Old Res Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 100241
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1041 PM EDT Tue Aug 9 2022

.SYNOPSIS...
Most of the scattered showers and thunderstorms across Rhode 
Island and Southeast Massachusetts will wind down by midnight. 
A backdoor cold front brings stratus and fog along tonight along
with much cooler temperatures Wednesday but humidity remains 
elevated. A wave of low pressure may bring some showers to 
mainly Rhode Island and southeast Massachusetts Wednesday night 
into Thursday if it tracks close enough to the coast. Mainly dry
weather Friday through Monday with seasonable temperatures and 
very comfortable humidity. So quite the change from the heat and
humidity of the last several weeks!

&&

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

1030 PM UPDATE...

Shower and thunderstorm activity has pretty much come to an end
across southern New England, except for a few isolated showers
across SE MA and southern RI. Nighttime Microphysics show the
low stratus coming in from the northeast behind the leading edge
of the backdoor cold front. Behind the cold front, NE winds are
gusting 15-20 mph and dew points have also dropped by 7-10F,
from mid 70s to mid 60s. This cold front will continue to make
its way southwestward, and eventually stall south of the MA/RI
south coast by the morning hours. Couldn't rule out a few
isolated sprinkles or showers alongside patchy fog, but most 
places will stay dry and cooler and less oppressive conditions 
will take hold. 

PREVIOUS DISCUSSION...

8 PM Update...

Isolated to scattered showers/t-storms were still impacting RI/SE
MA this evening. MLCapes are still on the order of 1500 J/KG in
this region. This coupled with the intersection of a surface
cold front to the west and a backdoor cold front approaching
from the north were the culprits. The bulk of this activity
should diminish by midnight as the main backdoor cold front 
drops south. However, mid level moisture and west to southwest 
flow aloft will still allow for widely scattered showers 
overnight particularly towards southeast New England. 

A deck of low stratus will invade much of central and eastern 
New England over the next several hours behind the backdoor cold
front. May see some patches of fog too; particularly towards 
the southeast New England coast right behind the backdoor cold 
front. We also may see some stratus too across western 
MA/northern CT overnight too. Low temps will be noticeably 
cooler than what we have experienced of late. Overnight lows 
should bottom out in the 60s to near 70.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Highlights

* Much cooler in wake of the cold front, but will have to deal
  with more clouds than sunshine at least for the first half of
  the day.

* Could potentially see some showers spreading in late on
  Wednesday and Wednesday night as a low rides along the front
  to our south, but confidence is quite low at this point.

Still under cyclonic flow across the Great Lakes and New England
Wednesday into Wednesday night, but will have a deeper trough
digging into the Great Lakes late on Wednesday. A weak high
builds into the region on Wednesday, but will have a frontal
boundary around/south of the region. A low may ride along this
front and push toward us bringing rain chances late on Wednesday
and Wednesday night.

Main change in the latest update was to dial back precipitation
chances on Wednesday and Wednesday night. Have some concerns
that the low develops along the front, but remains too far
offshore to bring us precip. A very big change amongst guidance
from yesterday with most models shutting us up precip wise until
perhaps Thursday. Given the big shift have just dialed back
things a bit at this point especially given the ARW/FV3
guidance. Risk is going to be the highest across the south
coast, where could have PWATS approaching 2 inches. Will need to
see how things evolve with future model runs.

Will have onshore flow for much of Wednesday, which will keep
high temps in the mid 70s to the mid 80s. May take a bit for the
low clouds/stratus to lift. At the moment have it lifting during
the afternoon, but could be tough given the persistent onshore
flow. Low temperatures will be in the 60s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Highlights...

* Some showers may impact mainly RI/SE MA into Thursday "If" a wave 
  of low pressure tracks close enough to the south coast

* Generally dry weather Fri through Mon with a pattern change to 
  seasonable temperatures and comfortable humidity

Details...

Thursday...

We will need to keep an eye on a wave of low pressure lifting 
northeast from the mid-Atlantic states along with a cold front from 
the west. Somewhat uncertain as to the northward extent of the 
shower shield associated with the wave of low pressure to our south. 
Greatest risk for a period of showers will be across RI/SE 
especially Thu morning, but this could also remain offshore. It is 
really difficult to forecast the northwest extent of a synoptic QPF 
field given limited baroclinicity this time of year coupled with any 
convective processes. Otherwise, the only thing will have to watch 
is for perhaps some scattered showers and isolated t-storms trying 
to enter western MA during the evening with the cold front 
approaching. Dynamics weaken as this moves east so may fall part as 
it tries to enter southern New England. Highs on Thu will mainly be 
in the 80s, but perhaps places on the immediate coast may not reach 
80.

