Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 252106
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
506 PM EDT WED MAY 25 2016

.SYNOPSIS...
High pressure off the mid-Atlantic coast will bring very warm
weather to most of the region through Saturday along with
increasing humidity this weekend. It will be cooler at times
along the immediate coast. A backdoor cold front will bring cooler
weather to Rhode Island and eastern Massachusetts Sunday with
warm weather continuing elsewhere. Warmer than normal temperatures
overspread the remainder of the area by early next week. A few
showers and thunderstorms are possible Thursday night into Friday,
and again this weekend but the vast majority of the time will be
dry.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...


510 PM Update ...

Did a quick update to include isolated to widely scattered
showers/sprinkles over Western MA in response to a short wave
trough moving across Northern New England. Most of these showers
will likely erode/diminish as airmass ahead of these showers is
very dry with dew pts in the low 40s along with downslope west-
northwest winds. Thus not expecting much if any shower activity
east of the Worcester hills. Otherwise remainder of the forecast
is on track. Earlier discussion below.

====================================================================

Temperatures have climbed in to the mid to upper 80s away from
the immediate coastline this afternoon. The sea breeze along the
immediate east coast of Massachusetts should push back out to sea
in the next hour. This will allow temperatures to make a last
ditch effort to get up to 80 at Logan Airport. Once the sea breeze
moves off, the temperature jump should occur rather quickly.

Tonight...A mid-level ridge starts to build over southern New
England from the west tonight, along with high pressure at the
surface.  Westerly winds shift more to the northwest overnight and
remain on the light side.  This will keep temperatures from dropping
too low.  Low temperatures tonight will be in the low to mid 60s for
most of the area, with mid to upper 60s in the urban centers.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Thursday...High pressure moves offshore slowly while the mid level
ridge centers itself over southern New England.  With a much weaker
gradient over the region, sea breezes along both coasts are a slam
dunk.  Therefore, temperatures will be cooler at the coasts but
still in the mid to upper 80s for the rest of the area under mostly
sunny skies.

Thursday night...Mid level ridge sinks south a bit but overall
conditions remain the same as previous couple of days.  Winds will
go calm overnight allowing temperatures to drop back into the upper
50s to lower 60s for most places.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
350 pm update...

Highlights...

* Temperatures warmer than normal much of the time

* Other than isolated showers/thunderstorms many hours of dry
  weather this period

Subtropical ridge builds northwestward from western Atlantic into
the northeast late this week into the weekend and lingers into at
least early next week. This will result in temperatures warmer
than normal much of the time along with mainly dry weather. Both
the 00z GEFS and 00z EPS offer 850 temp anomalies of +1 to +2
standard deviations above normal over southern New England during
this time. However there will be a brief cool down Sunday across
eastern MA and RI as a shallow cool airmass invades this area
behind a backdoor cold front. Otherwise much of this forecast
period will be warmer than normal (normal highs around 70, normal
lows around 50).

As for rain chances...a prefrontal trough will enter western
portions of MA and CT Friday. However rising heights and
increasing anticyclonic mid level flow will likely suppress most
convective development. Likewise on Sat with the ridge continuing
to build and heights reaching +2 standard deviations above normal
over the northeast. By late Sat and into Sunday the backdoor front
provides surface convergence and shallow low level forcing first
north of MA Sat and then across much of the region Sunday. However
large amplitude ridge over the region along with mid level
anticyclonic flow may suppress much of the convection once again.
Thus model guidance is likely too wet especially the 12z GFS.
Therefore have undercut guidance from chance to slight chance pops
Fri/Sat and Sun. Greatest risk (albeit low) of seeing any
showers/thunderstorms Fri/Sat & Sunday will likely be across
western portions of MA and CT. Thus a washout is not expected
just isolated to widely scattered showers/thunderstorms well
inland.

Mon and Tue of next week become interesting as area of convection
currently northeast of the bahamas advects northwestward around
the subtropical ridge into the mid Atlantic region. Then it
becomes a question if the upstream northern stream trough has
sufficient amplitude to capture this area tropical moisture and
advect it into southern New England. 00z GEFS and 00z EPS both
suggest bulk of tropical moisture remains offshore or just clips
south coast of New England and bulk of convection from northern
stream trough remains northwest across NY state and VT. Given the
time range and uncertainty chance pops seems reasonable here.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
Forecaster Confidence Levels.

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

Through 00Z...High confidence.  VFR.  Weak sea breeze should move
offshore by 21Z.

Tonight...High confidence.  VFR.

Thursday...High confidence.  VFR.  Sea breezes will develop early on
both coasts.

Thursday night...Moderate confidence.  VFR conditions likely for
much of the period.  Brief MVFR conditions possible in SCT -
SHRA/TSRA across W MA/N CT.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Friday through Monday/...

350 pm update ...

Friday...MVFR conditions likely with low risk of a few brief
showers/t-storms mainly across the interior. Also, some patchy
ground fog possible in the typically prone locations very early
Fri AM. Moderate to high forecast confidence.

Saturday...Moderate to high confidence. Any early MVFR conditions
should quickly lift to VFR by midday. Low risk of a few afternoon
and evening showers/thunderstorms well inland.

Sunday...Moderate confidence. MVFR likely with low risk of IFR in
spots. A few thunderstorms also possible Sun afternoon across the
interior.

Monday...Low confidence given time range and weather pattern. VFR
likely but period of MVFR in low risk of scattered showers/
thunderstorms.

&&

.MARINE...
Forecaster Confidence Levels.

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

High confidence.  Quiet boating weather is expected through the
short term.

Outlook /Friday through Monday/...High Confidence.

Winds and seas will generally remain below Small Craft Advisory
thresholds through the period.  The main concerns are a period of
near-shore southwesterly wind gusts of 20 to 25 knots Saturday
afternoon which will result in some choppy seas for mariners. May
also see some brief easterly wind gusts between 20 and 25 knots on
Sunday behind a backdoor cold front. Then winds become ssw Sunday
into Tue as front lifts north as a warm front.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Air Quality Alert from 11 AM to 11 PM EDT Thursday for
     CTZ002>004.
MA...Air Quality Alert until 11 PM EDT this evening for MAZ020>024.
     Air Quality Alert from 11 AM to 11 PM EDT Thursday for
     MAZ002>005-008>014-017-018-020-021-023-026.
RI...Air Quality Alert until 11 PM EDT this evening for RIZ003-004-
     006>008.
     Air Quality Alert from 11 AM to 11 PM EDT Thursday for
     RIZ001>008.
MARINE...None.

&&

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



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