Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 010700
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
300 AM EDT WED JUN 1 2016

.SYNOPSIS...
High pressure builds over New England with drier, less humid and
cooler weather today and Thursday. Two weather systems may bring
unsettled weather in the form of showers, Friday night and again
Sunday and Monday.

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...

3 AM Update ...

Short wave trough as seen on latest water vapor imagery is moving
across Quebec and will drag a cold front thru the region early this
morning. The front will not be accompanied by any precip but rather
a wind shift from southwest to northwest. Behind this front a
drier/less humid airmass will overspread southern New England today.
Thus any lingering low clouds and fog during the predawn hours
across the Islands of Marthas Vineyard and Nantucket will move
offshore around or shortly after sunrise.

Further upstream...1030 mb high over Hudson Bay builds southward
into New England this afternoon...providing subsidence and light
winds. Thus a very nice day ahead with lots of sunshine. Moisture
profiles suggest some cu/strato-cu clouds possible across the higher
terrain. Otherwise mostly sunny conditions prevail.

Cooler today than yesterday given airmass change and will be
enhanced with ridge axis across the region yielding onshore winds...
keeping eastern MA much cooler /65-70/ than the CT river valley/I-91
corridor of CT and MA where temps will climb into the lower 80s.
Normal high for June 1st is 70-75...which are the forecast highs for
much of RI...central MA into Southeast MA. Overall a very nice day
ahead. Enjoy.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...

3 AM update ...

Tonight ...

Quiet night with deep layer ridge over the area. Only wrinkle will
be moisture trapped beneath subsidence ridge and advecting onshore
from the ocean as maritime airmass invades the region. NAM is very
bullish bringing stratus onshore shortly after sunset. While the GFS
is much slower with stratus not arriving until sunrise Thu. Given
large spread will split the difference but lean toward the NAM given
better low level resolution to capture shallow low level moisture
and this also fits the climatology/pattern in a maritime flow
regime. Even a low risk of spotty light drizzle toward Thu morning
per 00z NAM/RGEM/ARW & NMM.

Thursday ...

Deep layer ridge lingers across New England as northern stream
trough moves across the Great Lakes. Main forecast dilemma Thu is
how stubborn low clouds /and possible patchy drizzle/ will be from
tonight. NAM has low level moisture lingering much of the
day...while the GFS burns low clouds off. Given the high June sun
angle there should be at least partial erosion of the low clouds. So
a model blend seems reasonable with a bit more weight toward the
GFS.

Cooler than today given less sunshine and maritime airmass fully
entrenched over the region. Highs mainly in the 60s along both
coasts to 70s elsewhere.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...

*/ HIGHLIGHTS...

 - Sweeping cold front and wet weather for Friday into Friday night
 - Quick shot of high pressure and Summer-like conditions Saturday
 - Unsettled and turning cooler beginning Sunday into early next week

*/ DISCUSSION...

Not a tremendous amount of change with respect to long term trends.
Continued signal of persistent low pressure across the N Pacific the
morphology of which modifies the downstream ridge - trough pattern.
But some challenges as deterministic solutions vary in handling the
+PNA / +EPO pattern perhaps subsequently related to the evolution of
N Pacific energy into the W CONUS. So inherent complications further
out in June with the forecast, but a consistent signal out through
early next week of a atypical anomalous H5 troughing set up on the
order of -1 to -2 standard deviations yielding an unsettled, wet
weather pattern with temperatures remaining closer to average. A
return to more spring-like conditions than the summertime warmth we
have experienced as of late.

Getting down into the details, we`ll start the forecast period with
some wet weather on Friday as a cold front sweeps the NE CONUS. The
exact timing is in question and whether instability within a modest-
shear environment can materialize (if you believe the 01.0z NAM).
Low clouds associated with onshore S/SE flow pooling moisture
beneath a forecast dry inversion, as well as the associated low
level maritime airmass beginning Thursday night into Friday are
likely to be an issue. Confident on such outcomes. Also confident
that as the front sweeps SE that it`ll encounter an inverted wedge
of high pressure and drier air over the cooler waters offshore,
squeezed between the front itself and S-stream remnants of Bonnie.
Thus anticipate rainfall outcomes to washout with S/E progression of
the front. Higher PoPs N/W with low-mid level frontogenetical
forcing beneath stretched mid-level vortex energy and the right-rear-
quadrant of an accompanying upper level jet. Willing to go likely
given the robust forcing.

