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Area Forecast Discussion

Forecast Discussion for BOX NWS Office
000
FXUS61 KBOX 170613
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
213 AM EDT Fri Sep 17 2021

.SYNOPSIS...
Low pressure south of New England will brings lots of clouds to
region today, along with areas of fog and drizzle to the area
this morning, and a spot shower this afternoon. The low will
also generate building waves and surf. As the low moves out to
sea Saturday, breaks of sunshine develop along with milder
temperatures. High pressure then settles in Sunday into the
middle of next week, yielding milder than average temperatures
and several days of dry weather. Then a strong cold front
brings the region first real taste of autumn by late in the work
week.

&&

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

2 AM Update...

Most of the 00z guidance 06 hr qpf ending at 06z Fri is too wet
when compared to latest radar imagery across SNE and the
adjacent waters. Thus, will base today`s forecast on the drier
guidance such as the HRRR and GFS. Drier solutions seem
reasonable given mid level ridging across the area today. BUFKIT
time sections reveal lots of mid level dry air, which will
likely erode showers as activity comes onshore, especially
farther inland where dry air aloft is deepest. Thus, other than
spotty drizzle this morning, then a spot shower this afternoon,
mainly dry weather prevails.

Mostly cloudy conditions, light onshore winds will result in
seasonably cool temps with highs in the 70s. Although, it will
feel a bit humid with dew pts in the mid to upper 60s.

&&

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

Friday Night & Saturday...

Skies will finally begin to clear by daybreak on Saturday, but fog
will again impact the region as northeast flow persists.
Given almost identical conditions to Thursday night, low
temperatures will fall into the 60s once again. Dewpoints will be
slightly higher across western MA, so even our coolest spots will
only fall into the mid 60s.

A tropical system being monitored currently monitored by the NHC is
expected to pass to our southeast beginning Friday night. The
impacts from this system are expected to be low in southern New
England. The primary threat will be choppy surf and rip currents,
primarily at our south facing beaches.

&&

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

* Scattered showers with cool and breezy conditions on Saturday
  before dry and seasonable conditions return on Sunday.

* Dry weather and above normal temperatures likely heading into
  middle of next week with high pressure in control.

* Could have our first real taste of autumn late next week.

Details:

Saturday...

The potential tropical cyclone mentioned in the short-term
discussion will track near or just south of the 70W/40N benchmark on
Saturday. This would mean best chances of rain across southeast New
England, though rains in most areas may prove more intermittent.
Otherwise, with onshore flow, expect mostly cloudy, breezy and cool
conditions with interval of rain showers along with increased swells
and heightened risk of rip currents. While effects and impacts will
ultimately hinge on the track and intensity of the cyclone, right
now the impacts to Southern New England appear minimal.

As heights rise behind the exiting cyclone, there should be
significant improvement on Sunday. Sunshine may even return on
Saturday afternoon if the low pressure system is faster to exit. Dew
points fall from the 60s into the 40s and with sunshine and
seasonable conditions returning, it will feel very comfortable for
outdoor activities on Sunday. For reference, normal daytime highs
are in the low to mid 70s.

Monday into Wednesday...

Monday looks to feature mostly dry and seasonable conditions with
high pressure in control. Then mid-level ridging amplifies over the
eastern US, with global guidance ensembles showing 588+ Dm ridge
building into Southern New England by middle of next week. With mean
850mb temperatures in the low to mid teens, expect daytime highs to
reach the upper 70s to lower 80s, which would be 5 to 10 degrees
above climatological normal. Have gone with NBM guidance for now
given we are so far out but it is possible that daytime highs will
be increased in future updates with southwest flow aloft boosting
downsloping adiabatic warming. In fact, the Climate Prediction
Center 6 to 10 day outlook features above 80 to 90 percent
probability of above normal temperatures. So even as we head into
astronomical fall for the Northern Hemisphere (beginning September
22), it will feel more like late August. PWATs look to be slightly
below to near normal so expect generally mild days and cool nights
given the dry air mass.

Thursday...

There are increasing signs that we could have our first real taste
of fall heading into the latter part of the upcoming work week. Some
deterministic guidance are showing 850mb temperatures in Celsius
crashing from the mid teens to the low single digits, with sub-
zero temperatures just north of our area. Trough digging into
the Great Lakes will eventually erode the ridge over Eastern US
by Wednesday/Thursday time frame. Models still differ on the
timing of the front and strength of the dynamics. But it is
reasonable to expect a line of showers and thunderstorms out
ahead of the advancing cold front. This far out, it is too
premature to speculate on the potential for severe weather but
it looks increasingly likely that the stretch of above normal
temperatures will come to an abrupt end by late in the work
week. &&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
Forecaster Confidence Levels.

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

06z update...

Today...high confidence on trends, lower on exact timing.

Trending toward IFR/LIFR across RI and eastern MA along with
areas of drizzle. MVFR across CT and western-central MA. Cigs
slowly lifting this afternoon from LIFR to IFR across RI and
eastern MA, and remaining MVFR elsewhere. Other than a spot
shower, mainly dry this afternoon. Modest ENE winds, except
lighter inland.

Tonight...high confidence on trends, lower on exact timing.

Trending back down to IFR/LIFR regionwide. Patchy fog and
drizzle possible along with a few spot showers over southeast MA.
Modest NE wind along the coast, lighter inland.

Saturday...high confidence on trends, lower on exact timing.

Any IFR/LIFR early in the morning, trends upward to MVFR/VFR in
the afternoon, as winds become northerly. Mainly dry, but a few
showers possible late in the day across CT and western-central
MA.

KBOS Terminal...high probability for IFR but low risk of LIFR
this morning and again tonight.

KBDL Terminal...Moderate confidence in MVFR category being the
prevalent conditions.

Outlook /Saturday night through Sunday/

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

Sunday: VFR. Breezy.

Sunday Night through Tuesday: VFR.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
Saturday: Mainly VFR, with local MVFR possible. Breezy. Slight
chance SHRA.

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

Sunday: VFR. Breezy.

Sunday Night through Tuesday: VFR.

&&

.MARINE...
Forecaster Confidence Levels.

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

Tonight...ridge of high pressure offshore builds across the waters.
Patchy dense fog will yield poor vsby at times. Light ENE winds.
A spot shower is possible across the southern waters.

Friday...ridge of high pressure remains across the waters, yielding
light ENE winds and mainly dry weather, a spot shower is again
possible. By 12Z, waves begin to build as a tropical system
approaches from out south. A small craft advisory has been hoisted
starting at this time.

Outlook /Saturday Night through Tuesday/...

Saturday: Winds less than 25 kt. Local rough seas. Slight chance of
rain showers. A small craft advisory will be in place for our
southern waters.

Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers. A small craft advisory will need to be
considered to cover this period.

Sunday through Monday: Winds less than 25 kt. Seas up to 5 ft. A
small craft may need to be considered for this period.

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

Tuesday: Winds less than 25 kt. Seas up to 5 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 AM this morning to 8 PM EDT
     Saturday for ANZ235-237-254>256.

&&

$$
SYNOPSIS...Chai/KS
NEAR TERM...Nocera
SHORT TERM...KS
LONG TERM...Chai
AVIATION...Nocera/Chai
MARINE...Chai/KS

NWS BOX Office Area Forecast Discussion

 



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