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000
FXUS61 KBOX 270209
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1009 PM EDT Fri Apr 26 2024

.SYNOPSIS...
High pressure over New England moves offshore tonight and
remains offshore on Saturday. Another chilly night tonight but
not as chilly as last night. Mostly sunny on Saturday, though
increasing clouds with chances for light showers arrive early
Sunday. Unsettled pattern sets up for Sunday into early next
week, though the best chance for showers is around Tuesday or
Wednesday. Temperatures turn quite mild for interior western New
England Monday, but a backdoor cold front brings much cooler air
to coastal areas.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Update: 10pm

Forecast remains on track with no notable updates to the
forecast. See prior discussion below.

High pressure will continue to gradually shift ESE
into the southern offshore waters tonight. Seabreezes should
diminish around or shortly before sundown, setting the stage for
another night of clear skies and light to calm winds. We should
see good radiational cooling conditions develop again. Frost
Advisories have been hoisted for several counties in CT, RI and
eastern MA where the frost/freeze program is active; that being
said, with temperatures running about 3-5 degrees warmer than
yesterday, prospects for frost are a little more borderline than
was the case last night. This was enough to hold Suffolk and
eastern Norfolk Counties out of the Advisory, and it also could
be more borderline in Hartford County and those counties around
the Providence area but will be close enough to hoist for these
locations. If you had planted early, even in areas outside where
the Frost Advisory is in effect, take the necessary actions to
protect your plants and crops from damage related to frost.
Following MOS based approaches to lows, lows range from the
upper 20s/around 30 in northwest MA, and around 33-36 for most
everywhere, though upper 30s/around 40 in the Boston area.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
355 PM Update:

Saturday:

High pressure continues to be anchored offshore on Sat, with a
highly amplified upper level ridge begins to build into western New
England. Expecting a good deal of sunshine again, with sea breezes
again developing near the southern and eastern coasts as has been
the case the last couple days. However will be seeing an increasing
canopy of high clouds spreading in later in the day into western
sections of SNE.

With temps gradually warming each day, continued strong heating
combined with an increased WSW wind away from the immediate coast,
it has the look of one of those pre-greenup spring days where temps
overachieve available guidance by a significant margin. Highs
Saturday away from the coasts should punch well into the 60s and
wouldn`t rule out some locations in the CT and Merrimack Valleys
reaching 70 degrees. Noticeably cooler near shore with highs only in
the 50s where seabreezes will govern.

Saturday Night:

Clouds that had been moving in later Sat aftn continue to lower,
thicken and spread eastward through much of the night. This is in
response to a burst of pretty strong warm and moist advection as
upper ridge axis crests offshore. Some indication in guidance that
lighter showers could develop in western MA/CT during the late-
overnight to pre-dawn period, but think modeled QPF is overdone as
low levels initially struggle to saturate up with several days of
preceding dry weather. In fact there`s quite a reservoir of dry
subcloud air shown on model soundings which even in western areas
only saturates enough to support light showers around 09-12z Sun.
Carried a 15-45% PoP mention for showers west of Providence, with
highest chances near the Berkshires. This would be a relatively
higher PoP but very low QPF scenario though.

With increasing overcast and warming temps aloft, lows project to be
considerably warmer than prior nights with no chance for frost. Lows
should only dip into the low to mid 40s, and a few of the urban
centers may stay around the mid/upper 40s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Key Points...

* Low chance for isolated showers Sunday and Monday. More widespread
  rain possible mid week

* Warming trend through much of next week, but a back door cold
  front will keep eastern SNE cooler then western SNE.

Sunday and Monday

The center of the high pressure drops south to the Carolinas, but
the upper level ridge axis continues to stretch north in SNE. Being
at the top of the ridge axis, weak vorticity impulses, along with
weak mid level warm air advection will bring mid to high clouds and
low chances for isolated showers both Sunday and Monday. High
temperatures Sunday and Monday will be very dependent on a back door
cold front working in. Guidance continues to struggle with how far
inland the back door cold front will penetrate Sunday, and again on
Monday. What will likely occur is that eastern SNE will see high
temperatures in the low to mid 60s, while western SNE will see mid
to upper 70s, with a chance at low 80s.

