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000
FXUS61 KBOX 102342
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
742 PM EDT Wed Apr 10 2024

.SYNOPSIS...
Areas of low clouds and fog develop overnight with perhaps some
drizzle too. A few showers are possible this evening and again
mainly Thursday morning into the early afternoon...but the heavy
rain and embedded thunder threat along with windy conditions
will hold off until late Thursday night into early Friday
morning. Not a washout this weekend, but rain chances still
exist, accompanied by brisk winds. Dry and warming to start
next work week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
3 PM Update...

* Brief showers this evening especially across northwest/western MA
* Areas of low clouds, fog and patchy drizzle developing overnight
* Overnight low temps only in the middle 40s to the lower 50s

Shortwave energy moving in from the west was allowing showers to
begin to impact areas of western MA at mid-late afternoon. Bulk of
the forcing/deeper moisture will remain to our west north.
Nonetheless...brief showers will graze parts of our region this
evening with the main shower threat across western/northwest MA.

Otherwise...shortwave energy will be lifting to our north later this
evening. We actually have some brief shortwave ridging that follows.
Therefore...other than the potential for some drizzle developing
overnight along with low clouds/fog patches do not expect any
organized precipitation after this evening. The increasing low level
moisture and low cloud development will keep overnight low temps in
the middle 40s to the lower 50s.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Key Points...

* A brief band of scattered showers Thu am into early afternoon
* Mainly dry thereafter Thu with highs in the upper 50s/lower 60s
* Showers with heavy rain & perhaps a few t-storms late Thu night
* Southerly wind gusts of 35 to 50 mph develop toward daybreak Fri

Details...

Thursday...

Another shortwave and mid level warm front will be lifting north
across the region Thu morning into early afternoon. Again...the bulk
of the dynamics will be passing to our west and north where the
steadiest showers will occur. However...enough forcing exists for a
brief band of at least scattered showers lifting north across the
region Thu morning into the early afternoon. Best chance for seeing
a few hours of rain will be across western and northern MA...but
brief showers are possible anywhere. Behind this shortwave...enough
subsidence should result in mainly dry weather with nothing more
than a few spot showers the rest of the day. High temps a bit tricky
on Thu...but thinking they will generally be in the middle to upper
50s across northern/eastern MA and probably 60-65 south of I-90 away
from the immediate coast.

Thursday night...

Strong shortwave energy will be approaching from the west late Thu
night. While nothing more than a few spot showers are expected early
Thu evening...the approaching shortwave will induce a strong
southerly LLJ late in the evening and especially after midnight.
This will increase the forcing for ascent and allow widespread
showers to overspread the region late Thu night. PWATS are depicted
to increase to 2-3 standard deviations outside climatology with the
southerly LLJ 4-5 above normal. These ingredients will yield some
heavy rainfall and there is enough elevated instability for a few
embedded t-storms. The other issue very late Thu night will be for a
period of strong southerly wind gusts. 850 MB southerly LLJ
increases to between 70 and 80 knots near daybreak Fri. Soundings do
show a robust inversion...but temps will remain in the 50s and
perhaps climb towards daybreak to near 60. So despite the
inversion...enough wind just off the deck for southerly wind gusts
of 35 to 50 mph especially if any convective elements get
involved...so the next shift may need to consider Wind Advisories
for areas near the coast toward daybreak Fri.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Highlights:

* Periods of heavy rain and gusty wind for the first part of Friday,
  then improving conditions during the afternoon.

* A few spotty showers Saturday morning and late Sunday night,
  otherwise looking more dry than wet for the weekend.

* Dry and warming up for early part of next week.

Friday: A soggy start to Friday from a strong low pressure system
moving across the eastern Great Lakes and the associated moisture
advecting north from a robust 925mb jet. No significant chances were
made to the forecast. Expecting period of soaking rain Friday
morning, periods of gusty winds, and perhaps minor coastal flooding
for Narragansett Bay during the late morning high tide.

Rain - Global ensembles are in good agreement rainfall totals will
be in the range of 0.75" to 1.5", the lesser amounts in eastern
Massachusetts, while higher amounts are in Connecticut and the east
slopes of the the Berkshires. However, there are low probabilities
based off the global ensembles and DESI, a 10 to 30 percent chance
for rain totals exceeding 2.0", mainly for Connecticut. This is
highlighted by the HREF 24 hour MAX QPF, isolated pockets of 2.0" to
2.25" mainly in Connecticut and along the western border with Rhode
Island. Due to the progressive nature of the system, think those
higher totals will be hard to come by. One caveat, there may be
embedded thunder - a convective shower may have the potential of
producing locally higher amounts.

Rivers - MMEFS does shows a couple area river that may reach minor
flood stage - mainly in Rhode Island and Connecticut. Over the past
couple of days, the probabilities have shown a downward trend, for
example;  rivers once showing a 70 percent chance of minor flood are
now down to 30 percent chance. One river still worth watching is the
lower Connecticut River as the forecast shows a 70 percent chance of
minor flood by Saturday due to the rain and snow melt from up north.

Wind - Strong 925mb jet with winds 70 to 80 knots ushers gusty wind
from the S/SSE during the first-half of Friday. Previously
mentioned, an inversion near the surface will limit the amount of
wind that could mix down to the surface. It is probable that half of
that could mix down, winds 30 to 40 knots possible along I-95 and
areas east, Cape Ann, Cape Cod, and the islands. As the NBM has a
higher bias with wind speed and gust, did cap the wind over the
water, no greater than 42 knots, as there is a stronger inversion
due to the colder SST. Finally, capped the winds over the land at 45
knots. Do think there is a time early Friday morning the sustained
winds may reach 25-35 knots, which the threshold for a Wind Advisory
is 27 knots. Confidence is not there yet, but could see an advisory
coming out either tonight or tomorrow if agreement remains.

