527
FXUS61 KBOX 191936
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
336 PM EDT Sun May 19 2024

.SYNOPSIS...
The coastal storm that has brought low clouds, drizzle and cool
northeast winds to RI and eastern MA, finally begins to exit out to
sea tonight. This gives way to a significant pattern shift to
drier and warmer weather beginning Monday. Very warm temperatures
are expected on Tuesday and Wednesday, with temperatures
reaching into the 80s, with an outside chance a few locations
see 90 degrees on Wednesday. Humidity levels will be on the low
side accompanying that midweek warmth, hence, a somewhat dry
heat. A cold front arrives on Thursday with the potential for
showers and thunderstorms. A more seasonable air mass then
filters in for late in the week into at least the early part of
Memorial Day Weekend.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
3 PM Update:

Low level moist onshore jet continues to deliver overcast
conditions and some spotty drizzle across RI and eastern MA,
including Cape Cod and the Islands. Meanwhile, breaks in the
overcast are occurring across CT into MA, eastward into the
Worcester Hills. Temps are responding to the strong May
sunshine, with temps warming through the 60s there and a few low
70s, including 71 at BDL currently. Meanwhile, short wave
energy traversing southward from the ME coast will continue to
delay height rises from advancing eastward today. This also
results in a nearly stationary low level ENE jet into eastern MA
and RI, with the low level jet slowly shifting southward
overnight, along with ridge of high pressure advecting south
into SNE.

Thus, drier trends overnight. However, low level moisture will
likely remained trapped beneath the subsidence inversion from
the surface ridge building southward. Hence, low clouds will
remain stubborn across RI and eastern MA tonight and likely
drifting back into CT and western/central MA, along with patchy
fog possible. This low level moisture will yield seasonably
cool temps overnight, with lows in the upper 40s and lower 50s.
Although, it will feel cooler with northeast winds 15-25 mph,
highest over southeast MA and RI, slowly slackening tonight as
the surface ridge builds southward.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
3 PM update...

* Big improvement, more sunshine & warmer temperatures
* Low 80s possible CT River Valley, including Hartford/Springfield

Monday...

Once short wave energy exits the eastern MA coast tonight, this
allows height rises to advect Monday across the region from west to
east and more importantly, low level jet easing and moving offshore.
This ridging and associated subsidence will allow strong May
sunshine to erode low level moisture/clouds and possible patchy fog
Monday morning and give way to at least partial afternoon sunshine
to the entire region. 12z models have trended warmer and this seems
reasonable given the height rises and morning clouds giving way to at
least partial late May sunshine. 850 mb temps increase to about +12C
and 925 mb temps warm to +18C to +20C western MA, to +13C across
southeast MA. This will support highs in the low 80s across western
MA/CT, with much of the region seeing highs in the 70s and as far
southeast into the I-95 corridor of MA/RI. With surface ridge over
the area, afternoon seabreezes will develop and cap highs in the 60s
for the coastline, possibly only into the upper 50s for the outer
Cape and Nantucket.

Monday night...

Deep layer ridge over SNE will provide dry weather. Light winds and
dew pts slightly above normal (low 50s), may yield patchy fog. This
will also result in mild overnight temps, with lows 50-55.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...

No big changes here, a warming trend continues Tuesday and Wednesday
with the chance for this summer-like warmth to continue on Thursday.
A cold front moves across the region on Thursday, perhaps bringing a
few stronger storms. Mixed signal heading into next weekend as the
deterministic guidance remains split over a dry or semi-wet weekend.

An anomolously warm air mass, driven by a modest mid-level ridge, is
expected to linger over much of New England into Thursday, leading
to well above normal surface temperatures. Global guidance
suggests 850mb temperatures are +6C to +11C above what is normal
over the course of those three days. The ridge does break down
late Thursday into Friday a mid-level trough swings through.

