Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 151114
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
714 AM EDT Fri Mar 15 2024

.SYNOPSIS...

Brief showers focused mainly north of the Massachusetts Turnpike
wind down early this morning. Otherwise...clouds linger today with a
large range in high temperatures from 45 to 50 in northern
Massachusetts and 60 to 65 degrees in Connecticut. Drying out
on Saturday with unseasonably mild temperatures away from the
immediate coast. Scattered showers, especially early on Sunday
as a frontal system slides through. More seasonable
temperatures for much of the upcoming week. Isolated diurnal
showers possible on Monday and Tuesday. May still be unsettled
by midweek.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

7 AM Update...

Have adjusted our precip chances based on latest observations.
Should have a bit of a lull in activity early this morning
before a line of diminishing activity slides in from eastern NY.
Not certain this will make it all the way to the eastern MA
coast, but should be out of here by mid/late AM. Leaned toward
the latest HRRR guidance. Rest of the forecast looks to be on
track at this point with colder air pushing in from northern MA,
but mild across the south coast.

345 AM Update...

* Showers mainly north of I-90 wind down early this morning
* Wide range in highs today...45-50 in N MA & 60-65 in CT

A wave of low pressure crossing the region this morning was
resulting in a brief band of showers. The bulk of these were focused
north of I-90...where there was a bit better overruning given the
track of the low. That being said...rainfall amounts will be light
across the entire region and the bulk of these showers will be
winding down early this morning. As the wave of low pressure pulls
east of the region...winds will shift to the north. This will allow
for low clouds to push south into much of central and eastern New
England. There may be a few left over spot showers across parts of
northern and eastern New England...but mainly just cloudy today. The
north winds and low clouds will hold high temps in the 45 to 50
degree range across northern MA with the coolest of readings in
northeast MA. Meanwhile...better chance for some breaks in the
clouds across parts of southwest MA and especially CT. Thinking that
it will not take much to allow that region to see highs reach 60-65.
Later shifts will have to monitor trends on winds/satellite and may
have to adjust these temps depending on how things unfold.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...

Key Points...

* Decreasing clouds from W to E overnight with lows in the 30s
* Partly sunny Sat with highs upper 50s/lower 60s...cooler coast

Details...

Tonight...

A weak ridge of high pressure to our southwest will take control of
our weather tonight. Limited push of dry air from the west...so
clouds may be slow to exit the region. That being said...we do
expect to see improvement from west to east overnight. Overnight low
temps should bottom out in the 30s with winds becoming light/calm.

Saturday...

A weak ridge of high pressure to our south will result in partly
sunny skies and another March day with above normal temps. 925T are
between +5C and +6C and a fairly dry airmass in pre-greenup should
allow for high temps to over-achieve away from the immediate coast.
Highs across most of the region should top off in the upper 50s to
the lower 60s. However...weak pressure gradient will likely allow
for sea breeze development will result in temps several degrees
cooler along the immediate coast once sea breezes kick in during the
afternoon.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...

Highlights

* A frontal system slides through Sun bringing scattered showers.
  May be a bit gusty at times.

* Dry for most, but will have isolated showers on Mon and Tue.
  Temperatures trending near to below normal.

* Still unsettled on Wed, but appears drier on Thu. Temps still near
  to below seasonable.

Saturday Night through Sunday...

Cyclonic flow in place through this timeframe. An elongated trough
will initially be in place over the Great Lakes Sat Night. The
trough lifts into the eastern Great Lakes by early Sun and into
northern New England/Nova Scotia by late Sun. A frontal system
swings through bringing scattered rain showers.

This is our next shot for more widespread shower activity across
southern New England. Still looks like a fairly progressive system,
so should see some breaks of sun late in the day. As mentioned
yesterday, we really do not have a whole lot of moisture to work
with. Expect PWATs to range from roughly 0.3-0.5 inches, which is
roughly around the 25th percentile to near normal for this time of
year. Should result in somewhat widespread scattered activity,
especially earlier in the day.

Sill looks like we could have a period of gusty winds, but should
remain well below advisory levels. Confidence remains low to
moderate here as guidance is spread on the intensity of the LLJ.
Risk appears highest early on Sun with SWly LLJ, but still could be
a bit breezy through the afternoon as colder Wly air advects in wake
of the system. For now am advertising gusts of 20-30 mph through the
day. High temps in the 50s.

Monday through Tuesday...

Still will be stuck in cyclonic flow. A deeper trough digs into the
eastern Great Lakes/Mid Atlantic on Mon and through by early Tue. A
shortwave digs from northern Ontario late Mon Night into norther n
New England on Tue. A surface trough or two rotates through New
England.

