000
FXUS61 KBOX 252256
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
656 PM EDT Thu Apr 25 2024

.SYNOPSIS...
Sprawling high pressure over northeast Ontario moves southeast
over Southern New England through Friday, bringing clear skies
and chilly nights tonight and Friday night. Unsettled pattern
sets up for Sunday into early next week with shower chances.
Temperatures turn milder but there is a good deal of uncertainty
as to how warm Sun/Mon are.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
7 PM Update:

Sprawling high pressure ridging in from northeast ON bringing wall
to wall sunshine, dry weather and light north winds (seabreezes near
the coast). It is a bit cool out with current temps inland in the
low to mid 50s, with cooler low/mid 40s near the coasts.

Center of high pressure will continue to progress SE into the
Adirondacks tonight, and ridging to extend SE from it into Southern
New England. Expect any seabreezes near shore to shift to land-
breezes (southerlies) after sundown. Optimal radiational cooling is
likely to begin tonight under clear skies, light to calm winds and
very dry air in place. Thus low temperatures should reach
subfreezing levels in many areas in the 20s to around 30, with lows
32-35F at Worcester and near Boston.

With forecast temps, the Freeze Watch was converted over to Freeze
Warnings for northern CT, all of RI and eastern coastal and
southeast MA, which are where the frost/freeze program is active.
Opted to keep things simple as some of the immediate city areas such
as Boston, Hartford and Providence probably stay around or just
above freezing, and the best chance at seeing freezes is in the
outlying less urbanized areas. If you have planted crops in Southern
New England, take the necessary protective actions to prevent frost
or freeze related damage.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
330 PM Update:

Friday and Friday Night:

Friday is essentially a carbon copy of today, as high pressure
continues to slide southeastward into our southern outer waters.
After a chilly start, full sunshine and dry weather should allow
temperatures to rise into the 50s to lower 60s, with mid 50s along
the southern and eastern coasts as seabreezes get going. Will have a
bit of a southerly flow develop later in the day as high moves to
our southeast.

Friday night should again feature clear skies and favorable
conditions for radiational cooling. Temps should project to be a
couple degrees warmer than tonight`s lows, utilizing a heavy dose of
MOS guidance. That yields lows in the 30s, though a few areas which
radiate well such as around I-495 in MA and NW MA could see
subfreezing temps. The uncertainty in the forecast here revolves
around winds, and it is possible that winds could be strong enough
to preclude frost from developing. It`s very close but it is
possible that frost/freeze headlines could be needed again where the
frost freeze program is active; but the wind speeds make it a
tougher call.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Key Points...

* Remaining dry Saturday.

* Low chance for showers Saturday then again Tuesday through
  Thursday.

* Warming trend into next week, but uncertainty remains high

Saturday...

Upper level ridge and surface high pressure remains centered over
the region through Saturday. With subsidence aloft and very dry mid
level air, skies look to remain clear with very little clouds until
late Saturday afternoon when high clouds ahead of a shortwave move
in. This will help moderate day time temperatures into the mid to
upper 60s Saturday. With a weak pressure gradient, local sea breezes
will occur again Saturday morning. However, winds begin to increase
out of the south Saturday afternoon, which could keep a true sea
breeze from continuing along eastern coasts.

Upper level ridge axis passes to the east by Saturday night with
some warm air advection ahead of the next shortwave trough. This
will lead to increased cloud cover and and isolated to scattered
showers. Lows stay warmer Saturday night in the upper 30s to low
40s.

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 vort impulses, along with warm
air advection aloft bring 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. Latest
GFS and EURO is still bringing that back door cold front through
Sunday and again Monday keeping temperatures in the low 60s for
Eastern MA and RI, while western MA and CT stay warmer in the 70s.
However, if that cold front stays offshore Sunday, temperatures
could easily top the mid to upper 70s.  NBM guidance still remains
significantly warmer then deterministic GFS and EURO guidance, so
again used a blend of warmer NBM guidance with cooler CONSALL
guidance.  Temperatures Monday look to continue to warm for western
MA and CT with a 30-40% chance highs top 80F per GEFS. Eastern MA
and RI will still struggle to top 70F with the back door cold front
stalled over SNE.

Tuesday through Thursday

Upper level ridge axis again moves offshore to the east, but this
time, a weakening shortwave trough moves through the region, but
details on exact timing and coverage of precip remains very
uncertain. Given this is a week out, stuck with NBM for precip
chances, which shows 30-40% chance for showers through the middle of
next week. This seems reasonable given the weak forcing from the
weakening trough. A cold front looks to move through behind the
trough which could bring an isolated thunderstorms with it.
Southerly flow Tuesday should kick the back door cold front out,
however guidance remains very spread out on highs temps with
ensemble 25th-75th percentiles showing anywhere from the 50s to the
70s through Thursday.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:

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

00z TAF Update:

Through Tonight: High confidence.

VFR. Light and variable winds

Friday: High confidence.

VFR. Winds become light SW for most, although with sea-breezes
near the coasts around 15-17z.

Friday night:

VFR: Light and variable winds.

KBOS TAF...High confidence in TAF.

Sea breeze should kick out shortly after 00z, with winds turning
to the southwest this evening and eventually north overnight
all under 10 knots. Sea breeze develops again tomorrow by
14-15z.

KBDL TAF...High confidence in TAF.

VFR with light and variable winds.

Outlook /Saturday through Tuesday/...

Saturday: VFR.

Saturday Night: Mainly VFR, with local MVFR possible. Chance
SHRA.

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

Sunday Night: VFR. Slight chance SHRA.

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

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

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight through Friday Night: High confidence.

Tranquil boating conditions are expected through Friday night as
high pressure gradually builds southeastward into the coastal
waters. Light north winds (easterly near shore) tonight and into
early Friday on all waters. Later Friday, winds turn southerly
around 10-15 kt. Seas 3 ft or less all waters.

Outlook /Saturday through Tuesday/...

Saturday: Winds less than 25 kt.

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

Monday: Winds less than 25 kt.

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Freeze Warning from 2 AM to 8 AM EDT Friday for CTZ002>004.
MA...Freeze Warning from 2 AM to 8 AM EDT Friday for MAZ007-014>024.
RI...Freeze Warning from 2 AM to 8 AM EDT Friday for RIZ001>007.
MARINE...None.

&&

$$

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