422
FXUS61 KBOX 121308
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
908 AM EDT Mon Aug 12 2024

.SYNOPSIS...

Isolated to scattered shower or thunderstorm this afternoon,
otherwise dry and comfortable today and Tuesday. Other than
scattered showers on Thursday, much of the workweek is dry with
seasonable temperatures. A frontal system brings our next best
chance at widespread rains either this weekend or into early
next week.

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...

910 AM Update...

* Scattered showers and a few thunderstorms possible this
  afternoon/early evening that may contain pea hail/gusty winds

Plenty of sunshine across the region at mid-morning.
However...we expect a fair amount of diurnal CU to develop later
today as a strong northern stream shortwave drops southward into
our region. Despite limited low level moisture...strong
dynamics and associated cold pool aloft will result in the
development of surface capes between 500 and 1000 J/KG. This
should result in scattered showers and probably a few
thunderstorms developing this afternoon into early this evening.
While the severe weather threat looks to be low...thinking we
may see small hail/graupel along with gusty winds given modest
T/Td spreads. Some of the latest CAMs show pretty good coverage
of this activity and that makes sense given the strength of the
northern stream energy. That being said...activity will not last
long in a given location with mainly dry weather much of the
day. Highs should range from well up into the 70s to the lower
80s but with rather comfortable humidity for this time of year.

&&

.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM TUESDAY/...

Updated: 2:50AM

Tonight:

Nearly a carbon copy of the previous night. Showers end and clearing
sky cover, the departing shortwave provides another reinforcing shot
of cooler and drier air. Light northwest winds overnight across the
interior, but the boundary layer remains mixed enough to continue
those winds near the coast. Where the winds are light, should have
falling temperatures into the 50s, while the urban centers are still
warm-ish in the lower 60s.

Tuesday:

All around a nice day across the region with surface high pressure
building in from the southwest. Aloft, flow is out of the northwest
to the north, reinforcing the lower dew points and humidity. A good
amount of sunshine with fair weather clouds mixed as there is a weak
shortwave moving through mid to late afternoon, but with low PWATs
likely only see added clouds rather than any rain.

Seasonably warm with highs in the upper 70 and lower 80s. Northwest
winds 5 to 10 mph.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...

Updated: 2:50AM

Highlights:

* Other than a chance for showers on Thurs, much of the workweek is
  dry, with seasonable temperatures.

* Next chance for widespread rains is with a frontal system moving
  in either on the weekend or early next week.

* Monitoring developments regarding Potential Tropical Cyclone Five
  east of the Lesser Antilles. See NHC Advisories on this system for
  more details. Increasing risk for high surf and rip currents from
  later this weekend, but any other specifics remain too uncertain
  to pinpoint at this time.

Details:

No significant changes were noted in today`s 00z guidance through
the remainder of the upcoming workweek, with pretty good consistency
run-to-run and across modeling systems. Broad cyclonic flow aloft
with surface high pressure will govern our weather pattern through
the rest of the workweek. This should bring a mix of clouds and sun
during the day, and while most of the workweek is generally dry,
there is a better chance at showers on Thurs as a weak vort maxima
rotating around a broad upper trough sparks shallow convective
development especially in/near the higher terrain. No significant
impacts are expected from any showers which develop, however.
Temperatures begin around seasonable levels with a modest warming
trend toward late week, but highs in the upper 70s to lower to mid
80s pretty common.

Still looks as though the next best chance at more widespread rain
chances is with a pretty robust frontal system moving in from the Gt
Lakes either this weekend or early next week. Previously the GFS was
at odds with the international guidance suite on this frontal
system. There are now more members from the 00z GEFS as well as the
00z GFS which lend support to at least the existence of this frontal
system nearing Southern New England. However pretty large
disagreement on its timing, with the Canadian GEM holding off until
early next week, the GFS late in the weekend, while the ECMWF is the
most pessimistic in showing rains developing Sat and continuing
through Mon. For now left a rather general broad-brushed Chance PoP
for the weekend into early next week, but that will need refinement
once there`s better agreement on the timing.

Finally, will be continuing to keep close monitor of developments
regarding what is now Potential Tropical Cyclone (PTC) Five located
near the Leeward Islands. For the latest on PTC 5, see the latest
advisories from the National Hurricane Center. Most available track
model forecasts indicate PTC 5 - forecast to become a strong
tropical storm or hurricane in the next five days, with the next
named system to be Ernesto - making a northward to northeast pass
well offshore east of 70W longitude late this weekend. However we
need to be cognizant of adjustments in storm track as it is still
very early in this system`s lifecycle. It thus remains way too early
to provide specifics/effects to Southern New England, if any, due to
that uncertainty. However, long-period swell well ahead of this
system may stand to increase the risk for rip currents and high surf
as we move into the weekend. This is supported by the ECMWF Wave
guidance, which shows 5-9 ft swells reaching our southeastern coast
around Sat night and Sun.

&&

.AVIATION /13Z MONDAY THROUGH FRIDAY/...

Forecast Confidence Levels:

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

12z TAF Update:

Today...High Confidence.

VFR. Increasing clouds this afternoon, but remain VFR with
clouds bases around 5,000 to 7,000 feet. Dry in the morning,
then scattered brief afternoon showers, have included PROB30 for
western terminals; -SHRA at BDL & BAF between 18z/22z, here is
where there is highest confidence in rain. Elsewhere VCSH in
the rest of the terminals, except Cape Cod and the Islands.

Very low prob (5-10%) of isolated thunder, but too low to
include in the TAF. WSW to WNW winds 10-15 kt. Could have some
higher gusts between 18z-23z up to 20 knots. Cape and Island
winds are SW 10-15 kt and gusts to 20 knots.

Tonight and Tuesday...High Confidence.

Dry & VFR. WNW winds are 5-15 kt.

KBOS TAF...High Confidence.

Mainly VFR, although risk for SHRA between 17-02z could bring
MVFR visby for a brief period of time. WNW winds around 10 kt
begin a slow backing to WSW with gusts 18-20 kt this aftn,
before shifting to NW around 10 kt after 02z Tue.

KBDL TAF...High Confidence.

Mainly W to WNW winds 5-15 kt and dry weather through this
morning. Then VCSH this afternoon, mainly 18z-22z.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Wednesday Night: VFR.

Thursday: VFR. Slight chance SHRA, isolated TSRA.

Thursday Night through Friday: VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

Updated: 2:50AM

Through Tuesday...High Confidence.

Tranquil boating weather with persistent SW winds 5-15 kt through
today, could have few stronger gusts to 20 knots for the near
shore waters off of the coast of RI and southeast MA. Wind
shifts to WNW tonight into Tuesday. Dry weather with the
exception of a few brief showers, an isolated thunderstorm this
afternoon, dissipating with sunset.

Outlook /Tuesday Night through Friday/...

Winds less than 25 kt.

&&

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

&&

$$

SYNOPSIS...Loconto/Dooley
NEAR TERM...Frank
SHORT TERM...Dooley
LONG TERM...Loconto
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley