976
FXUS61 KBOX 280729
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
329 AM EDT Tue May 28 2024

.SYNOPSIS...
Warmer and brighter today with a chance for an isolated
shower or thunderstorm across northern MA. Temperatures then
cool off to more seasonable levels into the mid to late week
period. Though dry weather should generally prevail, there are
better chances for rains develop on Wednesday night into
Thursday. Mostly sunny and dry weather conditions for the
weekend into early next week, with a warming trend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Highlights:

* Early morning showers and rumbles of thunder continue across the
  coastal waters of southeast Massachusetts.

* Sunny and warmer this afternoon away from the Cape and Islands.

* Low chance of an isolated thunderstorm this afternoon, mainly
  north and west of I-495.

Early this morning conditions are improving from west to east, but
areas of moderate to at times heavy rain continues across eastern
coastal Massachusetts, Cape Cod, and the Islands. Areas west of the
I-95 corridor have begun to improve as the axis of rain shifted east,
but areas across southeast Massachusetts - mainly Cape Cod and the
Islands will continue to see moderate to heavy rainfall through
early this morning, along with rumbles of thunder. Latest radar
trends show the storm motion out of the SSW, but the good news,
these storms are moving quickly at an average speed of 35 knots,
this should preclude any hydro issues. That said, training of storms
over the Cape and Island may lead to isolated areas of ponding on
poor drainage roadways.

While not a widespread concern, given high dewpoints this morning
not out of the question pockets of fog develop in prone locations.

Temperatures this morning are mild as many are starting the day off
in the middle 60s. Clearing skies from west to east will allow us to
warm up nicely this afternoon. 925mb temperatures are roughly +16C
to +19C ~ this yields high temperatures in the upper 70s and low
80s. Given the SW to WSW wind, the immediate coast of Rhode Island
and southeast Massachusetts will have cooler temperatures in the
lower 70s. But places like Nantucket could remain in the 60s. Do
think the low clouds and areas of fog linger for a good portion of
the day which will result in the cooler afternoon temperatures.

Surface low pressure system in southern Quebec lifts north this
afternoon, a mid-level trough slides to our north, this could
initiate an isolated shower or thunderstorm generally for areas west
and north of I-495. Convective parameters this afternoon have
limited instability, around 500J/kg of MUCAPE. Though there is fair
amount of shear, the bulk effective shear is ~40 knots, good low
level lapse rates 7-8 C/km, but it should come as no surprise, the
mid level lapse rates are poor, around 6C/km. Will note that
instability is much higher across southeast Massachusetts and Rhode
Island where temps/dew points will be a few degrees warmer, with
MUCAPE growing in excess of 1000J/kg, but shear and lapse rates are
not colocated with that axis of greatest CAPE.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
Highlights:

* Mild and dry overnight, followed by a seasonable midweek with
  renewed chance for showers and rumbles of thunder.

Tonight: A dry night ahead with mainly clear skies, clouds do linger
in the higher terrain of northwest Massachusetts. Wind shifts more
to the west, dewpoints fall into the low and middle 50s with
temperatures in the upper 50s and low 60s.

Wednesday: Our next chance at rain comes in Wednesday afternoon with
a shortwave riding the base of the mid-level trough. Do not think
the day will be a washout, but do think there will be a few
scattered showers and rumbles of thunder mainly across Rhode Island
and southeast Massachusetts after 16z/18z. NAM profiles show limited
MUCAPE around 500J/kg, but low level lapse rates are rather
impressive at 8-9 C/km. Limiting the growth are poor mid level lapse
rates, less than 6C/km. FWIW - SPC does keep us in general thunder
on Wednesday. Temperatures return to more seasonable highs,
temperatures aloft are cooling, leading to highs in the middle and
upper 70s, slightly cooler at the coast where highs are in the low
70s. Wind shifts northwest across the interior during the afternoon,
while at the coast wind direction remains out of the southwest.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Highlights:

* Temperatures will be cooler on Thursday, increasing steadily each
  day through early next week.

* Rain is expected to continue Wednesday night into Thursday
  followed by an extended stretch of dry weather through at least
  early next week.

Details...

The synoptic pattern for the extended forecast will feature a deep
mid level trough/cold pool aloft leading to unsettled weather
initially, followed by mid level ridging and a drier, warmer pattern
for late week into early next week.

