149
FXUS61 KBOX 302355
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
755 PM EDT Tue Apr 30 2024

.SYNOPSIS...
An approaching cold front will bring another round of showers to
the region tonight with a few embedded thunderstorms possible
across interior Massachusetts and Connecticut. Considerable
cloudiness persists on Wednesday, but peeks of sunshine too,
especially in the afternoon. Unsettled mid to late this week due
to a backdoor cold front nearby. This could bring spotty showers
and keep us a bit cooler, but there is a significant amount of
uncertainty with the fronts location. Better shot for more
widespread showers late Saturday into Sunday as a frontal system
slides through.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
* Showers/isolated t-storms move into western MA/CT, and reach
  the I-95 corridor in MA/RI after 10-11 pm in a weakened
  fashion

Made some tweaks to rainfall timing this evening based off the
last few runs of the RAP and HRRR. Still not expecting much
overall rainfall. Latest SPC meso showed virtually no shear and
CAPE across southern New England. While there is a chance for a
thunderstorm or two, they should be few and far between.

Minor tweaks to temperatures to reflect observed trends as well.

Previous Discussion...

An approaching shortwave/cold front coupled with diurnal heating
was allowing showers and embedded thunderstorms to develop this
afternoon across NY State & PA. As this shortwave/cold front
moves east, expect showers to enter western MA & CT after 7-8 pm
this evening. The environment across our region is not as
favorable though given the marine layer in place. So while we
may still a rumble or two of thunder across interior MA & CT
with a few brief downpours, expect a weakening trend. So will
just stick with showers across eastern MA/RI where the activity
will not enter the region after 10-11 pm.

The bulk of the showers should come to an end toward morning,
but a few showers may linger through daybreak especially towards
the southeast New England coast. Overnight low temps should
mainly be in the 40s to near 50 with some patchy fog possible.

&&

.SHORT TERM /WEDNESDAY NIGHT/...
Key Points...

* Considerable cloudiness Wed but a few peeks of sunshine too
* Highs Wed...50s coast, 60s inland & near 70 in parts of CT

Details...

Wednesday...

A few lingering showers possible early Wednesday morning across
southeast New England, but departing shortwave/front will bring
a quick end to this activity by mid to late morning. Otherwise,
a wave of low pressure passing to our south coupled with high
pressure across eastern Canada will generate a continued moist
NE low level flow. We expect a fair amount of cloudiness around
but a few peeks of sunshine especially in the afternoon.
Generally dry weather will prevail for most of Wednesday with
the lack of synoptic scale forcing, but a few spot showers can
not be ruled out.

Given the onshore flow, temperatures will vary considerably.
Highs should be held in the 50s along the immediate coast, to
60s further inland, while areas near the lower CT River Valley
will top off around 70. These temperatures may need to be fine
tuned depending on the amount of solar insolation and onshore
flow.

Wednesday night...

A northern stream shortwave will be dropping southward from
Quebec into northern New England Wed night. The better
dynamics/forcing will remain to our north where we expect most
of the precipitation. However, we may see a few showers develop
mainly across our northern zones toward daybreak Thu. Overnight
low temps should mainly be in the 40s.

&&

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

* Good amount of uncertainty during this portion of the forecast
  with timing and exact location of showers.

* Backdoor cold front on Friday. This could bring spotty showers
  and keep us a bit cooler, but there is a significant amount of
  uncertainty with the fronts location.

* Unsettled with rain chances continuing late this weekend as a
  front moves across the region.

Have the greatest confidence in the forecast into the first part
of this weekend. Then there are significant difference in the
larger synoptic pattern features into the middle of next week.
Expecting a fairly active pattern through most of next week.
This is leading to uncertainty, especially with the timing and
location of these showers. That is not unusual for this time of
year.

Some signs that a high pressure ridge off the east coast of MA.
How strong this high pressure will be is a factor to monitor.
Should this ridge be stronger, then we may get through most of
this weekend dry. More likely to see showers some time late
Saturday into Sunday. Trending drier early next week, but again
uncertainty regarding the timing details.

Thinking temperatures should be near to slightly below normal
into this weekend. Odds favor a switch to above normal
temperatures early next week.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:

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

Through tonight...Moderate Confidence.

MVFR-IFR conditions becoming more prevalent this evening and
overnight, with even some localized LIFR conditions given moist
onshore flow. Another round of showers will move in from the
west. We cannot rule out an isolated thunderstorm across the
distant interior, but we expect a weakening trend as any
thunderstorms move east into a less favorable environment. So,
for much of the region, mainly looking at showers, but a few
downpours are also possible. A few showers linger especially
towards the Cape/Islands through daybreak, but the vast majority
of the activity will have passed the region by 09z/10z. E winds
shifting to the NE at 5 to 10 knots tonight.

Wednesday...Moderate Confidence.

IFR-LIFR conditions early Wed morning will gradually improve to
MVFR, and even VFR, conditions in some spots through the
afternoon, but this will be a slow process and timing will need
to be refined. After any remaining showers depart early Wed
morning, mainly dry weather will prevail Wed other than perhaps
a brief spot shower. NE winds 5 to 10 knots.

Wednesday night...Moderate Confidence.

MVFR-IFR conditions will probably become dominant again as the
boundary layer cools again Wed night. A few showers may spill
into our northern zones through daybreak Thu, but much of Wed
night will feature dry weather with nothing more than a spot
shower. Winds becoming light S.

KBOS TAF...Moderate Confidence in TAF.

KBDL TAF...Moderate Confidence in TAF.

Outlook /Thursday through Sunday/...

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

Thursday Night: Mainly VFR, with local IFR possible.

Friday: Mainly VFR, with areas MVFR possible.

Friday Night: Mainly VFR, with local MVFR possible.

Saturday through Saturday Night: Mainly VFR, with areas MVFR
possible. Slight chance SHRA.

Sunday: 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.

Tonight through Wednesday night...High Confidence.

A weak pressure gradient will keep winds/seas below Small Craft
Advisory thresholds through Wed night. E winds shift to the NE
at 5 to 15 knots tonight and Wed, but then will become light S
tonight.

Outlook /Thursday through Sunday/...

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

Thursday Night: Winds less than 25 kt. Slight chance of rain
showers.

Friday through Friday Night: Winds less than 25 kt.

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

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

&&

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

&&

$$

SYNOPSIS...Belk/Frank
NEAR TERM...Belk/Frank
SHORT TERM...Frank
LONG TERM...Belk
AVIATION...Belk/Frank
MARINE...Belk/Frank