Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 281739
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
139 PM EDT SAT MAY 28 2016

.SYNOPSIS...

Hot today away from the immediate coast. Mostly dry but isolated
to scattered showers and/or thunderstorms will be possible. Into
Sunday a backdoor cold front will drop south over E/NE Massachusetts
behind which low clouds and poor visibility is expected, whereas
along and ahead scattered showers and thunderstorms are likely. Late
Sunday night and through Memorial Day, rain, locally heavy at times,
and chances for thunderstorms associated with tropical moisture
streaming north from Tropical Depression Number 2 expected. Dry
conditions with warm afternoons follows Tuesday into Wednesday,
but unsettled weather may return by the end of next week.

&&

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

130 pm update...

Cumulus emerging across W MA and CT to which webcams show having a
bubbly appearance, while observations in the area are picking up
on some distinct convergent lines. Per SPC mesoanalysis there is
instability to work with on the order of 2000 j/kg, though the
potential is seemingly limited by the presence of a mid to upper
level ridge and weak shear pattern. Meanwhile there is a slight
sea-breeze along the E-shore of MA.

Altogether, continued thinking of isolated to scattered thunderstorm
activity across S New England away from the immediate coast developing
over the next couple of hours and going through into evening. There
remains a possibility still for a rogue storm with heavy rainfall
and gusts up to 40 mph. Focus along convergent boundaries and
perhaps the high terrain with S flow impinging.

Otherwise hot. Temperatures warming into the low to mid 90s, near
record-breaking (see the climate section below).

&&

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

Tonight...

With continued S-SW wind flow in place, low to mid level moisture
will continue to increase as dewpts will rise to the lower-mid
60s. Leftover showers/thunderstorms may reach toward the coast
before dissipating this evening. May also see some patchy fog
develop across the normally prone inland valley after midnight.
Expect overnight lows mainly in the 60s, mildest in the urban
centers.

May see a backdoor cold front start to work southwestward down
from the Maine coast overnight. Model guidance suggesting winds
shifting to N-NE after 06Z around Cape Ann as well as temperatures
dropping to around 60, and may reach close to Boston by daybreak.

Sunday...

Expect the backdoor cold front to push further S-SW during the
day. The big question will be where this front will stall, as it
appears it will stall somewhere across the region. This will be a
catalyst for convection though, especially near and south of the
front. Have at least slight chance POPs across most areas, but
looks like best shot for convection will be from W of Fitchburg to
W of Willimantic where better instability is also in place along
with the mildest temperatures. SPC has a mention of general
thunder for central and western areas.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...

Highlights...

* Heavy rain showers Memorial Day with localized flooding possible
* Mainly dry w/near or above normal temps Tue/Wed
* Unsettled weather may return late Thu/Fri or next weekend

Details...

Sunday night and Memorial Day...

Any left over scattered convection across interior southern New
England will quickly diminish early Sunday evening with the loss
of daytime heating. The rest of the evening will mainly be dry
other than perhaps a spot shower or two, but some fog may develop.

Things then become quite interesting very late Sunday night into
Memorial day. Tropical depression 2 currently several hundred
miles southeast of Charleston South Carolina is expected to become
Tropical Storm Bonnie today. This storm is then expected to track
northwest and approach the Carolina coast Sunday, then move very
slowly northeast through the middle of next week remaining well
south of our region. This tropical storm will not have a direct
impact in southern New England, and none of Bonnie`s winds/storm
surge will affect our region.

While a direct impact will not occur, an approaching cold front
will pull a plume of its tropical moisture northward into southern
New England. PWATS approach or possibly exceed 2 inches, which
will be near record high levels based on historical upper air data
for this time of year. The guidance also signals the development
of a SSW 30 to 40 knot low level jet by 12z Monday which is 2+
standard deviations above normal. This all means we should see
bands of heavy rain showers develop very late Sunday night/early
Monday morning. Given the anomalously high PWATS combined with the
low level jet, there will be a risk for localized flooding.

While the models do a very good job these days in indicating
potential for heavy rainfall/localized flooding, they often
struggle with the location. At this time, appears that a lot of
the guidance is indicating an initial band of heavy rain showers
across eastern NY state towards 12z Monday, close to the
shortwave/better dynamics. Western MA and Northern CT may be on
the eastern edge of this band, so this will have to be watched. It
then appears that a second band may develop later Monday
morning/afternoon across southeast MA/RI on the nose of a 40+ knot
low level jet. Some of the guidance has this lingering into Monday
evening, while other data dries us out by then.

So in a nutshell, expecting numerous showers with locally heavy
rainfall. Given the above parameters, it is certainly possible
that a narrow swath may see 2+ inches of rain in less than an
hour. So while widespread flooding is not expected...there
certainly is potential for localized flooding especially if a
heavy rain band sets up in one of our more vulnerable urban
centers. Greatest risk for that appears to be in our far western
zones and perhaps southeast New England on the nose of the low
level jet, but again that certainly is subject to shift.

