Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 150918
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
518 AM EDT Sun Oct 15 2017

.SYNOPSIS...
Areas of dense fog this morning across the region associated
with an approaching warm front. The front lifts north of the
area later this morning giving way to a very warm and humid
afternoon. A sharp cold front sweeps across the region tonight
and will be accompanied by scattered showers into Monday
morning. Behind the front it turns sharply cooler and brisk
Monday afternoon with temperatures dropping down close to
freezing into Tuesday morning. Gradual warm-up Wednesday
followed by highs in the 70s Thursday into next weekend along
with dry weather.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Have extended the dense fog advisory across the remainder of
the region, which includes north central and western Mass.
Starting to see patchy dense fog develop there, which will
linger through mid morning. Dewpoint depressions across the
entire region are 2 degrees or less, along with mainly calm
winds as weak warm front sits S and W of the region at 08Z. With
low sun angle, will take a couple of hours to burn the dense
fog off especially along the coast where it may linger even if
the warm front comes through due to the high dewpoints over the
cooler waters.

Noting a band of spotty light showers which started to develop
from S of Long Island into the east entrance of LI sound on KBOX
88D radar around 07Z. The showers were moving NE, running from
near Montauk and Block Island and Westerly NE across Newport and
New Bedford, where -SHRA reported at 0808Z. May see a few
showers across near Nantucket as well. Visibility briefly
improved at both locations, likely due to the precip in the
vicinity, but has lowered back to 1/2SM at Nantucket again.

As for today, what is left of the warm front around NYC and
Long Island will work NE across the region as low pressure
across the central Great Lakes shifts E-NE into southern Ontario
and Quebec. All the short range and high res models do signal
some spotty precip moving across this morning, and could see
some spotty drizzle as well. Once the front shifts across, will
see some improving conditions though low clouds may linger into
the afternoon especially near the coast. Still noting H85 temps
rising up to +16C to +17C by around midday or into the
afternoon. Noting low level jet pushing into the region this
afternoon, with the H85 jet increasing to around 40 kt by midday
across central and eastern areas, with the good mixing below at
or below H9. Gusty SW winds will kick in, especially across
eastern Mass into RI and across the coastal waters, where gusts
up to 25-30 kt are possible.

Once the light precip moves out, expect mainly dry conditions
through the remainder of the day. Leading edge of precip ahead
of the front looks to hold off until this evening. With the
strong warm air advection across the region, should see temps
reach to the 70s during the afternoon, mildest across the lower
CT valley and N central and NE Mass. However, depending upon
whether there are breaks in the clouds, temps may soar even
higher.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
Tonight...
Strengthening low pressure system over the Great Lakes crosses
southern Quebec and northern New England. Associated cold front
will push SE across the region through the overnight hours.

Area of showers associated with the front tends to weaken as the
front moves across as best lift and moisture shifts NE. Could
still see some scattered showers mainly across central and
western areas through midnight or so, becoming spotty as the
front shifts across.

Some question whether some wind gusts may push across portions
of the interior, especially over the higher terrain, as the
front passes as a secondary low level jet approaches. Noting
some potential gusts up to 35 kt or so across the higher terrain
of the Berkshires and possibly as far W as the Worcester hills
around or after midnight. Good cold air advection as H925
temps drop quickly around or after 06Z. Readings in the lower-
mid 60s this evening across the higher inland terrain may fall
back to the upper 40s by 09Z-10Z. Will need to monitor
potential for even higher gusts as the cold air wraps in behind
the front.

Expect lows by Mon morning ranging from the mid-upper 40s across
the higher terrain to the lower 60s along the coastal plain.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
* Highlights...

  - Chilly Monday and Tuesday
  - Gradual warming begins Wed then 70s Thu into next weekend
  - Extended dry stretch of weather Mon afternoon into next weekend

* Synoptic Overview...

Ensembles from both the GFS and EC in good agreement that a series
of northern stream short waves will temporarily erode the
subtropical ridge over currently over the southeast states. The core
of the coldest air arrives Mon night into Tue associated with
trailing/secondary short wave energy. Then a gradual warming trend
starts mid week as heights begin to rise behind departing northern
stream short wave. By Thu the subtropical ridge reemerges over the
southeast states and peaks at 591 dam into the weekend. This pattern
will support a prolong period of dry weather across southern New
England along with temps warming into the 70s Thu into next weekend!

* Daily Details...

Monday and Tuesday...

Could be some leftover showers over southeast MA Monday morning
associated with departing cold front, otherwise deep layer dry air
invades the area from the northwest. Model time sections reveal post
frontal strato-cu likely to develop so a mix of sun and clouds for
the afternoon. Noticeable cool down behind the front with 925 mb
temps falling to about +7C 18z Mon, supporting afternoon temps in
the upper 50s, few degs cooler than normal. Although it will feel
cool with NW winds up to 25 mph at times. Strong short wave trough
moves across the area late in the day/evening. However not much
moisture with this feature so not expecting much fanfare other than
a reinforcing surge of cool air. This CAA (-4C at 850 mb, -1 SD)
combined with light low level NNW drainage flow temps will tumble
into the 30s regionwide, except low 40s downtown Boston. Given this
setup leaned toward the coldest MOS guidance. Will likely eventually
need frost/freeze headlines. Tuesday, temps only recover into the
mid and upper 50s, a few degs cooler than normal with avg highs for
mid Oct 59-64 degs. Although light winds and mostly sunny conditions
will help offset the cool temps.

