Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 250200
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1000 PM EDT Mon Jul 24 2017

.SYNOPSIS...
Cool and damp conditions will linger into Tuesday. High
pressure will bring a return to dry and pleasant weather for
Wednesday. Cold front with a surface low pressure wave
approaches southern New England Thursday night and exits the
area late Friday. Dry weather and seasonable temperatures
expected next weekend.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
10 PM Update...

Nose of the NE low level jet combined with abundant low level
moisture producing areas of drizzle across eastern MA. Hi-res
guidance suggests at least patchy drizzle will persist into the
overnight hours. Otherwise, lots of low clouds expected and a
few showers from leftover complex in NY may spill into western
MA/CT. Clouds will prevent much diurnal cooling with temps
nearly steady.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
A little better start to Tuesday. Despite clouds lingering to
start the day, we should see a drying and clearing trend during
the afternoon, and especially Tuesday night, as a high pressure
arrives from the north.

With winds expected to be more from the north than east, max
temperatures should be noticeably higher during the day than
Monday, but still below normal. Below normal temperatures
continue Tuesday night.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Highlights...
* Dry weather and seasonable temperatures on Wednesday
* Showers and possible thunderstorms late Thu with showers
  likely lingering into Fri
* Dry weather and seasonable temperatures likely for the weekend

Overview...

Ridge builds over the intermountain west while the eastern
United States looks susceptible to troughing. An anomalously
strong short wave trough for this time of year will cross the
Great Lakes region on Thu and New England on Fri. There is
considerable disagreement between the GFS and ECMWF operational
runs and ensemble output regarding strength of this short wave
trough. Dry weather should follow in the NW flow behind the
short wave passage for the weekend when there is much better
consensus among the medium range models. There is also fairly
reasonable model consensus on 850 mb temperatures for the
weekend time period with resultant surface temperatures likely
near seasonable levels. With a few tweaks in the Thu and Fri
period, have gone close to a model consensus for the longer term
forecast period.

Period of Focus...Thursday afternoon into Friday

The one period of extra focus in the longer term period covers
Thursday afternoon through Friday when operational and ensemble
model disparities result in somewhat below average confidence on
the outcome. All models depict the short wave trough passage
but vary considerably in strength and some in timing. The ECMWF
suite of model runs depict a much stronger and as one might
expect slower system than the GFS suite of model runs. Timing
could also play a role in convective potential on the front end
late Thursday afternoon and evening. Have opted to go close to
continuity with POPs and just a tad below model consensus due to
model discrepancies. Nevertheless, do believe there will be
enough energy to support likely POPs in most areas. Also,
adjusted temperatures down just a little across northern MA from
a straight model consensus due to a high probability of
cloudiness and at least scattered showers. If the latest ECMWF
run proves to be correct, then we will probably need to lower
those high temperatures on Friday at least a little more and
raise POPs.

As the short wave trough approaches and the 500 mb heights
begin to fall, the air mass becomes marginally unstable late
Thursday, mainly across western and northern MA and do have a
chance of thunder in the gridded forecast. The slower timing
scenarios, however, would bring the forcing into the region well
past the favorable diurnal time. There is relatively strong
vertical shear as one might expect to be associated with a
robust short wave trough, but the degree of instability remains
something of a question mark. For now, have high chance or low
likely showers and slight chance or chance thunder. We`ll be
able to refine this as we get closer.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

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

Short Term /through Tuesday Night/...Moderate confidence.

Tonight...Still expect mostly IFR or low MVFR CIGs to prevail
with lowest across high terrain terminals and E/SE coastal
areas. Patchy -SHRA/DZ especially along E MA coast and higher
terrain terminals. NE Winds gradually turn N. Winds remain
strongest along E MA coast sustained around 15 kt with gusts up
to 25 kt.

Tuesday into Tuesday night...
Improving trends. MVFR-IFR mix gradually lifting, especially
Tuesday night. Still a bit breezy along the east coast with
sustained winds up around 10 kt and gusts up to 20 kt Tuesday,
diminishing Tuesday night.

KBOS Terminal...NE winds back farther N tonight. IFR CIGS for
much of the night, possibly lifting to very low MVFR at times.
Moderate confidence in timing for improvement to MVFR during Tue.

KBDL Terminal...IFR or low MVFR ceilings persisting through
roughly midday Tuesday.

Outlook /Wednesday through Saturday/...

Wednesday through Thursday morning...VFR.

Late Thursday afternoon through Friday...MVFR ceilings and
visibilities in areas of showers. Isolated thunderstorms late
Thursday afternoon and evening.

Saturday...VFR.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

Short Term /through Tuesday Night/...

Low pressure moves farther away from the waters tonight, backing
winds from northeast to north across most of the waters. Reduced
visibility in rain and fog. rain diminishes this evening, but fog
and spotty drizzle likely to linger through daybreak Tuesday.

Small Craft Advisory for most waters continues, concluding late
Tuesday into Tuesday night as winds subside and seas diminish.

Outlook /Wednesday through Saturday/...

Conditions during most of the period will likely remain below
Small Craft Advisory thresholds. However, this is a risk that
winds and seas may approach 25 knots and 5 feet, respectively, in
an increasing SW flow Thursday afternoon and a northerly flow
Friday afternoon and night, depending upon the strength of a low
pressure area that passes across New England and the Gulf of Maine
on Friday.

&&

.TIDES/COASTAL FLOODING...
Continued strong NE flow continues tonight with sustained winds
around 10 to 15 mph with gusts upwards of 30 mph. This yields a
surge upwards of a foot for locations along the E MA coast N of a
low sweeping W to E along the waters south of New England.

A Coastal Flood Advisory continues for the evening high tide
accordingly, given surge on top of high astronomical high tides.

&&

.CLIMATE...
Here is where we stand for record low maximum temperatures for the
calendar day.

              Record     Max Temperature

Boston      63 - 1904         65
Hartford    67 - 1997         68
Providence  67 - 1997         66  * probable new record
Worcester   60 - 1964         61

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Coastal Flood Advisory until 3 AM EDT Tuesday for MAZ007-015-
     016-019-022-024.
RI...None.
MARINE...Small Craft Advisory until 2 AM EDT Tuesday for ANZ230.
     Small Craft Advisory until 2 PM EDT Tuesday for ANZ231-251.
     Small Craft Advisory until 9 AM EDT Tuesday for ANZ235-237.
     Small Craft Advisory until 8 PM EDT Tuesday for ANZ250.
     Small Craft Advisory until 3 AM EDT Wednesday for ANZ254.
     Small Craft Advisory until 2 AM EDT Wednesday for ANZ255-256.

&&

$$
SYNOPSIS...Belk/Thompson
NEAR TERM...KJC
SHORT TERM...Belk
LONG TERM...Thompson
AVIATION...Belk/Thompson
MARINE...Belk/Thompson
TIDES/COASTAL FLOODING...
CLIMATE...


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