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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 271339
AFDBOX

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

.SYNOPSIS...
A cold front will bring increased clouds today along with a period
of widespread rain showers. Locally heavy downpours are possible.
Rain ends early tonight as cold front moves offshore. Dry
conditions, cooler temperatures and low humidity levels then return
on Tuesday and Wednesday. Increasing temperatures late in the
week with more unsettled weather by the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
940 AM Update...

KBOX radar currently revealing scattered showers across southern
New England this morning. A few light showers moving over
portions of the south coast right now. Further west there are a
additional scattered showers with pockets of moderate to heavy
rainfall. Expect showers to expand in coverage and intensity
this afternoon as a cold front pushes through the region.
Forecast remains on track, have only made minor adjustments in
this update to reflect latest observations and more recent
short-term model guidance. See 3AM discussion for additional
details.


300 AM Update:

Warm sector air mass regime in place over Southern New England early
this morning, with south winds and current temps in the 60s to low
70s. Mostly clear skies generally prevail, but increasing clouds are
anticipated over the next couple of hours in association with a cold
front analyzed over western New York. Several clusters of rain
showers were noted along and just ahead of the boundary; these rain
showers are being infused by PWATs in the 2 inch range.

Cold front will continue to progress eastward, into western MA and
CT between 8 and 10 AM, into central MA/western RI/eastern CT around
noontime/early-afternoon, toward eastern MA/RI by mid to late in the
afternoon and approaching Cape Cod late in the day. Besides the high-
PWAT airmass which is expected to advect over our area before the
front arrives, warm cloud depths in the 13k range are very favorable
for heavy downpours. However rather fast individual storm motions
should keep these locally heavy rains from sitting over any one
area. Thus, not anticipating any significant flooding risks but
there will nonetheless be some reduced visibility in heavy
downpours. On the thunder potential, abundant cloud cover will
significantly limit destabilization. Though I`ve maintained a
mention of isolated thunder in the forecast, the lack of instability
makes prospects for thunder pretty limited. I did want to maintain
the mention of heavy rain but opted for rain heavy at times wording
versus the heavy downpours in thunder mention, because thunder
should be the exception vs the rule.

While rain will continue across Cape Cod into the early evening,
behind the front expect a much drier air mass and a windshift from
S/SW to W and eventually NW. Highs rise only a few degrees into the
70s today under considerable cloud cover.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
300 AM Update:

Tonight:

Moderate-intensity rains may still be ongoing early tonight across
Cape Cod and the Islands but the cold front will gradually progress
offshore. Rain should be ending areawide by midnight. As an upper-
level trough moves into eastern NY, NW flow will induce a cooler and
much drier air mass, with dewpoints falling from the 60s into the
upper 40s to lower 50s. While leftover cloudiness should be peeling
away from Cape Cod and the Islands, most areas will see mostly clear
skies and lows in the 50s.

Tuesday:

Mostly sunny skies prevail on Tuesday, though a cool pocket of air
aloft associated with upper level trough passage could lead to some
shallow-based fair weather Cu fields. Expect lots of sunshine, and
with 850 mb temps around +7 to +9C and dewpoints in the 40s to lower
50s, looking at pleasant weather conditions. Highs in the 70s to low
80s but with much lower humidity levels ideal for any outdoor
activities. Modest NWly breezes.

&&

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

* Dry and quiet for much of the week with temperatures trending
  upward.

* Spotty showers possible late Wed into Wed evening. More unsettled
  weather for this upcoming weekend.

Tuesday night through Friday...

Caught up in somewhat cyclonic flow Tuesday night into late
Wednesday before flow becomes more zonal. Will have a trough lift
from the Great Lakes region Tuesday night into New England by late
Wednesday. Behind the trough a ridge axis builds into and through
New England late in the week.

Generally anticipating dry and quiet weather across southern New
England through much of this period. High pressure moves offshore on
Wednesday, which allows a weak cold front/trough to slide through
the region late in the day. Think this combined with diurnal heating
will result in isolated showers late Wednesday into Wednesday
evening. Think for most it will be dry as there is not a whole lot
of moisture in place over our area. Precipitable Water values get up
to roughly 0.75-1 inch, which is around the 25th to 50th percentile
for CHH per SPC Sounding Climatology for this time of year.