Wednesday...

Will be our transition day toward milder weather as the high shifts
south of New England and low level WAA commences with 925 mb temps
jumping from +4C Tue afternoon to +12C Wed afternoon. Blyr will be
shallow given 1024 mb surface pressure but full sun and WSW winds
will support highs 65-70, about 5 degs warmer than normal.

Thu/Fri/Sat...

00z ECENS and GEFS both suggest warming trend continues Thu ahead of
an approaching northern stream short wave. Then brief cool down Fri
before warming trend returns next weekend as subtropical ridge
reemerges over the southeast states into the Mid Atlc region. Not
expecting any precip in this pattern.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

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

Short Term /through Tonight/...Moderate confidence.

Through 12Z...
Areas of IFR-VLIFR mainly across most of S central and E Mass
into RI and NE CT through around 12Z. Expect 1/4SM FG across
most areas, especially from KOWD-KPVD-KWST and S/E as well as
portions of interior NE Mass, NE CT and the CT valley.
Elsewhere, may see patchy IFR conditions at times through 12Z.

Today...
Gradual improvement S/E during the day. IFR-LIFR may hold long
over S-SE coast through at least midday, possibly all day. VFR
elsewhere, increasing S-SW winds with gusts 25-30 kts, highest
across E MA into RI and along the coastal terminals.

Tonight...
MVFR-IFR CIGS along the S coast. Lesser VSBY impact with
continued S-SW winds up to 25-30 kt through 04Z before
diminishing as cold front passes. Winds may gust up to around
30 kt or so as they shift to W-NW. Conditions improve to VFR.
A few -SHRA possible prior to the wind shift.

KBOS TAF...Moderate confidence in TAF.
IFR-LIFR conditions expected through the morning push. Light
S-SE winds become S-SW by mid-late morning with improving
conditions by around midday. Wind gust up to 25-30 kt this
afternoon and evening as cold front approaches.

KBDL TAF...Moderate confidence in TAF.
Conditions vary between IFR and LIFR into the morning push, then
VSBYS should improve while CIGS remain low through the push. By
mid morning, should be VFR. S-SW winds gusting up to around 25
kt this afternoon and evening as cold front approaches.

Outlook /Monday through Thursday/...Moderate confidence.

Monday...High confidence.

Possible MVFR-IFR in morning showers over southeast MA including
Cape Cod and Islands. Then improving to VFR by mid morning.
Elsewhere VFR in the morning then marginal MVFR-VFR in afternoon
post frontal strato-cu. NNW winds gusting up to 25 kt.

Tuesday through Thursday...High confidence.

VFR, dry weather and light to modest winds.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Tonight/...

Through 12Z...Moderate to high confidence.
Areas of dense fog across the near shore waters, and likely
further offshore. May see patchy drizzle as well. Light S-SW
winds. Seas remain at around 5 ft on the southern outer waters.

Today...Moderate to high confidence.
Warm front moves N of the waters this morning, then S-SW winds
increase with gusts up to 25-30 kt this afternoon, highest
across the near shore and eastern outer waters. Seas will also
build. Small Crafts continue for all waters. Areas of dense fog
with poor visibility through mid morning or so, then should
improve with increasing wind and milder air.

Tonight...Moderate confidence.
SW wind gusts ahead of the cold front will continue to gust up
to 25-30 kt through this evening, then will start to diminish on
the near shore waters as the front approaches. Low probability
of gale force gusts on the outer waters prior to frontal passage
after 06Z.

Outlook /Monday through Thursday/...Moderate confidence.

Monday...

Cold front sweeps across the waters during the morning hours
and may be accompanied by scattered showers and patchy fog.
Behind the front (by mid morning) NNW winds 15-20 kt with gusts
possibly up to 25 kt.

Tuesday thru Thursday...

High pressure shifts south of New England with winds becoming
WSW. Dry weather and good vsby expected.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Dense Fog Advisory until 10 AM EDT this morning for CTZ002>004.
MA...Dense Fog Advisory until 10 AM EDT this morning for MAZ002>024-
     026.
RI...Dense Fog Advisory until 10 AM EDT this morning for RIZ001>008.
MARINE...Small Craft Advisory from 3 PM this afternoon to 8 AM EDT
     Monday for ANZ231>234.
     Small Craft Advisory from 2 PM this afternoon to 5 AM EDT
     Monday for ANZ230-236.
     Small Craft Advisory from 2 PM this afternoon to 8 AM EDT
     Monday for ANZ235-237.
     Small Craft Advisory from 11 AM this morning to 9 AM EDT
     Monday for ANZ250.
     Small Craft Advisory from 2 PM this afternoon to 6 AM EDT
     Monday for ANZ251.
     Small Craft Advisory until 6 AM EDT Monday for ANZ254>256.

&&

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



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