052
FXUS61 KBOX 100215
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1015 PM EDT Sun Jun 9 2024

.SYNOPSIS...
Rain showers move offshore later this afternoon with decreasing
cloud cover from west to east. Brief dry weather early tonight
then gives way to increasing cloud cover and perhaps a few
showers overnight as a disturbance moves through. Variable
amounts of cloud cover are expected on Monday with seasonable
temperatures. Still unsettled into Tuesday with hit or miss
showers, then a warming and drying trend Wednesday will lead to
increasing heat and humidity for the end of the week. Another
frontal system will bring increasing risk for showers and
thunderstorms Friday.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
1015 PM update...

Mid level shortwave moving east from central NY and will sweep
across SNE after midnight then offshore by daybreak. Convective
showers ahead of the shortwave are moving into eastern NY and NE
PA but showers are diminishing somewhat as they move east. 00z
HRRR and 3km NAM have backed off on shower activity across SNE,
but area of deeper moisture tied to this shortwave moves
through so can`t rule out an isolated shower overnight. Will
see an increase in mid level clouds followed by clearing toward
daybreak.

Previous discussion...

Partial cloudiness should be the rule for at least the first
portion of the evening. However we should see increased cloud
cover from west to east as the shortwave disturbance near Lake
Huron rotates around and spreads its moisture eastward. A
significant enough majority (essentially excluding the HRRR/RAP)
carry at least isolated showers during the later-evening and
overnight hrs, with the NAM, its downscaled 3-km version, and
FV3 WRF being the most bullish. Lapse rates in the 700-500 mb
layer increase to around 6.5- 7 C/km too. So did carry a 20% PoP
mention for isolated showers, which should pass into the
eastern waters by daybreak. Given the history of lightning
upstream and the steepening lapse rates am a little leery about
leaving mention of thunder out, but there isn`t any instability
to speak of, even using a most-unstable parcel. SPC HREF 1-hour
probabilities of thunder are also zero too. These showers should
be passing and not result in any significant rain totals.
Lowering dewpoints tonight too with the more westerly flow, with
lows in the 50s.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
245 PM Update:

Monday:

Shortwave disturbance aloft will have moved offshore early Mon
morning. That should translate to weak shortwave ridging developing
into the morning hrs and at least starting the day with more sun
than cloud cover. However cooling temperatures aloft combined with
shallow instability from diurnal heating should bring increasing
cloud cover towards a scattered to broken cumulus look, greater
cloud cover north and west. There could be a spotty, hit-or-miss
shower underneath these with slight chance PoP mention but expect
dry weather to govern more often than not. Will have WNW breezes
around 10 kt, and that should keep the eastern MA and south coast
sea breezes just offshore. All in all, not a bad day with highs in
the 70s, boosted by downsloping effects on W/WNW flow. If any
showers do develop, it could get pretty cool in/near these showers
given progged well mixed PBL and low wet-bulb zero heights.

Monday Night:

Any hit-or-miss showers diminish in coverage to dry early Monday
evening (after sundown). However longwave troughing continues to sag
southward into the evening, with another rise in lower-level RH
especially in interior western MA/CT. Should see more of a variable
cloudiness look with much less east and considerably more over
western MA/CT for Mon night. Could trend rather cool in the interior
with lows in the upper 40s to lower to mid 50s, and mid to upper 50s
for eastern MA and RI.

&&

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

* There remains low chances for a few widely sct`d showers both
  Tuesday and Wednesday. A better chance for rain and thunder late
  this week with the passage of a cold front.

* Drying out for Father`s Day Weekend with surface high pressure
  returning, though showers could linger into the first-half of
  Saturday, depending on the timing of the cold front.

* Seasonable temperatures Tuesday with warming temperatures
  Wednesday into Friday, along with increased humidity late this
  week.

A few chances for rain for the upcoming week, albeit the chances are
on the lower side for both Tuesday and Wednesday. Higher probability
for active weather and storms Friday/early Saturday timeframe. That
said, there is some uncertainty with the exact timing of the arrival
of the cold front. Synoptically, an anomalous positively tilted mid-
level trough remains over the northeast with the mid-level low over
northeast Maine. Cyclonic flow promotes diurnal clouds and a few pop-
up showers. Think these are widely sct`d given PWATs are near-normal
to slightly below. Plus, BUFKIT soundings shows shallow pockets of
saturation aloft. Tuesday features a higher probability for rain as
there is better forcing from mid-level shortwave energy traversing
through and generally lower ceilings. With that said, did adjust the
POPs to show higher, `Chance` values on Tuesday, mainly in the
higher terrain of northern and western Massachusetts, with the
coastal plain in `Slight Chance` POPs. And as for Wednesday did cap
the POPs at `Slight Chance` with coordination of neighboring WFOs.
Drier conditions expected on Thursday with continued height rises
with the departure of the mid-level trough.

