Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 271130
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
730 AM EDT FRI MAY 27 2016

.SYNOPSIS...

Very warm to hot afternoon temperatures will continue today and
Saturday away from the immediate coast. A backdoor cold front
will bring cooler temperatures to eastern MA Sunday but it will
remain very warm across the interior, where hit and miss showers
and thunderstorms likely develop during the afternoon. The
potential exists for a period of heavy rain very late Sunday night
into Memorial Day. Dry weather likely follows Tuesday through
Thursday, with above normal temperatures trending back to
seasonable levels by late in the week.

&&

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

730 am update...

Low clouds and areas of dense fog along the Cape and Islands should
burn off over the next few hours.  Otherwise, no changes made to
previous forecast.

Noting a weak mid level short wave moving into central and
western areas this afternoon, so can not rule out some convection
developing. Looks like the best chance will occur from northern
Worcester county through into N CT and W Mass this afternoon. Have
low chance POPs going there. Marginal instability with K indices
into the lower 30s, plus TQs to the upper teens /indicative of
possible elevated convection/. Also noting brief period of CAPEs
up to 800-900 J/kg late in the day.

As the front shifts away from the region this afternoon, warmer
air works in, with H925 temps up to +20C to +22C by late in the
day across central and western. This along with S-SW winds picking
up during the day, temps will soar. Expect temps to top off from
85-90 away from the coast, but only in the 70s along the S coast.

&&

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

Tonight...Any isolated convection that may develop will diminish
this evening as diurnal heating ends. Expect dry conditions
overnight. With dewpoints continuing to slowly rise, expect
patchy fog to develop in the normally susceptible locations mainly
after midnight. May also more low clouds and ocean fog move in
along portions of the south coast. Overnight lows will only fall
back to the lower-mid 60s, though may remain a bit lower along
the immediate S coast with cooler ocean temperatures.

Saturday...Will see hot and humid conditions across the region as
mid level ridge builds across W New England. Expecting highs from
90 to 95 degrees away from the immediate coast with SW winds in
place. Temps will remain cooler along the S coast, Cape cod and
the Islands.

With the summer conditions in place, will see another round of
showers and thunderstorms developing during the late morning and
afternoon. The best shot looks to be from the interior Merrimack
Valley to northern Worcester county into the Conn valley. CAPEs
will increase to 1300-1400 J/kg, but some limiting factors also in
place with the strong ridge in place which could cap activity.
Will need to monitor for some storms producing locally gusty
winds.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...

Highlights...

* Turning cooler Eastern MA coast Sunday but still very warm
  inland

* Hit and miss showers/t-storms likely across interior southern
  New England Sunday afternoon/early evening

* Period of heavy rain possible very late Sunday night into
  Memorial Day with even a small risk of localized flooding

* Dry weather Tue into Thu with above normal temps trending back
  to seasonable levels late in the week

Details...

Saturday night...Isolated to widely scattered showers/t-storms may
linger into the evening but should be on the downward trend with the
loss of daytime heating.  Otherwise, expect mainly dry weather
Saturday night but it will be quite mild and muggy for late May. Low
temps may only drop into the middle to upper 60s for many locations
away from the cooling marine influence of the south coast.  Patchy
fog likely develops in the typically prone locations with dewpoints
in the 60s.

Sunday...Still timing differences with the backdoor cold front but
appears that it will still be east of the CT River Valley by mid
afternoon.  So its conceivable that Sunday afternoon temps will have
fallen into the 60s along the Eastern MA coast, while the Lower CT
River Valley might be in the lower 90s.  The morning should mainly
be dry, but expect 1000 to 2000 J/KG of Cape to develop across
interior southern New England.  Despite upper level ridging, decent
low level convergence/instability will allow low level moisture to
pool a bit. The result should be hit and miss showers/thunderstorms
developing across interior southern New England Sun afternoon. The
extent of this activity will be determined by how fast the front
moves and amount of instability that is able to develop.  Highest
risk for scattered activity is across western MA/northern CT but it
could extend back into portions of central MA/RI if front moves
slower.  0 to 6 km shear is weak, so overall severe weather threat
is low.  However, given decent instability can not rule out a strong
thunderstorm or two. Any storms that develop will be slow moving and
capable of producing very localized heavy rain.