Quick bout of high pressure for Saturday and temperatures closer in
resemblence to Summer. Then beginning Sunday into early next week we
find ourselves beneath an anomalous low center with a roughly 990 mb
center in proximity of New England. An initial over-running shot of
rainfall, perhaps some embedded thunder though thinking a slight
chance, Sunday is followed on and off periods of wet weather beneath
significantly cooler air aloft, in some instances diurnally driven.
It is during this timeframe, Monday through Wednesday, when the
chance of thunderstorms appears more likely. Will append to the
forecast accordingly. Variance within deterministic solutions
warrant an ensemble approach. Will keep with chance PoPs and
temperatures closer to average.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels.

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

Short Term /through Thursday/...

2 AM update ...

Thru 12z ...

VFR prevails with the only exception across MVY and ACK where IFR
and LIFR will improve to VFR 09z-12z as wind shift wsw to wnw.
Other than exact timing of departing low clouds high confidence
forecast.

After 12z ...

VFR..dry and winds becoming easterly this afternoon. High forecast
confidence.

Tonight ...

VFR to start but then MVFR/IFR possible toward daybreak especially
across Eastern MA. Spotty drizzle possible too. Low confidence on
areal coverage of MVFR/IFR conditions.

Thursday ...

IFR/MVFR early should improve to VFR/MVFR during the afternoon.
Spotty light drizzle possible early.

KBOS TAF ... High confidence in TAF today then lower confidence on
areal coverage of MVFR/IFR conditions late tonight into Thu.

KBDL TAF ... High confidence in TAF today then lower confidence
on areal coverage of MVFR/IFR conditions late tonight into Thu.

Outlook /Thursday Night through Sunday/...

Thursday night...

MVFR / IFR cigs with SE flow. Can not rule out the possibility of
lower conditions. DZ / BR possible along the shores limiting
visibility.

Friday into Friday night...

MVFR / IFR lingering but perhaps improving to low-end VFR prior to a
cold front / wind shift with S winds backing out of the W/NW. RA
along and ahead the cold front. Low risk TSRA. Confident with the
wind shift both cigs and vsbys improve to VFR.

Saturday into Saturday night...

VFR. W/NW flow becoming light allowing for sea breezes along the
shores.

Sunday into Sunday night...

Conditions deteriorating, lowering MVFR / IFR with RA as S winds
increase, becoming breezy with gusts up to 20 kts.

&&

.MARINE...
Forecaster Confidence Levels.

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

3 AM update ...

Short Term /through Thursday/ ... high forecast confidence thru
this evening then some uncertainty on areal coverage of low vsby
in patchy fog and drizzle.

Today ...

wind shift from wsw to ne today as frontal boundary moves offshore
and high pressure from Hudson Bay builds southward. Other than some
patchy morning fog...good vsby and dry weather prevails.

Tonight ...

High pressure builds over the maritimes yielding a modest east wind
across the coastal waters. Patchy fog and drizzle may limit vsby
late.

Thursday ...

High pressure remains over the maritimes then begins to move
seaward. This results in pressure gradient increasing somewhat with
east winds up to 20 kt possible. Also, patchy fog and drizzle may
limit vsby especially during the morning.

Outlook /Thursday Night through Sunday/...

Thursday night...

SE winds becoming S. Low clouds, drizzle, mist, anticipating
restrictions in visibility over the waters as seas remain below 5
feet.

Friday into Friday night...

S winds persist ahead of a cold front accompanied with light rain.
Low clouds persisting. Some visibility restrictions with the wet
weather if not mist. Winds back W/NW late. Waves remaining below 5
feet.

Saturday into Saturday night...

High pressure over the waters. Flow becoming light allowing for sea
breezes along the shores. Waves remaining below 5 feet.

Sunday into Sunday night...

Conditions deteriorating as winds increase out of the SE, gusting
upwards of 20 kts. Will see seas build 5 to 7 feet on the outer
waters in response. Potential for visibility restrictions given the
onset of rain / mist.

&&

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

&&

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



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