186
FXUS61 KBOX 140745
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
345 AM EDT Fri Jun 14 2024

.SYNOPSIS...
Warm and muggy Friday with dewpoints in the middle 60s.
Scattered severe thunderstorms possible north and west of
interstate 95 with the passage of a cold front this afternoon
and evening. Canadian high pressure will provide a comfortable
Father`s Day weekend along with dry conditions. Turning
unseasonably hot next week as an anomolous mid-level ridge
develops across the eastern third of the country. Prolonged
period of heat and humidly could linger well into the end of
next week.

&&

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

Key Points

* Warm and muggy start to the day
* Scattered severe thunderstorms NW of I-95

Friday will be a warm and humid day with temperatures quickly rising
into the mid to upper 80s and dew points reaching the mid to upper
60s. This will help set the stage for scattered severe thunderstorms
as a potent shortwave trough and cold front drops SE across the
region in the afternoon.  As the cold front moves through, a very
narrow corridor of instability will be set up across western MA and
CT. There continues to be some disagreement among the hi-res HREF
guidance on how much instability will be available mainly due to
timing differences on convective development. HREF mean shows near
1000 J/kg of SBCAPE with the 90th percentile showing around 2000
J/kg. With deep layer shear approaching 30-40 knots, the environment
will be supportive of organized clusters of severe thunderstorms.
Initiation remains a bit uncertain with some members of the
HREF initiating storms shortly after 12pm, while others holding
off as late as 4pm. Tend to favor a later start time as the
better forcing and height falls from the shortwave don`t arrive
until the late afternoon. Storms likely initiate off the high
terrain in Western MA/CT and southern VT then move ESE through
the afternoon. Storms should quickly weaken as the approach
eastern MA and RI as they run into a more stable environment
with less instability and shear. The severe threat at this time
looks highest north and west of the I-95 corridor as highlighted
by the SPC slight risk.

Severe threats:

The primary severe threat will be strong to damaging winds with
steep low level lapse rates, DCAPE values near 700 J/kg, and
linear storm mode promoting straight line winds. The hail threat
has increased since yesterday due to models steepening mid
level lapse rates to 6-7 C/km. The freezing level still remains
above 10kft which should help to melt most hail before reaching
the surface. The tornado threat remains very low at this time
with 0-3km SRH around 100 m/s and the Sig Tor parameter well
less then 1.0. Storm mode also appears to favor linear clusters
with upscale growth. Not completely out of the question that a
discreet supercell could form at initiation before merging with
other cells into line segments or clusters.

Heavy Rain Threat:

Although the storms will be progressive with little to no training
expected, PWATS will be increasing into the 1.5-1.6 inches. CAPE
profiles have become more fat and supportive of hail over the last
24 hours due to steepening mid level lapse rates. Warm cloud depths
have also decreased to 8000ft. Despite these less favorable changes
in the environmental parameters, the HREF 3hr PMM does still
highlights a small area in western MA and CT with 10% probs for
greater then 3 inches of rain in 3 hours. This could lead to areas
of street and poor drainage flooding along with isolated instances
of flash flooding.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...

Tonight

Thunderstorms quickly weaken into showers as they move east into
less favorable environment and lose support from daytime heating.
The shortwave axis crosses through the region overnight which
will prolong the rain for eastern MA before tapering off by
morning. Overnight lows stay on the warm side in the low 60s
with overcast skies and rain.

Tomorrow

Shortwave moves offshore with rising heights and high pressure
beginning to build in for the weekend. There may be some
lingering light showers in the morning in eastern MA, otherwise
mainly dry conditions with clearing skies in the afternoon.
Winds turn northerly advecting in cooler air for Saturday with
highs only in the mid to upper 70s. Humidity will also be
noticeably lower with dewpoints dropping into the 50s and even
the 40s across the western interior.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Highlights:

* A few showers possible Saturday morning, otherwise a dry and
  comfortable Father`s Day weekend.

* Seasonably warm on Monday, becoming hot and humid Tuesday through
  the end of next week with heat indicies potentially reaching
  between 95F and 104F.

* Early summer heat could challenge daily record high temperatures.


Father`s Day Weekend...

