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Weather Center


Area Forecast Discussion

Forecast Discussion for BOX NWS Office
FXUS61 KBOX 212016

Area Forecast Discussion
National Weather Service Boston/Norton MA
416 PM EDT Sun Jul 21 2019

A dry cold front will sweep across the region this evening with a
wind shift to the northwest and eventually north tonight, ushering
in an airmass with lower humidity and not as warm. The front stalls
just off the south coast Monday followed by two waves of low
pressure forming on the front. This will bring two rounds of showers
possibly heavy at times Monday afternoon and evening followed by a
second round Tuesday. The low and its frontal boundary move offshore
Tue night followed by a stretch of very pleasant summer weather with
dry conditions, seasonable temperatures and comfortable humidity
beginning Wednesday and possibly lingering into the beginning of
next weekend.



4 PM Update...

A dry cold front south of the Mass Pike (I-90) denoted by a wind
shift from WSW to WNW along with dew pts dropping into the mid and
upper 60s will continue to slowly sag southward this evening and
overnight. Thus lowering humidity along with temps not nearly as
warm as previous nights. Lows tonight in the upper 60s to lower 70s,
about 5-10 degs warmer than normal but much more comfortable than
last night with dew pts tonight falling to 60-65 except upper 50s
across western CT/MA.

Will continue with Excessive Heat Warning and Advisory as heat
indices continue to range between 95-105 with 107 at New Bedford.
Although with peaking heating over and frontal passage occurring a
downward trend in heat and humidity into this evening.

As for convection, can`t rule out an isolated shower/T-storm across
the high terrain thru this evening or along the frontal
boundary/wind shift line, however west winds lowering dew pts and
limiting surface convergence and lack of synoptic scale forcing,
most locations remain dry this evening and overnight.



4 PM update ...

Monday ...

Day begins dry along with some sunshine thru mid level clouds and
somewhat comfortable with dew pts in the 60s and a light NE wind.
However lead short wave approaches and induces a frontal wave over
the NYC area. Showers will overspread the area in the afternoon from
northwest to southeast. Embedded heavy rain is possible as PWATs
increase to around 2 inches along with some elevated instability
possible yielding isolated thunder.

Seasonably warm tomorrow with highs of 80-85 then falling late in the
day once showers arrive. Not as humid with frontal boundary south
of New England yielding NE winds.

Monday night ...

Showers become more widespread during the evening along with
embedded thunder with frontal wave moving along or near the south
coast. Additional lift via strong (+2 SD) RRQ of upper level jet
streak coupled with elevated instability and PWATs around 2
inches. Thus heavy rain possible.

2nd half of the night may have a drying trend as lead short wave
exits and then trailing short wave waits until Tue to arrive. So
perhaps a break in the showers 2nd half of Mon night.

Seasonable temps with lows in the 60s.



415 PM update ...


* Showers/some thunderstorms continue into Tue with eventually much
  cooler less humid air moving into the region

* Mainly dry with seasonable temperatures Wed through Sunday with
  comfortable humidity


Tuesday and Tuesday Night...

The upper trough axis remain to our west Tuesday morning as a second
surface wave/low pressure center moves up the coast following the
initial one late Monday. This will bring another day of rain,
potentially heavy, with local downpours and urban flooding
potential. In the upper reaches of the atmosphere we see plenty of
lift courtesy of the entrance region of an anomalous 110 kt jet.
This as disturbances continue to rotate through the base of the
passing trough. The best chance for heavy rain and potential urban
flooding issues looks to be over RI/southeast MA closer to the axis
of 2"+ PWATs. Exact locations of the heaviest rains aren`t certain
at this point, however. Importantly, though, there will be enough
moisture in the column across most of southern New England for
anyone to see some heavy rain and flooding potential. Stay tuned.
Convection on Tuesday should be limited given the axis of good
instability sinks south of the area by mid morning. One silver lining
of the rain on Tuesday is that it and associated cloudcover, with
850mb temps +10C will lead to very comfortable temperatures. Highs
should top out ~10F below average, in the low 70s. A modest LLJ may
be able to mix down over the islands and south coastal waters in
heavy showers, bringing gusty winds for a time on Tuesday.

The low lifts out of the region overnight and drier air filters in
but clouds are slow to thin. Some slight rain chances linger over
southeast MA associated with a third wave moving up the coast, but
most guidance keeps it far enough offshore that it may not impact
SNE at all.

Wednesday through Sunday...

