Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 271831

Area Forecast Discussion
National Weather Service Taunton MA
231 PM EDT SAT AUG 27 2016

High pressure centered over Northern New England brings dry
weather through Sunday. A cold front moves south across Northern
New England Sunday night and may bring a chance for a shower or
thunderstorm in northern Massachusetts. Weak high pressure brings
dry and less humid conditions late Monday and Tuesday. The risk
for thunderstorms along with warmer and more humid weather returns
Wed as yet another cold front moves across the area. Canadian high
pressure brings a period of dry and fall-like weather late next
week into the weekend with mild days followed by cool nights.



Through evening...

High pressure centered over Quebec is bringing fair weather to the
Northeast USA. Expect sunny skies through the evening. A sea
breeze is in place along the coastline and will linger through
evening. Dew points should remain in the mostly comfortable upper
50s/low 60s. Temperatures will remain in the mid 80s to around 90
inland, while the sea breeze keeps coastal areas in the upper 70s
to mid 80s.


High pressure shifts east into the Maritimes, but remains in
control of our New England weather. Expect fair skies and light
wind. This will allow radiational cooling, with min temps near
the dew point. This also means patchy fog in the usual places
with vsbys below 1 mile in spots.



Ridge aloft Sunday shifts east by evening. High pressure at the
surface will move out of the Maritimes and out to sea, but still
bring dry weather for Sunday. Temps at the top of the mixed layer
will be 16-17C so max temps should again be in the mid and upper
80s, cooler near the coast.

Shortwave from the Plains moves east to Quebec by Sunday night.
The supporting 110-knot upper jet eventually enters Northern New
England Sunday night along with the favored right entrance region.
Most of this remains to our north but may clip northern
Massachusetts. We will show 25 pct pops north of MA route 2 and 15
pct much of the rest of the region. That 15 percent contour could
possibly be moved north to the Mass Pike, but just enough upper
venting into southern sections to show something, and the various
QPF forecasts do extend 0.01 inch amounts south of the Pike late
Sunday night.




* Temps ... Very warm & humid Mon & Wed...more pleasant Tue
* Precip ... Isolated T-storm Mon...higher risk Wed
* Fall-like weather Thu-Sat with mild days and cool nights

Overview and model preferences...

Northern stream becomes more dominant this period and eventually
erodes the subtropical ridge. Thus trend will be not as warm and
less humid beginning Thu and likely lasting into next Sat. However
this transition will be marked by a very warm and humid day Wed
along with potential convection. Regarding guidance...both GEFS and
EPS ensembles are in very good agreement on the large scale flow
including timing of frontal passages Mon and Wed. However as
expected at this time range deterministic guid differing on
amplitude and timing of smaller features. For example 00z EC is
slower with fropa Wed ngt into Thu along with a cooler post frontal
airmass Fri with 850 temps dipping down to +4C! Typical biases
(slower and more amplified) for the EC at this time range. So for
this portion of the forecast there is above average forecast
confidence on trends and avg confidence on details.

Daily details ...

Monday ... warm and humid with the risk of a few showers and T-
storms. By afternoon the risk should shift south into CT/RI and
south of the MA turnpike with fropa along with exiting deep layer
moisture. Instability and shear is marginal along with forcing for
ascent. These attributes should keep areal coverage of any storms
isolated or widely scattered. Thus not a washout expected. Turning
much less humid in post frontal airmass Mon night.

Tuesday ... dry and comfortable humidity as ridging lingers across
New England. Seasonably warm. Seabreezes keep the shoreline slightly

Wednesday ... next northern stream short wave approaches along with
attending cold front. Warmer and more humid ahead of the approaching
cold front. Temps should surge well into the 80s away from south
coast. In fact with wsw surface winds and ensembles suggesting +17C
at 850mb and +22C at 925 mb...highs of 85-90 are possible.  Heavy
rainers possible as PWATs surge to about +1 SD along with surface
dew pts 65 to 70. Modest instability and marginal shear will yield a
low risk for a few strong storms possible.

Thursday thru Saturday ... a touch of fall weather this period
courtsey of 1025 mb Canadian high building across the Great Lakes
into New England.  Ensembles suggest 850 temps dropping to about +8C
(about -1 SD) for a number of days.  Likely see highs in the 70s and
lows in the 40s and 50s! Thus the theme will be for mild days
followed by cool nights. Very pleasant with dry weather and low


Forecaster Confidence Levels.

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

Short Term /through Sunday Night/...High Confidence.

Through this evening...

VFR. Light N-NE winds with sea breezes along both coasts.


VFR. Light and variable wind. Patchy fog after midnight in the
usually prone locations, mainly in the CT River Valley, with
IFR/LIFR cigs/vsbys through sunrise.


VFR with light winds increasing out of the south. Some increase in
high thin clouds during the afternoon.

Sunday night...

VFR. Increasing mid and high clouds. Areas of 4000 foot cloud
bases north of the Mass Pike late at night with widely scattered
MVFR in a shower or thunderstorm. Patchy fog with local IFR vsbys
after midnight.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Monday through Thursday/...

Monday ... Moderate to high confidence. Mainly VFR but isolated
SHRA/TSRA yielding brief MVFR which shifts into CT/RI and southeast
MA during the afternoon.

Tuesday ... Moderate to high confidence for VFR and dry weather.
Light winds with local seabreezes likely.

Wednesday ... Moderate confidence. Mainly VFR but Local MVFR
possible in scattered SHRA/TSRA.

Thursday ... Moderate to high confidence. VFR and dry weather


Forecaster Confidence Levels.

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

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

Winds and seas expected to remain relatively light through
Sunday night.

Sea breezes this evening will diminish, then return late Sunday
morning and continue through the afternoon. Seas trend slowly
higher Sunday and Sunday night in response to southeast swell
from distant Tropical Storm Gaston.

Widely scattered shower or thunderstorm possible late Sunday
night. Best chance will be along the Massachusetts North Shore.

Outlook /Monday through Thursday/...

Monday ... Cold frontal passage in the afternoon/evening. A few
storms possible with the front. Increasing south to southeast
swells across the ocean waters from TS Gaston.

Tuesday ... High pres overhead resulting in fine boating weather.
Only issue will be south to southeast swells across the ocean
waters from TS Gaston.

Wed ... Another cold front passage in the afternoon/evening along
with risk for T-storms.

Thu ... Quiet boating weather should return as high pres builds
into the Great Lakes and eventually the northeast.





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