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Area forecast discussion
National Weather Service Boston/Norton Massachusetts
702 PM EDT Mon Oct 21 2019

Synopsis...

Weak high pressure will bring dry weather tonight into Tuesday
morning. Spotty light drizzle/rain develops Tuesday afternoon,
with more widespread rain Tuesday night ahead of an approaching
cold front. Behind the front, dry conditions and seasonable
temperatures follow Wednesday afternoon into Friday. Another
cold front may bring a some showers Friday afternoon and night.
High pressure builds in for most of next weekend.

&&

Near term /until 6 am Tuesday morning/...

7 PM update...

Only concern is some of the high-res guidance coming in warmer
with overnight lows as low clouds develop and filter in sooner.
You can see the low cloud decks encroaching as the east wind begins
to accelerate out ahead of the North-Plains cyclone. This as mid to
high cloud decks are making their way over New York / PA into the New York
Hudson River valley. There's a lot of dry air still in place in
our area and it's quite possible we drop out quickly through
roughly about midnight and then level off from there as clouds
move in and provide the blanket to hold things steady. Will
leave it to the evening crew to evaluate.

Previous discussion...

Surface ridging remains in place tonight leading to dry weather.
Mainly clear skies, but will have to watch for possible lower
clouds developing late tonight near the coast, especially across
the islands. Patchy late night fog expected to develop in the
CT valley. With decent radiational cooling, leaned toward cooler
side of guidance with lows mid 30s to lower 40s, except
mid/upper 40s cape/islands.

&&

Short term /6 am Tuesday morning through Tuesday night/...

Tuesday ...
some morning sunshine possible, but low clouds will quickly
overspread the region as considerable low level moisture
develops. Weak surface ridging hangs on during the day with jet
dynamics assocd with approaching mid level trough remaining west
of new eng, so large scale forcing is limited. However, some
spotty light rain/drizzle will likely develop during the
afternoon with moist low level flow beneath mostly dry air
aloft. Cloud cover and increasing onshore winds will limit highs
to the mid and upper 50s.

Tuesday night...
approaching mid level trough and upper jet combined with
deepening moisture plume will result in an area of showers
moving west to east across southern New England ahead of the cold front. Low
level jet is somewhat fragmented with one piece moving up from
south of new eng, but stronger southeast jet developing in Gulf of
Maine. As a result, heaviest rainfall will likely be confined to
Maine. However, expect a decent slug of rainfall over the
interior where deepest moisture and area of enhanced low level
convergence assocd with a developing wave on the front lifts NE
across western and northern new eng. Expected rainfall amounts
0.50-1.00" in the interior decreasing to 0.25-0.50" closer to
the coast.

&&

Long term /Wednesday through Monday/...

*/ highlights...

- clearing out, drying out, seasonable Wednesday into Thursday
- light showers possible Friday into Saturday
- cool and dry Sunday
- the possibility of an early week warm-up ... if no clouds.
- My goodbye.

*/ Overview...

Seasonable, active pattern. Continued North Pacific cyclone development
signaled by a negative epo / wpo. From organization to an occluding
death, Arctic air has been bumped and downsheared within a preferred
trof pattern over central North America, digging, tapping into S-stream
Continental sub-tropical airmasses. Intangibles with pattern breaks,
upstream anti-cyclonic wave breaks / pv-streamers as well as remnant
cyclone energy from the North-Plains, at times we've been dealt with a
decent couple of storms. Looking ahead however this may not be the
case. As neoguri, especially, and bualoi are ingested into the North
Pacific maritime flow, the pattern retracts as it amplifies with
ensemble-weighted signals of a pronounced latent heat release over
Alaska into the Arctic. Echoing downstream, the preferred trof pattern
settles across the SW Continental U.S. Tapping into the east Pacific sub-tropics.
Subsequently we're left beneath a preferred ridge courtesy SW-NE
flow across the Continental U.S. Nudged to our north. Struggles among forecast
model guidance during the transition late this week into the week-
end, however good agreement early next week of an above average
temperature trend before it's likely the pattern breaks down for
late next week. With the transition we'll likely see some Pacific
energy skirt across our area with some shots of wet weather. Mainly
nuisance. Ebb and flow, looking as if temperatures remain overall
near-seasonable, highs around 60, lows around 40. Forecast thinking
below.

*/ Details...

Wednesday into Thursday...

Rain clearing out early, dry weather prevailing thereafter. The dry
slot wrapping into the Hudson Bay cyclone with rising heights and
warm air advection proceeding, surface high pressure dominates. A
well-mixed boundary layer, will keep west winds breezy, especially on
Wednesday. Cyclonic flow and wrapping moisture round the Hudson Bay
low, can't rule out some scattered cloud decks. Seasonable overall.