Friday could be interesting, as mentioned the past couple of shifts
a cold front moves across the northeast and could bring a round of
showers and thunderstorms. While it`s too early to get into the fine
details, there are signs that storms could have potential to be on
the stronger side. Global guidance suggests there would be enough
instability, modest jet dynamics, and high PWATs. The CSU machine
learning probs have most/if not all of the northeast within a 5%
prob for severe weather, 12z Friday to 12z Saturday. As always, the
timing of the cold front remains the burning question. If the front
arrives too late into Friday evening or overnight, that may squash
any strong storms. Pounds of time to keep an eye on this!

Behind the departing cold front, a drier airmass is ushered into
southern New England for Father`s Day Weekend. PWATs are falling to
less than 45% of normal. And surface high pressure builds in from the
west... This should promote a dry and settled weekend. The caveat,
it will all come down to, if the front comes in later Friday or
predawn on Saturday, if so, showers could linger into early
Saturday.

Now, those seeking summer warmth, it`s coming. There is a gradual
warm starting Tuesday, highs are in the middle and upper 70s, and
upper 70s to lower 80s on Wednesday. By Thursday, highs are in the
80s, with many locations topping out in the middle if not upper 80s
away from the immediate coast. Humidity is on the rise, though these
three days are bearable, with dewpoints in the upper 50s and lower
60s, not overly humid, but noticeable. Friday is quite warm, highs
are still in the middle and upper 80s, but it is not out of the
question a location or two in the Merrimack and CT Valleys touch 90
degrees. Once again, this will depend on how quick or not so quick
the cold front arrives. Dewpoints are noticeably higher Friday as
well, lower and middle 60s. Thursday and Friday are likely the
warmest days of the upcoming week, highs are middle to upper 80s, a
few spots in the CT and Merrimack Valleys may reach 90 degrees. This
coming weekend, post frontal airmass, highs are in the upper 70s to
middle 80s along with lower dewpoints. Nightly lows are comfortable
in the 50s Tuesday night, while Wednesday night to Friday night are
in the low and middle 60s.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

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

00Z TAF Update:

Tonight: High confidence.

SCT-BKN VFR cloud bases, although cloud cover increases again
later tonight as another disturbance moves thru. Could be a hit
or miss -SHRA which could reduce visby down to MVFR levels at
worst, but should be mainly dry. Winds become SW/WSW tonight
around 4-8 kt, then shift back to W/WNW toward daybreak.

Monday and Monday Night: High confidence.

SCT-BKN VFR bases, perhaps a hit-or-miss -SHRA during the
daytime hrs but largely dry. NW winds around 10 kt with gusts
18-20 kt, with easing gusts after sundown and speeds under 10 kt
Monday evening.

KBOS TAF...High confidence. VFR. Winds SW around 6-10 kt; low
risk of -SHRA after 06z Mon. SCT-BKN VFR Mon with NW winds
around 7-10 kt; it looks as though sea breezes will remain
offshore.

KBDL TAF...High confidence. VFR. NW winds around 10 kt with
gusts to 20 kt. Another possible period of -SHRA after 01z Mon,
before trending SCT-BKN VFR for Mon.

Outlook /Tuesday through Friday/...

Tuesday: VFR. Slight chance SHRA.

Tuesday Night: VFR.

Wednesday: VFR. Slight chance SHRA.

Wednesday Night through Thursday Night: VFR.

Friday: VFR. Breezy. Slight chance SHRA, isolated TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

245 PM Update:

High confidence through Monday night.

Area of showers with 2-6 SM visby will continue to shift
offshore through early tonight. SW winds around 15-20 kt to then
shift to W/WNW late this afternoon into tonight, with
decreasing speeds to around 10-15 kt. Seas around 2-4 ft. Could
see another round of lighter rain showers toward early Mon AM
but not enough to restrict visbys.

Winds and seas to remain below SCA levels Mon and Mon night with
WNW winds around 15-20 kt and seas 3 ft or less.

Outlook /Tuesday through Friday/...

Tuesday through Thursday: Winds less than 25 kt.

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

Friday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain showers.

&&

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

&&

$$

SYNOPSIS...Loconto/Dooley
NEAR TERM...KJC/Loconto
SHORT TERM...Loconto
LONG TERM...Dooley
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley