okx-afd on 2024-08-31

461
FXUS61 KOKX 312144
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
544 PM EDT Sat Aug 31 2024

.SYNOPSIS...
Weakening high pressure gives way to an approaching frontal system
which will move across the area tonight into Sunday morning. A cold
front will then pass through the area Sunday night. A large dome of
high pressure over the Upper Midwest will then build east through
the middle of next week, gradually moving offshore late next week.
A frontal system may approach the area Friday into next weekend.

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --At the time of this early evening update, overcast conditions
have creeped a little farther east than expected, so cloud cover
forecast has been adjusted accordingly through the evening.
Hourly temperatures were also lowered in a few spots to account
for current observations.

Weak troughing aloft will help push a surface trough towards us
tonight, preceded by a weak warm front. Associated lift and
deepening moisture bring a good chance of showers to most of the
forecast area. Instability is somewhat lacking, but enough for a
mention of a possible thunderstorm. Shear is fairly weak, so no
severe thunderstorms are expected. As for heavy rainfall concerns,
PWATs increase to around 2 inches, so showers with some downpours
will be possible. Flooding concerns are mainly of the minor nuisance
variety. WPC does have locations north and west of NYC under a
marginal risk of excessive rainfall. Any flash flooding is expected
to be isolated. Muggy conditions with low temperatures above normal.-- End Changed Discussion --

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
The surface trough is expected to drift east across the forecast
area during Sunday, reaching the eastern zones by the end of the
day. Moisture convergence will be greater along this boundary, and
as instability and upper support increase, anticipating shower and
thunderstorm chances to increase. Still somewhat uncertain where the
trough will be by the time the upper support and instability become
more of a factor, but the overall trend for the past 24+ hours has
been for a slower eastward progression. Regarding the severe weather
potential, shear will be stronger this time around - enough for a
threat of strong to severe wind gusts. Potential cloud cover
hampering destabilization and the aforementioned uncertainty
regarding the position of the surface trough limit confidence in the
convective forecast. With that said, it appears that overall higher
chances of showers and thunderstorms will be from around NYC
northeastward into SW CT and to points east. The flooding threat is
uncertain, but at least minor flooding will be possible. Can`t rule
out isolated flash flooding either, especially if the 12z hi-res 3km
NAM qpf fields are correct. HREF probability of 1-hour rain amounts
of greater than an inch are low at 10-20% for parts of the area, but
it`s at least a signal for the potential of something more than
just minor/nuisance flooding. Have nudged up the forecast rain
amounts during Sunday from WPC guidance with this in mind.

Highs on Sunday will be in the upper 70s to mid 80s with the warmer
spots generally west of the city. Still muggy, with dewpoints mostly
in the lower 70s.

A cold front is then forecast to pass through the area after Sunday
evening, ending the threat of showers and ushering in a cooler and
drier airmass.

.LONG TERM /MONDAY THROUGH SATURDAY/...
Following an exiting cold front on Monday, northwest winds will
advect in cooler, drier air into the area. Dewpoints will drop
through the day on Monday. With strong cold air advection aloft at
850 mb and a steady northwest wind, highs on Monday will be limited
to the low/mid-70s with a few reaching the upper-70s.

High pressure will continue to build in behind the exiting front
from the Great Lakes region on Monday and Tuesday with ridging
aloft, leaving a very sunny forecast for early next week. Overnight
lows will drop into the upper-40s to near-60 north-to-south Monday
night. Dewpoints drop into the 40s Monday night and remain there
through Tuesday night, reinforced by northwest flow. This will lead
to conditions feeling cool and crisp during the nights and pleasant
in the afternoons with highs in the mid/low-70s on Tuesday.

Most model guidance brings high pressure overhead on Wednesday, then
gradually push it offshore Thursday and Friday. This will lead to a
return flow from the southerly. High pressure will firmly remain in
place on Wednesday and still mainly in control on Thursday, allowing
for more cloud-free days, before cloud cover increases as the high
exits east Thursday night into Friday. Southerly winds will lead to
increasing temperatures and dewpoints late next week. Highs will be
in the mid-70s to low-80s by Friday.

Friday into Saturday, most global guidance show a developing mid-
Atlantic coastal low with a deepening trough and low over the Great
Lakes. Each model deals with these two systems in different ways.
Some bring a frontal system into the area from the west with the
coastal low well offshore. Some keep the frontal system to the west
as a coastal low sweeps up the Atlantic coast and into our area.
Which solution ends up occurring is hard to pinpoint, at this time.
However, looking ahead, more unsettled weather for next weekend
looks possible.

.AVIATION /22Z SATURDAY THROUGH THURSDAY/...
A pre-frontal trough slowly approaches tonight and slides
through Sunday into Sunday Night.

Gradual improvement to VFR through the late afternoon. A return
to MVFR/IFR conditions after 03-06z as showers chances
increase, continuing through Sun AM. Isolated tsra threat during
this time.

SE winds 10k or less, veering to S/SE this afternoon, then
shift to the S/SSW tonight into Sun AM.

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

Timing of return to MVFR or lower tonight, may be off by an
hour or so. Isolated TSRA threat for Sun AM/PM push.

OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY...

Sunday: Improvement to VFR likely in the afternoon with iso
shower/tstm threat into eve push.

Monday through Thursday: VFR.

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

.MARINE...
Winds and waves will remain below SCA criteria through the middle of
next week. Winds gusts may reach 20 kts both Monday morning and
Monday night into Tuesday morning, post-front.

.HYDROLOGY...
Showers and possible thunderstorms tonight through Sunday look
disorganized. The current forecast has up to an inch of rainfall
during this time, with the higher amounts generally from around the
city to points east. Locally higher amounts are also possible. The
flood threat will be mainly of the minor nuisance/poor drainage
variety. However, WPC maintains a marginal risk of excessive
rainfall north and west of the NYC metro through at least the first
half of Sunday morning. This means there is the potential for
isolated episodes of flash flooding. It appears that the period when
impacts are more likely to be realized are late tonight into Sunday
morning. No hydrologic impacts are expected thereafter.

.TIDES/COASTAL FLOODING...
Rip currents overperformed today with most Long Island beaches
reporting moderate rip activity. Given some guidance suggestion for
moderate in spots and a similar set up tomorrow, except stronger
winds, will go moderate for all beaches tomorrow. Steady offshore
winds and increasing surf height should lead to another day of
moderate rip activity on Monday.

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

SYNOPSIS...JC/BR
NEAR TERM...JC/BR
SHORT TERM...JC
LONG TERM...BR
AVIATION...NV
MARINE...JC/BR
HYDROLOGY...JC/BR
TIDES/COASTAL FLOODING...