810
FXUS61 KBOX 281941
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
341 PM EDT Fri Jun 28 2024

.SYNOPSIS...
Wonderful conditions with low humidity rest of Friday, still dry for
much of Saturday outside a couple hit or miss showers. A slow moving
frontal system brings two potential rounds of scattered showers &
thunderstorms...mainly Saturday night into early Sunday morning and
then perhaps again later Sunday into Sunday night. Drier weather
with seasonable temperatures and comfortable humidity levels returns
early next week as high pressure builds in from the west. This high
pressure system will slide east of the region late next week
allowing very warm and humid weather to return for the start of the
long Holiday Weekend.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...

A stunning afternoon and evening across New England due to surface
high pressure and mid-level height rises. The rest of today expect
mainly clear skies, comfortable temperatures in the 70s, along with
refreshing dew points in the 30s and 40s.

Clouds from a mid-level warm front approach from the west overnight
as seen already on satellite in far western New York. Good news, the
night is largely dry with a low chance light rain mainly in western
Massachusetts and northwestern Connecticut.

Winds are light and variable to start, but will become southerly
around or shortly after midnight, wind speeds between 5 to 10 mph.

Not as chilly tonight, low are generally in the middle 50s. Coastal
areas near 60F.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...

Surface warm front pushes through increasing humidity along with a
few nuisance showers and rumble of thunder, though most of the day
appears dry. Afternoon highs run a few degrees cooler than normal in
the upper 70s to 80F. WAA ushers in higher PWATs/dew points, with
dews returning to the low and middle 60s with PWATs around 1.5".
Though these values climb well over 2.0 inches Saturday night to
Sunday morning, which is impressive, per Sounding Climatology,
the daily max at CHH is 2.04". Plus, BUFKIT soundings indicate
the warm cloud layer is 10,000 FT to 12,000 FT - raises concerns
of heavy rains overnight and potential isolated flash flooding.


Steadiest rain arrives late, likely around 00z across the
western CWA getting to the Boston to Providence corridor closer
to 04z. Otherwise a mild night with lows only dipping into the
upper 60s to 70F.

In addition, there are fairly strong winds aloft, with a SW LLJ
increasing throughout the afternoon into the overnight hours. This
should promote a fairly consistent southwest wind with gusts
between 20 and 30 knots.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Highlights:

* Main concern is timing of showers & t-storms Sun/Sun night as well
  as assessing any severe weather & localized flooding potential

* Cooler/less humid Mon with seasonable temps Tue & Wed

* Warmer/Humid weather returns by Thu July 4th & into Holiday Weekend

Details...

Sunday and Sunday night...

Quite a complex forecast Sun into Sun night which we will break down
below. It appears that an initial round of scattered showers & t-
storms will be departing early Sun am in association with
shortwave/warm front. Otherwise...dry weather probably dominates the
region the rest of Sun morning into early afternoon. In
fact...southwest flow will result in a very warm and humid day.
Amount of solar insolation still somewhat uncertain...but thinking
there will be enough for highs in the upper 80s to near 90 away from
the south coast. A little bit of southwest breeze with gusts up to
25 mph. It also appears we may have an elevated risk of dangerous
rip currents on Sun especially near the south coast.

The main uncertainty revolves around the potential for scattered
showers & t-storms developing Sun PM from the approaching
shortwave/cold front. We should have moderate instability develop
with surface based Capes on the order of 1000 to 2000 J/KG. One
limiting factor will be poor mid level lapse rates...but 0 to 6 KM
shear values will be on the order of 40 to 50 knots which is quite
favorable. Timing of the front and other mesoscale processes will
ultimately determine the severe weather potential Sun PM. The CSU
Machine Learning guidance indicate some probs for severe weather
with the highest northwest of i-95. Appears the main threat will be
damaging wind gusts given steep low level lapse rates/strong jet
dynamics which is also supported by the CSU Machine learning
guidance. In addition...Pwats near 2 inches will support the
potential for torrential rainfall and a localized flood with any
thunderstorms.

Upcoming Work Week...

