Area Forecast Discussion
National Weather Service Boston/Norton MA
120 AM EDT Mon Jun 27 2022

.SYNOPSIS...
A cold front will bring a period of widespread showers Monday 
exiting the SE New England coast Monday evening. Locally heavy rain 
is possible. Generally dry and seasonable temperatures follow 
Tuesday and Wednesday. Increasing temperatures late in the week with 
perhaps more unsettled weather by the weekend.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
1000 PM Update:

Boosted dewpoints up especially for overnight. Overall though no
other significant change needed. Forecast is holding up well; it
remains a mild night with current temps still in the upper 70s
and more than a handful of sites in the low 80s! Only issue 
being the arrival of rain into our western MA/CT counties. Some 
high- res guidance brings cluster of moderate- intensity rains 
now over the eastern PA/western Philadephia suburbs NE toward 
the late- overnight/pre- dawn hrs (~2 to 4 AM) associated with 
pre- frontal convergence trough. However appears timing of the 
main cold frontal showers looks on track from the afternoon 
forecast package. Will re- assess once the full complement of 
00z/27th guidance arrives. Until then, a mild and increasingly 
muggy evening.

Previous discussion:

Mid level trough moves east across the Gt Lakes tonight with the 
attendant cold front progressing eastward across New York, reaching 
the Hudson Valley around 12z. Deepening moisture axis moves into 
western New Eng late tonight with decent moisture 
advection/transport which will result in scattered showers in 
western MA/CT toward daybreak. Instability is marginal with MUCAPES 
a few hundred J/Kg so can't rule out an isolated t-storm in the 
west. Otherwise, mainly dry conditions should prevail further to the 
east. Lows will range through the 60s.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
Monday into Monday night...

Strong signal for a period of widespread showers moving west to east 
across SNE during Mon into Mon evening. Mid level trough axis 
continues to move east from the Gt Lakes and into New Eng with the 
cold front sweeping across SNE Mon afternoon then moving off the 
coast Mon night. Well defined deep layer theta-e ridge axis with 
PWAT plume 2+ inches ahead of the front combined with good low level 
convergence and mid level omega will support a period of widespread 
showers and isolated thunder with brief heavy rainfall. Deep warm 
cloud depths 10-15k ft are supportive of warm rain processes. 
However, the meager instability will be a limiting factor to very 
high rainfall rates and cell motions are fast enough such that 
flooding will not be a significant concern. Rainfall will average 
0.25 to 0.75" with localized amounts exceeding an inch. Heaviest 
rainfall will be focused across western New Eng in the morning, 
shifting to the coastal plain during the afternoon, then the 
Cape/Islands Mon evening. Highs will be mostly in the 70s to near 80 
and it will be rather humid with dewpoints well into the 60s to near 
70, A gusty SW wind will develop along the south coast and 
Cape/Islands as a modest low level jet develops. 

Showers will exit the SE New Eng coast later Mon evening as the 
front gradually moves off the coast. Otherwise, clearing skies in 
western New Eng will overspread eastern areas overnight as good 
drying moves in from the west. Cooler and much less humid airmass 
moves in overnight with lows dropping into the 50s, except lower 60s 
Cape/Islands.

&&

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

* Pick of the week on Tuesday and Wednesday with plentiful sunshine 
  and rather seasonable temps.

* Warming trend heading into Fourth of July long weekend with return 
  of above normal temps but also increased chances for unsettled 
  weather and thunderstorms. 

Details...

Tuesday into Wednesday...

By Tuesday morning, dew points of mid to upper 60s will be replaced 
by dew points in the 40s to low 50s, except higher across Cape Cod 
and the Islands. High pressure builds in so expect plenty of 
sunshine and also light winds. Daytime highs should be slightly 
below to near normal in the mid 70s to low 80s. Bufkit soundings 
show deep mixing to 850-800mb but light boundary layer winds so sea 
breezes should have no issues developing. Tuesday night will be an 
open the window kind of night with good radiational cooling. 
Wouldn't be surprised to see a few 40s readings in the typical cool 
spots but majority of the locales will see low to mid 50s. 

For Wednesday, the gradient winds increase so sea breezes will be 
much more limited in coverage if they develop. Daytime highs will be 
a few degrees warmer so expecting upper 70s to mid 80s, which is 
near to slightly above normal for late June. Overall, Tuesday and 
Wednesday are expected to be pick of the week.

Thursday into Sunday...

While we are in a mean zonal flow upper pattern, the northern jet 
remains quite active with pieces of shortwave energy crossing our 
area every now and then. While majority of the available guidance 
points to a warming trend for the second half of the work week 
heading towards next weekend, there is some uncertainty how warm 
temps will get. Not out of the question we could see widespread 90s 
on Friday and even Saturday, depending on the timing of a cold 
front. Rainfall chances wise, Thursday should be another dry day 
before chance for unsettled weather and thunderstorms increases to 
start the month of July and heading into the Fourth of July long 
weekend.

&&

.AVIATION /05Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels:

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

06Z TAF Update: 

Through 12z Monday: High confidence. 

VFR for most with increasing mid to high clouds. Earliest 
arrival of showers into western New England airports 10-12z with
ceilings then lowering to MVFR. S/SW winds around 7-10 kt.

Today: High confidence in trends but moderate on timing.

Ceilings lower to MVFR-IFR with a line of cold-frontal heavy
showers, perhaps with thunder embedded therein. Local downpours
and reduced visby possible; opted to keep visbys at 3 SM but may
be into the IFR visby range in sustained downpours. Rain may 
prove lighter across the Cape airports and ACK, but a period of
heavy showers looks probable for most airports between 14-20z.
See TAFs for specific timing. SW winds to shift to W around 5-10
kt with frontal passage.

Tonight: High confidence in trends but moderate on timing. 

Improving flight categories to VFR for most airports. However rain
to continue across Cape Cod/ACK thru 04z before moving 
offshore with improvement thereafter. W to NW winds 5-10 kt, 
trending lower end of that speed range by Tue morning.

Tuesday: High confidence. 

VFR. NW winds 4-8 kt; sea-breeze possible at BOS.

KBOS Terminal...High confidence in TAF/trends but moderate on
timing.

KBDL Terminal...High confidence in TAF/trends but moderate on
timing.

Outlook /Tuesday Night through Friday/... 

Tuesday through Thursday Night: VFR. 

Friday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels:

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

Increasing S/SW winds tonight peaking on Monday with gusts around 25 
kt as a modest low level jet develops. SCA will be issued for most 
of the waters. Winds and seas diminish Mon night with a wind shift 
to NW. Areas of fog will reduce vsbys tonight over waters east of 
Cape Cod. A period of showers and perhaps a t-storm move across the 
waters during the afternoon Mon, shifting to the SE waters Mon 
night.

Outlook /Tuesday Night through Friday/... 

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

Tuesday Night through Wednesday: Winds less than 25 kt. 

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

Thursday Night: Winds less than 25 kt. 

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Rip Current Risk from 8 AM EDT this morning through this 
     evening for MAZ023-024.
RI...High Rip Current Risk from 8 AM EDT this morning through this 
     evening for RIZ008.
MARINE...Small Craft Advisory until 11 PM EDT this evening for 
     ANZ231>235-237-250.
     Small Craft Advisory from 6 AM this morning to 7 PM EDT this 
     evening for ANZ236-251.
     Small Craft Advisory until 2 AM EDT Tuesday for ANZ254>256.

&&