Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 261112
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
712 AM EDT THU MAY 26 2016

.SYNOPSIS...

Very warm to hot weather will continue through Saturday, but it
will be a bit cooler at times on the immediate coast. A backdoor
cold front will bring cooler weather to eastern MA Sunday with
warm weather continuing elsewhere. Dry weather dominates through
Sunday other than isolated showers/thunderstorms at times. Near or
above normal temperatures continue for much of next week and there
is the potential for a period of more widespread showers Monday
and/or Tuesday.

&&

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

710 am update...

Mostly sunny skies will allow temperatures to quickly jump over the
next few hours.

As high pressure ridge builds S of the region, expect a general
light pressure gradient. This will allow sea breezes to develop
along the coast by mid morning. H5 ridging also builds E today, with
H5 heights increasing to 580 to 582 dm by this afternoon. With W-SW
winds aloft, H85 temps will increase to +14C to +16C this afternoon,
and up to +22C across western areas at H925! Very warm airmass
indeed.

Expect temps to rise to 85-90 away from the coast, but held down to
the 70s along the immediate coast with the sea breezes. With weak
surface convergence across the region, there may be just enough lift
along with the diurnal heating to cause a few isolated afternoon
showers and perhaps even a t-storm.  If anything is able to develop
areal coverage/duration should be rather limited.

&&

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

Tonight...The weak stalled front should also lift N-NE as winds
become more S-SW and the ridge pushes offshore. Noting a weak mid
level short wave in the SW flow at the surface and aloft. Some
timing issues on the short range models in moving this E out of
the Appalachians and mid Atlc states. Have kept similar timing
going from the previous forecast and kept mention of slight chance
to low chance POPs, with only an isolated mention of thunder,
though think this will be very spotty.

With ocean temps mainly in the lower-mid 50s and the onshore
winds, expect overnight lows to fall back to 55-60 across eastern
and central areas, ranging to the lower-mid 60s across the CT
valley.

Friday...Expect another warm day with continued S-SW winds on
back side of high pres ridge over the western Atlc. With the high
in place to the E, weak trough will remain across western areas.
Also noting rather good instability with CAPEs rising to 1200-1400
J/kg as well as K indices in the low-mid 30s and surface based LIs
on around -1 to -2. So have kept chance POPs going from the
interior Merrimack valley across central MA to the CT valley, with
the best shot from late Friday morning through the afternoon.
Temps will be in the 80s away from the immediate coast, holding in
the 70s along S coastal areas with the onshore winds.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...

Highlights...

* Hot Sat w/highs mainly 90-95 away from the immediate coast.

* Near or above normal temperatures through much of next week

* Mainly dry Sat/Sun other than iso showers/t-storms but activity
  could be a bit more organized Sun afternoon across interior

* Its possible a more widespread area of showers affects the region
  Mon and/or Tue but that remains highly uncertain

Details...

Friday night...While it remains uncertain if any isolated convection
will affect the region late Friday it should diminish during the
evening hours. Otherwise, dry weather with upper level ridging in
control. Low temps will only drop to between 60 and 65 in most
locations.  Some patchy ground fog will likely develop in the
typically prone locations given increasing low level moisture.

Saturday...Unseasonably hot weather anticipated and records highs may be
challenged. 850T around +16c with plenty of sunshine and a well mixed
atmosphere should yield highs between 90 and 95 in most locations
away from the immediate coast where localized sea breezes may
develop.  Dewpoints in the lower to middle 60s will make it feel a
bit muggy.

The majority of Saturday will be dry, but there is the risk for some
isolated to widely scattered convection Saturday afternoon and
evening.  As usual, mesoscale processes will dictate what happens
and its not clear cut. A weak pre-frontal trough combined with
modest instability with Capes increasing to between 1000 and 2000
J/KG. Upper level ridging and lack of forcing will certainly be
limiting factors.  Sea breeze convergence and terrain impacts might
be enough to trigger isolated to widely scattered convection Sat
afternoon and evening. 0 to 6 KM shear is weak, so if anything
develops the overall severe weather threat would be low.
However, an isolated strong thunderstorm or two can not be ruled out
with decent instability and potentially large temp/dewpoint spreads.
Very localized heavy rainfall would also also be possible given any
storm that is able to develop will be slow moving.

