BOX issues Area Forecast Discussion (AFD) at Mar 18, 8:08 PM EDT
548
FXUS61 KBOX 190008
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
808 PM EDT Tue Mar 18 2025
.SYNOPSIS...
Dry weather with mild afternoon temperatures are on tap for the
interior Wednesday and Thursday...but it will be considerably cooler
on the coast particularly on Wednesday with onshore flow. A
system and accompanying cold front will bring rain Thursday
night into Friday. The rain may end as a brief period of snow
across higher elevations of the interior. Windy conditions are
expected Friday with highs around or slightly below normal.
Warmer temperatures for the weekend.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Key Messages...
* Lingering clouds along the coast dissipate tonight
* Mainly clear tonight with lows in the 20s & 30s
Mid level ridging building into southern New England tonight will
result in the lingering clouds near the coast departing
tonight...but may still flirt with the Cape and Nantucket tonight.
We also should see winds become light/calm away from the immediate
coast as well as the Cape/Islands. This will bring a good night of
radiational cooling tonight with the normally cooler outlying
locations bottoming out in the 20s...while many urban centers drop
into the 30s. Enough wind will remain in the boundary layer across
the Cape/Islands to prevent decoupling and keeping overnight lows in
the 30s.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Key Messages...
* Plenty of sunshine Wed with a large temp gradient in SNE
* Highs Wed 45-50 along immediate coast & well into the 60s interior
* Low clouds/fog and areas of drizzle develop late Wed night
Details...
Wednesday...
Mid-level ridge axis with well above normal heights will be in
control of our weather Wed. This will result in plenty of sunshine
and well above normal high temps across the interior. We will have
to watch for some low clouds and fog patches flirting with the
Cape/Islands...especially by late in the day.
Otherwise...the main story Wed will be the wide range in high temps
from the immediate coast to the interior. 925T rise to around
+9C/+10C...so despite the chilly start highs should recover well
into the 60s across portions of the interior. However...a ridge of
high pressure in the Maritimes coupled with low pressure well off
the mid-Atlantic coast will result in onshore surface winds. This
will keep the coastal plain cooler with highs mainly in the
50s...but probably only 45-50 along the immediate eastern MA coast
as well as the Cape/Nantucket.
Wednesday night...
High pressure over the Maritimes will continue to generate light
onshore flow. This combined with the cooling boundary layer will
allow low clouds and fog patches to back in off the ocean Wed night.
Specific timing of this still needs to be sorted out...but expect
low clouds and fog to have overspread the entire region by daybreak
Thu. We also expect areas of drizzle to develop overnight too.
Overnight low temps will mainly be in the 35-40 degree range.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Key Messages:
* System brings rain Thursday night with a transition to snow early
Friday AM mainly higher elevation areas in the interior.
* Light snow accumulation possible for high elevations such as
Berkshires, but more likely less than an inch.
* Windy Friday with gusts 30-40 mph for most areas, locally higher
gusts possible.
Thursday:
A mid-level trough approaches the region Thursday with an associated
low and cold front that will track through Thursday night. Overall
there is a good model consensus that this system will bring
precipitation across southern New England mainly later Thursday.
Thursday will feature increasing SE surface winds and precipitation
and gradually increasing moisture. High temperatures range in the
upper 40s-mid 50s closer to the coastline with the continued effect
of the onshore wind component. Temperatures will likely be slightly
warmer further inland in mid-upper 50s. With increasing moisture,
this will be accompanied by increased cloud cover through the day.
Can't rule out the chance for a some rain showers Thursday morning
(mainly east/SE MA) if the easterly flow keeps a shallow layer of
moisture intact at the surface. The higher chances for precipitation
comes Thursday night-Friday morning with the added lift of the front
and precipitable water values rising to 150-200% of normal.
As the cold front moves across overnight, gusty NW winds and colder
air work in from west to east. This will support a transition to
light snow across the interior early Friday AM, especially across
the higher elevations. There is still some question on how far east
this rain/snow transition will go. This is likely stemming from
uncertainty in low track, temps, and some timing difference among
guidance as well. Model guidance overall has the system exiting by
mid-afternoon Friday. For liquid amounts, ensembles show a range of
0.20-0.60". For snow amounts, the highest probabilities for seeing
>1" are confined to the Berkshires (40-60%). Worcester Hills north
of the Mass Pike has lower probabilities and will more likely see a
dusting to 1/2" if it does stick. Overall minimal impacts.