Tuesday afternoon there are high probabilities, greater than
80% for temperatures AOA 85 degrees, locations like Hartford,
Springfield, Worcester, and Lowell. Many spots across the
interior top out between 85F-89F, while closer to the coast a
southwest wind keeps locations south of
Providence/Taunton/Plymouth in the 70s, though the immediate
coastline in the upper 60s. Wednesday looks to be the warmest
day with a large portion of northern Connecticut, northern Rhode
Island, and much of Massachusetts (outside of southeast MA)
with greater than 80% probabilities of afternoon temperatures
AOA 85 degrees. It is not out of the question we have a few
spots pushing 90 degrees, places in the Merrimack and CT River
Valley have a greater than 70% chance. While less likely, there
are even low probabilities of temperatures at or above 95F,
around 40% in the Merrimack Valley. Thursday, the maximum
temperatures will really depend on what time a cold front moves
through and how much cold cover develops. Given the
uncertainties, continues with NBM guidance, highs likely reach
back into the middle 80s away from the coast. Temperatures
turning more seasonable with highs in the 70 for Friday into
next weekend.

Much of this week is dry, the mid-level ridge does support a drier
pattern. Not out of the question there could be a rouge afternoon
shower/thunderstorm mainly areas northwest Massachusetts, but
the better chance for showers is Thursday. Guidance is in pretty
fair agreement a cold front moves across the region with the
potential for thunderstorms - whether or not they are severe is
still to be seen, but there are signs that the atmosphere could
be favorable with modest CAPE, 1500 J/kg and effective shear of
40 kts. Based off the previous deterministic run, the CSU
machine learning have 5% to 15% of severe weather, something to
monitor as we head into this week. Drying out on Friday, but
there remains uncertainty with this upcoming weekend whether or
not we see rain or not.

&&

.AVIATION /20Z SUNDAY 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...

Improving cigs to MVFR continue to spread from west to east across
CT and MA into the Worcester Hills, RI and even into parts of
southeast MA. Some uncertainty how much farther eastward this
progresses before sunset. Radar still picking up some spotty drizzle
across southeast MA into RI. This should slowly shift south through
00z. NE winds 10-15 kt with gusts up to 25 kt across Cape Cod and
the islands.

After 00z...

Decreasing trends with IFR (possibly LIFR) cigs and MVFR vsbys in fog
drifting and developing westward from the coastline into the
interior overnight. Any areas of drizzle during the evening should
come to an end after midnight. NE winds 10-15 kt with gusts up to 20
kt in the evening across southeast MA, will slacken overnight.

Monday...

IFR/LIFR cigs with mainly MVFR vsbys in fog early, will slowly
improve to VFR all terminals, but obviously delayed until the
afternoon or late in the day across Cape Cod and the Islands. Light
NE winds become east and then southeast late in the day.

Monday night...

VFR but MVFR vsbys developing in patchy fog.

KBOS TAF...High confidence in TAF trends but lower on exact timing.
MVFR cigs and VFR vsbys this evening, then lowering to IFR/LIFR cigs
with MVFR vsby overnight into Monday morning. Then eventually
improving to VFR by Monday afternoon. NE winds tonight, becoming
east Monday and then southeast late in the day.

KBDL TAF...High confidence in TAF trends but lower on exact timing.
VFR continues into early evening, then some uncertainty how low cigs
and vsbys overnight into Monday morning, as low clouds and patchy
fog develop overnight. High confidence in improving conditions
Monday to VFR by midday or so.

Outlook /Tuesday through Friday/...

Tuesday through Tuesday Night: VFR.

Wednesday through Wednesday Night: VFR. Breezy.

Thursday: VFR. Breezy. Chance SHRA, chance TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

3 PM update...

Tonight...high confidence.

Offshore low continues to generate marginal SCA with NE winds up to
25 kt (in gusts, not sustained) and seas up to 6 ft across the
eastern MA waters, slowly subside tonight. Vsby may be reduced to 1-
3 miles at times in drizzle and fog.

Monday... High confidence

Lows clouds/drizzle and patchy early morning fog with vsbys 1-3
miles, slowly burns off with improving conditions mid to late
afternoon. High pressure over SNE results in light NE winds become
east and then southeast late in the day.

Monday night...high confidence.

Ridge of high pressure crest over the waters, yielding light SE
winds becoming SW. Patchy fog may limit vsby at times.

Outlook /Tuesday through Friday/...

Tuesday through Wednesday Night: Winds less than 25 kt. Seas
locally approaching 5 ft.

Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers, isolated thunderstorms.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 2 AM EDT Monday for ANZ250.
     Small Craft Advisory until 2 PM EDT Monday for ANZ254.

&&

$$

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