429
FXUS61 KBOX 031104
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
704 AM EDT Mon Jun 3 2024

.SYNOPSIS...
Other than a spot shower, dry weather prevails Monday with
increasing sunshine late morning into the afternoon, along with
warm temperatures away from the coast, highs 80-85, 70s at the
shore. A back door cold front will usher in cooler weather
Monday night and Tuesday. Warmer weather returns Wednesday as
winds shift to the SSW, with highs 80-85 away from the coast. A
pattern change Wednesday night and Thursday will be accompanied
by widespread showers and possible downpours, along with
isolated thunderstorms at times. Not as wet Friday and this
weekend, with coverage of showers and thunderstorms more
isolated to widely scattered.

&&

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

7 AM update...

Not as cool as previous mornings, as blanket of mid level clouds
precluded temps from free falling overnight. In fact, Boston did
not fall below 70 degs last night. Thus, off to a milder start
and this will help temps peak to 80-85 away from the coastline
today. Cooler at the shore (70s) as seabreeze develops by late
morning. As mid level short wave exits offshore, clouds will
give way to increasing sunshine from late morning into the
afternoon. Previous forecast captures these details nicely,
therefore no changes with this forecast update. Earlier
discussion below.

====================================================================

Highlights:

* Another nice day ahead with mixture of sun and clouds. A backdoor
  cold front brings cooler temperatures as a modified marine air
  mass moves across southern New England this afternoon.

Yet another wonderful day with surface high pressure in control,
though there remains a very low chance of a spot shower with the
passage of weak shortwave energy from a mid-level low off the coast
of Nova Scotia. The newest guidance show PWATs fall to or below 0.8"
as the shortwave drops from north to south. Do think, if anything
this will add more mid-level clouds, 6-10k ft, expect a good mixture
of sun and clouds this afternoon.

Previous forecast showed the potential for a spot shower or two, but
newer guidance trended away, opt to remove any `slight chance`
showers from the forecast grids. There is a better chance tomorrow
afternoon for scattered showers and a rumble of thunder, more on
that in just a minute.

A more interesting feature is a backdoor cold front this afternoon
as a modified marine airmass moves from east to west across southern
New England. Highs along the eastern coast of Massachusetts achieve
maximum temperatures in the lower 70s, though 15-20 miles inland
temperatures will have enough time to warm into the upper 70s and
lower 80s, while the Connecticut River Valley should be able to warm
all day without the influence of this marine air and top off in the
middle 80s.

&&

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

Highlights:

* Increasing low level moisture should bring in areas of low clouds
  and perhaps fog to SE MA.

* Spot shower or thunderstorm possible Tuesday afternoon mainly
  across north/central and western Massachusetts and northwest
  Connecticut.

Tonight: Low clouds advect in off the water, leading to a cloudy
night with areas of fog possible along the coast. A dry night, but
any areas of locally dense fog could lead to light drizzle, if this
were to happen, think it could occur on the Cape and/or Islands, but
confidence in that occurring is moderate to low, and have left any
mention of that out of the forecast grids... If confidence increases
today, don`t be surprised if subsequent forecast updates include it.
Temperatures tonight are seasonable int he middle to upper 50s.

Tuesday: Areas of morning fog and stratus lift with the high June
sun angle, leads to a mainly sunny day. Diurnal cu develop during
the afternoon with steep low level lapse rates, but mid-level lapse
rates remain less than ideal. Still, there remains chance of pop-up
showers and thunderstorms, they should remain widely scattered in
nature from the northern Worcester Hills to the Berkshires. Not
expecting anything severe. While not as warm as the previous days,
highs still top out in the middle and upper 70s, with the
Connecticut River Valley in the low 80s. A sea breeze sets up in
eastern Massachusetts and southern Rhode Island, leading to lower
than normal temperatures in the upper 60s and lower 70s. Dewpoints
are on the rise and climb into the upper 50s, while not overly
humid, after several days of rather low humidity - the humidity will
be noticeable.

&&

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

Highlights:

* Generally dry Wed, warm temps, 80-85 away from the coast

* Widespread showers with embedded heavy downpours and isolated
  thunderstorms Wed night into Thu, along with turning more humid.
  Temps seasonable to slightly cooler than normal given clouds/rain.

