Area Forecast Discussion
National Weather Service Boston/Norton MA
709 PM EDT Sun Jun 4 2023

.SYNOPSIS...
Unseasonably cool, raw conditions will continue tonight into
Monday, especially in eastern Massachusetts. Scattered showers 
will linger into Monday in eastern New England. Warmer Tuesday 
with more seasonable temperatures and a chance for 
thunderstorms. Things then turn cooler for the rest of the week.
Unsettled weather pattern will persist through the end of the 
week with signs up a warmer and drier pattern by next weekend.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...

700 PM Update...

Showers continues to rotate counterclockwise around the low
pressure centered over southeast MA this evening. This
circulation is very evident on both radar and visible/water
vapor satellite imagery. We're seeing a surge of more moisture
moving into northeast MA at this time and that will continue in
the evening/early overnight hours. 

Previous Discussion... 

Stubborn upper level low and associated sfc coastal low will 
continue to meander around the Gulf of Maine, making little 
eastward progress. Composite radar imagery as of 300 pm shows 
areas of rain showers ongoing across central and eastern MA, 
with steadier light rains further across NH and ME. With 
moisture levels slowly increasing/spreading onshore and little 
to modest warm advection, expect continued OVC skies with 
lowering cloud ceilings and periods of steady light rain. While 
rain amounts won't be significant or substantial, it will add to
the raw conditions. Onshore/northeast breezes will also 
continue and make temperatures feel even more unseasonably cold 
for early June. Lows in the mid 40s to around 50, only falling a
couple degrees.

Along the coastal zone, while the weather would be far from
ideal for beachgoing, because of seas over 7 ft against shore 
on N/NE winds, high surf advisories are in effect for the
eastern MA coast for the risk of high surf and rip currents 
through Monday.

&&

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

Monday and Monday Night:

Monday will continue with the cooler and raw weather with overcast 
for most of the day across eastern MA; more optimism to a mix of 
clouds and sun across CT and western MA where high temps have a 
better chance at reaching 70 degrees. As the sfc and upper air low 
will make greater eastward inroads into the Canadian Maritimes/NS 
vicinity through the afternoon, expect covg of showers to diminish 
and clouds scattering in central/eastern MA and RI, though it will 
take until late aftn to evening before we see overcast break across 
Cape Cod and SE MA. Highs in central and eastern MA into RI only 
reach into the low to perhaps mid 60s, which are some 10 degrees 
cooler than early June normals. 

While there may still be some clouds around for Monday night, 
conditions probably would be best described as partly cloudy. Looks 
like our dewpoints/moisture levels dry out some for the evening and 
winds should stay up just enough such that the risk for patchy fog 
should be minimal. Lows mainly mid 40s to lower 50s.

&&

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

* Continued periods of unsettled weather each day under a mid level 
  trough

* Temperatures remain cooler than average until a warm up toward the 
  weekend

* Chance of showers and thunderstorms on Tuesday, a few of which 
  could be strong to severe but not expecting widespread severe 
  weather

Details...

Tuesday...

Tuesday continues with more of the same as far as the synoptic 
weather pattern goes. This features a deep and persistent mid level 
trough over the eastern U.S. with periodic disturbances rotating 
around the base through much of the week. Tuesday, though, looks to 
feature the best chance of thunderstorms rather than garden variety 
showers. This is because of the combination of a cold pool aloft 
with diurnal heating at the surface which will lead to low level 
lapse rates approaching 7.5-8.5C/km and mid level lapse rates of 6-
8C/km. This, in combination with dewpoints potentially rising into 
the mid to upper 50s for some locations, will lead to mixed layer 
CAPE values between 500 and 1000 J/kg ahead of the cold front. A few 
potential complications will be how much clearing we can get early 
Tuesday to heat the surface...a cloudier outcome would generate less 
instability. There is also some model disagreement as to how far 
north those elevated dewpoints can push; something that will become 
clearer soon as we're just approaching the windows of some of the 
higher-res guidance. Either way, widespread severe weather doesn't 
look likely since the greater instability doesn't overlap with the 
necessary bulk shear. Current thinking is we'll see mainly typical 
pulse thunderstorms with sub severe hail possible and some strong 
winds given an inverted-v look to forecast soundings (though low/mid 
level flow isn't impressive). However, a few severe storms are 
possible given the impressive lapse rates (potential for larger 
hail). Temperature-wise Tuesday will continue the warm up ahead of 
the front, into the low to mid 70s. 

Wednesday through Friday...

The aforementioned closed low continues to stall overhead through 
the end of the week leading to more cool, cloudy, and unsettled 
weather each day. Given the cold pool and cyclonic flow aloft we'll 
likely see a good amount of clouds each day with periodic showers as 
difficult to time disturbances rotate through the base of the 
trough. As mentioned by the previous forecaster, it still doesn't 
seem like a washout for any day but there will likely be showers 
around each day. Given temperatures dipping down into the 3-5C range 
with clouds we can expect highs in the 60s to low 70s each day. 