For the Wednesday night through Thursday light rain showers will be
more likely as the trough and associated cold pool move overhead.
PWATs are not overly impressive at around an inch, and total
rainfall isn`t expected to be much more than a half inch or so where
the showers develop which is supported by ensemble guidance. Some
uncertainty as to the areal extent of the showers at this distance
in time, but odds are that not everyone will get a soaking. A
surface cold front sinking through on Thursday together with the
cooler airmass overhead will lead to the coolest day of the forecast
on Thursday, in the upper 60s/low 70s.

Late Friday into the weekend mid level heights will be on the rise
as high pressure moves overhead at the surface. This will lead to a
drying and warming airmass with steadily rising temperatures each
day. High temps will be back to normal by Friday (low to mid 70s)
and then steadily increase each day until by Monday we`re looking at
highs in the low to mid 80s. Humidity will be more comfortable early
in the weekend, with dewpoints steadily rising as we go into early
next week making it feel more humid next week but not excessive.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:

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

06z TAF Update:

Through 12z... Moderate confidence.

Moderate to heavy rain continues along and east of I-95 and
thunder primarily over the southern waters, Cape Cod, and the
islands. Rain generally diminishes in most areas between
09-12z, though may linger into Tue AM across a portion of SE MA.
SE to S winds around 10-13 kt with gusts 20-25 kt, and that
should be enough to preclude widespread fog development, though
isolated areas of dense fog does remain possible.

Today... High to moderate confidence.

Cold front stalls across southern New England, generally across
the eastern third, yielding VFR conditions after 15Z, exception
being the Cape and Islands, especially ACK, which will struggle
to shake IFR. Will say, have lower confidence in timing of
improvement of CIGs for Cape and Islands. Brisk WSW flow of up
to 20kt. Widely isolated low topped thunderstorms are possible
in northern MA after 21Z.

Tonight... High confidence.

Generally VFR, the outer Cape and Islands may return to MVFR,
there confidence is not as high. In addition, can not rule out
some marine stratus and fog. Breezy WSW flow continues.

Wednesday... High to moderate confidence.

Generally VFR, CIGs 040-060 ft with chance SHRA or an isolated
TSRA by early afternoon. Winds are W to NW across the interior
and SW to W across the coast.

KBOS TAF...High confidence in TAF trends, moderate in timing.

IFR, rain continues through about 07z-09z and shifts offshore;
the IFR cigs likely to continue until ~13z with a more rapid
return to VFR. S winds around 10-13 kt before shifting to SW by
early AM. Wind gusts increase to 18-20 kts after 16z, low chance
for a widely isolated thunderstorm after 21z, confidence remains
too low to include, even in a PROB30.

KBDL TAF...High confidence in TAF trends, moderate in timing.

IFR, cigs to trend MVFR by 09-12z with more rapid improvement
to VFR by mid morning. S winds around 10-12 kt before becoming
SW. Wind gusts increase to 18-20 kts after 15z, low chance
for a widely isolated thunderstorm after 21z, confidence remains
too low to include, even in a PROB30.

Outlook /Wednesday Night through Saturday/...

Wednesday Night through Thursday Night: VFR. Chance SHRA.

Friday: VFR. Slight chance SHRA.

Friday Night through Saturday: VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

Small craft advisories continue on outer waters tonight through
tonight, with SW winds 20 to 25 kt and seas building to around
4-5 ft.

Today into tonight, SW to WSW winds 15-20 kt, isolated gusts to
25 kt are expected with seas rising to around 4-6 ft on the
southern and eastern outer waters and around 3 ft or less
nearshore.

Wednesday, SW winds 10-15 kt, gust to 20 kt with seas 3-4 ft on
the southern and eastern outer waters and around 2 ft or less
nearshore.

Outlook /Wednesday Night through Saturday/...

Wednesday Night through Thursday Night: Winds less than 25 kt.
Chance of rain showers.

Friday: Winds less than 25 kt. Slight chance of rain showers.

Friday Night through Saturday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 5 AM EDT Wednesday for ANZ250-
     254>256.

&&

$$

SYNOPSIS...BW/Dooley
NEAR TERM...Dooley
SHORT TERM...Dooley
LONG TERM...BW
AVIATION...BW/Dooley
MARINE...BW/Dooley