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Area forecast discussion 
National Weather Service Taunton Massachusetts
706 am EST Tuesday Feb 9 2016

Synopsis...
cloudy and chilly weather is in store for southern New England
today. Fast moving low pressure may bring scattered locally heavy
snow showers to the region Wednesday with the highest risk across
northern Connecticut and near the South Coast. Some scattered
snow showers are likely on Wednesday and Thursday...with dry
weather mainly on Friday. Bitterly cold weather is expected this
weekend.

&&

Near term /through tonight/...
7 am update...
two areas of precipitation to watch this morning. The first is an area of
very light flurries that is gradually dissipating and shifting
into northern New England...associated with upper level shortwave just
now sliding on the eastern periphery of the cyclonic flow across
the region. The other is some coastal enhancement. Noting a
difference of about 10 degrees in dewpoints between ob sites such as
ghg and pym and inland...mainly owd/tan. This is accompanied by a
slight difference in wind direction...mainly northwest inland...to NE
near shore. So...a few ocean enhanced shsn may linger especially
over Plymouth County through the morning. Otherwise...mainly
cloudy...and cool today.

Previous discussion...

Band of scattered light snow showers/flurries lingered across
western Massachusetts/northern CT and Rhode Island very early this morning. Expect this
activity to lift northward through middle morning with mainly dry
weather thereafter...other than a spot flurry/snow shower. The
exception might be along the immediate eastern Massachusetts
coast...particularly cape and eastern Plymouth County where
scattered light snow showers may persist into early afternoon.
This a result of cold north-northeast low level flow resulting in some land/sea
interface.

Otherwise...a rather cloudy and chilly day is on tap for southern
New England with light/moist low level northerly flow.
This should hold high temperatures mainly in the upper 20s to around 30.

&&

Short term /Wednesday/...
***scattered locally heavy snow showers possible Wednesday with the
highest risk across northern CT/south coast***

Tonight and Wednesday...

Mainly dry weather will persist through at least midnight with an
abundance of clouds. A potent shortwave and its associated surface
low pressure system will approach from the southwest toward daybreak
Wednesday. This is an inverted trough situation and there is some
model disagreement on how far north it gets. While current guidance
has the highest risk southwest of our region...the 00z model suite
has trended further north. Will have to watch this
closely...because if it does impact US this could be one of those
short duration/localized but high impact snow event. Especially if
it moves in by the Wednesday morning rush hour. Very steep middle level lapse
rates near 8 c/km along with total totals in the high 50s to near 60
give an idea of the potential instability this system has going for
it.

For now will run with a period of likely probability of precipitation on Wednesday as most
areas should see at least brief snow showers. As for
accumulations...will go with a coating to 2 inches as the most
likely scenario. However...there is a low risk for localized 3 to 4
inch amounts if this trends further north. These inverted trough
scenarios have high bust potential in either direction...but
something will have to watch closely over the next 12 to 24 hours.
High temperatures will mainly be in the 30s on Wednesday.

&&

Long term /Wednesday night through Monday/...
highlights...

* shortwaves bring snow showers and clouds Wednesday night through Thursday
* snow showers continue Sat
* much colder air moves into southern New England for the weekend

Overview and model preferences...

Transitioning synoptic regime with the nao/ao beginning the week
strongly positive before shifting toward the negative by the
weekend and early next week. Positive pna suggests that the
amplified flow pattern across the area remains in place. So the
active pattern that allowed for this most recent storm development
isn/T going anywhere too fast. Several shortwaves will be sliding
through the longwave trough...including one directly out of the
Arctic late in the week which looks to deliver the coldest air of
the season by the weekend. There is modest agreement through the
long term such that a blend of operational guidance should be
good. However...will lean more closely on blend of the gefs and
ecens ensembles for Friday...when the aforementioned strong/Arctic
wave begins it/S influence. Some stream phasing at play...which
will culminate in the formation of a coastal storm. How close
remains the question...and will ultimately define the potential
impacts for southern New England.

Details...

Wednesday night into Thursday...high confidence.
First in a series of long term shortwaves will be moving through
the persistent longwave trough. This may lead to inverted trough
development between the upper shortwave and low pressure in the Gulf
of Maine and Bay of Fundy. Moisture is lacking as the overall flow
is northwest. So...expect only isolated to scattered shsn development. Any
accums will be light. H92 temperatures between -12c and -18c suggest
highs/lows generally below normal...exacerbated by persistent northwest
flow yielding low wind chills. Expect lows in the teens to low 20s
with highs in the upper 20s to low 30s. Wind chills likely remain
in the teens.