Next weekend...

Encouraging signs as we go into next week that we'll get at least a 
brief respite with a pattern change around Saturday/Sunday. Global 
guidance is indicating a breakdown in the pattern with the trough 
finally exiting east and a mid level ridge building in. Confidence 
in this outcome is low at this distance in time but this would mean 
warmer temperatures and drier days ahead.

&&

.AVIATION /23Z SUNDAY THROUGH FRIDAY/...
Forecaster Confidence Levels:

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

00z TAF Update: 

Tonight: High confidence in trends, moderate on timing.

MVFR ceilings mostly from Worcester eastward; VFR in the CT 
Valley. While VFR should prevail for BAF-BDL, downward trends in
ceilings/categories elsewhere as we move into the evening. NE 
to N winds 15-20 kt with gusts 25-30 kt (Strongest Cape airports
and ACK), with gusts decreasing slightly into the overnight.

Monday: High confidence in trends, but moderate on timing of
improvement.

BKN-OVC VFR continues in CT Valley. Elsewhere IFR-MVFR ceilings
experience slow lift/improvement as winds become NNW, but will 
emphasize that categorical improvement is likely to be slow
with no better than MVFR thru the daytime hrs Mon. N to NW winds
10-20 kt, gusts to 25 kt for Cape Cod and the Islands. 

Monday Night: High confidence.

Any lingering sub-VFR should improve to SCT-BKN VFR early 
Monday evening. NW winds decrease to 5-10 kt.

KBOS Terminal...High confidence in TAF/trends but moderate on
timing. MVFR ceilings to deteriorate to IFR very soon. NE winds
around 15 kt (gusts low 20s kt) back slightly to due N, but 
won't see NW winds develop until late- morning Mon at earliest.

KBDL Terminal...High confidence in TAF. 

Outlook /Tuesday through Friday/...

Tuesday through Tuesday Night: Mainly VFR, with local MVFR
possible. Breezy. Chance SHRA, isolated TSRA.

Wednesday through Wednesday Night: Mainly VFR, with local MVFR
possible. Breezy. Chance SHRA.

Thursday: Mainly VFR, with local MVFR possible. Chance SHRA.

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

Friday: Mainly VFR, with local MVFR possible. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Monday Night: High confidence.

Persistent northerly wind gusts around 25 to 30 kt will 
continue tonight into early Monday as a low-level jet of 35 kt
moves over the waters. NW winds gradually diminish Monday 
afternoon and into the evening. Strong N winds will continue to 
produce rough seas on near shore and coastal waters which may 
make conditions difficult to navigate for less experienced 
boaters. Seas should diminish into Monday night but they may
stay up enough to warrant extending existing SCAs on the eastern
waters.

We should see steadier rains that may at times reduce visibility
to 4 miles tonight into Monday; expect showers becoming more
intermittent for Monday afternoon and Monday evening. 

Outlook /Tuesday through Friday/...

Tuesday through Tuesday Night: Winds less than 25 kt. Seas
locally approaching 5 ft. Chance of rain showers, isolated
thunderstorms. 

Wednesday: Winds less than 25 kt. Chance of rain showers. 

Wednesday Night through Friday: Winds less than 25 kt. Slight
chance of rain showers.

&&

.TIDES/COASTAL FLOODING...
Key Points: 

* Pockets of Minor coastal flooding for tonight's high tide for
  eastern MA coast, possibly again for Monday night's high tide.

Coastal Flood Advisory remains in effect for the eastern MA
coast for tonight. Coastal flood headlines may be needed for 
Monday night's high tide as well. 

A storm surge around 1+ ft combined with 7-10 ft seas offshore 
will be enough for minor coastal flooding along the eastern MA 
coast during the high tide near midnight tonight.

Similar conditions and tides are expected during the Monday night 
high tide so another round of minor coastal flooding is possible 
along the eastern MA coast. 

Along the South Coast, surge values will be lower due to offshore 
flow (N winds). Locations such as Providence are forecast to remain 
well below flood stage.

&&

.CLIMATE...
Record Low Max Temps for Sunday June 4th.

BOS...52/1891 
PVD...55/2012 
BDL...59/2018 
ORH...51/2018

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Surf Advisory until 8 PM EDT Monday for MAZ007-015-016-
     019-022-024.
     Coastal Flood Advisory until 2 AM EDT Monday for MAZ007-015-
     016-019-022>024.
RI...None.
MARINE...Small Craft Advisory until 2 PM EDT Monday for ANZ230-233>235-
     237.
     Small Craft Advisory until 8 PM EDT Monday for ANZ231-232-250-
     251-254>256.
     Small Craft Advisory until 8 AM EDT Monday for ANZ236.

&&