Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 182259

Area Forecast Discussion
National Weather Service Taunton MA
659 PM EDT Tue Oct 18 2016

A warm front will lift north of the region this evening. This will
bring unseasonable warm temperatures through Wednesday. A cold
front will move also across the region Wednesday but with little
weather associated with it. Unsettled weather is likely at times
Thursday and Friday. Not as warm late week but still mild for mid
Oct. A drying and cooling trend likely next weekend.


7 PM Update...Areas of fog that developed north of the warm front
are starting to erode as the front moves northward. Boston cleared
out about an hour ago very quickly and expect areas to the north
to do the same in the next hour or so. On the other hand,
Nantucket also became socked in and that we expect to continue for
much of the night. Otherwise, the forecast is generally on track
aside from some minor temperature and wind discrepancies that were
updated to account for the latest trends.

Tonight... Expect fair skies for much of the night. A cold front
approaches from the Great Lakes later at night and will bring some
increasing clouds from the west. Meanwhile fair skies and
diminishing wind along with above normal dew points will generate
fog in some spots before the clouds move in. Low confidence on how
much of the fog will linger after clouds increase.

With dew points in the upper 50s and lower 60s, min temps should
no lower than that. The resulting small temp-dewpt differences
will also contribute to overnight fog.


The cold front slips through Southern New England during
Wednesday. Limited moisture, all of it below 700 mb, but enough to
generate 1.5 inch PW values. Cross sections show weak lift. The
upper jet remains across the St Lawrence Valley along with its
supporting dynamics. A few showers are possible, but widely
scattered at best.

Temperatures Wednesday will depend on the speed of clearing as the
front moves south of us. If clouds linger, then we may barely
climb into the lower 70s. If skies clear fast enough, we have
potential to reach 80 or the low 80s. At this time we will stay
consistent with the previous forecast.

At night,the front will stall to our south. High pressure moves
across Northern New England. This will keep us dry through the
night. Clouds may increase later in the night as the next system
approaches. Low level inflow ahead of the Ohio Valley system will
be focused on Eastern/Central PA. The right entrance region of
the upper jet will be even farther west over the Great Lakes. For
that reason we have eliminated pops from the forecast for Wed.
night. Dew points 45-55 and light north winds will define the min
temperature. The light flow may allow some fog to form, but the
speed of return of clouds ahead of the next system may interfere
with fog formation.


* Unsettled weather expected Thursday and Friday
* Cooler but still seasonable weather expected through Friday
* Temperatures fall a bit below normal this weekend into early next

On a broad scale, the models are in good agreement for the most
part.  There are some discrepancies, particularly Thursday and
Friday, that extend from potential tropical development in the
Bahamas and surface low developing in the Ohio Valley and how and
where they develop, strengthen, and interact.  The UKMET is one of
the faster solutions, while the Canadian is one of the slowest and
strongest.  The GFS and the ECMWF fall in the middle of these
solutions both speed and strength wise.  These solutions indicate
some interaction between the extra-tropical and tropical systems but
keep the bulk of the moisture offshore of southern New England. Both
show a brief period of heavier rain over some portion of the region,
but differ on where exactly this area of heavier rain develops. This
will be something to watch in the coming days.  Bulk of the guidance
indicates a widespread half to one inch of rainfall, with a
relatively small area possibly getting up to two to three inches.
Welcome rain once again, but not drought busting.  Beyond the end of
the work week, models are in decent agreement with the general
pattern and we will see a return to more normal autumn weather.

Thursday and Friday...High pressure will move into the maritimes
Thursday as low pressure and a cold front approach from the Ohio
Valley.  This low pressure will strengthen over southern New
England, possibly interacting with the above-mentioned tropical
low moving up the coast. Late on Friday the low pressure will move
northward into Maine and then Quebec. This will bring showers to
the region both Thursday and Friday. Models are showing the higher
PWAT values (tropical moisture) mainly over the eastern half of
southern New England on Friday. Thus, believe the heavier rain
will occur on Friday. There is some indication of some marginal
instability, so a few claps of thunder are possible, but for the
most part expect only showers. After the cold front Wednesday,
expect temperatures to fall back to near normal for mid October
through the end of the week.