Friday and Friday night...high confidence.
High pressure briefly ridges over the region suggesting a mainly
clear and dry period. -10c to -12c h92 temperatures suggest temperatures near to
slightly below normal.

Sat...moderate confidence.
Low pressure associated with an Arctic impulse will be sliding
through the region from Ontario. While the parent low is expected
to pass to the north...a Transfer of energy is expected...leading to a
bombing low pressure development in the Gulf of Maine to near Nova
Scotia. How close this rapid cyclogenesis occurs will be the
ultimate determining factor in sensible weather across the region. A
closer pass equals more significant impact with snows/winds the
primary issue. The current ensemble blend is too far offshore for
significant impact...but this will need to be monitored over the
next few days.

One likely impact will be the potential for ocean effect snows
across Cape Cod and immediate coastal Plymouth County in Massachusetts. The
cold advection aloft suggests Delta-T values between 25 and 30c
and flow 350-020. Some headlines may be needed for this alone.
Bitterly cold airmass begins to settle in...so expect temperatures well
below normal.

Sat night through sun...high confidence.
Ever considered visiting alert...or do the Queen Elizabeth
Islands excite you? If so you are in Luck...because backward
trajectories suggest that the airmass expected to arrive late Sat
into early next week are coming from that exact region. 850 mb temperatures
drop as low as -28c...not quite to the -30c developing across New York.
Expect bitterly cold temperatures...combined with brisk north-northwest flow which
will yield wind chills well into the negative double digits for
many. Will likely need at least wind chill advisories if not
warnings for a portion of this period. Some areas may only see
highs in the single digits in spite of an increase in sunshine.

Early next week...low confidence.
In spite of the cold start...an eastward shift in the trough
suggests the passage of an inside runner which may remain cold
enough for snow or even a mixed precipitation event. Lot/S of uncertainty
in timing and thermal profiles at this point.Temperatures during
this time will already be 5 to 10 degrees below normal for middle
February and the colder air is yet to come.

&&

Aviation /11z Tuesday through Saturday/...
forecaster confidence levels...

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

Today...high confidence in trends...lower confidence in timing.
Mainly a mix of MVFR through the morning hours...primarily due to
ceilings...although visibilities occasionally MVFR in light snow early.
Otherwise...a few breaks to VFR this afternoon and early evening
possible...before a gradual trend back down overnight.

Tonight and Wednesday...moderate confidence. Mainly low end VFR to
MVFR ceilings tonight. Scattered snow showers which may work into our
region towards 12z Wednesday. Highest risk will be across northern CT
and the South Coast and they may persist into the afternoon. MVFR
conditions dominate but brief localized IFR to LIFR ceilings/visibilities
possible locally heavy snow showers.

Kbos terminal...moderate confidence in taf.

Kbdl terminal...moderate confidence in taf.

Outlook /Wednesday night through Saturday/...

Wednesday night into Thursday night...moderate confidence.
Mainly VFR but periods of shsn are possible with light accums and
localized IFR conditions.

Friday...high confidence.
Mainly VFR.

Sat...moderate confidence.
Once again a risk for snow...particularly cape/islands. Otherwise
VFR outside of any snow.

&&

Marine...
forecaster confidence levels...

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

Short term /through Wednesday/...high confidence.

Today through Wednesday...high confidence. Winds will generally
remain below Small Craft Advisory thresholds through Wednesday.
However...persistent easterly swell from yesterday/S ocean storm
combined with additional waves of low pressure will keep seas above
Small Craft Advisory thresholds through Wednesday afternoon across most of
our outer-waters and western sounds.

Outlook /Wednesday night through Saturday/...

Wednesday night into Thursday night...high confidence.
Winds mainly west-northwest with gusts 25-30 knots at times...but dissipating
by Thursday night. This will yield seas around 7-10 feet. Small craft
advisories are expected.

Friday and Friday night...high confidence.
Brief high pressure will yield west winds...with gusts mainly 20 knots or
less and seas below 5 feet. Therefore...a period of relatively quiet
boating weather is expected.

Sat...moderate confidence.
Winds shift to the north and northwest. Gusts may reach close to gale force
but at least Small Craft Advisory levels are expected. Seas also
increase...along with a late day risk for freezing spray.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory until 7 PM EST Wednesday for anz235-237-
250-254>256.
Small Craft Advisory until 7 am EST Wednesday for anz251.

&&

$$
Synopsis...Frank/doody
near term...Frank/doody
short term...Frank
long term...doody
aviation...Frank/doody
marine...Frank/doody

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