Drier and cooler for the latter portion of the forecast. Overall
should be a pleasant stretch of days as we return to seasonable
temperatures with lower dewpoints. Cold pool aloft moves overhead on
Wednesday as the trough axis approaches, and this brings 850mb temps
around 10 to 12C through Friday, warming by the weekend. Wednesday
will be the coolest day of the period, in the 70s to near 80.
Thursday onward we`ll see a stretch of mid 80s, increasing by the
weekend, with lows in the 60s. Building surface high pressure (and
mid level ridging by the weekend) should keep things dry for the


Forecaster Confidence Levels...

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

Short Term /through Monday Night/...Moderate to high confidence.

1830z update ...

This afternoon into tonight ... high confidence.

Most terminals remain dry with just a remote chance of an
isolated shower/T-storm across RI and southeast MA this
afternoon into early evening. Thus VFR prevails along with gusty
WNW winds 15-25 kt, WSW along the south coast. Gusts diminish
with sunset.

Monday .... high confidence.

VFR and dry to start the day then showers overspread MA/CT/RI
from northwest to southeast lowering from VFR to MVFR. Light
east wind.

Monday night ... high confidence.

Showers become widespread with MVFR lowering to IFR especially
across eastern MA with onshore winds.

KBOS Terminal...High confidence in TAF. WSW winds shift to WNW
19z-20z. Dry weather thru Monday morning then showers developing
mid to late afternoon.

KBDL Terminal...High confidence in TAF. Dry weather thru Monday
morning then showers developing Monday afternoon.

Outlook /Tuesday through Friday/...High confidence.

Tuesday: Mainly MVFR, with local IFR possible. Breezy. Chance

Tuesday Night: Mainly VFR, with local IFR possible. Slight
chance SHRA.

Wednesday through Friday: VFR.


Forecaster Confidence Levels...

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

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

4 PM update ...

Tonight ... dry cold frontal passage with wind shift from SW to NW
and eventually north overnight. Other than an isolated shower/T-
storm dry weather prevails along with good vsby.

Monday ... Dry weather to start with showers overspreading the
waters late in the day as low pressure develops over NYC area on
frontal boundary south of New England.

Monday night ... Showers with embedded thunder and heavy rain
possible as low pres tracks along or near the southern New England

Outlook /Tuesday through Friday/...High confidence.

Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Chance of rain showers, slight chance of thunderstorms.

Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers. Areas of visibility 1 to 3 nm.

Wednesday: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers.

Wednesday Night through Friday: Winds less than 25 kt.


Min temps/record high mins for Saturday July 20:

BOS: 80 degrees, ties 80 in 1977
BDL: 77 degrees, breaks 73 in 1977
PVD: 77 degrees, breaks 76 in 1977
ORH: 75 degrees, breaks 72 in 1977

High temps/records for Saturday July 20:

BOS: 97 degrees, did not break 99 in 1991
BDL: 98 degrees, did not break 100 in 1991
PVD: 94 degrees, did not break 101 in 1991
ORH: 90 degrees, did not break 95 in 1991

Record highest min temps for Sunday July 21:

BOS: 81 in 1991
BDL: 74 in 1977
PVD: 77 in 1980
ORH: 73 in 1991

Record highest max temps for Sunday July 21

BOS: 102 in 1977
BDL: 101 in 1991
PVD: 102 in 1991
ORH:  95 in 1926

Last Occurrence of 100F or higher temperatures
BOS: 7/22/2011 (103F)
BDL: 7/18/2012 (100F)
PVD: 7/22/2011 (101F)
ORH: 7/4/1911 (102F)

Notable high dew points in past years for July 20 and July 21:

Saturday July 20

BOS 77 observed, breaks 76 in 2013
BDL 76 observed, ties 76 in 2005
PVD 79 observed, breaks 76 in 2013
ORH 76 observed, ties 76 in 2013

Sunday July 21

BOS 76 in 1994
BDL 78 in 1972
PVD 81 in 1977 (tied for highest all-time at PVD)
ORH 76 in 2011 (last of multiple years)


CT...Excessive Heat Warning until 8 PM EDT this evening for
MA...Air Quality Alert until 11 PM EDT this evening for MAZ020>024.
     Excessive Heat Warning until 8 PM EDT this evening for
     Heat Advisory until 8 PM EDT this evening for MAZ022-023.
RI...Air Quality Alert until 11 PM EDT this evening for RIZ003>008.
     Excessive Heat Warning until 8 PM EDT this evening for


NEAR TERM...Nocera

NWS BOX Office Area Forecast Discussion



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