Have bumped up our cloudiness and PoPs, especially during the
daytime. Will have an anomalously cold airmass overhead at 500 hPa
as temps cool to roughly -25 to -40 degrees Celsius. This is -1.5 to
-3 STD below model climo per the NAEFS/EPS. This in combination with
diurnal heating will result in a fair amount of cloudiness. The only
question especially for precip chances is how much moisture will be
available. At the moment appears PWATs will be 0.2-0.3 inches, which
is lower than normal for this time of year. Based on experience did
bump our PoPs up to slight for the risk of an isolated shower during
the day Mon/Tue. Actually wouldn`t be surprised if there is a bit of
graupel.

Temperatures trending near to colder the normal. Expecting 925 hPa
temps to range from 0 to -3 degrees Celsius with W to WNW flow. The
end result will be highs topping out in the 40s.

Wednesday through Thursday...

Bit of a pattern change setting up as flow shifts from cyclonic to
quasi-zonal. A fast moving shortwave slides through the Great Lakes
and New England on Wed. A ridge axis begins setting up across the
low/mid Mississippi River and TN Valley on Thu. May see a frontal
system move through on Wed before high pressure builds in Thu.

Considerable uncertainty in the forecast for the middle of the week
as there is little run to run and model to model consistency. Could
have a frontal boundary in place over the region. A low may ride
along the front, but there is a lot of spread amongst EPS/GEPS and
GEFS guidance at this point with the low tracks/intensity. Given the
spread think that the NBM slight chances of precip are fine. High
temps still cooler than seasonable with readings in the low/mid 40s.

Drier on Thu as high pressure builds into the region. Could see
temperatures starting to trend a bit milder with W/SW flow. Highs
top out in the 40s to low 50s.

&&

.AVIATION /11Z FRIDAY THROUGH TUESDAY/...

Forecast Confidence Levels:

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

Today...Low confidence.

A low confidence forecast in terms of coverage and timing of low
clouds. Appears the main risk of IFR-LIFR conditions through
daybreak will be across central to northeast MA. Otherwise, mainly
VFR conditions elsewhere. As this wave of low pressure works
across southeast New England this morning, low clouds have
temporarily scoured out near the Cape/Islands. However, behind
the departing wave of low pressure winds shift to the N at 10 to
15 knots with some 20+ knot gusts possible. This allows for
MVFR-LIFR ceilings to overspread much of the region east of the
CT River Valley through the morning with the lowest conditions
along the eastern MA coast.

Later shifts will have to monitor low cloud trends/timing today
for possible refinements given the uncertainty in the forecast.

Tonight...High Confidence.

Mainly MVFR ceilings will linger into the evening across eastern
New England, but VFR conditions overspread this region from the
west as the night wears along. Light and variable winds.

Saturday...High Confidence.

VFR. SW winds 5-10 knots but localized sea breezes developing
during the afternoon along portions of the immediate coast.

KBOS TAF...Low confidence in TAF.

Difficult forecast in terms of timing/duration of low clouds.
Current thinking is that IFR to perhaps even LIFR conditions
impact the terminal into the afternoon due to low clouds. Could
have another brief shower from 15-17Z. Winds shift from the E
this AM to the N by roughly 14-16Z.

KBDL TAF...High confidence in TAF.

Outlook /Saturday Night through Tuesday/...

Saturday Night: VFR. Breezy. Slight chance SHRA.

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

Sunday Night: VFR. Breezy.

Monday: VFR. Breezy. Slight chance SHRA.

Monday Night: VFR. Breezy.

Tuesday: VFR. Breezy. Slight chance SHRA.

&&

.MARINE...

Forecaster Confidence Levels:

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

Today...High Confidence.

Wave of low pressure passing to our east this morning will allow
winds to shift to the NNW today. We also expect several hours of 25
knot north wind gusts behind this low pressure system impacting our
eastern waters. Therefore...we have hoisted small craft for many of
our eastern and outer-waters where there might be some marginal 5
foot seas as well.

Tonight and Saturday...High Confidence.

Lingering marginal small craft wind gusts/seas should diminish this
evening as a weak ridge of high pressure to our southwest takes
control. This should result in winds/seas below small craft advisory
thresholds for the rest of tonight and Saturday as well.

Outlook /Saturday Night through Tuesday/...

Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft.

Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Seas up to 5 ft. Slight chance of rain showers.

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

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

Monday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft.

Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Seas up to 5 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 11 AM this morning to 11 PM EDT this
     evening for ANZ231-232-251.
     Small Craft Advisory from 2 PM this afternoon to 11 PM EDT
     this evening for ANZ250-254.
     Small Craft Advisory until 11 PM EDT this evening for ANZ255-
     256.

&&

$$

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


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