Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 260920
AFDBOX

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

.SYNOPSIS...
A cold front swings through our region today, bringing some
showers and a few thunderstorms. Dry and warm conditions through
this 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/...
Continuing to monitor the progress of showers over central and
upstate NY. So far, still not seeing much lightning, at the time
of this writing.

Latest mesoanalysis showed marginal lapse rates and meager
instability. Thinking it will take some sunshine this morning to
really pose a threat of thunderstorms. It will be a race for the
clouds to depart the coastal plain of southeast New England, but
this is the most likely area for thunderstorms given the later
timing of this cold front. Should we not get enough sunshine, then
the risk for thunderstorms will be diminished.

Most of the guidance, and especially the last few runs of the
HRRR, hinted at the idea of showers across southeast MA early this
morning. Latest radar data bearing that idea out, although the
guidance likely too bullish on measurable rainfall chances.
However, this does give confidence in the timing presented by the
guidance this morning. Expecting a cold front to cross the CT
River around noon, then reach the east coast of MA toward 8 PM.

Very warm start to the day, with overnight low temperatures not
too much below the normal high temperatures. It will not take much
sunshine to boost temperatures into the 80s, with some locations
even approaching 90 degrees.

&&

.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 /09Z 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/...

Today...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. Low-end VFR cigs where cigs
develop. However, can not rule out MVFR, with TEMPO MVFR-IFR
conditions, within any TSRA and/or +SHRA.

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...prevail -SHRA overnight. Towards 15z onwards will
be closely watching areas S/W for TSRA development. SW winds
overall with gusts around 20 kts during midday Friday into afternoon.

KBDL Terminal...low-end VFR to MVFR possible overnight. Clearing
into Friday morning, potentially, will be monitoring for TSRA
development around and E of the terminal midday into afternoon.

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 today 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...Belk
SHORT TERM...Belk
LONG TERM...EVT
AVIATION...Belk/EVT
MARINE...Belk/EVT



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