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fxus61 kbox 200211 
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Area forecast discussion
National Weather Service Boston/Norton Massachusetts
1011 PM EDT Sat Oct 19 2019

Synopsis...
high pressure and seasonable conditions through Sunday. Nestor
remnants tracking south of New England with the uncertain risk
of rain late Sunday afternoon and night. High pressure builds
in with dry weather Monday, then a sweeping cold front will
bring a period of showers Tuesday afternoon into early
Wednesday. High pressure follows late in the week with
seasonably mild temperatures and dry weather. Another storm
system may impact the region by Saturday but there is much
uncertainty.

&&

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

10 PM update...

Lowered min temps as it was already colder at mvy and ewb than
previously forecast. Cirrus clouds thin/erode as they climb over
mid/upper level ridge across New York state. Thus these clouds will
not preclude temps from falling into the 30s regionwide tonight
with a few upper 20s possible in the typically colder spots.
Given dew pts are in the 30s expect another round of frost
overnight. Get those ice scrapers ready for the windshield
Sunday morning.

&&

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

Sunday into Sunday night...

Challenging rainfall forecast. Nestor remnants preceding weak 500 mb-7
shortwave energy. An evaluation of frontogenesis, deformation, and
low-level moisture / thetae, there's a North-Draw along and around 300k
isentropic surfaces prior to mid-level synoptics and accompanying
trof axis. Squeeze out, the potential for mid-level outcomes.

However, heights rising out ahead of the North-Plains cyclone across the
NE conus, strengthening surface high pressure, enhancing The Wedge
of low-level drier air across the southeast Canadian Maritimes brought by
the isallobaric wind component. NE flow undercutting over-running
mid-level outcomes. Two subsequent thoughts: 1.) Nestor is nudged
further S to which latest 19.12z guidance has agreed upon despite
the disparity between global and high-res forecast guidance, and 2.)
That any outcomes, wherever they originate, may have difficulty in
getting to the surface, eroding before reaching the ground (virga).

Continued north-S spread of rainfall forecasts between model guidance
and individual ensemble members. For this forecast, will keep the
majority of pops (chance or greater) S of the Massachusetts-Pike and Reserve
likely pops for just Nantucket and the waters S. Collaboration with
the nerfc, not going to go with the completely dry forecast. Prefer
to trend southward but allow later shifts to re-evaluate and make
adjustments as necessary. Avoiding a flip-flop given both the spread
and uncertain rainfall risk. Don't want to say completely dry only
to have to re-introduce rain later. Confidence is lacking. Light
rain thinking, not a wash-out.

Watching the undercutting east/NE wind. With a nudge of Nestor further
S, the stronger gradient should lie immediately offshore. Still
breezy for the S-coast, but the gales well out over the S waters.

Increasing clouds through the day. A bit mild tonight. Looking at
highs around the upper 50s to low 60s, lows into the 40s Sunday
night with the possible of quick cooling as clouds clear over north/west
Massachusetts towards Monday morning.

&&

Long term /Monday through Saturday/...

Highlights...

* mainly dry and seasonable Mon
* patchy drizzle Tue morning, then a period of showers late Tue into
early Wed
* improving conditions Wed afternoon then dry and seasonably mild
Thu/Fri

Monday...

Remnants of Nestor south of the benchmark and drifts eastward as
surface ridging in place across new eng. Deep moisture mostly
offshore by Mon morning so only a low risk of a lingering shower
over ack early, otherwise expect a mostly sunny day as column is
rather dry. Highs should reach low/mid 60s with NE flow, which may
be gusty over the islands.

Tuesday into Wednesday...

Persistent NE flow into Tuesday will result in considerable low
level moisture developing later Mon night Onward with low clouds
overspreading the region by Tue morning. Models are indicating some
light quantitative precipitation forecast which will likely be in the form of drizzle given dry air
in the mid levels. By later Tue and especially Tue night moisture
deepens ahead of mid level shortwave and approaching cold front.
Expect a band of showers sweeping through southern New England late Tue into Tue
night with potential for some heavier rain elements as higher pwats
advect into region with frontal wave possibly developing which would
enhance low level convergence. Model guidance differs on timing of
the front which will impact how quickly it clears out on Wed. European model (ecmwf)
is slower with showers lingering into Wed morning, especially
eastern new eng while GFS is more progressive. Leaning toward slower
solution given consensus of global guidance but expect improving
conditions during Wed with increasing sunshine developing from west
to east with seasonable temps.

