Area Forecast Discussion
Issued by NWS Boston, MA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS61 KBOX 241953

Area Forecast Discussion
National Weather Service Taunton MA
353 PM EDT SUN JUL 24 2016

Summer heat will continue into much of the upcoming week. A weak
front will bring an increased risk of showers and thunderstorms
Monday afternoon and evening and again late next week.


Quiet night tonight with just a few mid/high clouds expected. Weak
shortwave triggering convective complex over Ohio valley will
track to the mid atlc region toward 12z with any convective
activity remaining to the SW of New Eng. Lows will be mainly in
the 60s with increasing dewpoints after midnight.


*** Potential for strong to severe thunderstorms Mon afternoon and
 evening along with hot and very humid conditions ***

Weak shortwave will be tracking south of New Eng in the morning
with any convection likely remaining to the south. However, models
indicate good influx of moisture as higher theta-e air moves into
the region during the morning and this will be accompanied by
some clouds and possibly even a few showers. These clouds may
affect temps and instability but confidence in the extent of cloud
cover is not high. We do expect at least partial sunshine and with
850 mb temps climbing to near 20C potential exists for a very hot
day. If we had full sunshine potential for upper 90s to around 100
degrees but due to expectation of cloud cover we will not go quite
this high, with high temps low to mid 90s away from the south
coast. It will become rather humid with dewpoints climbing into
the lower 70s. We will keep heat advisory for CT valley where heat
indices expected to approach 100 degrees, but confidence not high
enough to expand further east due to uncertainty in amount of

Other concern is the potential for severe weather Mon afternoon
and evening as mid level trof/shortwave approaches from the Gt
lakes. MLCAPES expected to peak around 1000-1500 J/kg during the
afternoon. Initially, mid level lapse rates will not be ideal but
pre-frontal trof will likely serve as a focus for developing
convection and 0-6 km shear increasing to 35 kt which will result
in an increased risk for severe weather.

Severe threat likely to continue into the first half of Mon night
as weakening remnant EML moves into the region. Mid level lapse
rates increase to 6.5 C/km aided by subtle cooling aloft which
will help to sustain convection as models indicate SBCAPES
500-1000 J/kg with deep layer shear above 30 kt during 00-06z.
Damaging winds will be the primary threat of severe weather,
especially with inverted V profile during the late afternoon.
Heavy rainfall and localized flooding will be a secondary concern
with PWATS increasing to near 2 inches.

Front moves through overnight Mon night with notable drying in the
column which will result in clearing skies and lower dewpoints
moving into the region.



* Hot temperatures continue through the middle of the week, away
  from the coast
* Should be a little less humid Tuesday and Wednesday
* Showers and thunderstorms are possible again late in the week

Overview...Models are in fairly good agreement throughout the long
term portion of the forecast.  Minor timing differences as well as
mesoscale differences show up, especially towards the end of the
forecast period.  Low pressure in the maritimes will bring the cold
front through southern New England Tuesday, drying out the low
levels.  High pressure is the rule for Wednesday.  Then Thursday and
Friday, the ECMWF has a front with a series of low pressures along
the front from the DelMarVa peninsula to the maritimes.  The GFS is
similar but less detailed with the areas of low pressure. This
could bring periods of showers and possibly thunderstorms to
southern New England. The front may push south of southern New
England Friday with the low pressure over the DelMarVa peninsula
traveling along the front south of the area. Question for Thursday
and Friday is how far south the front pushes, as a move too far
south may shut us out from any rain. High pressure starts to build
back in again on Saturday and possibly on Sunday, though low
pressure south of the region may bring another possibility of
showers Sunday.

Tuesday and Wednesday...Drier weather but still hot afternoon
temperatures with highs in the 90s likely, especially away from the
coast.  Sea breezes are more likely Wednesday, with temperatures a
bit cooler along the coasts that day.  Otherwise, sunny skies and
typical July weather.

Thursday and Friday...This is the period of greatest uncertainty.
Temperatures will cool a few degrees Thursday as clouds increase and
a cold front starts to move through southern New England.  The front
moves the rest of the way through and offshore on Friday.  This
could result in temperatures down into the low to mid 80s Friday,
quite a relief after the last week.

Showers and thunderstorms will be possible with this frontal
passage, particularly on Thursday when more instability is expected
with both diurnal heating and partial sun.  They may linger into
Friday, but as mentioned above, that will largely depend on how far
off the south coast the front pushes.  Regardless, Friday is likely
to be cloudy and cooler, though more humid than previous days.

Saturday and Sunday...High pressure will build in Saturday behind
the front with mostly sunny skies and temperatures in the low to mid
80s once again.  Sunday becomes a bit more uncertain with the
possibility of a low pressure system developing or passing quite
close to the RI/MA south coast.  This could bring clouds, fog, and
rain to the area, particularly near the south coast.  Models
disagree on how close to the coast this system gets, so quite a bit
of uncertainty here.  Still, confident enough to have chance pops in
the forecast for Sunday.


Forecaster Confidence Levels.

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

Short Term /through Monday Night/...

18z update...

Through tonight...High confidence. VFR.

Monday...Moderate confidence. Mainly VFR, but sct showers/t-storms
developing in the afternoon may bring temporary IFR/MVFR
conditions and gusty winds.

Monday night...Moderate confidence. Sct showers/t-storms in the
evening, otherwise areas of IFR stratus and patchy fog may
develop along the south coast.

KBOS TAF...Expect seabreeze to develop by 19z.

KBDL TAF...High confidence.

Outlook /Tuesday through Friday/...

Tuesday and Wednesday...High confidence.  VFR.  Sea breezes likely
to develop on both coasts Wednesday.

Thursday...Low confidence.  Mainly VFR.  Periods of MVFR/IFR in SCT
SHRA/TSRA Thursday afternoon and evening.

Friday...Low confidence.  Increasing clouds should lead to MVFR/IFR
conditions in low clouds/fog and possibly additional SHRA.


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.

Light winds tonight, then pre-frontal southerly winds increasing
to 10-20 kt Mon. Winds diminishing and becoming west later Mon
night. Seas remaining below SCA. There is a risk for late day and
evening thunderstorms Monday which will need to be watched.

Outlook /Tuesday through Friday/...Moderate to high confidence.

Quiet boating weather is expected through this time.  The exception
will be Thursday and Friday when winds and seas will remain below
SCA criteria, but low clouds, fog, and periodic showers and
thunderstorms will limit visibilities.


The KBOX radar is back in service.


CT...Heat Advisory from 11 AM to 6 PM EDT Monday for CTZ002.
MA...Heat Advisory from 11 AM to 6 PM EDT Monday for MAZ010-011.


EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.