In a nutshell, much of the region will likely remain dry Saturday
but isolated slow moving showers/t-storms with very localized heavy
rainfall can not be ruled out.

Sunday...

The backdoor cold front pushes across the region from east to west.
Timing of the front remains uncertain and a 6 hour shift in either
direction will make a huge difference in high temperatures. Overall,
thinking interior gets very warm while cooler air works into Eastern
MA.  A few showers may accompany the cold front, but will have to
watch for a bit more organized area of scattered
showers/thunderstorms with very localized heavy rainfall across
Western MA/Northern CT Sunday afternoon. This will depend upon how
much instability develops ahead of the backdoor front and its exact
timing.

Monday and Tuesday...

A disturbance currently northeast of the Bahamas will track
northwest and probably not directly impact our region.  However, a
plume of its tropical moisture may get pulled north into southern
New England ahead of a cold front.  Low confidence on how this all
plays out, but there is at least a risk for a more
organized/widespread area of rain showers.  Temps will remain near
or above normal and exact temps be determined by timing of potential
clouds/showers.

Wednesday...

Low confidence this far out but do not see any organized
precipitation threat.  Temps near or above normal.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels.

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

Short Term...

Today...High confidence. VFR. Expect sea breezes to develop by
mid to late morning on both coasts.

Tonight...Moderate confidence. VFR conditions likely for much of
the period. Brief MVFR conditions possible in SCT -SHRA/-TSRA
mainly across W MA/N central CT, but briefly may reach into NE
CT/central MA this evening. Patchy fog with MVFR-IFR conditions
after 07Z-08Z across interior valleys.

Friday...Moderate to high confidence. Mainly VFR. Local MVFR
conditions with low risk of a few brief scattered SHRA/TSRA mainly
across the interior. Also, patchy ground fog possible in the
typically prone locations through mid morning.

KBOS TAF...High confidence in TAF.  ESE sea breeze probably develops
by 14z.

KBDL TAF...High confidence in TAF.

Outlook /Friday Night through Monday/...

Friday night and Saturday...Moderate to high confidence.  Mainly VFR
other than a few hours of patchy ground fog toward daybreak Sat in
the typically prone locations.  Isolated showers/t-storms may also
result in brief/localized lower conditions.

Sunday...Low to moderate confidence. May see some MVFR CIGS work
into northern and eastern MA behind the backdoor cold front.
Otherwise, mainly VFR outside of any widely scattered convection.

Monday...Low confidence.  Potential for a period of MVFR-IFR
conditions in low clouds and some showers but that remains highly
uncertain.

&&

.MARINE...
Forecaster Confidence Levels.

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

Short Term /through Friday/...High confidence.

Today and tonight...Expect S-SE winds less than 15 kt and seas 4
ft or less. May see some visibility restrictions in patchy fog
late tonight along the coast.

Friday...S-SW winds 15 kt or less. Some gusts may approach 20 kt
on the near shore waters during the afternoon. Seas remain 4 ft or
less. May see local visibility restrictions in patchy early
morning fog.

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

Winds and seas will generally remain below small craft advisory
thresholds through the period.  Biggest concern is Saturday
afternoon along the south coast...where some near shore lower 20
knot wind gusts may occur resulting in choppy seas.

&&

.CLIMATE...

Warmest day of the week appears to be Saturday and some record
highs may be challenged.

Record highs for Saturday May 28...

Boston...92 set in 1931
Providence...91 set in 1931
Hartford...93 set in 1977
Worcester...88 set in 1911 and 1929
Milton/Blue Hill...90 set in 1929

&&

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

&&

$$
SYNOPSIS...EVT/Frank
NEAR TERM...Frank/EVT
SHORT TERM...EVT
LONG TERM...Frank
AVIATION...EVT/Frank
MARINE...EVT/Frank
CLIMATE...Staff



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