Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 131909
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
309 PM EDT Sat Apr 13 2024

.SYNOPSIS...

Clouds briefly decrease tonight, but increase again on Sunday as a
fast-moving frontal system moves through. This should bring another
round of light rain showers, but there is a chance for isolated
thunderstorms across portions of CT, RI and south of the Mass Pike
in MA Sunday afternoon and night. Showers diminish Sunday night,
setting the stage for a mild and dry start to the work week. More
unsettled by mid week, with a large degree of uncertainty revolving
around temperatures and precipitation timing.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...

A smattering of diurnal showers continues across much of southern
New England this afternoon driven largely by the broad trough
passing overhead. The axis of said trough (now just east of the
region) will continue to march east through the evening as the
shortwave lifts out. This loss of synoptic forcing together with
loss of daytime heating will mean diminishing showers and cloud
coverage toward sunset, with skies really clearing after 2-3AM. As
mid level heights briefly rise we`ll end the night and start Sunday
with mostly clear skies. While winds will remain breezy overnight,
temps should drop several degrees compared to lows last night under
the cooler air mass, into the upper 30s/low 40s.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...

If you get outside during the morning hours tomorrow you should be
able to get enjoy party sunny skies, though an approaching warm
front and associated mid level trough will mean skies quickly cloud
over after noon. It will be followed quickly by a cold front as the
weak surface low passes overhead or just to our north Sunday
afternoon and evening. Given the 30-60 kt LLJ passing just offshore
and a modest PWAT plume of ~1 inch this frontal system should bring
anywhere from a few hundreths of an inch to a half inch of
rain. Hi- resolution guidance is in general agreement that we`ll
see two distinct rounds of rain: first some light warm
advection showers in the late morning/early afternoon followed
by a lull and then a round of heavier rain accompanying the cold
front Sunday evening. Where confidence is lower is how much
drying we`ll have between these rounds or if showers hang around
much of the day. There remains potential for some rumbles of
thunder ahead of the cold front as well, depending on how far
the warm sector extends east into southern New England.
Currently decent mid-level lapse rates (6.5- 7.5C/km) and a few
hundred J/kg of CAPE extend into western CT/MA where the best
chance of thunder will be in the afternoon, and the SPC has
these locations under a Marginal Risk (level 1 of 5) of severe
storms. Can`t rule out a rumble of thunder along the immediate
south coast later in the evening as the low passes. The cold
front and line of rain/thunderstorms should move off of Cape Cod
by midnight leaving rapidly clearing skies under drying NW
flow.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...

Highlights:

* Drying trend develops Monday and Tuesday

* Mild start to the week, uncertainty in temperatures the second
 half of the work week

* Unsettled conditions should return late Wednesday into next weekend

Much of this portion of the forecast should feature a broad mid
level over southern New England through early next week. A stronger
mid level cutoff should move from Hudson Bay to the Saint Lawrence
Valley during this time as well. We should catch a brief break
beneath a ridge towards Wednesday. After then though, there is
quite a bit of uncertainty in the synoptic details within the latest
guidance suite. Have sketched out a general period of unsettled
weather from late Wednesday into next Saturday, but fully expecting
the timing details to change with later forecasts.

Not much different at the surface. High pressure starts to build
across southern New England for Monday, but is more in place for
Tuesday. Thus, despite the trough aloft, thinking we will see dry
weather with at least some sunshine. Will have to monitor the
humidity, as this could be a setup for more diurnal clouds, at least
for Monday.

Then the aforementioned timing issues become more of a factor. High
pressure should move off to the east, opening a path for a low
pressure to impact our region sometime from late Wednesday into
Thursday morning. This low pressure is currently projected to move
offshore for Friday, but a warm front should be lingering nearby. A
cold front should sweep most of the unsettled weather out over the
North Atlantic for Saturday, assuming the current timing holds.

Temperatures expected to be near to above normal through this
portion of the forecast.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
Forecast Confidence Levels:

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

18Z TAF Update:

This afternoon: High confidence.

VFR to MVFR cloud bases with BKN/OVC and bases 015-040. Hit-and-miss
light showers continue through around 22Z. Blustery W/SW winds
25-35 kt.

Tonight: High confidence.

VFR. Clearing skies by 6Z. West winds around 10-13 kt with
diminishing gusts.

Sunday: High confidence in trends, moderate in exact timing.

Quick-moving frontal system from the Great Lakes spreads
increasing/lowering cloud bases into the VFR/MVFR range. Best
chance of scattered showers during the afternoon after 18z;
there could be a rumble or two of thunder south and west of a
BDL-PVD line later in the day but confidence is on the low side.
W winds shift to SW then S around 10-12 kt.

Sunday night: High confidence.

VFR for most terminals except IFR in the high terrain of central
MA (ORH) early, but cigs will be lifting region-wide. Showers
move off of Cape Cod by 04Z. SW winds becoming lighter and
turning to the NW after 06Z.

KBOS TAF...High confidence in TAF. Mainly BKN VFR to at-times
MVFR bases (thinking 025-040). Could be a hit or miss shower
but not enough confidence in coverage to include as a TAF
mention. SW winds increase around 15 kt with gusts 25 kt, then
becoming W and decreasing to around 10-12 kt tonight.

KBDL TAF...High confidence in TAF. BKN to OVC VFR bases trend
MVFR early this morning, with periodic P6SM -SHRA. S winds
around 10 kt to start, then shift to SW/WSW and increase to
around 10-14 kt with gusts 25-28 kt late AM to aftn, easing to
10 kt tonight.

Outlook /Monday through Thursday/...

Monday: VFR. Breezy.

Monday Night: VFR.

Tuesday: VFR. Breezy.

Tuesday Night: VFR.

Wednesday: VFR. Chance SHRA.

Wednesday Night: MVFR/IFR conditions possible. Breezy. SHRA
likely.

Thursday: MVFR/IFR conditions possible. Breezy. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

High confidence...

Gusty SW to W wind gusts 25-30 kt on the eastern waters, and up
to 35 kt on the southern nearshore and offshore waters. Winds
subside later tonight. Seas will remain elevated and rough,
around 7-10 ft on the outer waters.

Sunday morning SW gusts ramp up again to around 15-20 kt with
seas around 4-6 ft on Sunday. Winds gust to 20-30 kts during the
early overnight hours, diminishing after midnight. Chance for a
few t-storms on the far southern outer waters very late Sunday
afternoon, but at least scattered showers develop during the
afternoon on all waters.

Outlook /Monday through Thursday/...

Monday: Winds less than 25 kt. Local rough seas.

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

Tuesday through Tuesday Night: Winds less than 25 kt.

Wednesday: Winds less than 25 kt. Chance of rain showers.

Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas locally approaching 5 ft. Chance of
rain showers.

Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 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 8 PM EDT this evening for ANZ230-
     236.
     Small Craft Advisory until 8 AM EDT Sunday for ANZ231-251.
     Gale Warning until 2 AM EDT Sunday for ANZ232-254>256.
     Gale Warning until 8 PM EDT this evening for ANZ233>235-237.
     Small Craft Advisory until 8 PM EDT Sunday for ANZ250.

&&

$$

SYNOPSIS...Belk/BW
NEAR TERM...BW
SHORT TERM...BW
LONG TERM...Belk
AVIATION...Belk/BW
MARINE...Belk/BW


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