Tuesday and Wednesday...

Dry weather with warm afternoon highs into the 80s are
anticipated away from the immediate coast Tue/Wed as a ridge of
high pressure builds over the region. Dewpoints will drop back
into the 50s though so will get rid of the humidity.

Thursday into Saturday...

Forecast confidence becomes quite low over this time. Upper level
ridge will eventually break down by the end of next week. Whether
that happens later Thu or holds off until next weekend is
uncertain, but once that occurs unsettled weather will return.

&&

.AVIATION /17Z SATURDAY THROUGH WEDNESDAY/...

Forecaster Confidence Levels.

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

18z update...

Remainder of today...High confidence.

VFR. Isolated to scattered TSRA to which TEMPO MVFR/IFR possible
with 20-40 kt gusts away from the coast. Confident to prevail in
BDL TAF. Sea-breeze continues along the immediate E-coast. S
winds overall around 5-10 kts.

Tonight...Moderate Confidence.

VFR. Isolated to scattered SHRA/TSRA erode SE across RI and SE MA
early with potential MVFR implications. Otherwise BR or patchy FG
possible E-coast MA and NW MA. Light winds.

Sunday...Moderate Confidence.

Winds back NE across E/NE MA with MVFR/IFR cig and vsby impacts.
Towards the SW of this wind shift, SCT SHRA/TSRA expected with
TEMPO MVFR/IFR impacts and possible 20-40 kt gusts. Focus around
midday into afternoon. S winds overall for those areas S/SW of the
NE wind shift.

Sunday Night into Monday...Moderate Confidence.

MVFR/IFR as RA/+RA with possible TSRA sweep W to E through the
day. Cig and vsby impacts with strong S winds gusting 20 to 25
kts. For those areas W that clear out earlier, there is the
potential for additional SHRA/TSRA activity late in the day. Low
confidence with respect to impacts/outcomes.

KBOS TAF...VFR. Sea-breeze holds offshore. Terminal likely to
waffle between SW and SE flow thus prevailed 200 accordingly. Dry
forecast through tonight. Sunday, winds backing E/NE during the
day as cigs lower low-end VFR possibly MVFR. Conditions prevailing
into Monday, lowering as RA/+RA move into the terminal during the
later-half of the day.

KBDL TAF...VFR. Vicinity SHRA/TSRA this afternoon thus prevailed.
Quiet tonight. Vicinity TSRA possible again Sunday, but greater
focus N/W of the terminal. With any TSRA, TEMPO MVFR/IFR. S winds
prevailing, increasing ahead of RA/+RA expected early Monday
morning through roughly the middle portion of the day.

Outlook /Sunday Night through Wednesday/...

Sunday night and Memorial Day...Moderate to high confidence.  MVFR-
IFR Cigs/Vsbys likely develop late Sunday night and continue into
Memorial Day.  This the result of low clouds...fog patches and heavy
rain showers.  Isolated thunderstorms are also possible.

Monday night through Wednesday...Moderate to high confidence.
Lingering MVFR-IFR conditions possible Monday evening, but
improvement to VFR Tue continuing Wed.

&&

.MARINE...

Forecaster Confidence Levels.

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

Short Term /through Sunday/...High confidence.

130 pm update...no major changes to the forecast.

Today...S-SW winds gusting up to 25 kt through midday then will
diminish. Seas 2 to 4 feet. Can not rule out some small craft
advisory conditions along the S waters.

Tonight and Sunday...SW winds may gust up to 20 kt on the
southern waters this evening, otherwise winds and seas below
small craft criteria through Sunday. May see patchy fog with
locally reduced visibilities tonight into Sunday morning.

Outlook /Sunday Night through Wednesday/...

Sunday night through Monday night...Moderate to high confidence.
Quiet Sunday night on the waters other than some fog. We may see
some southwest wind gusts to 25 knots develop Monday morning and
continue into the afternoon with the aid of a low level jet along
with heavy showers/isolated thunderstorms. Marginal 5 foot seas
may also develop across our southern waters late Mon into Mon
night.

Tuesday and Wednesday...Moderate to high confidence. Lingering 5
foot swell possible across our southern waters Tue, but should
diminish by late Tue night. Otherwise, a ridge of high pressure
will keep winds/seas below small craft advisory thresholds with
good visibility into Wed.

&&

.CLIMATE...

Record highs for today, 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.
MA...Air Quality Alert until 11 PM EDT this evening for MAZ004>007-
     009>018-026.
RI...None.
MARINE...None.

&&

$$

SYNOPSIS...Frank/EVT
NEAR TERM...Sipprell
SHORT TERM...EVT
LONG TERM...Frank
AVIATION...Frank/Sipprell
MARINE...Frank/EVT
CLIMATE...WFO BOX Staff


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