Saturday and Sunday...This will be a bit of a transition period as
the upper level trough slowly moves offshore and low pressure moves
into the Maritimes.  A decent pressure gradient and a strong low
level jet will make this a somewhat breezy time as well as a bit
cooler than normal.  Sunny skies will counter the cooler, breezy
conditions somewhat but it will definitely feel like typical October
out there.

Monday and Tuesday...High pressure starts building into southern New
England.  There is some uncertainty in the models with possibly a
shortwave or cold front moving through Monday bringing a period of
showers.  Otherwise, expect continued quiet, normal to below normal


Forecaster Confidence Levels.

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

Short Term /through Wednesday Night/...

Tonight...Moderate confidence. Mainly VFR with 4-8K FT cigs
developing. Low risk of a brief shower late tonight, especially
Northern MA. Low confidence on potential for IFR fog aside from
the outer Cape and Nantucket.  Gusty winds.

Wednesday...Moderate confidence. Mainly VFR cigs with clearing
moving north to south across the region during the afternoon. Low
risk of a brief shower south of the Pike in the morning.

Wednesday night... Moderate confidence. Generally VFR. Low
confidence on fog formation after midnight. This will depend a lot
on how fast clouds move back in from the southwest overnight.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Thursday through Sunday/...

Thursday and Friday...Moderate confidence.  A mix of conditions,
potentially all MVFR/IFR in low clouds, rain, and fog at times. Some
improvement is possible late Friday and Friday night.

Saturday and Sunday...High confidence.  Improving conditions to VFR
quickly on Saturday.  Westerly to northwesterly winds increasing,
gusting to 25 to 30 kts.


Forecaster Confidence Levels.

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

Short Term /through Wednesday Night/...Moderate-High confidence.

Tonight...Increasing SW winds with gusts of 25-30 kt developing,
best chance on the southern waters. These will diminish overnight.
Seas building to 5-7 ft over the outer waters and exposed southern
nearshore waters.

Wednesday...A weak cold front moves across the waters during the
day. Expect SW winds to shift out of the NW. Winds will be less
than 20 kt. Diminishing seas.

Wednesday night...Winds below 15 knots and seas less than 4 feet
through the night.

Outlook /Thursday through Sunday/...

Thursday...High confidence. Mainly quiet boating weather is
expected with occasional 5 foot seas on the outermost waters.

Friday...Moderate confidence. Seas and winds increase as low
pressure moves across southern New England and approaches the
waters. In addition, a potential tropical or sub-tropical low may
move up the coast and work in tandem with the low over southern
New England. This potential interaction is what keeps our
confidence in the moderate range. Especially with wind direction.
Small craft advisories will likely be necessary for most of the

Saturday and Sunday...High confidence. Small craft advisory
conditions will continue with a tight pressure gradient between
the departing low pressure system and building high pressure in
the Great Lakes. Westerly winds will shift to the northwest on


Winds from the south tonight will shift out of the northwest
during Wednesday. With an offshore wind, we do not anticipate any
coastal flood issues beyond perhaps very spotty minor flooding at
the times of the highest tides through Thursday.

Friday could be another story, but much uncertainty remains.
Depending upon the interaction of a fairly high amplitude short
wave trof and a possible low center with subtropical origins off
the coast, there could be a significant east to southeast low
level flow toward our coastline, possibly building a surge over a
foot or two. The range of possibilities are wide, but there
remains a low risk of at least some coastal flooding during the
Friday PM high tides. We will need to monitor trends with later
computer model operational and ensemble runs.


Record High Temperatures:

Tuesday October 18th                Wednesday October 19th

Boston 82 in 1947                   Boston 84 in 1945
Worcester 85 in 1908                Worcester 81 in 1963
Providence 85 in 1908               Providence 81 in 1945
Hartford 80 in 1968                 Hartford 82 in 1963


MARINE...Small Craft Advisory until 8 AM EDT Wednesday for ANZ232>235-
     Small Craft Advisory until 11 PM EDT this evening for ANZ230.
     Small Craft Advisory until 2 AM EDT Wednesday for ANZ231-236-


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