Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 011104
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
704 AM EDT Sat Oct 1 2016

.SYNOPSIS...
Low pressure southeast of New England will continue to generate
periods of rain today along with brisk northeast winds and cool
temperatures. Some improvement Sunday as winds slacken and rain
becomes more spotty along with periods of dry weather. A new risk of
showers are possible Monday followed by a stretch of dry weather Tue
thru Thu along with seasonably cool temperatures. Still watching
Hurricane Matthew, but lots of uncertainty whether it affects New
England or not.

&&

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

7 AM update ...

Robust 925 mb and 850 mb wind fields within the warm conveyor
belt (WCB) coming onshore into RI and southeast...eastern MA at 7
am. These wind fields acting on an airmass with PWATs of 1.5 to
2.0 inches. This is resulting in periods of heavy rain in this
area with observed hourly rainfall rates of 0.5 to 0.8 inches.
Thus have issued a flood advisory thru 830 am for eastern MA into
eastern RI for nuisance street/highway poor drainage flooding. In
addition have modified pops and qpf to better reflect radar
trends.

As these strong wind fields lift northeast along with drier mid
level air advecting in from the west...steady rains will wane this
afternoon and replaced with spotty light rain/drizzle this
afternoon from west to east. Otherwise forecast on track with
earlier discussion below.

=====================================================================

Radar continues to show bands of showers moving north across
Southern New England. Lift is rather weak, and mainly the result
of a low pressure passing by to our south. As this low pressure
moves offshore, we should start to start to get into a dry slot
later today.

Looking very much like a low QPF/high PoP kind of forecast. Most
rainfall rates were less then one tenth inch per hour. Will
continue categorical PoPs through this morning, before slowly
diminishing them this afternoon. In any case, not expecting a
total washout.

A large high pressure over the Maritimes will maintain persistent
northeast winds. Besides keeping southern New England below normal
temperature-wise, this will also keep the low level humidity
higher, particularly across RI and southeast MA. Max temperatures
today are not expected to be more than 10 degrees higher than the
low temperatures this morning.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Our region will still be in range of a potent mid-level cutoff low
late tonight into Sunday. This should be close enough to maintain
meager convective instability across our region. Despite a period
of lower precipitable water values, there should still be enough
moisture around for at least a continued chance of showers.

Temperatures still below normal thanks to flow off the Gulf of
Maine and continued cloud cover.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Update 4 am ...

Highlights ...

* Risk of showers Sun night and Monday
* Dry weather returns Tue thru Thu w/seasonably cool temps

Overview ...

Dry slot over the region Sunday evening with low level moisture
trapped beneath may result to spotty light rain/drizzle. Deeper
moisture and lift arrive Monday as closed low currently over the
Ohio Valley moves across New England. This will result in a risk for
scattered showers and isolated thunder given cold pool aloft
yielding steep mid level lapse rates. Then all model guidance agrees
on mid level trough moving offshore with rising heights over New
England Tue thru Thu. However this yields a 1035 mb surface high
over the Gulf of ME. So theme will be mainly dry weather Tue thru
Thu but accompanied by a cool maritime airmass. Then by late next
week still lots of uncertainty on the track of Hurricane Matthew.

Details ...

Sunday night ... dry slot still over the region especially during
the evening hours. Model time sections reveal lots of low level
moisture trapped beneath the dry air aloft so spotty light
rain/drizzle possible. So damp and cool however with pgrad relaxing
not expecting too much wind which will help take the edge off the
cool/damp conditions.

Monday ... Some breaks of sunshine possible however this will only
increase the risk of afternoon showers as closed low currently over
the OH Valley moves across southern New England. This combined with
cold pool aloft will yield steep mid level lapse rates and result in
a risk of thunder. Not as cool as previous days given some breaks of
sunshine along with winds off the ocean easing. Highs 65 to 70
likely.

Tue thru Thu ... building heights across New England supports dry
weather. However this setup also yields 1035 mb high settling over
the Gulf of ME resulting cool/brisk weather across Cape Cod and the
Islands with ENE winds gusting up to 25-30 mph. Also model time
sections reveal lots of strato-cu possible in this moist ENE flow
across Cape Cod and Islands. Thus more sunshine inland. Highs
slightly cooler than normal with afternoon temps in the low to mid
60s.

Friday ... still large spread of solutions regarding hurricane
Matthew. Models in better agreement this morning on latitude of
Matthew late next week...however models differ significantly on
longitude position. For example At 144 hrs/00z Fri 00z GFS has
Matthew along the east coast of FL...with 00z UKMET over the Bahamas
and 00z EC east of the Bahamas. The 00z GEFS indicates the 00z GFS
is on the western edge of all GEFS solutions. The 00z EPS wasn`t
available as of this writing but its 12z run was farther southeast
with most of its 51 members remaining well southeast and offshore of
New England. At this time range all possible outcomes remain in play
given large range of solutions and time range. However the bulk
of the guidance supports on offshore system as of now. Stay tuned.

&&

.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/...

7 AM update ...

Periods of heavy rain and IFR/LIFR this morning across eastern MA
into RI. Rain tapers to drizzle this afternoon from west to east.
Also gusty east winds up to 25 kt this morning along eastern MA
coast...slowly eases this afternoon. Earlier discussion below.

=======================================================================

Today...Moderate confidence. Low-end MVFR or IFR cigs linger
through the day with on-and-off rain showers lowering vsbys.

Tonight...Moderate confidence. May see some minimal improvement
during the overnight hours. However, low CIGS will remain an
issue. At least MVFR for most of southern New England, with IFR
CIGS toward the south coast.

Sunday...Moderate confidence. MVFR/IFR cigs and vsbys in showers and
fog. Diminishing northeast flow.

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

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

Outlook /Sunday Night through Wednesday/...

Sunday night ... Moderate confidence. MVFR/IFR cigs and vsbys in
spotty light rain/drizzle and fog. Diminishing northeast flow.

Monday-Tuesday... moderate confidence. VFR with areas of MVFR
across Cape Cod and Islands.

Wednesday...Moderate confidence. VFR.

&&

.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.

It will likely take until into Sunday for seas to drop below 5 ft
across the eastern, outer coastal waters. With northeast winds
gradually diminishing today and tonight, expecting seas to subside
as well. Small Craft Advisories will continue for at least a while
today. Will likely be able to convert the remaining Gale Warnings
to Small Craft Advisories later this morning. Still evaluating the
trends.

Outlook /Sunday Night through Wednesday/...

Diminishing Northeast wind Sunday night and Monday with gusts 20
knots or less. Northeast winds increase again Tuesday and Wednesday
on the Southern and Southeast waters with frequent gusts 20-25 knots.
Seas 5-6 feet on the eastern waters. Seas build again Tuesday and
Wednesday with 5-7 foot seas on the outer waters. Small Craft
Advisory will be needed for much of this time period.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 5 PM EDT this afternoon for ANZ232.
     Small Craft Advisory until noon EDT today for ANZ233-234.
     Small Craft Advisory until 8 PM EDT this evening for ANZ230-
     231-235-237.
     Small Craft Advisory until 10 PM EDT Sunday for ANZ250-254.
     Small Craft Advisory until 1 PM EDT Sunday for ANZ251.
     Small Craft Advisory until 8 AM EDT Sunday for ANZ255.
     Small Craft Advisory until 1 AM EDT Sunday for ANZ256.

&&

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


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