-- Discussion containing changed information from previous version are highlighted. --
480
FXUS61 KBOX 091444
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1044 AM EDT Sun Jun 9 2024

.SYNOPSIS...
Weak low pressure will bring a period of showers today, with
improving conditions in the afternoon from west to east. Still
unsettled early next week with a chance of a few showers, then
a warming and drying trend Wednesday will lead to increasing
heat and humidity for the end of the week. Another frontal
system will bring increasing risk for showers and thunderstorms
Friday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
930 AM Update:

Radar and observational trends indicate that models were
bringing in rain about 2 to 3 hours too slow and also a little
too far north with the precip shield. Updated PoPs through 20z
to reflect rain showers beginning sooner in most areas, and
indicated a period of steady moderate rain across the northern
two-thirds of the forecast area.

Surface low was located near Waterbury CT vicinity; while there
is a minor degree of uncertainty on its extract track, it is
expected to progress ENE or due E, passing near or south of the
Mass Pike. Steadiest rain should occur north of the position of
this surface low through the early to mid afternoon hours.
Visbys have dropped below 3 miles in several locations on the
northern end of the surface low where the steadiest rain is
ongoing. Narrow warm- sector air mass over the southern third of
the forecast area - mainly from Willimantic to Hingham south
and east - with dewpoints rising into the lower 60s bringing in
some modest higher theta-e could offer a rumble of thunder;
expect rain coverage to be more showery with perhaps a rumble of
thunder for these southeastern locations where there is some
modest instability through rising dewpoints, but based on the
earlier timing and advance of OVC sooner limiting stronger
heating, expect the thunder risk to be pretty low to nearly nil.

Clearing should begin to take place from west to east by 18-23z,
taking the longest over southeastern MA.

Think general trends to temps in the current forecast look on
track and didn`t opt to make much change there. There may not
be much in the way of significant warming really anywhere, but
especially for areas north of the Mass Pike given prevailing
northerly isallobaric flow, cloud cover and steady rain.

Previous Discussion

A robust mid level shortwave moves through SNE 12-18z
then exits to the east. Ahead of the shortwave, a strengthening
low level jet up to 40-45 kt develops across SNE with PWATs
increasing to 1.0 to 1.5 inches. Favorable large scale forcing
ahead of the shortwave along with enhanced convergence from a
frontal wave which develops and moves across SNE will lead to
numerous showers moving west to east across SNE this morning
into the afternoon. The showers will be mostly focused across
interior MA into CT this morning, then shift to RI and SE MA for
a few hours around midday to early this afternoon before
exiting Cape/Islands by late afternoon. Rainfall amounts of 0.25
to 0.50" are expected north of the MA Pike decreasing to around
0.10" in RI and SE MA. There is some weak instability with a
few hundred J/kg of MUCAPE so can`t rule out an isolated t-storm
but the risk is low. The system is progressive and not
expecting more than a 3-4 hour period of rain, maybe up to 6
hours across NW MA, then partial sunshine will develop after the
rain ends as decent drying moves in from the west.

It will be cool in the rain this morning across the interior with
temps in the 50s to lower 60s before recovering into the upper 60s
to lower 70s later this afternoon. Meanwhile, temps across RI and SE
MA may spike into the lower 70s this morning before briefly dropping
into the 60s in the showers then recovering back into the 70s by
late afternoon. It will become breezy across the Cape/Islands as low
level jet strengthens south of the low track. A period of gusts to
20-30 mph is possible late this morning into early afternoon.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Tonight...

Another shortwave rotating around the upper low to the north will
move into SNE this evening before moving to the east late tonight.
This may trigger a few showers across western MA/CT this evening,
otherwise a period of mid level clouds move across the region
followed by clearing overnight. Lows will be mostly in the 50s with
a modest west breeze.

Monday...

Weak shortwave ridging in the morning between shortwaves will lead
to mostly sunny skies to start the day, then diurnal cu will develop
in the afternoon. Next shortwave rotating around the upper low moves
into the region during the afternoon which may trigger a few spot
showers across northern MA, but otherwise a mainly dry day. Temps
will be seasonable with highs mid-upper 70s and low humidity.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Highlights:

* Near or slightly above normal temperatures Tuesday and Wednesday
  with spot showers possible during the afternoon

* Increasing heat and humidity to close out the week with temps in
  the mid to upper 80s Thursday and Friday

* A cold front front crossing the region Friday may support showers
  and potentially strong thunderstorms.

Tuesday

A 500 hPa upper-level low becomes centered over southern New England
on Wednesday. Temperatures will continue to hover in the near-normal
range with highs in the mid 70s. Some modest instability may support
a few spot showers or thunderstorms Tuesday afternoon, but any
convection would be battling an environment with little forcing,
limited moisture, and almost no wind shear. Thus, any showers or
storms on Tuesday would be expected to be short-lived.

