas possible south and east of Cape Cod and the
islands.
Thursday night...not much change, weak wave of low pressure tracks
southeast of the 40N/70W benchmark, modest NE winds continue, but
dry weather and good vsby. Marginal SCA conditions possible south
and east of Cape Cod and the islands.
Outlook /Friday through Monday/...
Friday: Winds less than 25 kt. Seas up to 5 ft.
Friday Night: Winds less than 25 kt. Areas of seas approaching
5 ft.
Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain.
Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain.
Sunday: Low risk for gale force winds with gusts up to 35 kt.
Rough seas up to 11 ft. Chance of rain.
Sunday Night: Strong winds with gusts up to 35 kt. Rough seas
up to 13 ft. Rain.
Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Rough seas up to 12 ft. Rain likely.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 7 AM to 8 PM EDT Thursday for ANZ250.
Small Craft Advisory until 8 PM EDT Thursday for ANZ254>256.
&&
$$
SYNOPSIS...FT/Nocera
NEAR TERM...Nocera
SHORT TERM...Nocera
LONG TERM...FT
AVIATION...FT/Nocera
MARINE...FT/Nocera
Source: BOX issues Area Forecast Discussion (AFD) at Mar 12, 3:39 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202503121939-KBOX-FXUS61-AFDBOX)
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