Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 270144
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
944 PM EDT Mon Oct 26 2020

.SYNOPSIS...
Spotty light rain or drizzle continues overnight. Morning fog
and clouds continue on Tuesday along with cool temperatures. The
remnants of Zeta should bring a soaking wind swept rain
Thursday into Friday, with rain possibly ending as wet snow
Friday across the interior, especially in the hills. Behind this
departing system, dry but blustery and cold weather follows
later Friday. High pressure returns next weekend with dry but
chilly weather Saturday followed by milder temperatures Sunday
and next Monday.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
945 PM update...

Widespread stratus and patchy fog across SNE this evening. But
mostly dry with just a few showers moving across Cape/Islands.
Cold front across northern New Eng will drop south across the
region overnight with wind shift to NW.  Patchy drizzle is
possible tonight given abundant low level moisture in place.
Also can`t rule out an isolated shower in northern MA overnight
as moisture deepens behind the front. Temps dropping to low/mid
40s across interior northern and western MA but remaining in the
50s near the south coast.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Little improvements will be made in the overall cloud cover on
Tuesday. As low clouds will fade out HREF supports mid and high-
level clouds sticking around for much of the day. As previously
stated CAA will take place as 925mb temperatures to our
northwest are between +0C and +4C. A northwest wind between 10
and 15 knots will help to transport that colder air into
southern New England. This will result in temperatures at the
surface to only reach the upper 40s inland and mid 50s at the
coast.

Tuesday night into Wednesday morning a weak vort max passes
southern New England which could pop-up a stray shower. Both the
ECMWF and GFS have indicated the possibility. Otherwise
another dry and colder night ahead with temperatures in the 30s
with upper 30s to 40 degrees at the coast.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Highlights...

 * Soaking rain Thu/Fri from remnants of Zeta, possibly ending as
   wet snow inland, especially in the hills.
 * Blustery/cold Fri and Sat, then milder Sun.

Overview...

Main concern is potential for a soaking rain Thu/Fri as remnants of
Zeta interact with closed low ejecting from desert SW. Large scale
pattern remains progressive and expect surface low to track off mid
Atlantic coast, since lack of downstream ridging should prevent
system from closing off or tucking closer to SNE. Seeing good
agreement in 06Z GEFS and EPS. If anything GEFS is a tad farther
south with majority of both ensemble members are fairly close to
mean. Main difference is with timing as EPS is about 6 hours slower.
That said, 12z ECMWF has come in with sharper upper trough and more
robust surface low that tracks just inside 40/70 benchmark. Seems to
be an outlier but something to watch for future trends.

System has a lot going for it from precipitation standpoint -
tropical moisture overrunning cooler low level airmass and signals
for banding from strong frontogenesis. Certainly beneficial rainfall
for region, perhaps on order of 1 to 2 inches.

Colder air arrives behind system later Thu night into Fri which
should cause rain to change to wet snow across interior, especially
across hills (East Slopes of Berkshires, Worcester Hills, and
perhaps even northern CT) where some minor accumulation is possible.
If winds can shift to N Fri morning, it`s also possible that we see
some wet snow mix in closer to coast, especially from Boston into
northern RI, but that is far from certain at this point (and it
probably wouldn`t stick either). NE flow combined with water temps
in 50s are certainly a limiting factor.

Brief shot of colder weather follows later Fri and Sat before
temperatures moderate Sun and Mon.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

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

Tonight: Moderate confidence.

IFR/LIFR with continued drizzle, mist/fog and low stratus for
the first part of this evening. A cold front arrives late
tonight, which should bring about improvement towards VFR-MVFR.
This improvement may start across western southern New England
around 05-07z, and towards early Tue AM towards the eastern
coast. Light south winds shift to northwest and increase to
around 7-12 kt, occasional gusts around 20 kt near eastern MA
and Cape Cod toward early Tue AM.

Tuesday: High confidence.

Improvement toward SCT-BKN VFR ceilings. Ceilings may lower
towards VFR-MVFR levels late for western TAFs as a weak
disturbance aloft approaches but should be predominantly VFR.
Very light showers possible underneath this deck late in the
day, but may be more along the lines of virga.

Tuesday Night: High confidence.

VFR.

KBOS Terminal...Moderate confidence in TAF, mainly timing
improvement later tonight. IFR cigs continue overnight.
Expecting quick improvement to VFR towards the morning push, but
timing may be off a couple of hours.

KBDL Terminal...Moderate confidence in TAF, mainly timing
improvement later tonight.

Outlook /Wednesday through Saturday/...

Wednesday: Mainly VFR, with local MVFR possible.

Wednesday Night: VFR.

Thursday: Mainly VFR, with local MVFR possible. RA likely.

Thursday Night: Mainly MVFR, with areas IFR possible. Windy
with areas of gusts up to 35 kt. RA.

Friday: Mainly VFR, with local IFR possible. Windy with gusts
up to 35 kt. Chance RA, chance SN.

Friday Night: VFR. Windy with local gusts up to 35 kt.

Saturday: VFR. Breezy.

&&

.MARINE...
Small Craft Advisories continue for the southern out coastal
waters through this evening. Waves continue to diminish
overnight. Could see a few gusts approach 25 kt across the
eastern coastal waters Tuesday behind a cold front.

Outlook /Wednesday through Saturday/...

Wednesday: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers.

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

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

Thursday Night: Low risk for gale force winds with gusts up to
35 kt. Local rough seas. Rain.

Friday: Moderate risk for gale force winds with gusts up to
35 kt. Rough seas up to 11 ft. Rain likely, chance of rain
showers.

Friday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 10 ft. Slight chance of
rain showers.

Saturday: Winds less than 25 kt. Rough seas up to 9 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 10 PM EDT this evening for
     ANZ254>256.

&&

$$
SYNOPSIS...Gaucher/JWD
NEAR TERM...KJC
SHORT TERM...Gaucher
LONG TERM...JWD
AVIATION...Belk/Gaucher/JWD
MARINE...Gaucher/JWD



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