So to sum up Sunday, dry weather expected for much of the day but
scattered showers/t-storms likely develop in the afternoon across
the interior.  While activity should be hit and miss, very localized
heavy rainfall and lightning will be the biggest concern with any
storm.

Sunday night and Memorial Day...

Hit and miss convection across the interior should diminish Sunday
evening with the loss of daytime heating.  Mainly dry weather
expected for the first part of the night.

Things then become very interesting very late Sunday night into
Memorial day. The National Hurricane Center is expecting low
pressure between the Bahamas and Bermuda to develop into a
tropical or sub tropical cyclone in the next 48 hours. While a
direct impact will not occur, an approaching cold front will
likely pull a plume of its tropical moisture northward. PWATS may
rise to around 2 inches in southern New England. Still plenty of
uncertainty on how this unfolds, but a period of heavy rain
showers and a few embedded thunderstorms are possible across the
region. Fortunately, this appears to be a progressive event but
given tropical connection there is a small risk of some localized
flooding. Something will have to watch closely, especially given
it will be on the end of a Holiday Weekend and a big travel day.

Tuesday through Thursday...

Looks like dry and warm weather follows behind the cold front on
Tuesday with highs mainly in the 80s.  It is a long way off, but
current guidance favors dry weather Wed into Thu as high pressure
builds down from the Canadian Maritimes.  This would also generate
an easterly low level component to the wind with temperatures likely
returning to seasonable normals by Thursday.

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels.

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

Today...High confidence. Mainly VFR, except IFR-LIFR CIGS/VSBYS
through mid to late morning across portions of Cape Cod and
Nantucket. Conditions should improve by midday. Low probability
for brief MVFR conditions in SCT -SHRA/-TSRA mainly across the
interior.

Tonight...High confidence. Mainly VFR. Patchy ground fog develops
resulting in local MVFR-IFR conditions. Leftover isolated -SHRA/
-TSRA this evening with brief local MVFR conditions, then ending.

Saturday...Moderate confidence. Mainly VFR. Local MVFR-IFR
conditions in patchy fog through mid morning. Low probability of
brief MVFR conditions in SCT afternoon SHRA/TSRA across the
interior.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Saturday Night through Tuesday/...

Saturday night...Moderate to high confidence.  Any isolated
convection diminishes early in the evening. Mainly VFR conditions
but a period of MVFR to even localized IFR condition may develop
late in patchy fog and perhaps a touch of low clouds.

Sunday...Moderate confidence.  VFR conditions may lower to MVFR
thresholds across Eastern New England behind backdoor cold front.
Otherwise, mainly VFR across the interior but briefly lower
conditions possible in hit and miss showers/t-storms during the
afternoon.

Sunday night and Memorial Day...Moderate confidence.  MVFR-IFR
conditions may develop late Sunday night into Memorial Day in a
period of rain showers which may be locally heavy.

Monday night and Tuesday...Moderate to high confidence in mainly
VFR conditions.

&&

.MARINE...
Forecaster Confidence Levels.

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

Short Term /through Saturday/...High confidence.

Expect S-SW winds in place across the waters through the period,
picking up to around 15 KT tonight and continuing on Saturday.
Seas look to build to around 5 feet on the southern outer waters
tonight, so have issued small craft advisory for those waters.
Areas of fog will move across the southern outer waters to E of
Cape Cod, with some patchy dense fog possible through mid to late
morning today, then again tonight into early Saturday.

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

Winds and seas will generally remain below small craft advisory
through the period with a relatively weak pressure gradient.
Biggest concern for Mariners will be late Sunday night into
Memorial Day, when a period of heavy rain showers/isolated
thunderstorms are possible.

&&

.CLIMATE...
Still expect highest temperatures of the week on Saturday. Some
record highs may be challenged. However, might even see temps
getting close to records today as well.

Record highs for today May 27...

Boston...96 set in 1880
Providence...90 set in 1914 and 1981
Hartford...94 set in 1914 and 1965
Worcester...91 set in 1914
Milton/Blue Hill...92 set in 1914

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...None.
RI...None.
MARINE...Small Craft Advisory for hazardous seas from 11 PM this
     evening to 8 AM EDT Saturday for ANZ255-256.

&&

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


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