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Area forecast discussion 
National Weather Service Taunton Massachusetts
327 PM EDT Friday Oct 31 2014

Synopsis...
dry and seasonable conditions will continue today as high pressure
moves across northern New England. A developing coastal storm
will move up the coast Saturday and pass offshore Saturday night
and early Sunday bringing high winds and rain to the region. High
pressure builds over the eastern USA early next week. One or two
cold fronts may cross southern New England Wednesday through
Friday.

&&

Near term /until 6 PM this evening/...
130 PM update...did not make any major changes to the forecast at
this time. Updated winds and probability of precipitation through the period but did not
stray far from the morning update...only incorporated new guidance
which is on track with earlier guidance. Will be looking closer at
temperatures and weather /any p-type issues/ for the remainder of
the afternoon. Current weather is on track with temperatures in
the upper 40s to low 50s as of 1 PM.

***Updates made to weekend storm***

1015 am update...based on latest model guidance have increased
winds for the Saturday to Sunday time period. While there is still
a bit of uncertainty on the track of the coastal low...believe it
will be close enough to southern New England to result in very
gusty to possibly damaging winds for at least a portion of the
region. The highest confidence for high winds to occur is over the
cape and islands Saturday night and Sunday. However...with the 06z
GFS bringing the low a bit closer to southern New England...have
issued a high wind watch for all of eastern Massachusetts and
Rhode Island.

Overall...the forecast for today is on track...no changes were
made to the forecast for today.

745 am update...

Only minor tweaks to the forecast this morning.

Previous discussion...

Area of low to middle level clouds remain across central and eastern
areas at 07z...though noting some clearing across the CT valley as
well as along the S coast on latest infrared satellite loop. NAM and GFS
BUFKIT soundings indicating that the 5-6kft ceilings may break up
briefly around middle to late morning before redeveloping as NE winds
bring in increasing low level moisture during the afternoon...
again across central and eastern areas.

Low pressure moves southeast out of the Great Lakes...then secondary
development begins off the middle Atlantic coast. Looks like most of the
deep moisture with the cyclogenesis will remain S of the region so
have kept a dry forecast going. May see some sprinkles and patchy
drizzle develop late in the day along the East Coast...but not enough
to mention at this point.

Expect temperatures to only rise to the upper 40s across the higher
inland terrain...then mainly in the 50s elsewhere with the
freshening east-NE winds especially during the afternoon.

&&

Short term /6 PM this evening through 6 am Saturday/...
tonight...short range models appear to be in better agreement in
the development of not one but two centers of low pressure as 500 mb long
wave trough digs across the southeast U.S. Noting two strong upper level
jets moving around the base of this digging trough...the first
90-100 knots 300 mb jet axis works NE overnight. This will help
intensify the first low off the middle Atlantic coast around 12z Sat.

Area of rain will work steadily northward...especially around or
after midnight. Will also see NE winds increase along the coast
with gusts up to 25-30 knots...highest along the S coast...Cape Cod
and the islands. Best shot for precipitation will be across Rhode Island/east Massachusetts.

Expect overnight lows to range from the upper 30s over SW New Hampshire to
between 45 and 50 along the coast.

&&

Long term /Saturday through Friday/...

Big picture...

The long term period starts with a closed low over the northeast USA
a trough over The Rockies...and a ridge in between. The closed low
lifts northeast into the Maritimes early in the week. The ridge and
trough to our west move east...but the overall flow becomes more
zonal with time with a detached southern stream wave near the
Mexican border. Heights start the period below normal due to the
closed low...then climb to normal or a little above normal in the
zonal flow. Depending on timing...could be cooling back to below
normal late in week.

This suggests a cold start to the week but quickly trending back to
normal middle week...then cooling at end of week. Once the upper flow
becomes zonal...confidence in the timing of individual waves in the
flow and their associated surface systems will be reduced.

The dailies...

Sunday night-Monday-Tuesday... the axis of the upper low and cold
pool start Sunday night overhead and move off through the Maritimes
by Monday. Drier air moves in at all levels Sunday night and remains
overhead Monday. Fair mixing should reach to around 900 mb. Temperatures
of zero to -1c at that level translate to maximum surface temperatures int he upper
40s and around 50. The high moves off to the east Tuesday with
milder air moving in especially aloft. Cross sections show
increasing moisture at middle and high levels...so expect some middle and
high clouds together with the sun. Temperatures warm up a little but
mixing will be shallower...950 mb temperatures support maximum temperatures middle 50s.

Wednesday through Friday... two shortwaves move across the northeast
and eastern Canada during middle to late week. The first wave lifts
through Quebec with limited curvature in New England. The second
wave digs deeper over the Great Lakes and sweeps across New England
24-36 hours later than the first. As the upper flow is roughly
zonal...exact timing of the two passages is low confidence at this
time.

