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Area forecast discussion 
National Weather Service Taunton Massachusetts
529 am EST Wednesday Jan 28 2015

Synopsis...
strong low pressure will move across Nova Scotia today. Other
than a few ocean effect snow showers across the cape and
Nantucket...it will be dry and cold as the cleanup begins. Clipper
type system moves out of the plains states...bringing another
chance for snow Thursday night into Friday night. Dry...blustery
and frigid conditions move in for this weekend. A third storm may
affect the region Sunday night and Monday.

&&

Near term /until 6 PM this evening/...
WV imagery shows comma head losing its punch across new eng as
drier air moves in from the west. Snow bands have weakened
considerably across east Massachusetts and light snow will come to an end before
daybreak with exception of Cape Cod where ocean effect snow
showers will develop.

For today...scattered ocean effect snow showers will likely continue
into the afternoon over the Outer Cape. Steep low level lapse
rates over the water with Delta T from SST to top of the mixed
layer exceeding 20c which is quite unstable. However...northwest
trajectory and shallow mixed layer will limit areal extent
somewhat. Could see an additional coating to an inch over the
Outer Cape. Otherwise...clouds will gradually give way to ptsunny
skies from west to east during the afternoon...except for the
cape/islands where clearing will be delayed until evening. High
temperatures will reach low/middle 20s...except upper teens higher terrain
in northern and western Massachusetts. Northwest winds gusting to 20-25 miles per hour will
result in wind chills in the single numbers and teens.

&&

Short term /6 PM this evening through 6 am Thursday/...
high pressure builds in from the west tonight with clearing skies and
light winds developing. With deep fresh snowpack...the stage will
be set for ideal radiational cooling and a very cold night. Leaned
toward colder MOS guidance and undercut by 2-3f which yields mins
in the single numbers above and below zero...except teens
cape/islands. Coldest mins will be across west Massachusetts.

&&

Long term /Thursday through Tuesday/...

Overview...
active but progressive northern and southern streams across the
lower 48 through this long term period. First northern stream
short wave works out of the northern rockies today...crossing into
the region Thursday night and Friday...possibly lingering along
the East Coast Friday night. This will usher in Arctic air for this
weekend along with blustery winds and frigid wind chills. A pair
of 500 mb short waves may merge as they approach the East Coast Sunday
night and Monday.

While operational models did show timing and track differences
especially with the possible late weekend system...used an overall
model blend including ensembles. This gave good continuity with
the previous forecast.

Details...

Thursday...
high pressure ridge builds across in fast upper flow. Will see mostly
clear skies and light winds. The ridge will push offshore during
the afternoon with a light S-SW wind flow setting up. Clouds will
also increase ahead of next approaching system. Expect highs
mainly in the upper 20s to middle 30s.

Thursday night-Friday night...
pretty vigorous 500 mb short wave with clipper type system working east
out of the eastern Great Lakes/Ohio Valley. Looks like this system
will redevelop off the New England coast as the short wave begins
to negative tilt and cutoff...but this looks like it will happen
across central New England. The low does not deepen until later
Friday...which will be into the Gulf of Maine by then. However...
the low looks to spin there Friday night as it deepens...which may
keep moisture across eastern areas.

With milder air working into the developing low Friday...looks
like there may be a period of mixed rain/snow or even a brief
change to rain along the S coast...Cape Cod and the islands.
Otherwise...looks like another shot of snowfall for the region
though not nearly as high as the blizzard. Total quantitative precipitation forecast looks to be
from 0.15 to 0.25 inches across most areas...but will see some
enhancement across east coastal areas as the low forms with quantitative precipitation forecast
possibly up to 0.40 inches. With the cold air in place...will
likely see snowfall totals from 2-4 inches but could see a bit
more across NE Massachusetts closer to the developing low with some snow
lingering Friday night.

With strong pressure falls as the low develops offshore...expect
tightening pressure gradient bringing increasing northwest winds behind the
storm later Friday night. Will likely see gusts up to 25-35 knots
around or after midnight...bringing in Arctic air as well as low
wind chill readings. Lows Friday night plunge to below zero across
the higher inland terrain as well as the east slopes of the
Berkshires to 10-15 along the S coast...Cape Cod and the islands.
The combination of the low temperatures and blustery winds may mean very
low wind chill readings. Advisories may be needed for portions of
the interior.

Saturday-Sunday...
high pressure begins to shift east during Sat...but the departing storm
into the Maritimes will cause blustery conditions to continue.
Arctic airmass entrenches itself across the region with 850 mb temperatures
dropping to -11c to -16c. This translates to temperatures only recovering
to the teens to around 20 on Sat...though wind chills will make
it feel much colder.

