Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 301209
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
809 AM EDT SAT JUL 30 2016

.SYNOPSIS...
Most of today will be dry across the area, with increasing clouds
west to east during the afternoon. A series of weak low pressure
areas will bring periods of showers across southern New England
tonight into early Tuesday, bringing scattered showers. A few
thunderstorms are also possible each afternoon and evening. The
low will move offshore during Tuesday. High pressure will build
out of northern New England, with a return to dry conditions for
the middle and latter portion of next week. Temperatures will warm
up toward the end of next week.

&&

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

750 AM Update...

Area of dense fog along the S coast of Mass, Cape Cod and the
islands has tended to dissipate after sunrise, except for some low
clouds lingering around the mid and outer Cape as well as
Nantucket at 12Z. Elsewhere, skies were mainly mostly sunny with
some high clouds moving across. Temps have risen to the mid 60s to
mid 70s at 12Z.

Noting some patchy showers moving slowly E-NE in the mid level
flow across S central NY into NE PA as seen on latest NE regional
88D radar imagery. Also noting area of mid and high clouds across
central and western NY/PA that will slide slowly E toward the
region, probably pushing into western areas by midday or early
this afternoon. This is in good agreement with the previous
forecast.

Have updated near term forecast to bring conditions current.

Previous Discussion...

Believe nearly entire forecast area will remain dry through the
daylight hours today, although clouds will be on the increase from
west to east during the afternoon. Slight chance of showers
developing along and west of the CT river valley during the late
afternoon. Max temperatures under partial sunshine will likely reach
near to slightly above normal. Have gone with a model blend for the
dewpoint, which lowers values about 5 to 8 degrees from Friday
across most of the region outside the south coast zones where
dewpoints may only drop one or two degrees.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
What looks to be a series of short wave trofs moving about a slowly
progressive long wave upper trof will initiate a series of weak
waves along the front stalled south of the area for tonight through
Sunday. The pattern looks conducive to at least modest overrunning
in an environment depicted with deep moisture from Bufkit soundings
and precipitable waters around 1.5 inches. Due to at least some of
the area in a drought, we are taking a conservative approach on both
POPs and QPF forecasts. Also, models appear to be influenced by some
convective feedback.

The focus for showers is expected to be across the western half of
the area tonight. For Sunday, have the POPs highest north and west
where the models suggest the better forcing. With K indices in the
lower 30s, cannot rule out isolated thunder this evening and again
Sunday late afternoon and evening.

Clouds will keep temperatures elevated some tonight with lows in
the mid to upper 60s across most of the region. The combination
of clouds and generally onshore flow is expected to keep
temperatures in the mid to upper 70s on Sunday.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Highlights...

* Unsettled Sunday night through early Tuesday with scattered
  showers, mainly in northern and western areas
* Isolated thunderstorms possible across central and western
  areas Monday afternoon/evening
* Dry weather expected Tuesday afternoon through Friday, with a
  warming trend toward the end of next week

Overview and model preferences...

00Z model suite showing a bit better agreement through a good
portion of the long term forecast period, but do note timing
differences toward the end of next week as one would expect that
far out in the forecast. GFS/ECMWF ensembles also showing pretty
good continuity through most of the period.

Models maintain a slow moving open H5 trough across the northeast
Monday into Tuesday, with weak low pressure waves moving along a
stalled front just off the southern New England coast. The trough
will finally push seaward on Tuesday, with a slow improving trend
during the day. Large high pressure will build out of southern
Ontario to the Great Lakes later Tuesday, slowly pressing eastward
with dry conditions Wednesday and Thursday. The high will work
offshore on Friday, with an approaching cold front late in the
day. There are some timing differences amongst the model suite
with this approaching front, so lower confidence with that portion
of the forecast.

Used a blend of available model and ensemble guidance for this
portion of the forecast.

Details...

Sunday night through early Tuesday...

Expect a couple of low pressure waves to slowly ride along a
stalled front just off the southern New England coast into early
Tuesday. This will keep a good low to mid level moisture feed
across the region thanks to an E-SE wind flow that will slowly
back to NE late Monday night into Tuesday as the final low pushes
offshore.

