Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 250546
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
146 AM EDT Fri Sep 25 2020

.SYNOPSIS...
High pressure will remain over the western Atlantic through
Friday night. A weak disturbance approaches from the south late
Friday night and will pass south of the area on Saturday. High
pressure will settle south of the area on Sunday. A series of
cold frontal passages will take place through the middle of next
week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Mostly clear skies have allowed for enough cooling outside of
the NYC metro for patchy fog and stratus to develop. This will
have to be watched through the night as some of the HiRes
soundings pointing toward a really shallow saturated boundary
(less than 500 ft). Partly to mostly cloudy skies are possible,
especially across coastal areas and river valleys toward
daybreak.

Despite near calm winds, and mostly clearing skies, a light
southerly flow will keep a warm airmass in place, with overnight
lows slightly above seasonal normals.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/...
During Friday morning a northern stream and southern stream
shortwaves merge, keeping a amplifies open wave moving through
the Ohio Valley and toward the mid Atlantic coast Friday night.
The guidance is still indicating that some of the energy with
the wave moves up along the coast late Friday night. And with
some weak lift will keep slight chance probabilities in the
forecast. With a moistening lower level in a persistent
southerly flow Friday and Friday night, there may be patchy
fog, and some stratus.

There is a moderate risk of rip currents at the Atlantic Ocean
beaches on Friday due to a lingering E-SE swell.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
There is a moderate risk of rip currents at the Atlantic Ocean
beaches on Saturday due to a lingering E-SE swell.

Low pressure will move well south of the area on Saturday.
Enough low level moisture on a southerly flow could very well
lead to some low level stratus and some patchy fog early in the
day. Otherwise the current thinking is that much of the day will
be dry. An open upper level disturbance will be around early,
then depart later in the day into the evening. Thought it
prudent to go with a general slight chance, especially for the
first half of the day. The broad southerly flow will keep
temperatures above average for late September through the entire
weekend. By late Saturday night and early Sunday morning there
will be a somewhat higher chance of lower stratus and patchy
fog. The winds will still be relatively light late at night and
into the early morning with the guidance suggesting another
surge of low level moisture moving in from the south. Moving
into the late morning and afternoon partly sunny skies are
expected, leading to another warm and somewhat humid day for
late September with areas away from the shore likely climbing
into the lower 80s.

By Sunday night a cold front will start to draw closer from the
Great Lakes and Ohio Valley region. Also a weak disturbance in the
lower levels will begin to approach from the southwest. Thus
precipitation chances increase late Sunday night into Monday
morning.

A pattern transition will then begin to occur into next week.
Long wave amplification will take place as heights rise out
west, and a trough develops over the Midwest and begins to
translate east. The first cold front will approach towards
Monday night. Ahead of the front showers should develop, and
with some instability cannot rule out a thunderstorm. There will
only be a subtle drop in temperatures and humidity, if at all
into Tuesday as another cold front approaches. This cold front
may have more in the way of overall forcing to work with, thus
there will be higher likelihood of rain along with a slight
chance of a few thunderstorms across the area into Tuesday
afternoon. The 12z ECMWF is at odds with much of the remainder
of the global guidance as it came in a lot slower, and holds off
on bringing rain to the area until late Tuesday night into
Wednesday. For now leaned mostly away from the ECMWF and went
more with a GFS, ICON, Canadian solution. However, did extend
chance and slight chance POPs for a bit longer into Tuesday
night and Wednesday morning in case the ECMWF has some merit.
Thereafter temperatures will fall back to near seasonable levels
behind a series of cold fronts. Near normal temperatures will
last into later Wednesday through the remainder of the week as
the long wave trough will be stubborn to push out of the area.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
Mainly VFR as high pressure over the Mid Atlantic region moves
to the south. Some patchy fog til about 13Z outlying arpts with
IFR or lower. Light SW winds tonight will increase to 5-8 kt
after 13Z-14Z, with a more southerly coastal sea breeze in the
afternoon. KEWR/KTEB should shift SE late afternoon, with speeds
at KJFK around 10 kt.

 ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...

No unscheduled AMD expected. High confidence on winds.

.OUTLOOK FOR 06Z SATURDAY THROUGH TUESDAY...
.Late tonight through Sunday...Chance of late night/early
morning fog with IFR conds, otherwise mainly VFR.
.Sunday night...Chance of MVFR conds with any showers late.
.Monday and Tuesday...Chance of MVFR conds with any showers or
isolated afternoon tstms. S-SW winds G20-25kt.

Detailed information, including hourly TAF wind component
forecasts, can be found at: http:/www.weather.gov/zny/n90

&&

.MARINE...
Winds and seas will remain below SCA levels through the weekend.
By late Sunday into Sunday night the southerly flow will
increase ahead of an approaching frontal boundary. This should
lead to SCA conditions to develop out on the ocean into Monday
as seas approach 5 ft or thereabouts. There may be a period
where seas become more marginal and may actually fall below SCA
conditions. However, the south to southwesterly flow is expected
to increase into the day on Tuesday. This will make small craft
conditions more likely once again on the ocean, with marginal
small craft conditions becoming more likely for the near shore
waters towards Tuesday afternoon.

&&

.HYDROLOGY...
No hydrologic impacts are anticipated at this time through the
entire forecast period.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$


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