Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 301148
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
748 AM EDT Fri Jul 30 2021

.SYNOPSIS...
A cold front will move through early this morning, followed by a
secondary front this afternoon. High pressure will then build
from the upper Midwest tonight through Saturday, then weaken
Saturday night. Weak low pressure will then pass well to the
north across upstate New York and New England on Sunday while
another weak low develops along the Mid Atlantic coast and heads
out to sea. A cold front will then pass through late Sunday
into Monday, followed by a broad high pressure system building
in behind the front early next week. The high will shift east
and offshore by mid week. A low pressure trough over the Ohio
Valley could then bring unsettled conditions for late week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Cold front bisects the area as of 08Z. The front will continue
offshore this morning with skies becoming mostly sunny, then a
secondary front will move through this afternoon accompanied
by bkn Cu. NW winds after passage of this front will pick up to
15-20 mph with gusts up to 30 mph during the late afternoon and
early evening. Temps this afternoon via downslope flow and
mixing up to 825-850 mb should reach 80-85 in most areas,
except upper 70s across the interior lower Hudson Valley.

The NW flow will bring in a cooler air for tonight, with lows
ranging from the upper 40s in the interior valleys well NW of
NYC and in the Long Island Pine Barrens, to the lower 60s in
NYC. If winds inland diminish sooner the interior valleys could
bottom out in the mid 40s.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
Fair wx with mostly sunny skies expected on Sat under sfc high
pressure. High temps ranging from the mid 70s inland, to upper
70s most elsewhere, perhaps still touching 80 in urban NE NJ.

Sat night will also remain dry, with clouds increasing over the
interior as a warm front lifts through nrn PA and upstate NY.
Return flow will begin to set up along the coast as the sfc high
weakens and moves east, so low temps will moderate, ranging from
the mid 50s to mid 60s.

Clouds should increase daytime Sunday, with chance of showers in
the afternoon as weak low pressure passes to the north, and as
another weak low takes shape along the Mid Atlantic coast. If
the second low tracks close enough to the area, some of these
showers could be on the heavy side going into Sunday evening,
but this remains uncertain with the ECMWF low track farther
south and the NAM perhaps suffering from upstream convective
feedback and overdoing the low strength and northward track.
High temps should be a touch warmer than those of Sat, mostly
upper 70s/lower 80s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The low to the north and associated frontal boundary extending
along the Eastern seaboard exits east Sunday night into Monday.
Showers and isolated thunderstorms along the front will likely
linger in the area into the early morning hours. Expect post-
frontal conditions Monday with breezy north winds and clearing
skies. Temperatures in the afternoon change little and despite
the cold front highs will still be in the upper 70s and low 80s.

By Tuesday a 1020mb high pressure system builds behind the front
and settles into New York state. Conditions over the forecast
area should be stable and with 1000-500mb RH values at or below
50% rain chances are very minimal. Though one feature that will
have to be monitored is the previous surface boundary. As it
retrogrades northward as a warm front, models are depicting a
broad coastal low forming offshore. This low is enhanced an
deepened by upper level jet dynamics, but should remain south of
the area.

Once the high slides offshore mid to late week, south winds from
the boundary and warm front continue to moisten the
surrounding environment. Southern New York could see
precipitable water values around 1.9 to 2.0 inches Thursday.
This combined with a mid level trough extending through the Ohio
River Valley could lead to a series moderate to heavy rain
events late in the week. Much uncertainty remains with the long
range forecast and will have to be monitored for updates.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
High pressure builds into the area following the cold frontal
passage.

VFR at all terminals following the passage of a cold front.

Cold front is passing through this morning from NW to SE,
pushing offshore. NW winds around 10 kt following the cold
frontal passage, will ramp up, especially between 12-15Z, with
gusts 20-25 kt. A few higher gusts will be possible in the
afternoon.

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

No unscheduled amendments expected.

.OUTLOOK FOR 12Z SATURDAY THROUGH TUESDAY...
.Saturday...VFR.
.Sunday...Mainly VFR with chance of showers...mainly at night.
.Monday...VFR.
.Tuesday...MVFR or lower with a chance of rain.

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

&&

.MARINE...
Seas on the ocean waters should diminish below 5 ft going into
the early daylight hours. A stronger NW flow will then take
hold after a secondary cold frontal passage this afternoon.
Gusts over 25 kt expected on all waters, with ocean seas
building back to 5 ft. Conds should fall below SCA criteria on
the non-ocean waters during Fri evening, and on the ocean late
Fri night.

Quiet thereafter into mid week. Combo of S winds and incoming
swell from a low off the coast could build ocean seas back up
to 3-5 ft on Wed.

&&

.HYDROLOGY...
No additional hydrologic issues are anticipated.

&&

.TIDES/COASTAL FLOODING...
There is a moderate risk of rip current development at the
ocean beaches today despite offshore flow, due to residual 2-ft
long period S swell.

There is a low risk of rip currents on Saturday.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 2 PM this afternoon to midnight EDT
     tonight for ANZ331-332-338-340.
     Small Craft Advisory from 2 PM this afternoon to 8 PM EDT this
     evening for ANZ335-345.
     Small Craft Advisory until 2 AM EDT Saturday for ANZ350-353-
     355.

&&

$$
SYNOPSIS...BG/DJ
NEAR TERM...BG
SHORT TERM...BG
LONG TERM...DJ
AVIATION...DJ
MARINE...BG/DJ
HYDROLOGY...BG/DJ
TIDES/COASTAL FLOODING...BG


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