Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 261414
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1014 AM EDT FRI AUG 26 2016

.SYNOPSIS...
A cold front swings through New England this afternoon, bringing
some showers and a few thunderstorms. Dry and warm conditions
follow for the weekend. There may be some widely scattered
showers and thunderstorms late Sunday night into Monday as a cold
front crosses the region. Some showers and thunderstorms may
linger Tuesday and Wednesday before another front clears through.
High pressure noses across the northeast late next week with dry
and mild conditions.

&&

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

Late morning obs show the cold front over the Hudson Valley with
showers from Southern VT through the Catskills. Additional showers
have popped up ahead of the front over CT and Cape Cod. CAPE is
building, especially over Western CT/Western MA with values around
500 J/Kg. Model CAPEs are forecasting patches of 1000-1500 J/Kg
this midday and afternoon.

Satellite images show clearing in Western CT/MA ahead of the cold
front and spreading east. This will allow for some afternoon
heating, supporting the idea of increasing CAPE and resulting
convection. Continue to expect scattered showers/t-storms until
the cold front moves through.

Morning soundings show max temp potential in the 80s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Tonight...

Cold front moves offshore by around midnight. Humidity levels
diminish noticeably. Expecting clearing skies and winds shifting
from the northwest. Seasonable temperatures.

Saturday...

High pressure starts to build in from the Great Lakes. Plenty of
sunshine and light north winds to start. Seabreezes likely to
develop along both coasts. even so, still expecting max
temperatures to be at or slightly above normal.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Highlights...

* Mild and dry conditions through the remainder of the weekend
* Scattered showers and thunderstorms late Sunday night and
  Monday
* A few showers and thunderstorms may linger Tuesday and
  Wednesday before another front sweeps across
* Looking dry and mild late next week

Overview and model preferences...

Continued summer pattern across North America and beyond with E-W
elongated Bermuda-Azores high from the mid Atlantic and SE states
over the subtropical Atlantic, stretching further across the
southern tier states to off the California coast, while the
northern stream steering currents have remain shunted into the
northern Plains states to Quebec around 00Z Sunday. H5 heights
increase further Saturday night into Sunday as closed high pres
builds across with H5 ridging into eastern Quebec.

Noting an H5 short wave in the flow trying to push SE into
northern New England Monday, bringing a weak cold front with it.
Should clear the region Monday night.

Models get a bit messy with the evolution of slowly lowering mid
level heights around Tuesday-Wednesday timeframe. Appears the 00Z
GFS is a bit stronger with another H5 short wave in the steering
flow, but the GGEM and ECMWF do show a weaker wave. May see
isolated convection mainly around max heating both days, with the
better shot on Tuesday.

A lot of questions beyond late Wednesday with timing of features
in the northern stream flow, but looks like it should be dry and a
bit cooler for Thursday.

Continue to monitor a tropical wave (99L) as it moves near or N
of Cuba. At this point, looks like it will remain out of the
northern stream weather picture. Will continue to monitor.

Leaned toward a blend of available guidance through Tuesday, then
went closer to ensemble guidance for Wednesday-Thursday. This gave
good continuity to the previous forecast.

Details...

Saturday night-Sunday...Looks dry as high pressure crosses New
England, heading for the Maritimes late Sunday. Expect highs on
Sunday to run 5-10 degrees above seasonal normals for late August,
though will be cooler along the immediate E coast with onshore
winds. Some clouds will begin to approach the Route 2 area of N
Mass during Sunday afternoon.

Sunday night-Monday...Cold front slowly approaches in the W-NW
upper flow. Most of the energy with the associated N5 short wave
remains across northern New England Monday, but could see enough
to kick off some isolated showers/thunderstorms mainly during max
heating. Noting a thin band of 1.7 to 1.8 inch PWATs cross with
this front Monday afternoon/ evening, along with some marginal
instability (LIs around zero to -1, Showalter around zero, TQs at
17-18 for elevated convection). Have kept only slight chance POPs
going for very spotty convection. Front should push offshore
Monday evening.

