Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 262300
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
700 PM EDT THU MAY 26 2016

.SYNOPSIS...
Warm weather will continue through Saturday, except at times
along 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, then a period of more
widespread showers are possible Monday. Above normal temperatures
continue through midweek then turning cooler toward the end of the
week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
7 pm update...
A few showers developed along the sea breeze boundary from
southern NH into northeast MA but this activity is diminishing.
HRRR is indicating a few showers tonight across northern MA as
weak shortwave moves through. Current forecast on track.

Previous Discussion...
Mid level ridge sinks south a bit but overall conditions remain
the same as previous couple of days. Winds will keep an onshore
direction overnight so with sea surface temperatures in the mid to
upper 50s, expect low temperatures in the same range along the
coast. Temperatures will be warmer farther inland, with lows in
the low 60s expected.

A very weak shortwave will move through the westerly mid-level flow.
This could result in a few showers occurring during the night. Think
this will be very spotty and while there is enough instability for
thunder to be possible, don`t think it will be frequent or common.
Continued slight chance to very low end chance pops mainly for the
western zones.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Friday...Mid level ridge continues to be the main influence of our
weather.  It will be another warm day for much of the area with
southerly winds.  The pressure gradient is a little tighter, so we
may get away without a sea breeze developing on the east coast.  The
south coast will be the larger concern with southerly winds keeping
temperatures along the coast cool.  Expect high temperatures into
the mid to upper 80s for most locations away from the south coast.

A pre-frontal trough will move into southern New England during the
day which could result in some convection.  However, there are some
limiting factors, including rising heights, that will limit this
potential somewhat. There will be enough instability generated
during the day as well as elevated instability for thunder to
develop.  Again, think this will be rather spotty and isolated for
the most part.

Friday night...Any isolated convection that does occur will diminish
during the evening hours.  Then dry weather is expected.  Low
temperatures are expected to be in the 60s.  With dewpoints in the
upper 50s to lower 60s, patchy ground fog will likely develop in the
typically prone locations.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Highlights...

* Hot Sat w/highs mainly 90-95 in the interior, cooler coast
* Cooler Sun east coastal MA but continued very warm further in the
  interior
* Mainly dry Sat/Sun other than iso showers/t-storms in the interior
* More widespread showers may affect the region Mon then mainly dry
  for the rest of the week
* Above normal temperatures through midweek then turning cooler

Details...

Saturday...
Hot and increasingly humid conditions as anomalous mid level ridge
builds across New Eng.  850 temps up to 17C will result in highs 90-
95 degrees in the interior, mainly west of I-95 corridor. SW flow
off cooler SST will yield cooler temps in the SE coastal plain and
especially along the south coast as mixing is more shallow and
cooler 925 mb temps noted. Expect highs in the 80s coastal plain
with 70s along the immediate south coast and Cape/Islands.

The hot temps and increasing dewpoints will destabilize the
atmosphere with CAPEs 1000-2000 J/kg developing in the interior.
However, there are limiting factors with building mid level ridge
and anticyclonic flow which will serve to suppress activity in the
absence of notable synoptic forcing. And mid levels will be fairly
dry. Most of SNE should remain dry but can`t rule out a few
showers/t-storms across northern and western MA into western CT
late in the day into Sat evening. Severe threat is low given
weakly sheared environment, but if any convection develops there
is potential for gusty winds with decent instability and inverted
V sounding profile.

Sunday...
Timing of a backdoor cold front remains very uncertain which will
significantly impact temps. GFS is most aggressive moving the front
through much of SNE by morning while NAM/ECMWF are much slower and
keep much of the region in the very warm air. Will continue the
theme of the previous forecast indicating cooler air moving into
eastern MA with temps mostly in the 70s, but warmer 80s further west
and especially CT Valley where temps may approach 90 again if
front is delayed. This is not a high confidence temp forecast as
a 6 hour change in timing will make a big difference. Models
generating 1000-2000 J/kg of SBCAPE west of the boundary so a few
showers/t-storms possible ahead of the front, mainly central/W New
Eng but this will be dependent on the timing and location of the
front. Deep layer shear remains weak so severe threat is low.

Monday...
Models indicate a mid level shortwave moving through as a plume of
tropical moisture surges northward ahead of possible tropical
disturbance to the south. Models indicate PWATs increasing to near 2
inches with marginal instability developing, depending on extent of
cloud cover. This may lead to more widespread showers and sct t-
storms with locally heavy rainfall possible. Confidence on how this
plays out is not high but the potential exists for wet weather. Temps
will be dependent on extent of clouds/showers but a cooler day is
likely.

Tuesday through Thursday...
Deep moisture plume will be exiting the region by Tue as a cold
front moves offshore with significant decrease in PWATs. Looks
mainly dry Tue although if front is slower, shower threat could
linger. Then mainly dry Wed/Thu as high pres builds in from the N.
Temps cooling mid to late week as easterly flow develops.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels.

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

Tonight...High confidence. VFR conditions likely for much of the
period. Low probability of brief MVFR conditions in SCT -SHRA/-TSRA
mainly across W MA/N CT.

Friday...High confidence. Mainly VFR. Low probability of brief
MVFR conditions in SCT -SHRA/-TSRA mainly across the interior.

Friday night...High confidence. Mainly VFR. Patchy ground fog
develops resulting in patchy MVFR/IFR conditions.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Saturday through Tuesday/...

Saturday...High confidence. Mainly VFR other than a few hours of
patchy ground fog toward daybreak Sat in the typically prone
locations. Isolated late day/evening showers/t-storms possible
distant interior.

Sunday...Moderate confidence. Mostly VFR but patchy MVFR cigs
possible eastern MA depending on location of backdoor front.
Widely scattered showers/t-storms possible interior.

Monday...Low confidence. Potential for a period of MVFR-IFR
conditions in low clouds and showers/t-storms.

Tuesday...Moderate confidence. Mainly VFR, but lower conditions
possible in the morning especially near the coast.

&&

.MARINE...
Forecaster Confidence Levels.

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

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

High confidence.  Quiet boating weather is expected through the
short term.  There is a low probability of seas reaching 5 feet on
the outer waters Friday night.  Winds will generally be out of the
south.  Fog may develop over the waters Friday night, limiting
visibilities.

Outlook /Saturday through Tuesday/...High confidence.

Winds and seas will generally remain below small craft advisory
thresholds through the period, but there may be a period of SW
gusts approaching 25 kt on Monday over nearshore waters.

&&

.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 until 11 PM EDT this evening for CTZ002>004.
     Air Quality Alert from 11 AM to 11 PM EDT Friday for
     CTZ002>004.
MA...Air Quality Alert until 11 PM EDT this evening for MAZ002>005-
     008>014-017-018-020-021-023-026.
RI...Air Quality Alert until 11 PM EDT this evening for RIZ001>008.
MARINE...None.

&&

$$
SYNOPSIS...KJC/RLG
NEAR TERM...KJC/RLG
SHORT TERM...RLG
LONG TERM...KJC
AVIATION...KJC/RLG
MARINE...KJC/RLG
CLIMATE...



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