Wednesday

Upper-level low that has been supporting somewhat unsettled
conditions for the better part of the previous 7 days finally ejects
east by Wednesday. A mid-level ridge begins building over the
eastern US on Wednesday, but downstream of the ridge axis, there may
be some embedded short-wave energy that could support another
afternoon with some spot showers. Otherwise expect a mix of sun and
clouds and slightly warmer temperatures on Wednesday in the upper
70s to low 80s.

Thursday through Saturday

Mid-level ridge builds over the eastern US by Thursday. This will
support a southwest flow regime that will allow for an uptick in
both temperatures and humidity. 925 hPa temps likely to near 20
Celsius which should support high temps well into the 80s on
Thursday and Friday. Thursday looks to be the sunnier of the two
days as subsidence aloft and limited low-level moisture should
suppress any extensive cloud cover. As humidity increases into
Friday we`ll begin to see some increasing cloudiness ahead of an
approaching cold front. With temps in the upper 80s to perhaps low
90s and dewpoints in the mid to upper 60s, we should have the
instability in place to support thunderstorm development if the
aforementioned cold front crosses the region Friday afternoon or
evening. Model guidance is also hinting at an impressive wind field
for mid-June. We`ll be watching the forecast for Friday closely as
the ingredients may be in place for some severe weather. CSU machine
learning probs have a broad 5% chance of severe weather area over
The Northeast on Friday, so while the signal for severe weather
isn`t overly strong at this time it certainly warrants close
observation as we head into next week. Should the front push through
the region Friday afternoon as guidance currently indicates,
Saturday would feature dry/sunny condition with less humidity and
slightly lowers temps. We`ll have more details later this week.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
Forecast Confidence Levels:

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

15Z TAF Update:

Today: High confidence in trends, though moderate on timing.

Through 20 to 22z...lowest categories (MVFR-IFR) from BDL to
BOS north and west associated with steadier SHRA and ceilings
005-015 thru 20-22z. For PVD and the Cape airports, categories
generally VFR to MVFR range in -SHRA/SHRA, though with a lower
prob of TS. With low pres tracking through CT-RI and SE MA,
winds mainly NE to N under 8 kt for most airports, with SW
winds around 10 kt for PVD-Cape Airports-ACK.

Later in the day (after 20-22z)...conditions should return to
VFR with showers ending and winds becoming WNW with speeds
around 10-12 kt with gusts in the low 20s-kt range.

Tonight...High confidence.

VFR. Low risk for a few showers this evening in western MA. W
wind 5-15 kt.

Monday...High confidence.

VFR with diurnal CU developing. A spot shower is possible in the
interior.

KBOS TAF...High confidence in trends, moderate on timing.
Categories deteriorate to MVFR/IFR with 2-3 SM SHRA, wet runways
and light NE to N winds thru 18z. Gradual return to VFR with
winds becoming WNW around 10-12 kt with gusts to 20 kt. Winds
then shift to SW around 6-10 kt around 03z Mon with another
round of VFR -SHRA overnight.

KBDL TAF...High confidence in trends, moderate on timing. MVFR-
IFR with low ceilings, SHRA and north winds thru about 19z.
Conditions trend VFR thereafter with NW winds around 10 kt with
gusts to 20 kt. Another possible period of -SHRA after 03z Mon.

Outlook /Monday Night through Thursday/...

Monday Night: VFR.

Tuesday: VFR. Slight chance SHRA.

Tuesday Night: VFR.

Wednesday: VFR. Slight chance SHRA.

Wednesday Night through Thursday: VFR.
-- End Changed Discussion --

&&

.MARINE...
Forecaster Confidence Levels:

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

High confidence through Monday...

Strengthening low level jet will result in a period of SW gusts to
25 kt over the south coastal waters later this morning into the
afternoon and we have issued a SCA here. Diminishing winds becoming
W by late afternoon with generally W winds 10-15 kt tonight into
Mon, becoming SW Mon afternoon. An area of showers move across the
waters later this morning into the afternoon. Vsby may lower to 1-3
miles at times across the northern MA waters.

Outlook /Monday Night through Thursday/...

Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 5 PM EDT this afternoon for
     ANZ231>235.
     Small Craft Advisory until 8 PM EDT this evening for
     ANZ254>256.

&&

$$

SYNOPSIS...KJC/RM
NEAR TERM...KJC/Loconto/RM
SHORT TERM...KJC
LONG TERM...RM
AVIATION...KJC/Loconto/RM
MARINE...KJC/Loconto/RM