Scientific Forecaster Discussion
fxus61 kbox 190916
Area forecast discussion
National Weather Service Boston/Norton Massachusetts
416 am EST Tue Nov 19 2019
an approaching upper-level disturbance will spread a period of
rain for most areas, with a wintry mix across the higher
elevations through this morning, with dry conditions expected by
afternoon. Low pressure passing south and east of the region
may bring some light precipitation overnight tonight into
Wednesday, though most areas will be dry. High pressure
building in from the west Thu yields dry conditions and
seasonable temperatures. Milder and breezy Friday ahead of an
approaching cold front that may be accompanied by scattered
showers late Friday/Fri evening. Behind the front, colder,
blustery but dry weather follows Fri night. Cool dry weather
lingers much of Saturday followed by coastal low pressure
bringing a risk of rain/snow Sat night into Sunday morning. As
the low exits a drying trend and seasonable temperatures should
Near term /until 6 PM this evening/...
Winter Weather Advisory remains in effect until 6 am today for
the eastern slopes of the Berkshires (western Franklin/western
Hampshire counties in ma).
Radar as of 230 am shows band of steady precipitation mainly
across interior western New England into northern CT, and was
moving into the Pioneer Valley of Massachusetts and the east slopes of the
Berkshires. Lighter/intermittent rain and drizzle was common
across central and eastern Massachusetts into Rhode Island and adjacent waters.
Driving mechanism behind this band of precip is a shortwave
trough progressing quickly northward, currently moving into
southern New York. Though noted some bright banding and higher returns
in east-central New York indicating some p-type mixing, temperatures
across southern New England remain above freezing. Dry low-
levels for wet-bulb cooling potential also appears limited as
northerly drainage flow has been slow going. Did note North
Adams and Pittsfield was in the low 30s early this morning, so a
transition over to wintry precip (per 00z raobs and model
soundings, rain to sleet and then wet/dense snow) still looks on
track, likely to start as we move into the pre-dawn hours.
Forecast ice and combined snow/sleet accumulations were
generally little changed from previous and convey at least some
wintry Road impact through the Berkshire mountain passes.
Following good consensus in timing in the 00z href, sref mean
and the individual cams, expect this precipitation band to
spread northeastward and fill in across eastern CT into Rhode Island and
the remainder of Massachusetts into the morning commute. Though rain may
briefly mix with wet snow in the hills of Worcester and
Tolland/Windham counties and part of the CT valley given
favorable uvvs shown most bullishly in NAM-based output...the
marginal temps, low snow-liquid ratio and short/brief
accumulation period argues for negligible accumulations. Much of
eastern Massachusetts and Rhode Island will stay as cold rain throughout. Should see
a rather rapid S->n decrease in pops by late morning and dry by
For the rest of the afternoon, looking at what could probably be
best described as variable cloudiness: greatest north, though
some breaks in low clouds/overcast appears possible by afternoon
into the cape, islands westward into coastal Rhode Island following the
href sky cover forecasts. Cool advection on west-northwest winds and
described cloud cover trends lend to temperatures ranging from
the upper 30s to low 40s mainly north of the Mass Pike, and into
the mid/upper 40s in northern CT, central/southern Rhode Island into southeast
mass/cape and the islands given greater prospects for cloud
breaks. Winds light west to northwest amid a weakening
Short term /6 PM this evening through 6 PM Wednesday/...
Cool advection continues in earnest, as another shortwave
disturbance aloft passes into the central Appalachians and off
the mid-Atlantic Seaboard through 12z Wednesday. This
disturbance will result in distant coastal cyclogenesis passing
well south/southeast of the 40n/70w benchmark. This will likely
encourage winds to become light northerly over the land and a
bit stronger northerlies over the waters, with skies filling
back in with overcast.
Models pick up on some very spotty/light precip especially for
the overnight northeast of a Providence to Hartford line late
tonight/overnight, and model soundings indicate this moisture is
only partially rooted in the ice Crystal layer. With temps in
the 30s, could see potential for very light rain/drizzle, or
flurries/"freezing snizzle" with only trace accumulations. Most
areas should stay dry, though given a low probability concern
for spotty light/trace icing, will allude to potential for
spotty very light icing in the severe weather potential statement. Whether or not that
transpires will come down to temps - think potential is somewhat
greater in the Merrimack valley/northern Worcester Hills than
into the urban corridor.
Distant coastal low continues to wrap-up into Wednesday as it
moves into the eastern Canadian Maritimes, with winds in eastern
Massachusetts and over the waters. Its parent mid-level trough closes off
and becomes centered over southeast Massachusetts and the southern coastal waters.
Still looking at continued mostly cloudy conditions with light
precip from the overnight dissipating in the interior, while
becoming more focused from Plymouth County southeastward by late
afternoon. Prevalent clouds should keep temps from risng much,
into the mid/upper 30s to lower/mid 40s, mildest towards the
southern and eastern coasts.
Long term /Wednesday night through Monday/...
* dry, pleasant and seasonable Thu with highs 45-50
* milder (50s to possibly near 60!) Fri ahead of an approaching
cold front, bringing scattered showers late Fri/Fri evening
* rain/wet snow possible Sat night into early Sunday
Wednesday night ...
