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Area forecast discussion 
National Weather Service Taunton Massachusetts
436 am EDT Thursday Oct 23 2014

Synopsis...
a powerful early season coastal storm will bring strong winds and
periods of heavy rain in squalls and isolated thunderstorms this
morning. Rain will become more showery this afternoon along with
winds not quite as strong. Showers continue to diminish Friday as
the storm slowly pulls away from New England. Showers possible
again Saturday evening and overnight as low pressure moves into
southern Quebec. Dry and seasonably cool weather returns Sunday
into early next week.

&&

Near term /until 6 PM this evening/...

*** a powerful early season coastal storm will continue to bring
strong winds...heavy rainfall and tidal flooding into Thursday morning ***

415 am update...

Impressive early season coastal storm south of New England early
this morning with its warm conveyor belt/trowal rains and
embedded convection pinwheeling from Georges Bank into
Massachusetts and southern New Hampshire...slowly pivoting northwest. Details
on the individual storm hazards are below.

1)heavy rain/flood threat...

Dual pol has been estimating hourly rainfall rates of about an
inch or so in the rain band over Massachusetts much of the night. Radar may
be under estimating given the strong low level winds /precip
drift/. As this warm conveyor belt slowly lifts northward the
heavy rainfall and flood threat will be focused across northern Massachusetts
into southern New Hampshire this morning. Thus worst conditions for the
morning commute will be across this region.

Elsewhere precipitation will be more showery and not as intense. However
another potent short wave/pv anomaly was pivoting northward around
the middle level low and this new warm conveyor belt may clip
southern Rhode Island and southeast Massachusetts later today with additional heavy
rainfall. Lapse rates not as impressive later today as this
morning but can/T rule out isolated T-storms later this afternoon
and evening across southern Rhode Island into southeast Massachusetts. Given the risk
of additional flooding will leave the Flood Watch as is with the
greatest risk across northeast Massachusetts and southeast New Hampshire this morning.



2) strong winds:

Kbox radar indicates low level jet has weakened somewhat and
shifted northward. Elevated observing platforms such as Isle of
Shoals off the New Hampshire coastline confirms this with NE winds continuing
to gusts over 50 kt! However surface winds have slackened a bit
over the region as wind trajectory as shifted from NE to north during
the predawn hours. This is a result of the development of a subtle
coastal front. This more land trajectory is a more stable than
over the relatively warmer ocean along with more friction/drag.
Hence wind speeds have lessened overnight. However given the core
of the low level jet will be closest to northeast Massachusetts along with
heavy rain/convection enhancing wind threat from precipitation drag will
continue the High Wind Warning for Essex County.

Elsewhere low level jet will remain strong enough to support wind
speeds approach advisory criteria. While speeds may fall just shy
of criteria...fully to partial leaved trees will increase the risk
of down limbs and branches. Hence will continue the Wind Advisory
until 11 PM this evening when the low level jet is expected to
weaken.




&&

Short term /6 PM this evening through 6 PM Friday/...

Tonight...

Occluded low slowly moves seaward. However lighter comma-head
rains will likely impact the region much of the night. However the
flood threat appears to diminish. Gusty northeast winds should
begin to slacken later in the evening as the low level jet
weakens.

Friday...

Further improvement especially during the afternoon from west to
east as comma-head exits and moves offshore. Risk for showers will
be highest in the morning with best chance of drying and late day
sunshine is across the CT River Valley.

&&

Long term /Friday night through Wednesday/...

* showers possible again Saturday as low pressure moves into Quebec
* mainly dry and seasonable weather early next week

Overall the 12z model suite is in fairly good agreement through the
long term. There are some discrepancies in the mesoscale details but
otherwise they are in good agreement. After the coastal storm
currently affecting the region moves away from southern New
England...the weather starts to dry out and become more seasonable.
There are a couple of cold fronts expected to move through the
region and each of these may bring some showers with them.



Saturday...another upper level trough moves over the northeast with
low pressure moving through southern Quebec and into the Maritimes.
The models Don/T show a whole lot of moisture or a big wind shift
with this front but we could see some showers. The GFS has a
stronger low level jet than the European model (ecmwf) which could enhance the amount
of rainfall but there is still much to be seen with this system.

Sunday through Tuesday...high pressure starts to build into southern
New England bringing dry and seasonable weather. Temperatures begin
to climb and may warm to well above normal by Tuesday.

Wednesday...low pressure moving through the Great Lakes and into
Quebec may bring a cold front through southern New England. Another
chance of some showers possible with this front but plenty of
uncertainty.

