Area Forecast Discussion
Issued by NWS Boston, MA

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784
FXUS61 KBOX 311431
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1031 AM EDT TUE MAY 31 2016

.SYNOPSIS...
A cold front crossing Southern New England brings drier air to the
region. High pressure then builds over New England with dry and
cooler weather Wednesday and Thursday. A frontal system may bring
unsettled weather by the end of this week then a low pressure may
affect the region sometime Sunday into next Monday.

&&

.NEAR TERM /THROUGH TONIGHT/...

Clouds and fog lingering along the south coast, but with a
improving trend in clouds and visibility. A couple of showers near
Nantucket will move east of the island by midday. Over land,
surface observations show northwest winds and dew points in the
50s across much of the interior. Southwest wind and dew points in
the 60s remain across coastal RI and Southeast MA. Trend on the
cold front will bring it through Cape Cod and Islands by evening.

This update has made small adjustments to temps/sky cover/pops.
Morning RAOBs show 8-9C at 800 mb which, fully mixed, would
support max sfc temps in mid 80s. Late morning surface temps were
in the mid and upper 70s inland, supporting max temps mid and
upper 80s inland.

&&

.SHORT TERM /WEDNESDAY/...
Tonight...
A second cold front will move south across the region which will
shift winds to north as high pres builds to the north across
Canada. Mainly clear skies expected with low temps dropping into
the 50s.

Wednesday...
High pres shifts to the Maritimes with surface ridging extending
across SNE. Expect mostly sunny skies, but enough low level
moisture for some BKN cumulus developing, especially across
central and western New Eng. A cooler airmass will overspread the
region as easterly flow develops. Highs will range from the upper
60s across east coastal MA to around 80 in the CT valley, with 70s
elsewhere.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
*/ HIGHLIGHTS...

 - A shift from Summer-like conditions back to more typical Spring
 - A bit of a chill Thursday and Friday with onshore flow
 - Cold front and wet weather for late Friday into Friday night
 - Mostly quiet for the weekend
 - Unsettled and prolonged cool, wet weather by early next week

*/ DISCUSSION...

Persistence and morphology of low pressure over the Gulf of Alaska
maintains and manages ridging across the W and Central CONUS. The
+PNA / +EPO pattern over time modifies -NAO / -AO teleconnections.
Subsequently the warmer than average conditions under higher heights
this week shift towards around average beneath anomalously low H5
heights on the order of -1 to -2 standard deviations per ensemble
means. In other words, a shift away from the Summer-like feel
towards a slightly atypical Spring-time pattern.

Nothing noteworthy stands out through the extended forecast. Onshore
flow looks to keep the E cool Thursday and Friday. An isallobaric /
pressure gradient response with high pressure N/E and a sweeping
cold front for late Friday into Friday night. A good chance of wet
weather with the sweeping cold front but will prevail with chance
PoPs as the cold front becomes removed from more favorable dynamics
into a region of low-level ridging and poor low-level lapse rates
over the immediate SE neighbored by S-stream disturbances, namely
the remnants of Bonnie moving NE from the Carolinas. High pressure
and a slightly cooler airmass aloft follow for the weekend. Perhaps
some shower activity to the N driven by additional mid-level energy
and destabilization of the local atmosphere per a reinforcing cooler
airmass from the N during the day via diurnal heating.

Into early next week, looking at the bigger picture and focusing on
ensemble means. Quite the spread in individual ensemble member
forecasts. Anomalous troughing pattern with accompanying mid-
level vortex energy and jet dynamics. An unsettled, cooler, wet
weather pattern unfolding. Plausible such a pattern lasts into the
end of the week. Will keep with chance PoPs and lean towards
temperatures that are near or below average for early June.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels.

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

Short Term /through Wednesday/...

This afternoon...High confidence. VFR most areas with a west-
northwest wind. A mix of MVFR/IFR lingering for the SE coastal
terminals aloing with a southwest wind, improving to VFR during
the afternoon along with a wind shift from west-northwest.

Tonight and Wednesday...High confidence.
VFR. Easterly winds developing Wednesday.

KBOS TAF...Will hold the terminal at VFR for the forecast period.

KBDL TAF...A low risk of nearby fog becoming an issue, but
confident the morning and thus the remainder of the day will be
VFR.

Outlook /Wednesday Night through Saturday/...

Wednesday night into Friday...

VFR. E onshore flow, breezy especially across E-coastal terminals,
turning SE late.

Late Friday into Friday Night...

MVFR / Low-End VFR. S flow, potentially breezy, backing W/NW. SHRA
possible.

Saturday into Saturday Night...

VFR. Breezy N/NE flow persists becoming light towards Sunday
morning.

&&

.MARINE...
Forecaster Confidence Levels.

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

Short Term /through Wednesday/...

This afternoon and Tonight...High confidence. Windspeeds will
remain below 20 kt with SW winds today shifting to north tonight.
A southerly swell will result in seas building to 4 feet over the
southern waters with a low prob of 5 ft seas.

Wednesday...High confidence. NE winds and seas below SCA.

Outlook /Wednesday Night through Saturday/...

Thursday into Friday...

E onshore flow, breezy especially across the E-coast, turning SE
late. A low risk of 5-foot waves over the E/SE outer waters.

Late Friday into Friday Night...

S flow, potentially breezy, backing W/NW with the passage of a cold
front along and ahead of which some shower activity is possible. Not
thinking any restrictions to visibility. Waves remaining below 5-
feet.

Saturday into Saturday Night...

Breezy N/NE flow persists becoming light towards Sunday morning as
high pressure moves across the region. Waves remaining below 5-feet.

&&

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

&&

$$
SYNOPSIS...WTB/KJC/Sipprell
NEAR TERM...WTB
SHORT TERM...KJC
LONG TERM...Sipprell
AVIATION...KJC/Sipprell
MARINE...KJC/Sipprell



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