Tuesday through Friday

Upper level ridge axis begins to break down Tuesday into Wednesday
as a weakening shortwave trough moves through the region. Details on
exact timing and coverage of precip remains very uncertain with weak
upper level forcing and large spread in the guidance. LREF probs for
0.25 inches of rain remain low, less then 30% each day through
Friday. The temperature forecast remains very uncertain during this
time period as another upper level ridge builds in to our west
allowing another surface high pressure to build over the Gulf of
Maine. This could bring continued onshore flow to the region along
with continued back door cold fronts. Ensembles are still showing
significant amount of spread with the 25th to 75th percentile for
high temperatures ranging from the upper 50s to upper 70s across the
region.

&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

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

00z TAF Update:

Tonight: High confidence.

VFR SKC. For this afternoon, Light S winds for all areas
overnight.

Saturday: High confidence.

VFR, although with an increasing canopy of high clouds late-
day. Light SW winds increase thru the day to around 7-10 kt;
though sea-breezes again develop near the coasts between 14-16z
Sat.

Saturday Night: High confidence in trends though moderate on
exact timing.

Cigs start VFR but will be steadily lowering. Best chance at
sub-VFR ceilings and light rain showers is after 06z and mainly
from ORH westward; cigs could be as low as IFR but think MVFR
predominate for those interior western terminals. Still think
we`re looking at OVC VFR for eastern terminals. SW winds around
8-12 kt to start, but decrease to around 5-8 kt late. Low prob
of low level wind shear south of I-90.

KBOS TAF...High confidence in TAF. VFR. Winds become light
southerly tonight. Seabreezes again likely for Sat, following
similar 14-16z timeframe as prior days.

KBDL TAF...High confidence in TAF. VFR. Light north winds most
of today, but will trend southerly around 4-7 kt late today into
tonight.

Outlook /Sunday through Wednesday/...

Sunday: Mainly VFR, with local IFR possible. Slight chance
SHRA.

Sunday Night: VFR. Slight chance SHRA.

Monday: Mainly VFR, with local MVFR possible. Slight chance
SHRA.

Monday Night: Mainly VFR, with local IFR possible. Slight
chance SHRA.

Tuesday: Mainly VFR, with areas MVFR possible. Chance SHRA.

Tuesday Night: Mainly VFR, with areas IFR possible. Chance RA.

Wednesday: Mainly VFR, with areas IFR possible.

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight through Saturday Night: High confidence.

Pleasant boating weather conditions for mariners through most of
Saturday, and while that should generally be the case into
Saturday evening as well, there is a low chance for showers on
the southern waters late Sat night into pre-dawn Sunday.

Light southerly winds tonight and into early on Sat. SW winds
increase a bit to around 10-15 kt on Sat on all waters, though
will become ESE on the eastern nearshore waters Sat late-morning
to early evening. Seas mainly 3ft or less all waters.

Outlook /Sunday through Wednesday/...

Sunday through Sunday Night: Winds less than 25 kt. Slight
chance of rain showers.

Monday: Winds less than 25 kt.

Monday Night through Tuesday: Winds less than 25 kt. Slight
chance of rain showers.

Tuesday Night through Wednesday: Winds less than 25 kt. Seas
locally approaching 5 ft. Slight chance of rain.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Frost Advisory from 2 AM to 8 AM EDT Saturday for CTZ002>004.
MA...Frost Advisory from 2 AM to 8 AM EDT Saturday for MAZ007-014-
     017>024.
RI...Frost Advisory from 2 AM to 8 AM EDT Saturday for RIZ001>007.
MARINE...None.

&&

$$

SYNOPSIS...Loconto/KP
NEAR TERM...Loconto/Dooley/KP
SHORT TERM...Loconto/KP
LONG TERM...KP
AVIATION...Loconto/KP
MARINE...Loconto/KP