Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 190512

Area Forecast Discussion
National Weather Service Boston/Norton MA
112 AM EDT Fri Apr 19 2024


A more seasonable day on Friday, along with dry conditions
during the daytime hours. A cold front brings another round of
showers overnight into early Saturday morning. Dry for the rest
of Saturday and all day Sunday with breezy conditions both days.
The dry stretch of weather continues as we head into early next
week, with the next chance for unsettled weather being



935 PM Update...

* Considerable cloudiness overnight...lows upper 30s/lower 40s

The last of the light showers/sprinkles from a mid level cloud
deck across far southeast MA will be exiting the region in the
next 1-2 hours. This is response to the deamplifying shortwave
moving east of the region. So while dry weather will prevail
for the overnight hours...mid level cloud deck will be stubborn
given there is not a strong push of dry air and low level winds
will remain onshore. A few breaks are possible in the
clouds...but expect a fair amount of clouds to hang tough
overnight. This should hold overnight low temps in the upper 30s
to the lower 40s.



345 pm update...


* Slight improvement for Friday with drier weather for the daylight
  hours and near seasonable temperatures.

* Unsettled overnight with another chance for light rain,
  especially along the south coast near daybreak on Saturday.

Some improvement weatherwise on Friday with surface high pressure
expanding into southern New England, along with mid-level ridging. A
warmer, more seasonable day with highs in the upper 50s and low 60s
are on tap. Where temperatures may struggle are along the immediate
coast as the winds are still coming off of the water. Areas of low
clouds to start gives way to breaks of sunshine late morning into
early afternoon, short-lived as mid and high clouds move in from
west to east ahead of a cold front. Winds are more or less out of
the southeast due to the flow from the surface high based in eastern
Quebec and surface low well off to the south near Bermuda. The
pressure gradient eases allowing for gusts less than 20 MPH at the

Increasing clouds from west to east during the second-half of the
day ahead of an approaching front. A prefrontal trough could set off
a few showers across western Massachusetts and northern Connecticut
late afternoon, but do think the bulk of any perception will come
with the frontal passage overnight, then kick off shore shortly
after sunrise on Saturday. That said, do not anticipate a soaking
rain, much of southern New England receives a few hundredths of an
inch, and the immediate south coast, Cape, and Island receive around
a quarter to a third of an inch.

Wind shifts overnight from southeast to southwest, no strong gusts
are expected. Overnight lows dip into the middle 40s.



345 pm update...

Key Point:
* Fire weather concerns this weekend through Tuesday

Fairly high consistency amongst the 12z global guidance runs as
well with prior runs. So that results in overall higher than
average confidence. In general, most of us will consider the
weather for most of the period to be pretty nice. A weak front
will be moving offshore during the first part of Saturday, only
bringing a few light showers. Behind the front, a much drier
airmass will be spreading in. So that will result in clearing
skies. Have again blended in the warmer side of guidance for
temperatures and lower side of guidance for dewpoints. Forecast
soundings still show excellent mixing (5000-6000ft) developing
in the afternoon along with westerly winds. Being still a "pre-
greenup" phase of vegetation, that usually means temperatures
overachieve and humidity levels go lower than most guidance
thanks to the combo of downsloping and deep boundary layer
mixing. We should see widespread mid 60s for highs, perhaps
making a run at 70F in the CT River Valley.

Sunday will be similar, though with 850mb temperatures slightly
cooler (down around -1C vs +1C on Saturday), daytime highs will
be a few degrees cooler, primarily either side of 60F. Again
deep boundary layer mixing (6000-7000ft) will act to bring down
some of the 25kt winds aloft along with dry air. Thus winds will
be gustier than on Saturday and lower dewpoints. The combo will
mean we will be flirting with some of the fire weather
thresholds (RH <30%, Frequent gusts >25mph, less than 1/4" of
rain in 3 days).

Monday, high pressure will move overhead and maintain the dry
weather. Still a dry airmass and deep mixing, but winds will be
weaker, so will still need to monitor fire weather aspects, but
don`t think it`s as significant a concern. Tuesday will still be
dry, but with high pressure moving off the east coast, winds
will start to turn southerly.

Guidance showing another weak front coming through Wednesday, so
stuck with NBM PoPs. Rainfall amounts again will be light. Dry
weather should return for Thursday.



Forecast Confidence Levels:

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

06z TAF Update...

Today...High Confidence.

VFR. SSE winds 5 to 15 knots.

Tonight and Saturday...High Confidence.

An approaching cold front will bring a period of MVFR-IFR
conditions late tonight into Sat morning. This will also be
accompanied by several hours of showers with a few downpours
too. Most locations should see conditions improve to VFR by
early Saturday afternoon...but this process may take a few hours
longer towards the Cape and Islands. S winds 5 to 10 knots
tonight becoming W at 10 to 15 knots by Sat afternoon. A few
gusts in the 20 to 25 knot range may also develop across the
interior by mid to late afternoon.

KBOS TAF...High Confidence in TAF.

KBDL TAF...High Confidence in TAF.

Outlook /Saturday Night through Tuesday/...

Saturday Night through Sunday Night: VFR. Breezy.

Monday through Monday Night: VFR.

Tuesday: VFR. Breezy.



Forecaster Confidence Levels:

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

345pm update...

Tonight and Friday...High confidence.

Pressure gradient weakens as the wave of low pressure continues to
move further southeast and away from the region. Seas will also
diminish, but some 5 foot seas to linger across our southern outer-
waters, extending small craft headlines in those locations through
Friday late afternoon. Winds on Friday remain out of the east and
less than 20 knots.

Friday Night...High confidence.

Wind direction from southeast to southwest with the passage of a
frontal boundary, along with rain chances. Areas of fog is possible
with reduced visibilities. Seas remain below 4 foot.

Outlook /Saturday Night through Tuesday/...

Saturday: Winds less than 25 kt. Chance of rain showers. Local
visibility 1 to 3 nm.

Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft.

Sunday through Tuesday: Winds less than 25 kt.


MARINE...Small Craft Advisory until 7 PM EDT this evening for ANZ255-



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