Coastal Flooding - A bit of better news, the core of the 925mb jet
seems more progressive, which would lead to the strongest winds
blowing up Narragansett Bay well before high tide, which is 11:48
AM. Stevens Flood Advisory System (SFAS) ensemble mean forecast has
the total water level half a foot below minor flood, but the 95th
percentile (reasonable worst case scenario) would have total water
level around half a foot above minor flood stage. The astronomical
high tide is 4.5`, which means would need 2.5` of storm surge at Fox
Point. No headlines at this point, but a Coastal Flood Statement
could be needed for the high tide on Friday morning, the overnight
crew will want to reassess the latest guidance before making a
decision.

Saturday & Sunday: Trending more dry, though guidance has hinted at
a weak surface low developing off shore early Saturday morning that
could ring out a few light rain showers Saturday morning. While the
NBM had zero POPs, opted to brings in and cap POPs at 15 percent
across much of southern New England - this would leave a slight
chance of a rain shower through late morning before drying that
afternoon. Clouds otherwise on Saturday with highs in the 50s. As
for the daylight hours of Sunday, looks still dry, though a quick
moving surface low pressure system will slide across the region with
a quick hit of light rain - ending before sunrise on Monday. The
west to west/southwest flow will help boost temperatures into the low
and middle-60s.

Next Week: Synoptic picture shows surface high pressure setting up
with a amplified mid-level ridge through midweek. This over all this
period is dry with no major weather systems. Temperatures are
trending well above normal with highs in the upper-60s and low-70s
for Monday and Tuesday, possibly Wednesday.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:

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

00z TAF Update...

Tonight...High Confidence in trends but more uncertainty with
the timing.

VFR/MVFR conditions, we do expect IFR with localized LIFR
conditions to develop from southwest to northeast during the
evening in low clouds/fog patches. A few brief showers possible
into the evening mainly across northern MA...but the majority of
the period will be rain free except for perhaps some drizzle
developing overnight. Winds generally light from an E direction.

Thursday...High Confidence.

IFR to LIFR conditions dominate Thu...but may see a few spots
improve to low end MVFR. A band of showers looks to impact parts
of the region for a few hours during the morning into early
afternoon. However, dry weather probably dominates thereafter.
SE winds 5 to 15 knots.

Thursday night...High Confidence.

IFR to low end MVFR conditions persist. Northing more than a few
spot showers expected during the early evening...but
heavier/steadier rain with perhaps even a rumble of two of thunder
overspreads the region late Thu evening and especially after
midnight. SE winds 10 to 15 knots increasing to between 15 and 25
knots with 30-40 knot gusts developing toward daybreak...strongest
of which near and southeast of I-95. LLWS will also be a concern
overnight with a southerly LLJ of 70 to 80 knots.

KBOS TAF...High confidence in trends but more uncertainty with
the timing.

KBDL TAF...High confidence in TAF.

Outlook /Friday through Monday/...

Friday: Mainly IFR, with local MVFR possible. Strong winds with
gusts up to 45 kt. Chance SHRA, areas BR.

Friday Night: Mainly VFR, with local MVFR possible. Windy with
local gusts up to 30 kt. Slight chance SHRA.

Saturday: Mainly VFR, with areas MVFR possible. Strong winds
with local gusts up to 40 kt. Slight chance SHRA.

Saturday Night: Mainly VFR, with local MVFR possible. Strong
winds with local gusts up to 40 kt.

Sunday: VFR. Breezy. Slight chance SHRA.

Sunday Night: VFR. Breezy. Chance SHRA.

Monday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels:

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

** Gale Warning late Thu night into Fri **

Tonight and Thursday...High Confidence.

A relatively weak pressure gradient will keep winds/seas below small
craft advisory thresholds tonight and Thu. However...areas of fog
will develop overnight and persist into Thu which will reduce vsbys
for mariners.

Thursday night...High Confidence.

A shortwave approaching from the west will induce a strong
southerly LLJ of 70-80 knots late Thu night into early Fri.
While there is a robust inversion...enough wind just off the
deck should allow for southerly wind gusts of 35-40 knots late
Thu night into Fri. In addition...seas will build to between 7
and 13 feet by daybreak Fri. We went with Gale Warnings all
waters...except maintained Gale Watches for Boston
Harbor/Narragansett Bay but those will likely need to be
upgraded in later packages.

Outlook /Friday through Monday/...

Friday: Moderate risk for gale force winds with gusts up to
40 kt. Rough seas up to 14 ft. Chance of rain showers, areas
fog. Visibility 1 to 3 nm.

Friday Night: Moderate risk for Small Craft Advisory winds with
areas of gusts up to 30 kt. Rough seas up to 12 ft. Slight
chance of rain showers.

Saturday: Strong winds with gusts up to 35 kt. Rough seas up to
11 ft. Slight chance of rain showers.

Saturday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Areas of rough seas.

Sunday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft.

Sunday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers.

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Gale Watch from late Thursday night through Friday evening for
     ANZ230-236.
     Gale Warning from midnight Thursday night to 8 PM EDT Friday
     for ANZ231>235-237-250-251-254>256.

&&

$$

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