Friday through Weekend:
Cooler during the day Friday with temperatures in the 40s and windy
conditions. With a LLJ moving across and CAA, this may support gusts
30-40 mph, potentially up to 45 mph in isolated higher elevation
spots.
Mid-level ridging moves in for the weekend with dry conditions.
Warming 850mb temperatures and breezy downslope winds will support
temperatures rebounding back into the 50s Saturday. Ensemble
guidance shows a shortwave trough moving across sometime Sunday.
There are still differences in the track of the system among model
guidance which will play into precipitation chances/amounts. With
limited forcing and moisture, precip chances are lower and limited
to some scattered showers this far out.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update:
Tonight: High confidence.
VFR, with SCT-BKN high clouds. Lower borderline VFR/MVFR deck
possible just offshore of ACK but will stay away from the
terminals. NE winds 4-8 kt, though stronger (10-15 kt / gusts
20-25 kt) Cape and Islands.
Wednesday: High confidence overall, though trends moderate late.
VFR for the majority of SNE; however MVFR marine stratus may
try to return to the Cape and Islands during the morning/early
afternoon, and could get into BOS as soon as 18z, but think more
likely after sundown as moisture is shallow and prone to being
mixed out. Opted for VFR for now. NE winds around 4-8 kt with
stronger winds Cape and Islands, though winds will become E/ESE
late in the day.
Wednesday night...High Confidence in trends, moderate confidence
in timing.
Light/moist onshore flow coupled with a cooling boundary layer
will allow low clouds and fog to back in off the ocean as the
night wears along. While specific timing still needs to be
sorted out...thinking IFR with localized LIFR conditions
dominate by daybreak Thu. In addition...areas of drizzle will
also likely develop late Wed night.
KBOS TAF...High Confidence in TAF.
KBDL TAF...High Confidence in TAF.
Outlook /Thursday through Sunday/...
Thursday: Mainly VFR, with local IFR possible. Breezy. Areas
DZ, slight chance RA.
Thursday Night: MVFR/IFR conditions possible. Breezy. RA.
Friday: MVFR/IFR conditions possible. Windy with gusts up to
30 kt. Chance RA.
Friday Night: VFR. Windy with local gusts up to 30 kt.
Saturday through Saturday Night: VFR. Breezy.
Sunday: Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Wednesday night...High Confidence.
Mid-level ridging will continue to build into the region tonight and
allow the pressure gradient to continue to gradually weaken. Still
expect NE small craft wind gusts towards the waters by the
Cape/Islands. These wind gusts should gradually diminish below
criteria by daybreak Wed. Otherwise...mid level ridge axis will keep
wind gusts below small craft advisory criteria through Wed night.
However...lingering easterly swell will result in the need for small
craft advisories for seas to persist across the outer-waters through
Wed night. Areas of fog will develop late Wed and especially Wed
night which will reduce vsbys for mariners.
Outlook /Thursday through Sunday/...
Thursday: Winds less than 25 kt. Local rough seas. Slight
chance of rain, patchy drizzle.
Thursday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain.
Friday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Rough seas up to 8 ft. Chance of rain.
Friday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 9 ft. Slight chance of
rain.
Saturday: Winds less than 25 kt. Seas up to 5 ft.
Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.
Sunday: Winds less than 25 kt. Seas up to 5 ft.
&&
.HYDROLOGY...
In response to Monday's rainfall and some contributions from
snowmelt upriver along the Connecticut River basin, river flood
warnings for minor flooding are active on portions of the
Connecticut River and on the Wood River at Hope Valley.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 2 AM EDT Wednesday for ANZ231>234.
Small Craft Advisory until 11 PM EDT this evening for ANZ235-
237-251.
Small Craft Advisory until 8 AM EDT Thursday for ANZ250-
254>256.
&&
$$
SYNOPSIS...Frank/Loconto/FT
NEAR TERM...Frank
SHORT TERM...Frank
LONG TERM...Loconto/FT
AVIATION...Frank/Loconto/FT
MARINE...Frank/Loconto/FT
HYDROLOGY...BW
Source: BOX issues Area Forecast Discussion (AFD) at Mar 18, 8:08 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202503190008-KBOX-FXUS61-AFDBOX)
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