764
FXUS61 KBOX 241813
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
213 PM EDT Mon Jun 24 2024

.SYNOPSIS...
A disturbance aloft over the Northern Adirondacks moves
southeastward tonight, bringing evening cloudiness, northwest
breezes and a drier air mass to Southern New England. Warmer
temperatures then return for Tuesday but humidity levels remain
comfortable. Increasing humidity levels on Wednesday with the risk
for showers and thunderstorms, and some could become strong. Drier
and less humid to end the workweek, although summerlike warmth and
humidity return by this weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
145 PM Update:

Other than across Cape Cod where dewpoints remain in the upper 60s
to around 70 as westerly windshift still is working its way into the
Cape, further inland humidity levels are dropping. For the vast
majority of locations, dewpoints are falling into the mid 50s to
around 60, leading to a far more comfortable air mass than we`ve
experienced of late. From a bigger picture view, a rather potent
shortwave trough aloft circulating over the Northern Adirondacks in
NY is leading to an increasing coverage of puffy stratocumulus
cloudiness this afternoon in Southern New England. Radar is
picking up on either sprinkles or very light rain showers
dotting the Berkshires with the cooler pocket of air aloft tied
to the shortwave trough. This shortwave trough aloft will be the
main driver of our weather tonight.

So for tonight, shortwave disturbance aloft and its cool pocket
of air aloft will be moving through the interior Northeast and
offshore through midnight. The approach of this disturbance
should at least maintain cloud cover if not increase it a bit.
Think cloud cover should trend more partial to mostly cloudy. An
outside chance (20% or less) of a sprinkle or light shower as
the shortwave moves through. Am a little skeptical the coverage
will be as numerous as some of the high res models indicate with
drier air moving into the lowest hundred or so mb of
atmosphere. Carried a mention of isolated showers but with nil
QPF over northern and northeast portions of Southern New
England, but many areas however stay dry. Should also see more
northwesterly breezes for the evening and overnight, which will
continue to usher in lowering dewpoints and a more comfortable
air mass. Humidity levels should be low enough tonight to give
fans/ACs a break for more open-windows. Lows tnoight in the mid
50s to lower 60s, with mid 60s out over Cape Cod.

&&

.SHORT TERM /TUESDAY/...
4 AM update...

Tonight...

* Dry, cooler and comfortable humidity

Dry, cool NW flow across SNE in response to vertically closed low
over the Gulf of Maine. Derived mins from a blend of the cooler MOS
guidance and the milder NBM. Should be enough WNW pgrad to preclude
cooler MOS guidance from verifying, thus followed a blend, which
still yields cool temps, with lows in the upper 50s to lower 60s.

Tuesday...

Could be pick of the week, with dry NW flow continuing. However,
temps will be warming aloft as vertically stacked low over the Gulf
of ME exits into the Maritimes. 850 temps warm from +12C to +16C by
days end, along with 925 mb temps warming to +22C. These temps aloft
combined with WNW winds 10-15 mph shifting to WSW support highs of
85-90 Tue afternoon. Although, not humid with dew pts in the 50s.
Given dry column (PWATS ~0.75 inches) and dew pts in the 50s, not
expecting much if any clouds, hence full sun.

&&

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

* Hot and humid Wed with showers/t-storms Wed afternoon and night
* Showers may linger SE New Eng Thu AM, otherwise improving
  conditions
* Dry & seasonable Fri and Sat
* Humidity increases Sat night and Sun with risk of showers/t-storms

Wednesday into Thursday...

Next mid level trough and shortwave amplifies across the Gt Lakes
Wed before moving into northern New Eng Thu. Pre-frontal SW flow
will bring increasing temps and humidity with highs likely reaching
upper 80s to lower 90s away from the south coast, while dewpoints
increase to near 70. The heat and humidity will help to generate
modest instability beneath favorable mid level lapse rates from a
remnant EML. While we do expect scattered showers and t-storms to
develop in the afternoon, better chance will likely be during Wed
night when best height falls move into the region along with right
entrance region of upper jet at a time when diurnal instability will
be diminishing. So there is some uncertainty with severe weather
risk as peak forcing will not be lining up with peak diurnal
instability. Still have to monitor this closely as deep layer shear
will be increasing and it is possible we have a narrow window for
severe potential late Wed and Wed evening when instability and shear
overlap. It is interesting that CSU machine learning probs have
ramped up on severe wind potential for Wed-Wed evening. Heavy
rainfall will also be a concern Wed night as deep moisture axis
moves across the region with PWATs increasing to near 2 inches.