Winds will diminish Sat night...but may remain high enough with
the dropping temperatures to see possible wind chill advisories. Lows
will bottom out from zero to 5 below well inland to the middle teens
on the Outer Cape and Nantucket.

Another low begins to move NE across the Mississippi Valley during
Sunday as high pressure crests across the region. Northwest winds diminish
and begin to back to west late in the day. Clouds will also increase
during the afternoon.

Sunday night-Monday...
pair of upper level systems begin to approach. Low confidence on
the timing and track of these systems...as well as how surface low
pressure forms as it approaches. Of concern is the track of this low
on the 00z European model (ecmwf)...which takes the low S of the region meaning
another shot for more snow. The 00z GFS and ggem models keep the
low further inland...with possible mixture or a change to rain for
some locations. May also see decent rainfall with some infusion
of southern stream moisture with this low. Something to keep a
close eye on...though again confidence remains low.

Tuesday...depending upon the departure of the low...looks like
more cold air works in as another high approaches.

&&

Aviation /10z Wednesday through Sunday/...
forecaster confidence levels...

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

Short term...through tonight...high confidence.

Through 12z...areas of MVFR/IFR in snow across east Massachusetts will improve
08-09z...except lingering in ocean effect snow showers across
Cape Cod. Diminishing wind.

Today...VFR ceilings most areas...but MVFR ceilings along with scattered snow
showers across Outer Cape cod and ack. Northwest gusts to 20 knots.

Tonight...VFR. Winds becoming light.

Kbos taf...high confidence in taf.

Kbdl taf...high confidence in taf.

Outlook /Thursday through Sunday/...

Thursday...moderate confidence. Mainly VFR. Winds becoming light
S. Middle and high clouds approach during the afternoon.

Thursday night-Friday night...low to moderate confidence.
Expect ceilings lower to MVFR with MVFR-IFR visibilities in snow. Conditions
improve to VFR Friday afternoon but northwest winds increase with gusts
up to 25-30 knots...possibly higher along the East Coast.

Saturday-Sunday...low to moderate confidence. VFR. Gusty
northwest winds 25-35 knots Saturday...lighter winds Sunday.

&&

Marine...
forecaster confidence levels...

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

Short term /tonight/...high confidence.

Gale force gusts have diminished over east waters and Small Craft Advisory in effect
for all waters. Winds will continue to diminish below Small Craft Advisory later
this morning into the afternoon...with gradual subsiding seas.
Freezing spray diminishing.

Diminishing northwest winds through tonight. Seas mostly below Small Craft Advisory
thresholds...except subsiding to near 5 feet over east waters toward
daybreak Thursday.

Outlook /Thursday through Sunday/...moderate confidence.

Thursday...
conditions remain below small craft thresholds on Thursday...
though S winds may gust up to 20 knots Thursday night.

Friday...
low pressure will cross the waters. Expect reduced visibilities in snow.
Expect winds to shift to northwest by Friday night...increasing to 25-35
knots...so gales will likely be needed. Seas also build up to 6-8 feet
over the open waters. Freezing spray will likely develop Friday
night.

Saturday...northwest gales expected with potential for a light freezing
spray. Seas remain high...possibly up to 7-9 feet on the exposed
waters. Winds will begin to diminish Sat night.

Sunday...winds and seas at Small Craft Advisory levels early
Sunday...but will diminish through the day.

&&

Tides/coastal flooding...
anticipate pockets of minor coastal flooding for the early morning
high tide along north and northeast facing shorelines as well as
some additional erosion. Impacts for this tide cycle will be much
less than what we experienced during Tuesday/S high tides.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...coastal Flood Advisory until 7 am EST this morning for maz019-
022-024.
Rhode Island...none.
Marine...Small Craft Advisory until 1 PM EST this afternoon for
anz232>235-237.
Freezing spray advisory until 8 am EST this morning for
anz231>235-237-251.
Small Craft Advisory until 9 am EST this morning for anz230.
Small Craft Advisory until 7 PM EST this evening for anz231-
251-255-256.
Small Craft Advisory until 6 am EST early this morning for
anz236.
Small Craft Advisory until 7 am EST Thursday for anz250-254.

&&

$$
Synopsis...kjc/evt
near term...kjc
short term...kjc
long term...evt
aviation...kjc/evt
marine...kjc/evt
tides/coastal flooding...kjc

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