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Area forecast discussion 
National Weather Service Taunton Massachusetts
136 PM EDT Friday Jul 3 2015

high pressure over southern New England this afternoon will shift
east by Saturday. Big changes in the forecast for Independence
day. It is now looking more likely for at least some showers
across southern New England. Any rainfall will come to an end
Saturday night. High pressure then returns with warming conditions
into early next week.


Near term /until 6 PM this evening/...
high pressure over the region with plenty of subsidence. That
means lots of sunshine and light winds. The light winds will allow
sea breezes along the coastlines.

Morning balloon soundings showed easy mixing to 850 mb...then an
isothermal layer between 850 and 800 mb. Middle morning amdar
soundings showed the mixing had indeed reached 850 mb at that
time. Temperatures at 850 mb were 7c which would support surface temperatures in the
lower 70s. Similar temperatures at 800 mb would be equivilent to 12c at
850...which would support maximum surface temperatures in the lower 80s. With
plenty of sun working on the airmass we would expect the inversion
to eventually mix out. Continue to forecast maximum surface temperatures in the
upper 70s to middle 80s...except cooler coast with the sea breezes.


Short term /6 PM this evening through 6 PM Saturday/...
tonight...high pressure shifts east but remains in control over
the weather of southern New England. Another shortwave moves over
the Great Lakes and forms another wave along a front to our south.
This should generate another area of clouds and showers that
approach from our south.

Independence day...
huge changes to the forecast. The charge lead by previous runs of
the GFS...has been taken up by the rest of the 03/00z guidance
suite. Model solutions now feature an anomalously deep middle level
trough moving into New England. The proximity of this trough has
shifted the projected track of a low pressure farther north from
the Middle Atlantic States. GFS remains the most robust...with the
slowest timing. Favored a consensus the details are
still somewhat murky.

Despite the consistent shift among all the guidance members...
decided to only trend the forecast wetter...rather than going with
the washout from prior runs of the GFS. Heaviest rainfall will be
closer to the South Coast of New England. Since this is more of a
winter-time setup...went with rain instead of showers. That
said...still not expecting a washout as there is a lot of low
level dry air to overcome. Stay tuned for more potential changes
to this portion of the forecast.


Long term /Saturday night through Thursday/...

* rain ends Saturday night.
* High pressure and warming conditions into early next week.
* Unsettled conditions return middle-late next week.

Overview and model preferences...the most recent GFS operational
GFS remains the more amplified outlier in the short term with the
deepening of a shortwave and low pressure development this weekend.
This overamplifcation continues beyond the weekend looking at the
synoptic pattern. Therefore...will be leaning away from the GFS
with this long term update and applying a blend of the gefs/ecens
and persistence with the operational European model (ecmwf).

A near zonal flow pattern will slowly give way to a building ridge
across the deepening cutoff across the Canadian prairie
continuously feeds warm advection into the ridge. Therefore...the
moderating temperature/dry weather pattern we have been advertising for
early next week still looks like a good starting point. By middle to
late next is a matter of the influence of this cutoff.
There is some suggestion of a more east shift in the cutoff...which
would suggest a longer unsettled period. While others are further
west...and southern New England remains in the zonal flow within the southeast
quadrant of the cutoff. In any case...cooler and more periodic wet
weather is possible in comparison to the early week.


Sat night into sun...upper level wave will be sliding across the
region through the period. There are two surface features to watch.
The first...Sat night is an ocean low pressure wave moving offshore
which...could lead to a few remaining showers. The second is a
weak cold frontal passage on sun. In either case...overall precipitable waters
in the column are near seasonal normals and there is a fair amount
of dry air with in the lowest 300hpa. In either isolated
shower is likely to be most rainfall to contend with. 850 mb temperatures
near +10c suggest temperatures near highs on sun remain in
the upper 70s to low 80s.

Monday into Tuesday...with upper level ridge building over from the
west...combining with the Bermuda high...expect high pressure and dry weather
to prevail. Temperatures will be warming through thee period...along with
rising humidity. 850 mb temperatures are closer to +15c by Tuesday.
Therefore...highs ranging in the 80s will be forecast.

Wednesday...the first in a series of waves ejecting from the strong
cutoff well to the west will move across the region. Increasing
column moisture with precipitable waters approaching 2.0 Standard deviations above
normal...cooling 500 mb temperatures and leftover warm/moist lower levels
suggest decreasing static stability. Therefore...with the wave and
attendant cold front...could see development of T-storms and
showers. Shear is not too strong at this point...but will likely
need to monitor this as we get closer.

Thursday and Friday...uncertainty remains high during this period as it
will depend on how close the Upper Cutoff gets to the NE Continental U.S..
the front will stall in the vicinity and provide a focus...but
exactly how many wave/how strong and when they occur will have to
be better defined once the cutoff develops and becomes better


Aviation /18z Friday through Wednesday/...
forecaster confidence levels...

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

Short-term /through Friday night/...

This afternoon...high confidence. VFR. Sea breezes along the

Tonight...high confidence.

Saturday...moderate confidence.
VFR to start. MVFR possible in scattered areas of light rain late
in the chance is at terminals along the South Coast. We
are monitoring the possibility of low conditions at Boston toward
evening depending on the strength of developing east/northeast
flow at that time.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook /Saturday night through Tuesday/...

Sat night...moderate confidence. Some rain...mainly across southeast Massachusetts/Rhode Island
will gradually come to an end. Any MVFR conditions will give way to
VFR through the night.

Monday into Tuesday...high confidence. Mainly VFR. A few showers or
thunderstorms possible on Tuesday.


forecaster confidence levels...

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

Short-term /through Saturday/...relatively light winds winds and
seas expected through this period. A developing low pressure to
our south should lead to building seas across the southern coastal
waters late tonight into Saturday. Small craft advisories may be
needed due to rough seas. Only moderate confidence in the track
and timing of this low pressure.

Outlook /Saturday night through Tuesday/...

Sat night into sun...moderate confidence. Winds will shift from
easterly to NE as low pressure moves east of the waters. Wind gusts may
approach 20-25 knots through the evening...but it will take seas on the
waters S and southeast of New England into sun to decline from 5-7 feet below
Small Craft Advisory conditions. Therefore...small craft advisories
may linger through the day on sun.

Sun night into Monday night...high confidence. High pressure yields mainly
quiet boating weather.

Tuesday...moderate confidence. Winds shift to the S...and while quiet
boating weather is likely to dominate...there is a low chance that
increasing seas and winds will approach Small Craft Advisory


Box watches/warnings/advisories...
Rhode Island...none.


near term...wtb/Belk/doody
short term...Belk
long term...doody

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