Friday through Monday...

The EPS/GEFS are in excellent agreement in an overall pattern change 
compared to what we have experienced over the last several weeks. 
Upper level trough sets up over the mid-Atlantic and Northeast 
States over this time period. This will result in very pleasant 
weather and comfortable humidity! Mainly dry weather will prevail 
outside a few spot showers possible with a couple of moisture 
starved northern stream shortwaves. High temps will mainly be in the 
lower to middle 80s with perhaps 75 to 80 at times along portions of 
the immediate coast. Overnight low temps will mainly be in the 50s 
to the lower 60s. Again though the main story will be the change to 
cooler/seasonable temps and pleasant humidity.

Tuesday...

Approaching/digging shortwave may increase the chance for some 
showers by Tuesday. Still quite the ways in the future, but 
something to watch in the coming days. Humidity may increase a bit 
too, but nothing like what we have been experiencing.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
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 in exact timing. 

Bulk of isolated to scattered showers/t-storms across RI/SE MA 
dissipate by midnight, but widely scattered showers will still 
be possible after that time. Otherwise, main story will be a 
backdoor cold front which will bring IFR-LIFR ceilings to much 
of central/eastern New England as the evening wears along and 
into the overnight hours. Some patches of fog possible 
especially right behind the cold front near the southeast New 
England coast. The distance interior probably realizes a period 
of MVFR ceilings. Winds shift to the NNE at 5 to 10 knots behind
the cold front, but will briefly gust stronger along the 
immediate coast right behind the front.

Wednesday...Moderate confidence.

MVFR/IFR ceilings slowly improving to VFR. E/NE winds turning 
to the SE at 5-10 kts. 

Wednesday night...Low confidence.

MVFR to IFR conditions with perhaps some rain showers spreading
in toward the south coast. Lots of uncertainty with this
activity as a low develops along the frontal boundary nearby.
Light SE/S winds perhaps shifting to the SW toward daybreak.

KBOS...High confidence in trends moderate in timing of the
stratus/fog spreading in for the evening push.

KBDL...Moderate confidence in thunderstorm coverage and timing.
Could see MVFR stratus spreading in tonight, but lower
confidence here.

Outlook /Thursday through Sunday/...

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

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

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

Friday Night through 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.

Through 00Z...High confidence in trends, moderate in timing.

Scattered showers/t-storms dissipate from north to south through
6z. Will have an abrupt wind shift in wake of the front with 
winds shifting to the N/NE in wake of the front, but out of the 
SW/W ahead of it this evening. Should see speeds of 10-15 kts 
with perhaps some brief 20 to 25 knots gusts right behind the 
front. Will see a surge of low clouds and fog especially across 
the eastern waters. 

Lingering small craft headlines across the southern outer-waters
for seas should come down in the next few hours. Otherwise, just
brief 20-25 knots wind gusts right behind the backdoor cold
front over the next several hours but just below headline
criteria.

Wednesday...High confidence. 

Winds out of the NE to E at 5-10 kts with seas of 2-4 ft.

Wednesday night...Low confidence.

Winds out of the E/SE around 5 kts. Should have seas of 2-4 ft,
but uncertain on weather. A low will lift along a frontal
boundary to the south of the region. This could bring some rain
along with embedded thunder late, but also could be a shutout
especially for the eastern waters.

Outlook /Thursday through Sunday/... 

Thursday through Thursday Night: Winds less than 25 kt. Chance
of rain showers. 

Friday through Friday Night: Winds less than 25 kt. 

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

Saturday Night through Sunday: Winds less than 25 kt.

&&

.CLIMATE...
Record Maximum Temperatures

August 9th:

BOS 99F [1949] 
ORH 95F [1949] 
PVD 100F [2001]
BDL 102F [2001]

&&

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

&&

$$
SYNOPSIS...Frank/BL
NEAR TERM...Frank/Chai
SHORT TERM...BL
LONG TERM...Frank
AVIATION...Frank/BL
MARINE...Frank/BL
CLIMATE...