000
FXUS61 KOKX 180054
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
854 PM EDT Sun Sep 17 2023

.SYNOPSIS...
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A cold front approaches tonight and stalls over the area on
Monday as low pressure passes to the south and east late
Monday into Monday night. High pressure builds Tuesday and
remains over the area through early Friday, before shifting
offshore late Friday. Low pressure then approaches from the
south on Saturday.
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&&

.NEAR TERM /THROUGH MONDAY/...
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The forecast remains on track this hour with only minor
adjustments made for the onset of precipitation across the
interior. KOKX radar shows returns across northern NJ and the
LoHud, though very little appears to be reaching the ground as
of yet per sfc observations in these areas. Inspection of NYS
mesonet profilers at Red Hook, Suffern and Staten Island still
show a depth of fairly dry air at low levels, suggesting
widespread precip is not yet making it to the ground. Trends in
these data do show some moistening of the the column through
time, so expect precipitation coverage to increase as the
columns saturate over the next few hours. Previous discussion
follows.

After a very dry airmass during the previous 24 hours, lower
latitudinal air moves up from the south with high theta-e values
and PWATs. To help quantify the airmass change taking places
PWATs from the previous 24 hours were below 0.50 PWAT, with
values by late Monday morning climbing above 1.50 PWAT as warmer
and more humid air surges northward out of the south ahead of
an slowing advancing cold front. Therefore, look for showers to
break out from the WSW to ENE this evening. It may take several
hours, say closer to or after midnight before far eastern
sections lock in with rain. Precipitation looks to become
moderate in nature later in the overnight and into Monday
morning. Instability will increase subtly, but it will be
elevated. With the lack of sfc instability the threat of severe
weather is not on the table. With dew points rising through the
60s tonight, temperatures will hold steady or even rise a degree
or two on a light southerly flow. Look for temperatures to be
in the milder 60s tonight into early Monday morning.

On Monday look the rain to vary in intensity from light, to
briefly moderate with most of the embedded convective elements
being suggested by the convective allowing models (CAMs) moving
across far eastern areas and just offshore. The upper level jet
axis at around 100 kt from the global guidance is still
residing far enough back to the west to suggest that moderate
rain could get a bit further west than some of the guidance is
suggesting. Thus some embedded rainfall rates of a quarter of an
inch are possible towards the mid to late morning with the axis
of higher PWATs and weak instability pivoting through slowly.
The trend in the guidance has been suggesting the heavier precip
/ rates sliding just to the east of the CWA during the day
Monday. Overall, expecting around a half inch of rain on average
across the area, with perhaps far eastern / southeastern
sections see closer to 3/4 of an inch to around or just over 1
inch of rain. Have chosen to keep slight chance thunder in the
grids for tonight and into a good portion of the day on Monday.
As low pressure spins up just south of the area and starts to
get further north late in the day, look for drier air to begin
to work in at the mid levels. The rain should taper from west to
east late in the day and into Mon evening.
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&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/...
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As the low gets east of the area the winds will back to the N
and eventually NW later Mon night. Much of the area will clear
from west to east for the late evening and closer to midnight
further east. The breeze will attempt to pick up a bit later Mon
night into Tue AM as the pressure gradient increases with high
pressure building to the west. Later Mon night another air mass
change takes shape as dew points begin to lower closer to and
just before daybreak Tue AM. Temperatures will get into the 50s
NW late, and around 60 closer to the coast.

Tuesday will feature a NW breeze with lower humidity and
seasonable temperatures. Look for a good deal of sunshine with
NW winds gusting up to 25 mph or so, as temperatures top out
mostly in the middle 70s.
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&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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A fairly tranquil period in store for much of the extended with
a dry period expected through Friday. Global ensembles are in
good general agreement with the evolution of the synoptic
pattern over this period, and as such the NBM was used as the
basis for this forecast update.