* Not as wet Fri into the weekend, with less areal coverage of
  showers and embedded thunderstorm.

Precipitation...

Above normal heights and anticyclonic flow into New England persist
thru Wed. Hence, mainly dry weather prevails, although a low risk
for a few showers/thunderstorms across western MA/CT as cyclonic
flow approaches. However, by Wed night and especially into Thu,
below normal heights advects into the Great Lakes with cyclonic flow
into New England. This pattern change is accompanied by a slug of
PWATs about 180% of normal. This combination of anomalous moisture
coupled with cyclonic flow and an accompanying surface wave, should
yield widespread showers Wed night into Thu. Instability is lacking
so not expecting widespread convection, but isolated storms are
possible, which will enhance rainfall potential. Main hazard will be
heavy downpours given anomalous moisture coupled with modest jet
dynamics. Ensembles indicate low probabilities for 1+ inches Wed
night into Thu, but zero probabilities of 2+ inches. This seems
reasonable given how progressive pattern becomes. Mid/upper low and
associated cold pool lingers across the Great Lakes Fri,Sat and Sun.
This proximity to SNE will yield lots of diurnal clouds each day
along with the risk for scattered diurnal convection, but by no means
a washout, with many hours of dry weather.

Temperatures...

Return flow Wed yields low level WAA with 925 mb temps warming to
+18C to +20C. This will support a warm day with highs in the low to
mid 80s. Humidity remains in check with dew pts 55-60. Clouds and
widespread showers Thu hold temps in the 70s. Although, it will be
humid Thu with dew pts in the 60s. Despite cold pool aloft Friday,
drier weather than Thu helps boost highs to 75-80. Below normal
heights/cold pool aloft lingers across the Great Lakes into New
England next weekend. This will yield mild days with highs in the
70s and cool nights with lows in the 50s.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

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

12z TAF Update: no change from previous forecast. VFR cloud
bases, dry weather and light and variable winds, except becoming
NE and then east along the coast late morning into the
afternoon. Earlier discussion below.

===================================================================

Through 12z: High confidence.

Mainly VFR, though did include a TEMPO mention of MVFR BR over
the Cape airports toward early AM due to possible marine fog.
Winds light southerly to start, though will begin a gradual
clockwise turn to N for most, with NE winds developing along the
immediate eastern MA coast towards daybreak.

Today... High confidence.

VFR and dry. Back door cold front will turn winds ENE in the
morning eventually turning ESE in the afternoon.

Tonight... Moderate confidence.

Continued onshore flow could begin to bring in MVFR/IFR CIGS
for coastal terminals. Winds remain ENE/ESE

Tuesday... Moderate confidence.

VFR. Widely scattered showers/thunder possible develop after
15z/18z mainly across western MA/northern CT. Winds are S, while
eastern MA winds are ESE.

KBOS TAF... High confidence.

VFR. Winds turn slowly to the north through daybreak and become
ENE around mid-morning (~13z-15z) as a back door cold front
passes through. Winds slowly trend ESE tomorrow afternoon. Could
see lower CIGS move in late tonight as near surface moisture
increase due to onshore flow.

KBDL TAF... High confidence.

VFR. Light SSW winds, though will trend ENE/E today.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Wednesday: VFR.

Wednesday Night: Mainly VFR, with local IFR possible. Chance
SHRA.

Thursday: MVFR/IFR conditions possible. Breezy. SHRA likely,
isolated TSRA.

Thursday Night: Mainly VFR, with areas IFR possible. Chance
SHRA.

Friday: VFR. Chance SHRA, isolated TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Tuesday...

Surface high pressure continues to be the dominant weather
feature. A backdoor cold front will bring ENE winds to all the
waters today and tonight, wind shifts to the ESE across the
eastern waters on Tuesday while southern waters are more SSE.
Areas of low stratus and fog are possible overnight into early
Tuesday, leading to poor visibilities. Winds and seas continue
to remain below advisory criteria, wind speeds are 10 to 15
knots today, and 5 to 10 knots tonight into Tuesday. Waves
during this period are 1-2 ft.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Wednesday: Winds less than 25 kt.

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

Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers, isolated thunderstorms.

Thursday Night through Friday: Winds less than 25 kt. Areas of
seas approaching 5 ft. Chance of rain showers.

&&

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

&&

$$

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