Significantly cooler and less humid air moves in behind the cold
front on Monday. High temps will only be in the upper 70s to near 80
with lowering humidity. Strong upper level trough/shortwave energy
should allow for plenty of CU and perhaps a few diurnally driven
showers...but the majority of the day will feature dry and pleasant
weather.

High pressure then builds into the region Tue and Wed bringing
dry/seasonable temperatures...but with tolerable humidity for this
time of year. Highs will mainly be in the 80s with the
warmer/slightly more humid day on Wed.

The high shifts east of the region by Thu, July 4th and into Fri.
This will result in very warm and humid weather returning. Low
confidence on timing any potential risk for scattered showers & t-
storms...but regardless plenty of dry weather expected over this
time too.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

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

Tonight... High confidence.

VFR and dry, increasing mid to high clouds pushing in from west
to east. Winds are south/southwest between 5 and 10 knots.

Tomorrow... High confidence.

VFR, low probability for a spot light shower and thunderstorm,
mainly during the afternoon. Then trending MVFR to perhaps IFR
conditions before 00z for western half of southern New England.

Winds increasing out of the south, speeds of 10 to 15 knots
during the afternoon with gusts of 20 to 25 knots.

Tomorrow Night... Moderate confidence in timing, higher
confidence in trends.

IFR/LIFR, may remain MVFR for outer Cape and Island terminals.
Rain and thunderstorms overnight with poor visibilites at times
less than 2SM within TSRA.

Gusty southwest winds 10 to 20 knots, gusts 25 to 30 knots.

KBOS TAF... High confidence in TAF.

VFR through the TAF period. Sea breeze, east to southeast,
through 03z and from there winds become south/southwest. For
Saturday, gusty south winds 10 to 15 knots and gusts 20 to 25
knots. While not in the TAF period, rain and embedded thunder is
possible after 02z/04z Sunday, which may continue through the
Sunday AM push.

KBDL TAF... High confidence in TAF.

VFR through the forecast. Light and variable winds this
afternoon will become south overnight around 5 to 8 knots. Winds
increasing Saturday between 15z and 20z, with speeds 12 to 16
knots with gusts 20 to 25 knots. Low chance for spot shower
during Saturday, but low confidence in areal coverage to put
into TAF, but widespread rain and embedded thunder is possible
late Saturday afternoon, have opt to use PROB30 between 22z and
00z to highlight this threat.

Outlook /Sunday through Wednesday/...

Sunday: Mainly MVFR, with local IFR possible. Breezy. Chance
SHRA, slight chance TSRA.

Sunday Night: Mainly VFR, with areas MVFR possible. Breezy.
Chance SHRA, isolated TSRA.

Monday: Mainly VFR, with areas MVFR possible. Breezy. Slight
chance SHRA.

Monday Night through Tuesday Night: VFR.

Wednesday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight through Saturday Night... High confidence.

Tranquil boating conditions this afternoon and evening with
surface high pressure. Light winds will become south overnight
with stronger gusts expected on Saturday. Increasing southerly
winds to 15-20 kts by the afternoon. Will have some 20-30 kt
gusts, seas building 3-6 ft. Have opt to issue a Small Craft
Advisory, going into effect for all waters Saturday afternoon
for the northeast zones, while the rest of the ocean waters by
Saturday evening. Have included Boston Harbor and Narragansett
Bay during the overnight hours as well. All waters will remain
under a Small Craft Advisory though at least Sunday evening.

Areas of rain and thunder arrive late Saturday night into Sunday
morning.

Outlook /Sunday through Wednesday/...

Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Seas up to 5 ft. Rain showers likely, slight
chance of thunderstorms.

Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers, slight chance of thunderstorms.

Monday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers.

Monday Night through Wednesday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from midnight Saturday night to 7 PM EDT
     Sunday for ANZ230-236.
     Small Craft Advisory from 8 PM Saturday to 7 PM EDT Sunday for
     ANZ231>235-237-254>256.
     Small Craft Advisory from noon Saturday to 7 PM EDT Sunday for
     ANZ250-251.

&&

$$

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