697
FXUS61 KBOX 121006
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
606 AM EDT Wed Jun 12 2024

.SYNOPSIS...

Partly to mostly cloudy again today with scattered showers
mainly in eastern Massachusetts. Dry and warm tomorrow with mostly
sunny skies with humidity returning by Friday. An approaching cold
front will bring scattered showers and thunderstorms Friday
afternoon and evening...a few of which may become strong to severe.
High pressure builds in for the weekend bringing beautiful weather
with cool nights and mild days. Warming trend begins next week with
the potential of excessive heat and humidity in the Tuesday through
Thursday timeframe of next week.

&&

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

605 AM Update...

* Diurnal Clouds with a few spot showers esp eastern MA
* Highs middle-upper 70s with lower 70s on the coast

Previous forecast remains on track. Upper level closed low
begins to move NE, but the region remains under cyclonic flow
for much of the day. Today will ultimately be very similar to
yesterday with diurnal cumulus forming in the mid to late
morning due to the cold pool aloft allowing for the convective
temp to be around 70F again. This will hold temps in the low to
mid 70s, with upper 70s in the CT river valley. Shower chances
today are highest in eastern MA due to slightly higher dewpoints
near 60F and convergence along the sea breeze front with a
westerly winds. Further west, weak ridging begins to move in
suppressing shower activity. A 700mb warm layer will keep
showers light and make it difficult to reach -10C isotherm and
produce thunder. As for timing of these showers, the best chance
looks to be after 2pm and ending around sunset.

&&

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

Tonight:

A weak shortwave moving through the zonal flow could allow for weak
showers to linger past sunset, otherwise mainly dry. Weak ridge
moves in quickly behind the shortwave overnight allowing for skies
to begin to clear. Overnight lows drop into the mid to upper 50s
with light and variable winds.

Tomorrow:

Southwest flow and WAA begins to kick in for thursday allowing for
850mb temps to climb to +15C. With much warmer temps aloft, the
convective temp jumps into the mid 80s across the region, meaning
the diurnal cumulus will not be as widespread as the past two days.
With mostly sunny skies and WAA, temperatures should be able to
reach the mid to upper 80s. Winds will become gusty near 20mph in
the afternoon with steep low level lapse rates and mixing potential
up to 750mb.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...

Key Points...

* Warm & Humid Fri with scattered strong to severe t-storms possible
* Beautiful this weekend with cool nights/mild days & low Humidity
* Excessive Heat & Humidity Possible next Tue/Wed/Thu

Details...

Thursday night...

Shortwave trough moving across the Great Lakes will allow for a
southerly flow of air and 60+ dewpoints moving into the region.
While dry weather should prevail increasing low level moisture will
result in a mild night with low temps mainly in the middle 60s.

Friday...

A rather warm & humid day is on tap for Friday. Shortwave
trough/cold front approaches from the west allowing for a southwest
flow of very warm & humid air into the region. The amount of solar
insolation remains to be seen as there is uncertainty on if/how
extensive any low cloud development ends up being. Thinking highs
should still reach well into the 80s with a shot at 90 if enough
sunshine is realized. Dewpoints in the middle to upper 60s will
result in a rather humid day too.

The main concern will be the potential for scattered strong to
severe t-storms Friday afternoon and/or evening with the approaching
shortwave/cold front. Specific timing and amount of instability that
are generated remain uncertain at this time. That being said...SPC
SREF is indicating modest probabilities that MUCapes will exceed
1000+ J/KG. This combined with the approaching shortwave energy
should increase 0-6 KM Shear on the order of 40 to 50 knots. Appears
low level lapse rates are rather steep...which would support the
primary risk being locally strong to damaging wind gusts. The latest
CSU Machine learning probs do indicate some probs for severe wind
and even some low probs for hail. Given all the ingredients
mentioned above this seems reasonable. A lot of mesoscale factors
that still need to be considered...but certainly the potential
exists for scattered strong to severe t-storms Fri afternoon and
evening. The other issue will be the potential for heavy rain &
localized street flooding. Pwats on the order of 1.5-2" support
torrential rainfall possible...so localized flooding will be a
concern if there is any training.

This Weekend...

Large high pressure builds in from the northwest this weekend behind
Friday/s cold frontal passage. This will bring us a beautiful
weekend with cool nights/mild days and low humidity. Highs should
mainly be in the 70s to near 80. Good radiational cooling and a dry
airmass in place will allow for cool nights...especially Sat night
when many outlying locations will probably bottom out in the 40s!

Next Week...

High pressure moves east of the region as a strong upper level ridge
builds northward into southern New England. In response, a warming
trend begins on Monday. The concern then shifts to the potential for
excessive heat & humidity in the Tue/Wed/Thu timeframe. There has
been a strong signal amongst all the model guidance the last few
days. In fact...the EPS situational awareness table indicates
parameters outside the models climatology which is signal for the
potential of a highly anomalous event. There are fairly high probs
of temps reaching well into the 90s for at least 1-2 days and
perhaps flirting with 100 degrees in some spots. Whether this comes
to fruition remains to be seen...but the potential for highly
anomalous heat for late June standards. Heat Indices of 95-100+
degrees are possible.

&&

.AVIATION /10Z WEDNESDAY THROUGH SUNDAY/...

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. Light west winds with localized sea breezes this morning on
the immediate coast. A few spot showers later today especially
in eastern MA in the vicinity of the coastal front.

Tonight: High Confidence

VFR. light and variable winds.

Tomorrow: High Confidence

VFR. Increasing WSW winds.

KBOS TAF...High confidence in TAF.

VFR. Sea breeze should develop by 12-13z.

KBDL TAF...High confidence in TAF.

VFR. Light west winds.

Outlook /Thursday Night through Sunday/...

Thursday Night: VFR. Breezy.

Friday: Mainly VFR, with areas MVFR possible. Breezy. Chance
SHRA, chance TSRA.

Friday Night: Mainly VFR, with areas MVFR possible. Chance
SHRA, slight chance TSRA.

Saturday: VFR. Breezy.

Saturday Night through Sunday: VFR.

&&

.MARINE...

Forecaster Confidence Levels:

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

Today:

Showers should remain inland today but could meander out over
the near shore water. Winds turn WSW at 10 knots in the
afternoon. Seas 1-2 feet.

Tonight:

Calm conditions with continued WSW winds near 10 knots at seas
1-2 feet.

Tomorrow:

Increasing SW winds gusting to 20 knots. Seas increase to 2-4
feet.


Outlook /Thursday Night through Sunday/...

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

Friday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft. Chance of rain showers, isolated
thunderstorms.

Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Rain showers likely, slight chance of thunderstorms.

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

Saturday Night through Sunday: Winds less than 25 kt.

&&

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

&&

$$

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