Few showers linger Saturday morning, mainly across southeastern
Massachusetts and Rhode Island as a mid-level trough moves east and
away from the region. By no means a washout for Saturday, PWATs fall
dramatically as Canadian high pressure moves into the area. This
yields a comfortable air mass, dewpoints fall from the 50s into the
40s! As for highs, low to mid 70s near the coast and upper 70s to
low 80s inland. Overnight into Sunday morning will be cooler, given
the dry atmosphere and weaker wind fields, should have effective
radiational cooling for many locations, thus have deviated away from
the NBM and favored the cooler MAV and MET blend. Areas like KORE
could experience morning lows in the low 40s! Elsewhere, low
temperatures are expected to drop to the upper 40s and low 50s along
the coast, the exception would be Boston, where lows are generally
in the mid 50s. Comfortable conditions follow on Father`s Day, with
mainly sunny conditions thanks to high pressure, low humidity values
and highs in the mid 70s to 80 degrees.

Next Week...

As advertised, we continue to expect well above normal temperatures
heading into next week. Starting Monday, mid-level high pressure
should be located over the southeast, leading to increasing mid-
level heights across the northeast. Could be a rouge shower Monday
afternoon with shortwave energy passing to our north, albeit a low
chance at this point. Highs warm into the low and middle 80s.

Tuesday into Thursday, the mid-level high expands into the northeast
with continued signals this will be an anomolous event. NAEFS
ensemble situation table indicates the 500mb heights and surface
temperatures could exceed forecast model climatological reference
points, in addition to PWATs nearing 97th to 99th percentile!

So, hot and humid conditions are expected with peak intensity around
Wednesday and Thursday. Given this is still a week away, there is
still time to iron out off the wrinkles/details. Additionally, there
are high probabilites, greater than 60 percent, that highs could
exceed 90 degrees across northern Connecticut, the majority of
Massachusetts (away from the southeastern portion of the state, Cape
Cod, and the Island), and northern Rhode Island starting Tuesday,
with the peak Wednesday, Thursday, and Friday. It is not out of the
question a few spots could reach 100F from Wednesday to Friday.
There are low probabilities on DESI, around 20 to 40 percent, for
areas such as the northern Connecticut River Valley and Merrimack
Valley. Likely will challenge daily record highs, see the climate
section for those details.

This period appear more dry than not, but with a juiced up atmosphere
and a few bouts of shortwave energy passing through, can`t rule out
pop-up showers during this period as well.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:

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

Today: Moderate Confidence

VFR with gusty SW winds to start today. Still some uncertainty
with how thunderstorms evolve today with some guidance showing
weak thunderstorms developing by 16 to 17z and moving east.
Higher confidence in thunderstorms to develop around 19 to 20z
over the Berkshires and begin moving east through the evening.
The highest confidence in thunderstorms is at the BDL, BAF, and
ORH between 20-23z. Further east, still some uncertainty on how
well thunderstorms will hold together for BED, BOS, and PVD
between 22-02z. FMH, HYA, and ACK should only see rain showers
but not out of the question for embedded thunder after 00z.

Tonight: Moderate Confidence

Showers begin to taper off after 00z in the west and 06z in the
east. MVFR/IFR possible across eastern terminals.

Tomorrow:

VFR with northerly winds at 10-15 knots.


KBOS TAF...Moderate confidence in TAF.

VFR with gusty SW winds to start today. Low chance for a shower
or weak thunderstorm between 17z-20z, otherwise the main event
thunderstorms shouldn`t arrive until 21 to 22z and could last
to 01 to 02z. Light rain showers continue behind the
thunderstorms through about 06z before tapering off.


KBDL TAF...High confidence in TAF.

VFR with gusty SW winds to start today. Strong thunderstorms are
likely starting 20/21z through about 23z/00z.


Outlook /Saturday Night through Tuesday/...

Saturday Night through Sunday Night: VFR.

Monday through Tuesday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today:

Increasing SW winds gusting up to 25 knots. A cold front will
sweep across the waters this evening. Thunderstorms will form
along this cold front inland this afternoon and weaken as they
approach the waters. A couple storms could still reach the
waters and bring strong wind gusts and lightning near the
coastal waters this evening. Seas 2-4 feet.

Tonight:

Steady light to moderate rain with embedded thunder possible.
Winds shift WNW and decrease to 5-10 knots overnight. Seas 2-3
feet.

Tomorrow:

Rain tapers off in the morning with clearing conditions in the
afternoon. Winds turn north and gust 15 to 20mph. Seas 2-4 feet.

Outlook /Saturday Night through Tuesday/...

Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.

Sunday: Winds less than 25 kt. Seas locally approaching 5 ft.

Sunday Night through Tuesday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 AM this morning to 8 PM EDT this
     evening for ANZ230>237-251.
     Small Craft Advisory from 11 AM this morning to 11 PM EDT this
     evening for ANZ250-254.

&&

$$

SYNOPSIS...Frank/KP
NEAR TERM...KP
SHORT TERM...KP
LONG TERM...TD
AVIATION...Frank/KP
MARINE...Frank/KP