&&

Aviation /08z Thursday through Monday/...
forecaster confidence levels...

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

Short term /through Thu/...

Through 12z...

Band of heavy showers with embedded T-storms over Cape Cod
northwest into western Massachusetts will continue to slowly pivot northward
with time. Strong NE winds continue with highest gusts over
northeast Massachusetts. IFR persist along the coast with MVFR elsewhere.

After 12z...

Band of heavy rain with embedded T-storms should be across
northern Massachusetts into southern New Hampshire and slowly lifting northward.
Marginal IFR/MVFR conditions continue. Gusty NE winds continue
with strongest winds focused across northeast Massachusetts.

Tonight...

IFR eastern Massachusetts with MVFR elsewhere. Slow improvement with showers
becoming less numerous and winds slowly easing.

Friday...

MVFR but trending toward VFR late. Scattered showers becoming less
numerous as the day progresses. North-northwest winds 10-20 knots.

Kbos...high confidence in taf on trends but lower confidence on
exact timing of details.

Kbdl...high confidence in taf on trends but lower confidence on
exact timing of details.

Outlook...Friday night through Monday...

Saturday through Monday...moderate confidence. VFR. Low probability
of scattered showers Saturday.

&&

Marine...
forecaster confidence levels...

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

Short term /through Friday/...

*** dangerous coastal storm impacts the New England waters ***

Today...

Coastal storm south of New England will bring northeast gales and
dangerous seas to the Massachusetts and Rhode Island waters.
Strongest winds and largest seas will occur over the northern Massachusetts
waters into New Hampshire coastal waters. Winds and seas not quite as
intense this afternoon but nevertheless dangerous sea conditions.
Heavy rain squalls with embedded T-storms mainly confined to the
northern Massachusetts waters.

Tonight...

Low slowly weakens and moves seaward with winds becoming subgale
as the night progresses. Also any lingering rain squalls not as
intense as this morning.

Friday...

Slow improvement continues with winds becoming more north-northwest and
showers becoming less numerous late in the day and at night.

Outlook...Saturday through Monday...

Saturday and Sunday...moderate confidence. After a brief lull...seas
and winds will increase ahead of a cold front. Small craft
advisories will likely be needed for at least a portion of the
waters.

Monday...moderate confidence. Winds and seas diminish as high
pressure builds over the waters.

&&

Tides/coastal flooding...

Last night/S high tide yielded a storm surge of 1.5 feet to 2.0 feet.
This combined with large wave action resulted in widespread minor
coastal flooding/inundation from Plymouth County northward. Both
etss and estofs are about 50% too low with their surge values when
compared to current observations. Thus have increased guidance by 50
percent.

Next high tide is late this morning toward midday. While this
astro tide is about 0.5 feet higher surge values may be somewhat
less than last evening. Reason being is that winds have become
more northerly...limiting the fetch and wave growth somewhat. Also
the low level onshore jet is expected to weaken somewhat as midday
approaches. So while this next high tide is about 0.5 feet higher...
thinking water levels will be similar to last evening/S high tide.
In addition wave action may be slightly less given winds more
northerly limiting fetch/wave growth. Hence impacts regarding
coastal flooding/inundation and erosion should be similar to last
evening. As a result will not upgrade to a warning and continue
with a coastal Flood Advisory. Greatest impacts will likely be in
the Cape Ann area northward to Salisbury including Plum Island.



&&

Box watches/warnings/advisories...
CT...Wind Advisory until 11 PM EDT this evening for ctz004.
Massachusetts...Flood Watch until 11 am EDT this morning for maz005>007-
013>022-026.
Wind Advisory until 11 PM EDT this evening for maz005-006-
012>021.
Coastal Flood Advisory until 2 PM EDT this afternoon for
maz007-019.
High Wind Warning until 10 am EDT this morning for maz007.
New Hampshire...Flood Watch until 11 am EDT this morning for nhz012-015.
Wind Advisory until 11 PM EDT this evening for nhz012.
Rhode Island...Wind Advisory until 11 PM EDT this evening for riz001>007.
Marine...Small Craft Advisory until 11 PM EDT this evening for
anz231>234-236-254-255.
Gale Warning until 11 PM EDT this evening for anz230-250-251-
256.
Gale Warning until 10 PM EDT this evening for anz235-237.

&&

$$
Synopsis...nocera
near term...nocera
short term...nocera
long term...rlg
aviation...nocera/rlg
marine...nocera/rlg
tides/coastal flooding...nocera

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