Longwave trough and attendant closed low located over New
England head east offshore by late Tuesday, as the flow
flattens and ridging begins to build in from the Central Plains.
The ridge axis slowly builds to the east during midweek before
moving offshore by Saturday. By week`s end, a slow moving upper
low originating over the southeast pushes slowly north and is
somewhat impeded by the ridging in place over the northeast. As
this upper low progresses north, the chances for unsettled
weather/clouds and precipitation increase into next weekend.

With respect to sensible weather, dry conditions are expected
under subsidence and surface high pressure Tuesday through
early Saturday. Some high level clouds may begin to move into
the area by Friday in advance of the system that approaches from
the south. Otherwise, the incoming air mass is not anomalously
warm or humid, so daily highs near climatological norms, in the
mid and upper 70s, are forecast through the period. Near normal
lows are also expected, in the upper 50s to near 60.

An inverted trough associated with the main sfc low over the
southeast will approach the area Saturday. Moisture advection
increases on Saturday (sfc dewpoints back into the 60s) with
probability of precip. chances increasing by Saturday afternoon
into Sunday. NBM probabilities of >1" in any 6 hour period
through Sunday remain low at this time, less than 10% over the
past few cycles, suggesting little concern for excessive
rainfall rates with the system at the onset.
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&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
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A cold front will approach tonight and stall over the area on
Monday, while low pressure passes to the south and east late
Monday into Monday night.

Some MVFR cigs have developed in the NYC metro area in response
to onshore flow and area of light rain moving across. Don`t
think those lower cigs will last but may have to amend to keep
them in longer at KJFK/KEWR and possibly expand TEMPO coverage
to KLGA/KTEB as well early this evening. Otherwise think the
metros will see mostly VFR conds tonight, with main push of MVFR
conditions coming in after 08Z along with a few hours of IFR
possible during the AM push. Can`t rule out IFR cond lasting
there into the late AM and early afternoon.

Farther east, expecting MVFR cond in rain to hold off until
late tonight or early Mon AM, then lowering to IFR during the
late morning and possibly hanging on thru the day at KISP/KGON.

SE-S flow generally less than 10 kt tonight should become E-NE
during the AM at the NYC metros, then NW mid to late afternoon.

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

Unscheduled AMD likely this evening to handle patch of MVFR
cigs. IFR cond could last longer than fcst into late morning or
early afternoon on Mon.

OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY...

Monday night: Showers ending, becoming VFR.

Tuesday through Friday: VFR.

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

.MARINE...
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Sub-SCA conditions should last through the first half of Monday
night with ocean seas averaging mainly around 3 ft. Towards
the second half of Monday night the winds start to pick up in
response to an increasing pressure gradient. Therefore SCA
conditions for at least the ocean waters appears to return late
Monday night into Tuesday AM in the wake of departing low
pressure. Marginal SCA gusts are then possible on all waters
during the day on Tuesday, with the higher likelihood of SCAs on
the ocean waters with seas close to 5 ft.

Winds remain below SCA levels across the forecast waters Tuesday
night through Thursday night. East to southeast swells from
distant Tropical Storm Nigel could bring elevated seas to the
ocean waters Thursday into early Friday.

Monitor https:/www.weather.gov/okx/tropical or
https:/www.nhc.noaa.gov for the latest NHC forecasts on Tropical
Storm Nigel.
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&&

.HYDROLOGY...
A half inch to one inch of rain is expected tonight into
Monday. No hydrologic impacts are anticipated.

No hydrologic problems are expected through the week.

&&

.TIDES/COASTAL FLOODING...
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There is a moderate rip current risk for Monday and Tuesday with
a mix of 1-2 ft swells and 6-9 second periods. There is a
borderline high risk on Tuesday with increased surf heights
and swell especially for eastern Long Island.
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&&

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

&&

$$

SYNOPSIS...JE/DBR
NEAR TERM...JE/DBR
SHORT TERM...JE
LONG TERM...DBR
AVIATION...BG
MARINE...JE/DBR
HYDROLOGY...JE/DBR
TIDES/COASTAL FLOODING...