Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 240904
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
504 AM EDT WED AUG 24 2016

.SYNOPSIS...
High pressure will remain in control with higher temperatures
today, but continued low humidity. More warm, humid conditions
will return late this week. There is a risk for showers and
thunderstorms Thursday night and Friday as a weak front passes.
Another high will bring dry and somewhat less humid weather this
weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Still expecting a high pressure to move farther offshore while
remaining to our south. This will mean a more dominant southwest
flow, leading to slightly higher temperatures later on. Humidity
levels will remain low as mixing of dry boundary layer keeps
dewpoints down into the 50s for most.

The big question will be the formation of an east coast seabreeze.
Boundary layer winds should remain less than 10 kt, which is a
sign the seabreeze could form. Seeing hints at it is some of the
high resolution guidance. Based on the expected pattern, with a
high pressure moving farther offshore, thinking a weak east coast
seabreeze will form, but it will start later than usual.

With synoptic southwest onshore flow, expecting lower temperatures
along the immediate south coast.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
High pressure continues to move farther offshore. South to
southwest winds continue to increase ever so slightly through this
period. Expecting near to above normal temperatures through
Thursday.

Latest guidance continues to show the slow approach of a
prefrontal trough toward western New England late Thursday. Given
weak forcing, and relatively lower humidity, decided to keep the
forecast dry through Thursday. There is a possibility for a few
isolated showers across western MA, but not enough of a risk to
put showers in the forecast at this time. This timing may change.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...

Highlights...

* Scattered showers/thunderstorms Thursday night and Friday
* Drier weather this weekend
* Another front may bring shot of wet weather Sunday night and
  Monday

Overview and model preferences...

Overall summer pattern remains in place across North America
during most if not all of this timeframe as high pressure remains
across the south central and SE U.S., keeping a rather fast mid
level W-SW wind flow in place late this week across the northern
tier states. Noting the overall H5 pattern begins to shift S Thu
night/Fri as a surface front works SE out of central Ontario/Quebec.
This will push off the south coast of New England by early this
weekend, with high pressure bringing more dry and somewhat less
humid conditions.

00Z operational models are in lower agreement in bringing an H5
short wave and its associated weak low pressure/front in the fast
flow aloft, with the ECMWF a bit more bullish with its precip
field vs. the GGEM and GFS for Sunday night and Monday. Less
confidence with the timing of this feature.

Have lower confidence with evolution of the upper level pattern
early next week. Big questions as to the development and track of
a tropical wave /99L/ near or east of the Bahamas. At this point,
does not appear to affect the region, but may influence the
overall upper level pattern, potentially somewhere across the
southern Gulf states, but could be further into next week before
any possible effects are felt.

Details...

Thursday night-Friday...High pressure remains along the eastern
seaboard with SW wind flow in place. H5 heights lower somewhat,
with surface low pressure and associated cold front moving slowly
across during this timeframe. PWATs increase to 1.8 to 1.9
inches, so should see some rainfall with this front. However,
noting rather limited instability but best near and with the
passing front. Have mentioned scattered showers/thunderstorms in
the forecast, with best shot across central and northern areas
Thu night through midday Friday.

Will remain warm/humid Thu night with lows only in the mid 60s to
around 70. As the front passes, winds will shift to W-NW during
the day Friday. However, somewhat drier air will be delayed until
Friday night so will still feel rather humid. Highs will be in the
mid-upper 80s.

Saturday-Sunday...Large high pressure will cross the northeast U.S.
with somewhat cooler and drier conditions. Dewpts will only fall
back to the lower-mid 60s, with some upper 50s Saturday night
across the inland valleys. N-NW wind to start off Saturday, then
will veer to E-NE during later Saturday and E-SE on Sunday. With
the warm sea surface temps on place, not much cooling air off the
ocean. Expect highs both days in the lower-mid 80s, except in the
mid- upper 70s along the immediate S coast.

Another front may begin to approach Sunday night, which push a few
widely scattered showers around the Route 2 area of N Mass. However,
timing is in question with the large high across the mid Atlantic/SE
U.S. states.

Monday-Tuesday...Low confidence on timing of the approaching front
during Monday, which is somewhat faster on the GFS vs. the ECMWF.
Went along with ensemble guidance for this timeframe, with chance
POPs going for most of Monday into Monday night. Still quite a few
questions on Tuesday, as the front may stall near or just off the
southern New England coast.

&&

.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels.

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

Short Term /through Thursday/...High Confidence.

Mainly VFR. Increasing mid and high clouds Thursday. Low risk for
patchy IFR/MVFR in fog later tonight at the most fog-prone
locations.

KBOS Terminal...Moderate confidence in the TAF. Some of the latest
guidance develops a late seabreeze. Based on the expected light
winds within the lowest 2 kft, thinking a weak seabreeze develops
late. It is possible southwest winds dominate, and keep this
seabreeze just east of the terminal.

KBDL Terminal...High confidence in the TAF.

Outlook /Thursday night through Sunday/...

Thursday night...Moderate to high Confidence.
Mainly VFR. S-SW winds gusting to 20 kt along the S coast Thu
evening. Scattered showers/isolated thunderstorms push into N and
W areas overnight along with patchy late night fog in normally
prone valley locations. Local MVFR-IFR conditions.

Friday...Moderate Confidence.
Scattered SHRA/TSRA as cold front moves across the region. Mainly
VFR with local TEMPO MVFR-IFR CIGS/VSBYS possible with any storms.
Conditions improve from NW-SE Friday night, though may see brief
patchy fog across portions of CT valley after 07Z-08Z.

Saturday and Sunday...High Confidence.
VFR. Light winds. Likely sea breezes on Saturday. Winds becoming
E-SE Sunday.

&&

.MARINE...
Forecaster Confidence Levels.

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

Short Term /through Thursday/...High confidence.

Tranquil boating conditions through the period as high pressure
remains in control of our weather.. Mainly SW winds 15 kt or less
with light seas and good visibility. A few gusts up to 20 kt
possible Thursday, especially during the afternoon.

Outlook /Thursday night through Sunday/...

Thursday night...High Confidence.
S-SW winds gusting to around 20 kt Thursday evening along the
southern near shore waters. May see local MVFR-IFR VSBYs in
patchy fog mainly after 06Z along the southern near shore waters.
Seas may briefly reach 5 ft on the outer waters east of Cape Ann
early.

Friday...Moderate Confidence.
S-SW winds gusting up to 25 kt on the southern waters to east of
Cape Cod with seas building to around 5 ft. Winds will diminish as
they shift to W-NW Friday night. Seas subside below 5 ft. Patchy
fog may develop overnight on the southern outer waters.

Saturday and Sunday...High Confidence.
Expect N winds shifting to E-NE during Saturday, then E-SE on
Sunday. Winds and seas remain below small craft criteria.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$
SYNOPSIS...Belk/EVT
NEAR TERM...Belk
SHORT TERM...Belk
LONG TERM...EVT
AVIATION...Belk/EVT
MARINE...Belk/EVT


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