The best chance for showers will continue Sunday night and Monday
across central and western areas. Have kept 50-60 pct chance POPs
across western areas, but will still see scattered activity pretty
much everywhere. With the onshore flow, albeit light, will tend to
hold off any organized instability. However, can not rule out
elevated instability that will linger across central and western
areas Monday afternoon and evening, so kept mention of isolated
thunderstorms there.

Will see the final low push offshore early Tuesday as it becomes
better organized. The last of the showers should start to
dissipate during the morning.

With the mainly onshore flow, expect temperatures to run several
degrees below seasonal normals. Expect highs mainly in the 70s,
though a few spots may touch 80 over the southern CT valley both
days.

Tuesday afternoon through Friday...

Models continue to signal high amplitude H5 ridge building E out
of central Canada into Quebec. This will bring large surface high
pressure from southern Ontario and the Great Lakes slowly eastward
during this timeframe. Will see dry conditions through most if not
all of this period.

Temperatures will return to seasonal levels on Wednesday, then
will warm further as winds become more S-SW as the high crests
across the region, then slowly pushes offshore. Expect highs Thu
mainly in the 80s, then in the mid 80s to around 90 on Fri.
Humidity levels will also slowly increase.

Some model solution variance with the approach of a cold front
out of the Great Lakes to Hudson Bay later Friday. Have pretty
much a dry forecast going, though did mention slight chance POPs
late in the day and Fri night mainly near and N of the Mass Pike.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels.

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

Short Term /through Sunday/...

Today...High confidence. IFR CIGS lingering on the outer Cape and
Nantucket, but should move offshore by 15Z. Otherwise mainly VFR.
Expect mid to high clouds to increase west to east during the
afternoon.

Tonight...Moderate confidence. VFR ceilings are expected to prevail
with areas of MVFR visibility and ceilings in vicinity of some
showers tonight. More widespread MVFR conditions expected in areas
of fog along southeast coastal areas. Light winds with sea breezes
developing along both the south and east coasts by afternoon.

Sunday...Moderate confidence. Becoming mostly VFR ceilings with some
MVFR ceilings in vicinity of showers. Pockets of IFR ceilings and
visibilities due to morning fog across southeast coastal
sections.

KBOS TAF...High confidence. Generally VFR conditions expected
through the period, although occasional MVFR ceilings possible in
vicinity of showers and fog late tonight/early Sunday.

KBDL TAF...High confidence. VFR conditions expected through the
period except patchy fog may develop late tonight.

Outlook /Sunday Night through Wednesday/...

Sunday night through Monday night...Moderate confidence.
Mainly VFR. Scattered showers possible at any time. Cannot rule
out a heavier shower or thunderstorm with local MVFR-IFR
conditions, mainly from central Mass into N Connecticut Monday
afternoon and evening. Areas of late night/early morning fog with
IFR CIGS/VSBYS both nights.

Tuesday...Moderate to high confidence.
Mainly VFR. Scattered showers across the CT Valley through N
central and NE Mass Tuesday morning, then improving. May see brief
local MVFR conditions in any showers. Patchy late night/early
morning fog with MVFR-IFR conditions Tuesday night in the normally
prone areas.

Wednesday...High confidence.
VFR. Just a few areas of MVFR possible in patchy late night/early
morning valley fog and in the usual fog prone locations.

&&

.MARINE...
Forecaster Confidence Levels.

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

Short Term /through Sunday/...High confidence.

Winds and seas are expected to remain below Small Craft Advisory
thresholds through Sunday. Areas of visibilities 1 to 3 nm in areas
of late night/early morning fog are expected.

Outlook /Sunday Night through Wednesday/...High confidence.

Sunday night...Expect light E-SE winds with seas 3 ft or less.
Visibility restrictions in scattered showers and late night/early
morning fog patches.

Monday through Tuesday...Winds will back to E-NE with gusts up to
20 kt, mainly across the eastern waters Monday night/Tuesday. Seas
build up to 4 ft over the open waters mainly over the eastern
waters to south of Nantucket. Visibility restrictions in patchy
late night/early morning fog both night, and in scattered showers
Monday and Monday night, slowly improving on Tuesday. Isolated
thunderstorms possible off the RI coast Monday into Monday
evening.

Tuesday night and Wednesday...NE winds continue, gusting up to 20
kt on the open waters Tuesday night. Winds shift to E later
Wednesday but remain light. Local visibility restrictions continue
Tuesday night in patchy fog, mainly after midnight through mid
morning.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

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



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