Old Res Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 260523
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
123 AM EDT Fri Apr 26 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 THIS MORNING/...
Update: 10:00pm 

No changes to the forecast as it remains in good shape. One area
made a minor adjustment was the CT River Valley, here T/Td have
been slow to cool, did blend in newer HRRR guidance, that seems
to handle the slightly warmer T/Td. Nevertheless, still expect
those locations will watch the mercury drop quickly over the
next several hours. Headlines remain the same. Please see the
prior discussion below. 

---------------------------------------------------------------

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 THIS MORNING THROUGH 6 PM SATURDAY/...
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 NIGHT 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 /06Z 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 12Z... High confidence. 

VFR. Light and variable winds

Today... High confidence.

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

Tonight... High confidence. 

VFR: Light and variable winds.

KBOS TAF...High confidence in TAF.

VFR. Sea breeze develops again by 14-15z.

KBDL TAF...High confidence in TAF. 

VFR. Light and variable winds.

Outlook /Saturday Night 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 Night 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 until 8 AM EDT this morning for CTZ002>004.
MA...Freeze Warning until 8 AM EDT this morning for MAZ007-014>024.
RI...Freeze Warning until 8 AM EDT this morning for RIZ001>007.
MARINE...None.

&&

$$

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