BOX issues Area Forecast Discussion (AFD) at Mar 20, 1:49 PM EDT127
FXUS61 KBOX 201749
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
149 PM EDT Thu Mar 20 2025
.SYNOPSIS...
Weak low pressure system and accompanying cold front will bring
rain overnight into early Friday. Once the rain ends Friday it
will become windy with seasonable temperatures. Dry and mild on
Saturday with some scattered showers possible later Saturday
afternoon. A cold front moves through Saturday bringing breezy
and cooler conditions Sunday. Another round of precipitation
Monday and Tuesday with mainly rain, but perhaps a period of
wet light snow across parts of the interior early Monday
morning.
&&
.NEAR TERM /THROUGH TONIGHT/...
130 pm update...
Key Messages...
* Showers developing overnight
12z guidance hasn't shifted much from the overall expectations
we've had. A rather fast moving system will be moving into the
region late this evening. We should see rain showers developing
across the western half of the area by 10pm, and about midnight
for eastern areas. Not a lot of moisture or dynamics with this
system. With east/southeast flow out ahead of the system, we
will continue to see low clouds and fog pretty much everywhere
this evening -- so for those lucky areas across eastern CT, RI
and into central MA that did see some sun break out early this
afternoon, the clouds will fill back in prior to sunset. Some
differences in the track of an expected surface low to develop
along a cold front, but consensus suggests it will track from
Long Island into southeast MA late tonight. South of the low
track, we should see a brief period of breezy south/southeast
winds develop. With the cold frontal passage (about 4am out west
to 6-7am for eastern areas), we will see a switch to NW winds
for all areas. Cant rule out a few wet snowflakes mixing in
across the highest terrain in the Berks just prior to sunrise as
colder air starts to come in. But it won't otherwise be
noteworthy.
&&
.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
130 pm update...
Improving weather (as in the rain ends and skies begin to clear)
as we move into mid-day Friday. Stuck close to NBM guidance
given the agreement betwen models. Northwest winds will become
gusty as cold air advection helps deepen the boundary layer to
about 4000ft. This should allow some mixing of 30-40 mph winds
aloft down closer to the surface. So definitely becomes breezy
by the afternoon. Those winds diminish as we get into the
evening. Despite colder air coming in, it's not all that cold
compared to normal. So we should still see highs in the 40s to
low 50s Friday, dropping into the 20s across the interior to
lower 30s at lower elevations and closer to the coast.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Key Messages:
* Mainly dry & milder Sat with highs well up into the 50s with
nothing more than a brief spot shower or two across the interior
* Dry but blustery & colder Sat night into Sun
* Rain on tap for Mon perhaps beginning as a brief period of wet
snow mainly across portions of the interior
The Weekend:
Mid-level ridging moves in for the weekend with dry conditions.
Warming 850mb temperatures and breezy SW winds will support
temperatures rebounding back into the 50s and even a few spots
hitting 60 on Saturday.
Ensemble guidance shows a shortwave trough moving across late
Saturday into Sunday. With limited forcing and moisture, this will
be more likely result in some scattered showers Saturday later
Saturday afternoon/early evening. A cold front accompanies the
trough passage Saturday night which will bring a cooler day for
Sunday with high temperatures in the 40s and dry conditions.
Sunday Night - Wednesday:
There is good agreement among model guidance for an upper level
trough and associated low pressure system approaches the region
overnight Sunday. Guidance depicts New England in the left exit
region of the upper jet coupled with anomalous moisture. This will
bring another round of precipitation to the region. Precipitation
chances gradually increase early Monday morning from west to east,
continuing through late Monday night/early Tuesday.
There are still some details with the system that are in lesser
agreement among model solutions and runs. Mainly with respect to
track and cold air availability ahead of the system. This will play
into the potential for light wet snow at the onset of the system
that ensembles are signaling at. Additionally, it precipitation
will need to start when the airmass is still cold enough early
Monday morning. Ensembles show probabilities for a trace to
light snow accumulation across the interior, mainly MA.
Ensembles show generally a 20-50% chance for seeing over an 1"
north of the Mass Pike with locally higher probabilities over
the Berks. This period of snow will be likely short-lived as the
vertical column warms into mid-morning Monday. The rest will be
rain that continues through Monday night.
Tuesday and Wednesday:
Conditions trend drier Tuesday behind Monday's system with highs in
the 40s and low 50s. Ensemble guidance shows another shortwave
trough moving across mid-week that could bring some precipitation to
southern New England. There is uncertainties especially in the track
which will impact QPF and precipitation chances across the region.
&&
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18z TAF Update...
Moderate confidence.
Currently the gamut from LIFR to VFR across southern New
England, with the IFR/LIFR tending to be closer to the coast. We
will see IFR/LIFR conditions redevelop area wide this evening.
Quite a bit of spread in guidance for how low visibilities will
get, so although TAFs don't go as low as 1/4sm, it's possible
later this evening at nearly all sites. Rain will overspread the
region between 02z (west) to about 07z (east). With the rain, I
suspect there will be slight improvements in visibility, though
still IFR. Cold front moves through from about 08z (west) to 13z
(east) and winds will quickly switch to the NW. Expect
improving conditions by late morning/early afternoon with VFR
developing everywhere. However NW winds will gust 25-35kt in
most areas, especially after 16-18z. VFR continues Friday night,
with winds diminishing.
KBOS TAF...Moderate Confidence. Visibility could bounce between
1/2 to 4SM for the rest of the afternoon, but it's nearly
impossible to time out those details. IFR/LIFR is a certainty
beginning this evening. Timing in cold front passage and switch
to NW winds has an error bar of a couple of hours, but 12-14z
seems most likely.
KBDL TAF...Moderate confidence. Timing in the return to IFR
conditions, as well as rain and cold frontal passage and NW wind
switch is good to within a couple of hours.
Outlook /Saturday through Tuesday/...
Friday Night: VFR. Windy with gusts up to 30 kt.
Saturday: VFR. Breezy.
Saturday Night through Sunday: VFR. Windy with local gusts up
to 30 kt.
Sunday Night: VFR. Chance SN.
Monday: Mainly MVFR, with local IFR possible. Breezy. RA
likely, chance SN.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
130 pm update...
Moderate confidence.
Rather fast moving low pressure should move across the region
late tonight. Brief period of gusty south/southeast winds are
expected for the southern waters. Cold front passes through
early Friday morning, with a wind switch to the NW. Expect those
winds to become rather gusty -- up to 30kt after the front and
especially Friday afternoon and early evening. Thus the Small
Craft Advisories will remain in place.
Outlook /Saturday through Tuesday/...
Friday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas.
Saturday: Winds less than 25 kt. Areas of seas approaching
5 ft.
Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft.
Sunday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas.
Sunday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain.
Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Rain likely.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 AM to 8 PM EDT Friday for ANZ235-
237.
Small Craft Advisory until 8 PM EDT Friday for ANZ250-254>256.
Small Craft Advisory from 8 PM this evening to 8 PM EDT Friday
for ANZ251.
&&
$$
SYNOPSIS...Nash
NEAR TERM...Nash
SHORT TERM...Nash
LONG TERM...Frank/Mensch
AVIATION...Nash
MARINE...Nash
Source:
BOX issues Area Forecast Discussion (AFD) at Mar 20, 1:49 PM EDT----------------
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