Any light nuisance rain/snow Wed evening will taper off as low
pressure south of Nova Scotia and mid level low southeast of
Nantucket at 00z exits seaward with rising heights to follow. The
exception will be Cape Cod and Nantucket as cold air advection via northerly flow
streaming across relatively warm SST may result in scattered
rain/snow ocean effect showers. Turning colder via blustery north
Chilly and blustery to begin Thu but with upper trough exiting
seaward rising heights from west to east will yield warming temps
aloft and weakening pressure gradient. Thus much more pleasant in
the afternoon with lots of sunshine and diminishing winds.
Seasonable with highs 45-50 but more pleasant given slackening
Progressive upper air pattern with next short wave trough
approaching from the Great Lakes. Increasing low level warm air advection ahead of
cold front will likely yield highs of 55-60! However scattered
showers after 18z will accompany the front along with breezy west-southwest
winds. Given models 925 mb temps trending toward +9c Fri afternoon
across CT/Rhode Island and southeast MA, leaned toward the warmest guidance
which supports 55-60.
The weekend ...
Dry, cool weather likely lingers thru much of Saturday. Late in the
day and esp Sat night an open wave of low pres likely to impact the
region with rain, possibly snow depending on exact thermal profiles
and if heavier qpf/lift can provide additional cooling. Low pres
expected to track along or near the 40n/70w benchmark. New 00z Euro
ensembles only have about 4 of the 50 members supporting
accumulating snowfall Sat night. This seems reasonable given
antecedent airmass only seasonably cold and frontal wave is
progressive. However given time range (120 hrs) here will just have
to be patient and see how models trend.
Early next week ...
Behind departing coastal wave a trend toward dry weather along with
seasonable temps Monday.
Aviation /09z Tuesday through Saturday/...
forecaster confidence levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short term /through Wednesday/...moderate confidence.
09z taf update:
Generally IFR/LIFR from orh/pvd eastward, with MVFR/IFR toward
baf/bdl, as a band of precipitation fills in from southeast to northwest. Much
of this precipitation falls as rain, though may briefly mix to
wet snow at orh, baf and bdl. Visbys mainly at VFR-MVFR levels,
though brief IFR possible in wet snow.
Precipitation ends from S to north mid morning to noon, W/dry
conditions with improvement in ceilings/visbys toward MVFR to
even low end VFR towards the South Coast, Cape Cod and islands.
Winds become west/northwest with speeds 3-6 kts.
Ceilings likely to lower again to MVFR levels and eventually
MVFR-IFR from NE to SW as Tuesday night progresses. Late
overnight, shallow moisture from a distant coastal low could
bring a potential for unrestricted rain/drizzle or very light
snow, with low prob of light freezing drizzle. Best chance of
frozen precip mainly northwest of bed/orh. Light west-northwest/west winds initially,
though become northwest 3-8 kts, highest towards the cape/ack.
Low pressure and northerly flow results in continued overcast MVFR-
IFR ceilings with spotty/unrestricted light precip early
becoming more confined to the cape and islands. North/northwest winds
increase to 6-10 kts most tafs, 10-15 kts with gusts to 20 kts
across Cape Cod terminals.
Kbos taf...high confidence in taf and trends.
Kbdl taf...high confidence in taf and trends. Rain may briefly
mix with snow showers early Tuesday am.
Outlook /Wednesday night through Saturday/...
Wednesday night: mainly VFR, with local MVFR possible. Breezy.
Thursday: VFR. Breezy.
Thursday night: mainly VFR, with local IFR possible. Breezy.
Slight chance shra, slight chance fzra, slight chance shsn.
Friday: mainly VFR, with areas MVFR possible. Windy with local
gusts up to 30 kt. Chance rain showers.
Friday night: mainly VFR, with local MVFR possible. Windy with
areas of gusts up to 30 kt. Slight chance rain showers.
Saturday: mainly VFR, with local IFR possible. Breezy. Chance
short term /through Wednesday/...moderate confidence.
Small craft advisories continue across most waters mostly from
residual higher seas as winds have subsided below Small Craft Advisory levels.
Scas end this morning in Cape Cod Bay and Nantucket Sound, but
will linger at least into tonight for the outer offshore waters.
Today: northwest/west winds 5-10 kts. Seas range from 2-5 feet near shore,
though offshore are in the 6-10 ft range. Early showers/mist may
reduce visbys to 3-5 miles, though improvement late.
Tonight: distant coastal low passing south of the region results
in increases in wind speeds. Northwest winds become north and increase to
10-15 kts, gusts 20-23 kts. Seas 4-6 feet offshore waters.
Light showers overnight.
Wednesday: winds continue to increase to 10-15 kts with gusts
nearing or at Small Craft Advisory levels especially eastern/southeastern
offshore waters. Seas offshore waters 4-6 ft, highest with
eastern extent. Better chances for showers and reduced
visibilities late Wednesday.
Outlook /Wednesday night through Saturday/...
Wednesday night: moderate risk for Small Craft Advisory winds
with gusts up to 25 kt. Areas of rough seas. Slight chance of
Thursday: low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas.
Thursday night: winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers.
Friday: moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Areas of rough seas. Chance of rain showers.
Friday night: low risk for gale force winds with gusts up to
35 kt. Rough seas up to 10 ft. Slight chance of rain showers.
Saturday: low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Chance of rain.
Massachusetts...Winter Weather Advisory until 6 am EST early this morning for
Marine...Small Craft Advisory until 7 am EST this morning for anz231-
Small Craft Advisory until 2 am EST Wednesday for anz250-254.
Small Craft Advisory until 10 PM EST this evening for anz251-