Cold front will be moving across SNE overnight Wed night and likely
stalling in the coastal plain on Thu. However, moisture axis will
shift to SE New Eng by 12z Thu with good drying moving in from the
west during the day. Showers may linger in SE New Eng during Thu
morning, otherwise expect improving conditions with increasing
sunshine developing from west to east. Highs will reach upper 70s to
mid 80s with decreasing humidity in the afternoon, especially
interior.

Friday and Saturday...

High pres builds across New Eng Fri which will bring sunshine and
somewhat cooler temps, especially along the coast as sea-breezes
develop. High pres moves offshore Sat with increasing SW flow
developing which will result in dewpoints increasing. Dry weather
should hang on for much of the day, but can`t rule out a few showers
in the afternoon.

Saturday night and Sunday...

Unsettled weather returns as next mid level trough approaches from
the Gt Lakes with moisture axis moving into SNE with 2+ inch PWATs.
Expect scattered showers and t-storms through Sunday as cold front
may be delayed until later Sun or Sun night. Rather humid conditions
likely Sun as 70+ dewpoints return.

&&

.AVIATION /18Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

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

18z TAF Update:

Through 00z Tuesday: High confidence.

SCT-OVC VFR bases 045-060. W to WNW winds 10-15 kt with gusts
20-25 kt for most, with SW to WSW winds around 10-12 kt for the
South Coast, Cape and Islands.

Tonight: High confidence.

BKN-OVC VFR bases 035-050 to start tonight, with an outside
chance (20% or less) of a sprinkle or light unrestricted shower
00z thru 04z but will leave out of the TAFs due to low prob. NW
to NNW winds around 12-15 kt with gusts low 20s kt range thru
midnight, then becoming NW around 8-12 kt, highest east.

Tuesday and Tuesday Night: High confidence.

VFR with increasing mid/high clouds arriving later Tue night.
NW winds 5-10 kt ease a bit and shift to W/WSW by aftn.

KBOS TAF...High confidence in TAF. VFR with WNW winds around
10-15 kt with gusts up to 25 kt today. Low (< 15%) chance of an
unrestricted-visby shower tonight with winds shifting to NW
around 15 kt overnight. Winds then shift back to WNW/W Tue AM with
decreasing speeds, becoming SW late in the day on Tue.

KBDL TAF...High confidence in TAF. VFR. W winds around 10-15 kt
become NW/N late this aftn and tonight at similar speeds. Winds
then shift early Tue to W and then SW later Tue aftn.

Outlook /Tuesday Night through Friday/...

Tuesday Night: VFR. Breezy.

Wednesday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA, slight chance TSRA.

Wednesday Night: Mainly MVFR, with local IFR possible. Breezy.
SHRA likely, isolated TSRA.

Thursday: Mainly VFR, with local MVFR possible. Slight chance
SHRA.

Thursday Night through Friday: VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

*** SCA remains in effect ***

Today...

Robust low level SW jet of 40-45 kt at 2 kft over Cape Cod and
Nantucket, slow exits offshore today. Therefore, SW winds surface
winds of 15-25 kt during the predawn hours, ease this afternoon and
shift to the WSW and then west late. Although, given the long wind
fetch, it will take sometime for seas to subside across the southern
RI/MA waters. Scattered showers and thunderstorms south of the
islands in the predawn hours, slowly moves offshore late this
morning.

Tonight...

Wind shift to the NW 15-20 knots. Seas continue to slowly subside.
Dry weather and good vsby.

Tuesday...

Low pressure over the Gulf of Maine exits into the maritimes. This
yields NW winds 10-15 kt in the AM, WSW in the afternoon. Dry
weather and good vsby prevail.

Outlook /Tuesday Night through Friday/...

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

Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain
showers.

Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas. Rain showers likely,
isolated thunderstorms.

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

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

Friday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Surf Advisory until 7 PM EDT this evening for MAZ020>024.
RI...High Surf Advisory until 7 PM EDT this evening for RIZ006>008.
MARINE...Small Craft Advisory until 3 AM EDT Tuesday for ANZ232>235-237.
     Small Craft Advisory until 3 PM EDT Tuesday for ANZ254>256.

&&

$$

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