Friday into Saturday...

Perhaps some showery weather. Combination of north-stream and S-stream
energy with accompanying Continental moisture. Could see some light
showery weather beneath an open-wave trof axis. However run-to-run
model trends of lesser troughing as well as intertwined dry air as
the two systems do not phase, higher heights and dry air quickly
following with the upstream transition ongoing. Keep with chance
pops. Accompanying clouds will lean slightly cooler on temperatures
with frost possible into Sunday morning as high pressure builds in.

Sunday into early next week...

Even if energy cuts off midweek across the S-conus, heights will be
on the rise across the NE Continental U.S. With the upstream transition noted
in the overview section. If any energy ejecting through the evolving
SW-NE flow it may end up being suppressed by the time it gets here.
A low confidence forecast so far out, the possibility of maintaining
high pressure and dry air from Sunday, altogether it's not entirely
clear if we'll see a warm-up should clouds become an issue before
the pattern breaks down late week and we find ourselves beneath a
potentially renewed west/northwest mid-latitude flow and cooler air aloft. But
will keep it a dry forecast for now.

*/ Goodbye...

It has been a pleasure for over 8 years forecasting weather for S
New England. Failures and successes, a lot of challenges and a
lot of learning opportunities when it came to messaging threats
and impacts, I enjoyed every minute of it, and for my fans out
there I hope you did too. I always tried to make it an effort to
share some meteorological observation and thinking along the way,
pattern recognition from the classroom to the real world in other
words. As I Endeavor on a new career path I want to thank you all
for reading. Born and raised here, New England weather never ceases
to amaze. I will greatly miss forecasting for this area. Those who
do are worthy of great respect. Take care and all the best.

Benjamin sipprell

&&

Aviation /00z Tuesday through Saturday/...

Forecaster confidence levels...

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

Short term /through Tuesday night/...

Tonight...moderate confidence.
Mainly VFR. But a couple of concerns. Low clouds over the waters
east of the cape and islands. A NE-steering flow, hopefully these
will stay offshore. And with mid-high cloud pushing east from New York/PA
it's a question as to whether we remain sky clear. If we do, IFR-vlifr
fog is possible in the CT River Valley around Oregon. Interior light
North/East winds however more robust along the coast around 10 kts.

Tuesday...moderate confidence.
Trending low-end VFR to MVFR through the morning with areas of
IFR in the afternoon. Areas of drizzle and light rain developing
in the afternoon. East winds becoming brisk around 10 to 15 kts,
gusts up to 20 kts especially along the shore.

Tuesday night...high confidence.
Widespread IFR/LIFR developing with period of showers moving
west to east across the region. Winds becoming southeast strengthening
over the waters with 15 to 20 kts sustained, gusts up to 25 kts
right up to the immediate shore.

Kbos terminal...
high confidence in taf trends.

Kbdl terminal...
high confidence in taf trends.

Outlook /Wednesday through Saturday/...moderate confidence.

Wednesday: VFR. Breezy. Slight chance rain.

Wednesday night: VFR. Breezy.

Thursday through Thursday night: VFR.

Friday through Friday night: VFR. Chance rain showers.

Saturday: VFR. Breezy.

&&

Marine...

Forecaster confidence levels...

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

Short term /through Tuesday night/...

7 PM update (no major changes)...

Persistent east/NE winds up to 20 kt through Tue with some 25 kt
gusts will result in building seas over the waters. Small Craft Advisory expanded
across the open waters. Southeast gusts 25-30 kt develop Tue night over
eastern Massachusetts waters with seas building up to 10 ft. Vsbys reduced
in rain and fog late Tue through Tue night.

Outlook /Wednesday through Saturday/...moderate confidence.

Wednesday: low risk for Small Craft Advisory winds with gusts
up to 25 kt. Areas of rough seas. Chance of rain.

Wednesday night: winds less than 25 kt. Local rough seas.

Thursday through Thursday night: winds less than 25 kt. Areas
of seas approaching 5 ft.

Friday through Friday night: winds less than 25 kt. Chance of
rain showers.

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

&&

Box watches/warnings/advisories...

CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory until 8 am EDT Tuesday for anz235-237.
Small Craft Advisory from 10 PM this evening to 6 am EDT
Wednesday for anz250.
Small Craft Advisory from 2 PM Tuesday to 6 am EDT Wednesday
for anz251.
Small Craft Advisory until 6 am EDT Wednesday for anz254>256.

&&

$$

Synopsis...kjc/sipprell

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