Tuesday-Wednesday...With a weak H5 short wave moving across on
Tuesday, along with some marginal instability remaining across the
region both days and dewpts mainly in the 60s to around 70 on the
S coast, may see some diurnal convection try to develop but will
remain spotty both days. Better shot for thunder on Tuesday, but
even weaker on Wednesday near the S coast so left thunder mention
out for now. Appears another front will cross the region later
Wednesday or Wednesday night.

Thursday...Not a lot of confidence for this timeframe, though
models and ensembles are tending to signal more dry conditions
with slightly cooler temperatures.

&&

.AVIATION /14Z 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/...

This afternoon...Moderate Confidence, mainly due to timing
issues.

SCT SHRA/TSRA, with higher confidence over S/E interior S New
England terminals. S-SW winds continue with gusts up to 20 kts
before shifting out of the NW late. VFR cigs observed along with
patches of MVFR cigs about 1500 feet in the east and MVFR cigs
about 2500 feet along the cold front. Potential continues this
afternoon for a period of MVFR cigs/vsbys within any
shower/thunderstorm.

Tonight...Moderate Confidence.

SW winds shifting out of the W/NW, 10 kts or less. VFR with the
possibility of IFR conditions prior to the wind shift over S/E
coastal terminals. Will also need to monitor whether light winds
and radiational cooling can yield interior fog issues.

Saturday...High Confidence.

VFR. Light north winds, with seabreezes likely to develop along
both coasts.

KBOS Terminal...VFR with potential for brief MVFR especially in
showers/tstms.  SW winds overall with gusts around 20 kts during
the afternoon.

KBDL Terminal...VFR with potential for brief MVFR especially in
showers/tstms.  SW winds overall with gusts around 20 kts during
the afternoon. Conditions improve with clearing after 3 pm.

Outlook /Saturday Night through Tuesday/...

Saturday night and Sunday...High Confidence.
VFR. Light/variable winds Saturday night become E-SE up to 10-15
kt at the NE Mass coastal terminals Sunday afternoon. Patchy fog
after 05Z-06Z across normally prone valley locations may bring
MVFR-IFR conditions. Should improve by 12Z-13Z.

Sunday night-Monday...Moderate Confidence.
Mainly VFR. May see widely scattered SHRA/TSRA late Sunday night
through Monday with brief local MVFR conditions. S-SW winds may
gust up to 20 kt across coastal NE Mass Sunday evening, then
diminish. Winds shift to W-NW late Monday/Monday night but remain
light.

Tuesday...Moderate Confidence.
Mainly VFR. May see a few isolated SHRA/TSRA across interior
Tuesday afternoon/evening. Light N-NE winds shift to S-SW late in
the day.

&&

.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.

Winds and seas expected to remain below small craft advisory
thresholds through Saturday. Gusty southwest winds this afternoon
shift northwest tonight, then become light north Saturday. Local
seabreezes likely Saturday near shore.

Outlook /Saturday Night through Tuesday/...

Saturday night and Sunday...High Confidence.
Expect light E-SE winds Saturday night increase to up to 15 kt
late Sunday into Sunday evening. May see gusts up to 20 kt on the
waters east of Cape Ann. Seas remain below 5 ft.

Monday...Moderate Confidence.
Winds become S-SW ahead of an approaching cold front. Low risk of
gusts up to 20 kt on the southern near shore waters Monday
afternoon/evening. May see some showers/thunderstorms with brief
visibility restrictions into Monday evening as the cold front
pushes across. SE swells from TS Gaston may build to 5 ft on the
eastern outer waters Monday night.

Tuesday...Moderate Confidence.

Winds veer to N-NW but remain light during the day, then shift back
to S-SW again Tuesday night ahead of another front. Swells up to 5
or 6 ft across the outer waters from distant TS Gaston.

&&

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

&&

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



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