593
FXUS61 KBOX 101741
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
141 PM EDT Fri May 10 2024

.SYNOPSIS...
Low pressure tracks well south and east of New England through
Saturday as high pressure builds in from the north. This will bring
drier conditions after any lingering shower this morning, but cool
temperatures as a persistent NE wind prevails. Continued cooler than
normal Sunday with chance of showers as an upper level low pressure
moves into the region. Milder temperatures return next week but an
unsettled pattern persists through midweek.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

Dry air has arrived from the north allowing for some significant
clearing especially over northern Massachusetts. This has also
pushed showers further south and offshore which will be the case
for the rest of the day.

Previous discussion:

Mid level trough moves into New Eng today as low pres moves off
mid Atlc coast and tracks well to the south. Modest forcing
ahead of the mid level trough combined with area of deep
moisture is resulting in showers pushing into SNE early this
morning, mainly south of the MA Pike. A few showers will linger
here this morning after daybreak, but expect a drying trend
thereafter as low level drier air moves in from the north and
east. While lots of cloud cover is expected today, this drier
air will likely lead to partial sunshine developing later this
morning into the afternoon, especially across eastern MA. NE
flow and pocket of cold temps aloft with 850 mb temps falling to
near 0C will keep temps in the mid-upper 50s today, except
lower 60s CT valley. This is about 10 degrees below normal. NE
winds 10-20 mph expected with some higher gusts possible along
the south coast where weak low level jet present.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Tonight...

Mid level trough moves south and east of New Eng with further
drying from the north as PWATs drop below 0.50". Partial
clearing expected overnight in the interior, but more clouds
will linger near the coast. Decent radiational cooling may
develop in the interior as winds decouple. This may result in
lows dropping into the upper 30s in portions of the interior,
with low-mid 40s elsewhere.

Saturday...

Weak shortwave ridging develops across SNE between departing
shortwave to the east and upstream trough moving into the Gt
Lakes. This will maintain surface high pres with mainly dry
conditions and partial sunshine, although can`t rule out a spot
shower in eastern MA with marginally cold temps aloft and steep
low level lapse rates with lingering low level moisture.
Another cool day with temps several degrees below normal as 850
mb temps 0 to -1C. Expected highs will be in the mid-upper 50s
with lower 60s in the CT valley.

&&

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

* Unseasonably cool and mainly dry Sunday

* Temps become more seasonable Monday and Tuesday

* Unsettled wet weather Monday - Wednesday, but uncertainty remains
  high.

Sunday:

Upper level closed low becomes centered over SNE. This leaves the
region under cyclonic flow along with a cold pool aloft. The best
forcing with the closed low remains south of SNE. There is a low
chance for a weak hit or miss diurnally driven showers Sunday,
however, guidance doesnt show much if any instability and bufkit
soundings show a rather capped atmosphere with some warming at
700mb. Skies look to turn mostly cloudy Sunday with onshore flow and
a moist column. High temps remain unseasonably cool in the upper 50s
to low 60s with 850mb temps still around -1C.

Monday - Wednesday

Upper level closed low and cold pool finally move to the NE. 850mb
temps quickly begin to warm to +7C by Monday. This will allow
temperatures to become more seasonable with highs in the low to mid
70s. Precipitation is rather messy during this time period with
considerable uncertainty. Monday should be mainly dry for the most
part with rising heights. However, WAA and PWATS near 1.1 inches
enter the region and could bring a few weak showers late in the day.
Better forcing doesnt look to arrive until late Tuesday night into
Wednesday as a weakening shortwave exiting the Great Plains sends
weak impulses of energy along with falling heights to the region.
The best forcing from this shortwave once again looks to stay south
of the region sending most of the widespread rain south as well.
Ensemble guidance remains very spread out with this system with very
little agreement between the GEFS and Euro members.  Using the LREF,
which combines the GFS, Euro, and Canadian ensembles, 24 hour
probabilities for 0.5 inches of rain max out Wednesday at 40-50%
along the south coast, with 30% or less further north.

Thursday and Friday

A very dry airmass looks to follow behind the shortwave with PWATS
falling below 0.4 inches. An upper level ridge and rising heights
should allow skies to be mostly sunny. Weak CAA and NW winds should
keep daytime high temps in the low to mid 70s.

&&

.AVIATION /18Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:

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

18z Update:

This afternoon...High confidence.

VFR. NE wind 10-20 kt with higher gusts over the Islands.

Tonight...High confidence.

VFR with the exception of ACK where low clouds to the south will
lift far enough north to impact the terminal...low prob of
-SHRA there. NE wind 5-15 kt becoming N overnight.

Saturday...High confidence.

VFR, but areas of MVFR cigs developing across portions of eastern
MA and Cape/Islands where a spot shower possible. NE wind 10-20
kt.

Saturday night...High confidence.

VFR except for chance of MVFR/IFR over ACK and potentially
FMH/HYA. Light E winds to start becoming NE/N.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Saturday Night through Tuesday/...

Saturday Night: Mainly VFR, with local MVFR possible.

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

Sunday Night: VFR.

Monday: VFR. Breezy.

Monday Night: VFR. Breezy. Slight chance SHRA.

Tuesday: VFR. Breezy. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Saturday...

Low pres tracking south and east of the waters will bring NE
winds 10-20 kt with occasional 25 kt gusts over southern waters
through Sat with seas building to 5 ft. Extended the SCA for
outer southern waters through Sat.

Outlook /Saturday Night through Tuesday/...

Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers.

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

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

Monday Night: Low risk for Small Craft Advisory winds with
gusts up to 20 kt. Areas of seas approaching 5 ft.

Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain
showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT Saturday for ANZ254>256.

&&

$$

SYNOPSIS...KJC/KP
NEAR TERM...KJC/BW/KP
SHORT TERM...KJC
LONG TERM...KP
AVIATION...BW/KP
MARINE...KJC/KP