High pressure reasserts itself for the rest of the week as it nudges
in offshore/well east of the Mid Atlantic coast. Given the position
of the high will see increasing heat and humidity. Bumped up highs
to the 80th percentile of guidance for Thursday and Friday due to W
and WNW downslope flow. On Thursday, temps at 850 hPa increase to 11-
15 Celsius. The result will be highs well into the 80s for most, but
it should be a bit cooler along the immediate coastline due to local
seabreezes. As for Friday we get into 16-19 degree Celsius air at
850 hPa. The result is fairly widespread low/mid 90 degree readings.
Coastal locations generally range from the upper 70s to the upper
80s.

Late Friday through and Sunday...

Flow over our area becomes more cyclonic as a cutoff digs into
Hudson/James Bay and northern Quebec. A shortwave trough lifts into
and potentially through southern New England on Saturday. There may
be another wave that lifts into the region for Sunday, but
confidence not as high in this next wave moving in. A cold front
slides into and through southern New England bringing showers and
thunderstorms. At this point appears to be mostly on Saturday, but
not completely out of the question the front is still over us on
Sunday.

Per WPC Cluster analysis the most variance at this point deals with
the amplitude of the trough. At this point all clusters show
precipitation on both days. Deterministic guidance paints the cold
front pushing completely through the region and being dry on Sunday.
However, am going to lean toward the ensemble guidance at this
point. Have slight chances to chances of precip through the
weekend. Could see some thunder as there is at least a few
hundred J/kg of CAPE per GEFS/GEPS/EPS probabilities of CAPE AOA
500 J/kg. On top of this will have increasing deep layer shear.
Cannot completely rule out there could be some stronger storms,
but really need to time when the front moves in and convective
parameters. Stay tuned as we will hone in on more
specifics/details as we get closer. Stuck with the NBM which
keeps temps in the 80s and low 90s in Saturday. As for Sunday
appears a bit cooler with highs ranging from the mid 70s to the
mid 80s.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels:

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


Today...High confidence in trends but moderate in exact timing.

VFR to start for most. Expect ceilings and visibilities to lower
to MVFR/IFR levels as showers with perhaps some embedded
thunder as a cold front pushes in. Should have efficient
rainfall processes today, so will likely have heavy downpours at
times bringing visby down to IFR range. Thinking that the
thunder risk is highest for BDL/BAF/ORH/PVD, but have held off
from including the latest update. Gusty S/SW winds shifting to
the W once the front passes. Gusts of 20-30 kts with the highest
gusts over the Cape terminals.

Tonight...High confidence in trends but moderate on timing.

Conditions improving to VFR as showers come to an end. May not
be until roughly 06-09Z for the Cape/Islands. 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 Night through Wednesday: VFR.

Wednesday Night: VFR. Isolated SHRA.

Thursday 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.

Continued small craft advisories into today as southerly winds
gusting to the low to mid 20s kt range and seas building into the 3-
6 ft range (highest offshore). In addition, there is a high rip
current risk today for Block Island, Martha`s Vineyard and
Nantucket. South facing shores could see rip currents due to these
seas and SW winds.

Decreasing winds and seas with a wind shift to NW as a cold front
moves over the waters tonight. Periods of rain, perhaps heavy at
times could reduce visibility tonight. By Tuesday, NW gusts around
10 kt with seas in the 2-3 ft range should lead to favorable boating
conditions.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Wednesday: Winds less than 25 kt.

Wednesday Night: Winds less than 25 kt. Seas locally
approaching 5 ft. Isolated rain showers.

Thursday through Thursday Night: Winds less than 25 kt.

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

&&

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

&&

$$
SYNOPSIS...BL/Loconto
NEAR TERM...RM
SHORT TERM...Loconto
LONG TERM...BL
AVIATION...BL/Loconto
MARINE...BL/Loconto