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Area Forecast Discussion
National Weather Service Taunton MA
750 AM EDT Fri Sep 30 2016

.SYNOPSIS...
While high pressure remains across Quebec, low pressure will move
along a nearly stationary front south of New England to bring
cloudy, cool conditions with showers and patchy fog through this
weekend. Another low moves east from the Great Lakes across New
England early next week. High pressure then brings dry weather
midweek. Attention then turns to Hurricane Matthew. Still
uncertain what impacts our region will see, if any at all.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

No major changes to the forecast this morning. Tweaked the timing
of the rainfall this morning. Still thinking showers become more
numerous later this morning. Brought the near term forecast
temperatures back in line with observed trends.

Previous Discussion...

First slug of precip working slowly NNW, heading toward central
and eastern areas as seen on latest KBOX 88D radar loop. The
precip is running into drier air across the region and higher
pressure across northern New England in Quebec. Current radar
trends suggest that the leading edge of the rain will reach the S
coast by around 12Z, then move steadily across most of the region
through midday. With drier air aloft across central and northern
areas, will take a while for the rain to reach the ground.

The area of showers is associated with PWAT plume as seen on
short range models, on the order of 2 to 2.2 inches. So, once the
airmass becomes saturated, may see some brief heavy downpours.
Models are showing this plume will slowly move N as it pushes
against the strong Quebec high.

Strong E-NE pressure gradient in place with wind gusts up to
25-35 mph expected south of Boston down to Cape Cod and the
islands where the highest gusts are forecast.

Will be a cool, raw day with the E-NE winds in place. Highs will
only reach the upper 50s to lower 60s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Tonight and Saturday...Weak low pressure will move along the
front stalled south of New England, which will enhance the
rainfall tonight into early Saturday. PWAT plume will remain just
offshore, but will also help to enhance the rainfall especially
across central and eastern areas. Current QPF amounts suggest
rainfall of 0.5 to 1 inch may fall during this timeframe, with
some locally higher amounts possible across E Mass into RI with
the moisture rich airmass there. This will put a small dent into
the long term drought across the region. Depending upon timing,
could see the showers start to taper off across the CT valley late
in the day, but low confidence on this timing with the blocking
pattern in place.

Temps will bottom out in the upper 40s across the higher inland
terrain to the mid-upper 50s along the coast tonight. Highs
Saturday will be mainly in the 50s to around 60 inland, ranging to
the lower-mid 60s along the immediate coast.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Big Picture...

Latest guidance remains in decent agreement with overall themes,
and even some details through Tuesday. Beyond Tuesday though, have
above normal uncertainty with the details, largely due to the
large spread of model solutions for Hurricane Matthew.

Still looking at a potent high pressure over the western Atlantic,
with a cutoff low over the Great Lakes region this weekend. This
cutoff low slowly lifts northeast into the Maritimes, while the
high moves farther offshore toward the middle of next week. This
leaves Hurricane Matthew in a position where it could make a run
toward the East Coast late next week.

At this time, favor a model consensus through Tuesday to smooth
over the minor differences. Beyond Tuesday, favor a solution
closest to the 00Z GFS, which is more in line with the official
forecast for Hurricane Matthew. This is a storm which will bear
watching over the next several days.

Details...

Saturday night into Sunday...

We should still be dealing with a close upper low over the Great
Lakes for much of this time. All signs still point to a
significant onshore flow with abundant moisture. This should
result in widespread showers during this time. Some of these
showers could be locally heavy. Even when it's not raining, we
likely will not see any sunshine late this weekend. Rainfall
chances slowly diminish Sunday.

Monday into Tuesday...

Upper low and cold pool moves overhead late Monday and Tuesday.
This will generate some instability, but not enough for
thunderstorms. Thinking scattered showers continue Monday, then
slowly diminish Tuesday with the cold pool moving offshore. Surface
wind flow will maintain a northeast direction, meaning near to
below normal temperatures continue.

Wednesday into Thursday...

High pressure builds over our region from the Maritimes with dry
weather and partly sunny skies. Northeast flow continues. As
noted above, will need to keep an eye on Matthew for possible
impacts late next week.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels.

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

Short Term /through Saturday/... 

Today...High confidence. Will see mainly VFR VSBYS through midday
across the region, then will lower to MVFR in showers and patchy
fog moving from S-N, though will likely hold off across central
and N Mass until tonight. MVFR CIGS running from near KLWM-KIJD
southward with the low level moisture in place, which will lower
to areas of IFR from S-N across the entire region by midday or
early afternoon. Gusty NE winds to 25-30 kt continue along the
east coast.

Tonight...Moderate confidence. CIGS lower to IFR this evening,
though timing may be later across N Mass. May see periods of LIFR
CIGS across N CT/RI/SE Mass. Mainly MVFR VSBYS this evening, with
areas of IFR moving across central and southern areas after 06Z-
08Z when steadiest rain moves in. NE wind gusts up to 25-30 kt
continue along the coast.

Saturday...Low to moderate confidence due to timing. MVFR-IFR
CIGS/VSBYS, lowest across RI/E and central MA. May see areas of
LIFR CIGS across higher terrain at times. NE winds continue to
gust to around 25 kt.

KBOS TAF...High confidence in trends, moderate confidence in
timing.

KBDL TAF...High confidence in trends, moderate confidence in
timing.

Outlook /Saturday Night through Tuesday/...

Saturday Night into Sunday...Moderate confidence. MVFR/IFR cigs
and vsbys in showers and fog. Northeast flow diminishing.

Monday into Tuesday...Low confidence. Mainly VFR with areas of
MVFR in scattered showers.

&&

.MARINE...
Forecaster Confidence Levels.

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

Short Term /through Saturday/...

High confidence. Marine headlines continue, with gale warnings
extended across RI sound and the outer waters S of Nantucket and
the Vineyard with gusts up to 35-40 kt this afternoon and early
tonight. Otherwise, small crafts continue through Saturday, but
winds will gradually diminish. Seas remain high, up to 8-12 feet,
highest across the southern outer waters today into tonight then
will slowly subside from N-S but remain AOA 5 feet.

Outlook /Saturday Night through Tuesday/...

Persistent northeast winds through this portion of the forecast.
Speeds diminishing Saturday night into Sunday, then increasing
again toward Tuesday. Rough seas across the outer coastal waters
diminish Sunday into Sunday night. Seas likely to build again
Tuesday as winds increase.

Small Craft Advisories will likely be needed at times during this
time.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 5 PM EDT Saturday for ANZ232.
     Small Craft Advisory until noon EDT Saturday for ANZ233-234.
     Small Craft Advisory from 10 PM this evening to 8 AM EDT 
     Saturday for ANZ230.
     Small Craft Advisory until 8 PM EDT Saturday for ANZ231-250-
     251-254.
     Small Craft Advisory until 11 AM EDT Saturday for ANZ236.
     Gale Warning until 2 AM EDT Saturday for ANZ235-237.
     Gale Warning until midnight EDT tonight for ANZ255.
     Gale Warning until 5 AM EDT Saturday for ANZ256.

&&

$$
SYNOPSIS...Belk/EVT
NEAR TERM...Belk/EVT
SHORT TERM...EVT
LONG TERM...Belk
AVIATION...Belk/EVT
MARINE...Belk/EVT

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