With the first wave directed through Canada and the upper flow
remaining southwest...there is a good chance the surface front
stalls over or near southern New England. The second deeper wave
turns the upper flow northwest and should push a cold front well
offshore with colder air then flowing in. We will go with chance
probability of precipitation north of the Pike late Wednesday/night with the first wave and
front...then more widespread chance probability of precipitation Thursday with the second
wave and front. Timing on this will likely change somewhat with
successive model runs.

&&

Aviation /20z Friday through Wednesday/...
forecaster confidence levels...

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

Short term /through Sunday/...

Through 00z...high confidence. VFR. There are a few locations on
the cape and islands that are having patchy MVFR ceilings.

Tonight...moderate confidence. Conditions deteriorate through the
night to MVFR-IFR from south to north with lowest conditions along
the coast. Expect scattered showers south of the Mass Pike with
the greatest chance of steadier rainfall along the South Coast.

Saturday through Sunday...moderate to high confidence. MVFR/IFR
conditions continue through 12z Sunday when ceilings start to rise
from west to east as low pressure pulls away from southern New
England. Northeasterly winds increase through the period...peaking
in the 40 to 50 knots range Saturday night into Sunday morning for
the eastern terminals. Windspeeds will be lower across the western
terminals but still gusting up to 35 to 45 kts peaking more on
Sunday. Widespread rain expected through Sunday morning most
locations and continuing on the East Coast...cape...and islands
into Sunday afternoon.

Kbos...high confidence in taf trends. Lower confidence on exact
timing of onset of rain and higher winds.

Kbdl...high confidence in taf trends. Lower confidence on exact
timing of onset of rain and higher winds.

Outlook...Sunday night through Wednesday...moderate confidence

Sunday night through Tuesday...VFR. Northwest winds Monday will gust
25 to 30 knots during the day.

Wednesday...VFR. Possible brief MVFR ceilings/visibilities in showers late
in the day and at night.

&&

Marine...
forecaster confidence levels...

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

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

Today...winds and seas remain below small craft criteria. Winds
will veer to east-NE during the day and begin to pick up. Gusts up to
20 knots reach the southern outer waters by late in the day. Seas
remain below 5 feet.

Tonight...E-NE winds increase with gusts up to 25-30 knots. Small
crafts remain in effect for most of the waters...but not quite
there for Boston Harbor and mass/Ipswich bays. Seas will also
build especially on the southern open waters during the night.

1015 am update...given the latest forecast guidance...have
increased the winds quite a bit over the coastal waters. Looks to
be a high likelihood of northeasterly storm force
gusts...particularly over the eastern waters. Depending on the
exact track of the low...could see storm force gusts as far west
as the waters south of Rhode Island.

Sunday...rain moves off to the east. Winds shift northwest.
Expecting these winds to diminish below gale force Sunday night.
With the wind shift...rough seas will transition farther offshore
with diminishing seas closer to shore. Gale warnings will likely
linger into the evening hours.

Outlook...Sunday night through Wednesday...moderate confidence.

Sunday night and Monday...gusty northwest winds at gale force early
Sunday night. Winds then diminish but remain 25 to 30 knots through
Monday. Seas diminsh Sunday night but linger 5 to 10 feet through
Monday.

Tuesday...winds and seas will remain below small craft levels.

Wednesday...seas will remain below 5 feet. Southwest winds will
increase with frequent gusts 20 to 25 knots.

&&

Tides/coastal flooding...
1015 am update...a coastal Flood Watch was issued for the Saturday
evening and early Sunday morning high tide cycles for the eastern
Massachusetts coast...including the north facing portion of Cape Cod and
Nantucket. This is for the potential of minor to isolated pockets
of moderate coastal flooding possible along with beach erosion.

Astronomical high tides are rather low Saturday evening and again
early Sunday morning. However...strong north to northeast wind gusts
up to 50 knots may result in seas building to around 20 feet over
the open waters. Still some uncertainty as to how strong the winds
will get...given model spread. However...there certainly is the
potential for a 2 to 2.5 storm surge to combined with significant
wave action. This will result in minor coastal flooding with
perhaps isolated pockets of moderate coastal flooding.
Therefore...we felt it was Worth at least a watch at this time.

The highest risk areas appear to be Hull and Scituate. We also have
to be concerned with the typical hot spots...such as Salisbury and
Plum Island which are very susceptible to beach erosion. Will also
have to keep an eye on Nantucket Harbor...as strong northerly winds
can cause issues for them.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...high wind watch from Saturday afternoon through Sunday morning
for maz005>007-013>021.
Coastal Flood Watch from Saturday evening through Sunday
morning for maz007-015-016-019-022-024.
High wind watch from Saturday afternoon through Sunday
afternoon for maz022>024.
New Hampshire...none.
Rhode Island...high wind watch from Saturday afternoon through Sunday morning
for riz001>008.
Marine...storm watch from Saturday morning through Sunday afternoon for
anz230>237-250-251-254>256.

&&

$$
Synopsis...wtb/evt
near term...Belk/rlg/evt
short term...evt
long term...wtb
aviation...wtb/rlg
marine...wtb/evt
tides/coastal flooding...

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