Thursday into Saturday...

High pres in control south of new eng Thu with dry weather and mild
temps, possibly well into the 60s. Then forecast confidence
decreases Fri into Sat as models show significant differences on
evolution and timing of next upstream trough. Complex pattern with
possible interaction of multiple shortwaves. Dry weather should hang
on for Fri with seasonably mild temps, then low confidence into Sat.
GFS is wet Fri night/Sat while European model (ecmwf) is dry with rain delayed until
sun. Have chance pops for Fri night into Sat given eps indicating
moderate quantitative precipitation forecast probs.

&&

Aviation /02z Sunday through Thursday/...
forecaster confidence levels...

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

Short term /through Sunday night/...

02z update...

No changes from previous tafs. Earlier discussion below.

===============================================================

Tonight...high confidence.
VFR. Light and variable winds.

Sunday into Sunday night...moderate confidence.
VFR. Increasing clouds lowering to low-end VFR 4-6 kft agl S of
the Massachusetts-Pike towards 0z Monday through 12z. MVFR possible along
the S-coast, cape and islands. An increasing east wind approaching
10 to 15 kts along the S-coast as Nestor sweeps by. Will keep
the forecast dry through 18z Sunday and then introduce the chance
of -ra S of the Massachusetts-Pike through 12z Monday, likely -ra for ack
around 6z Monday.

Kbos terminal...
high confidence in taf.

Kbdl terminal...
high confidence in taf.

Outlook /Monday through Thursday/...moderate confidence.

Monday: VFR. Breezy.

Monday night: mainly VFR, with local MVFR possible. Breezy.

Tuesday: mainly MVFR, with areas IFR possible. Breezy. Chance
rain showers.

Tuesday night: mainly MVFR, with local IFR possible. Breezy.
Chance rain showers.

Wednesday: mainly VFR, with local MVFR possible. Breezy. Slight
chance rain showers.

Wednesday night through thursday: VFR. Breezy.

&&

Marine...
forecaster confidence levels...

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

Short term /through Sunday night/...

230 PM update...

Rest of today...high confidence.
Northwest gradient winds continuing to diminish. Around 5 to 10 kts at
this point, becoming variable, some immediate shore sea-breezes
have emerged along east Massachusetts coast. However, a decent west wind has
emerged along the S-coast around 10 to 15 kts. It too should
diminish towards evening with building high pressure. Seas less
than 5 feet. Clear conditions. Dry.

Tonight...high confidence.
Light winds around 5 to 10 kts diminishing to variable. Seas
less than 5 feet. Clear conditions. Dry.

Sunday into Sunday night...moderate confidence.
Majority of wind and wave impacts over the S/southeast waters.

Light winds initially increasing out of the east to around 10 to 15
kts especially over the S/southeast waters as remnants of Nestor approach,
15 to 20 kts with gusts up to 30 kts overnight into Monday morning.
Will keep waves below 5 feet even on the S waters mostly throughout,
increasing up to around by Monday morning for the S outer waters.

Chance to likely light rain during the overnight hours for the S
waters, however some uncertainty in the north-S gradient given nestor's
track.

Outlook /Monday through Thursday/...moderate confidence.

Monday: low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas.

Monday night: winds less than 25 kt. Areas of rough seas.
Slight chance of rain showers.

Tuesday: winds less than 25 kt. Rough seas up to 8 ft. Chance
of rain showers.

Tuesday night: winds less than 25 kt. Rough seas up to 8 ft.
Rain showers.

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

Wednesday night through thursday: winds less than 25 kt. Seas
up to 5 ft.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...none.

&&

$$
Synopsis...kjc/sipprell
near term...nocera

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