BOX issues Area Forecast Discussion (AFD) at Mar 20, 7:05 AM EDT538
FXUS61 KBOX 201105
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
705 AM EDT Thu Mar 20 2025
.SYNOPSIS...
Low clouds and areas of fog...some of which will be locally dense
continue today. A system and accompanying cold front will bring rain
Thursday night into early Friday...perhaps ending as a very brief
period of wet snow across the highest terrain. Once the rain ends
Friday it will become windy with afternoon temperatures mainly in
the 40s. 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-Tuesday with mainly rain, but perhaps a
period of wet light snow across parts of the interior early Monday
morning.
&&
.NEAR TERM /THROUGH TONIGHT/...
Key Messages...
* Cloudy on Thursday with periods of drizzle but largely dry.
Today the region remains downstream of a deep shortwave digging into
the Midwest which will eventually bring widespread rain overnight.
Given the saturated low levels indicated by surface observations
this morning and forecast soundings in the future, periods of
drizzle and mist will be possible through the day as low clouds
remain. The thick cloudcover coupled with 925mb temps decreasing to
near 7C will mean highs topping out in the mid to upper 50s for
everyone; quite the cool down for much of western SNE. Thanks to
continued onshore flow the coolest spots will be along the immediate
coast where temperatures won't get out of the upper 40s.
&&
.SHORT TERM /FRIDAY/...
Key Messages...
* Rain moves through the region in about 12 hours, from midnight to
noon.
* Precipitation could end as brief light snow in the highest
elevations of the Berkshires.
Out ahead of a shortwave and surface low a plume of moisture moves
overhead (PWATs > 0.75"). 500 mb PVA and synoptic lift from
placement beneath the left exit region of an upper level jet will
lead to widespread rain overspreading from west to east.
Precipitation begins in western CT/MA around midnight, overspreading
SNE through 4 AM before coming to an end between 7 AM and noon on
Friday. Guidance has been slower to close off the 700 mb low which
would limit CAA on the back side and time for precip to flip to
snow. While some of the highest elevations of the Berkshires could
still see a dusting to a half inch of snow, any wintry precip that
falls is not expected to be impactful.
As drier air moves in behind the front on increasingly gusty NW
winds, forecast soundings show a well mixed boundary layer able to
mix down wind gusts as high as 30-40 mph in the afternoon. We'll see
increasingly sunny skies from west to east in the afternoon and
evening.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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 /11Z THURSDAY THROUGH MONDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12z TAF Update...
Today and tonight: High confidence in trends, but moderate in
exact timing.
IFR-LIFR conditions in low clouds, fog and drizzle this morning
may improve to MVFR in some locations by mid afternoon with ESE
wind 8-12 knots, but confidence in improvement is low.
Conditions will trend back to IFR with localized LIFR levels by
this evening as the boundary layer cools. RA arrives late
Thursday evening through early Friday morning with IFR
conditions. Backing winds overnight becoming north by Friday
morning.
Friday: High confidence in trends, moderate confidence in
timing.
RA ending between 12z and 15z. Friday starts off VFR for
terminals generally west of ORH, IFR east, but improving to VFR
15Z-18Z. Increasingly gusty NW winds gusting 30-40 kts.
KBOS TAF...High Confidence in TAF. Areas of dense fog & drizzle
will impact the terminal through the am push. Some minor
improvements to IFR low end MVFR conditions are possible by the
afternoon but confidence in improvement is low.
KBDL TAF...High Confidence in trends with moderate confidence in
timing.
Outlook /Friday Night through Monday/...
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.
Today through Friday: High Confidence.
Small craft advisories for the outer waters for marginal seas
through Friday, with building seas outside of Boston Harbor and
Narragansett Bay tonight into Friday morning. Poor visibility
continues early this morning, at time less than 1/2 mile.
Today near shore seas 2-4 ft and off shore seas 4-5 ft.
Southeast winds 10-15 knots today. Tonight near shore seas 3-5
ft and offshore seas 5-7 ft, wind are backing tonight as
surface low pressure moves into the southern waters. Friday
winds become NW and increase, gusting 25-35 kts with seas
increasing to 5-7 ft.
Outlook /Friday Night through Monday/...
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...Dense Fog Advisory until 10 AM EDT this morning for MAZ006-007-
014>016-018-019-021>024.
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...BW/Mensch
NEAR TERM...BW
SHORT TERM...BW
LONG TERM...Frank/Mensch
AVIATION...BW/Mensch
MARINE...BW/Mensch
Source:
BOX issues Area Forecast Discussion (AFD) at Mar 20, 7:05 AM EDT----------------
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