000
FXUS61 KOKX 172237
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
637 PM EDT Sun Sep 17 2023
.SYNOPSIS...
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.
&&
.NEAR TERM /THROUGH MONDAY/...
-- Changed Discussion --
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.-- End Changed Discussion --
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/...
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.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
-- Changed Discussion --
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.-- End Changed Discussion --
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Weak high pressure moves offshore as a cold front begins to
approach from the west as a wave of low pressure moves into the
mid Atlantic region from the southeastern states tonight.
VFR through late afternoon with showers developing around
21Z-22Z. Conditions gradually lower, becoming MVFR early
this evening, and then IFR late tonight. IFR/MVFR conditions
prevail through Monday morning with on and off showers. CIGS
improve gradually by afternoon on Monday.
A southerly flow during the afternoon at the coast terminals as sea
breezes develops. Winds SW along the coast this evening and
overnight, and light and variable inland tonight. Winds then shift
around the NW-N by Monday afternoon with precipitation tapering
off.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
No unscheduled AMD expected through this afternoon. Low confidence
on timing of the onset of precip and lowering conditions to MVFR
this evening, to IFR late tonight, and may be later than forecast.
OUTLOOK FOR 18Z MONDAY THROUGH FRIDAY...
Monday: MVFR, chance IFR especially in the morning, with
showers.
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
&&
.MARINE...
Sub-SCA conditions are expected today 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.
&&
.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...
There is a moderate rip current risk for today and Monday with
a mix of 1-2 ft swells.
&&
.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...20
MARINE...JE/DBR
HYDROLOGY...JE/DBR
TIDES/COASTAL FLOODING...