discussion on 2023-08-31

000
FXUS61 KOKX 010004 CCA
AFDOKX

Area Forecast Discussion...CORRECTED
National Weather Service New York NY
804 PM EDT Thu Aug 31 2023

.SYNOPSIS...
High pressure builds in through Friday, then remains in control
through much of next week.

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Minor adjustments made with the latest update.

Upper ridging continues to build to the west as surface high
pressure moves into the region from the eastern Great Lakes. The
ridging has suppressed the high clouds from Idalia south of
Long Island. Idalia is forecast to pass well to our south, and
Tropical Cyclone Franklin will continue to bring indirect
impacts to the coast. See the Tides/Coastal Flooding section
below. Monitor https:/www.weather.gov/okx/tropical or
https:/www.nhc.noaa.gov for the latest NHC forecasts on these
and other tropical systems.

With a dry airmass in place, winds becoming light, and clear
skies, near ideal radiational cooling will set up tonight, and
temperatures will be 5 to near 10 degrees below seasonal
normals.

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/...
Upper ridging moves across the region Friday into early Friday
evening. A shortwave trough then approaches in the near zonal
flow Saturday, moving well to the north, across southern Canada
and into northern New England. This trough will bring an
increase in mainly high clouds across the interior Saturday.
With subsidence, as the surface high becomes centered across the
region Friday, and little low level moisture few, if any,
cumulus will be developing Friday or Saturday.

Temperatures will remain around 5 degrees below normal Friday
and Friday night, and modify to near normal levels Saturday.

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
-- Changed Discussion --The long term forecast remains largely dominated by a large
high pressure system that traverses the area through the middle
of next week.

A weakness in the high pressure system on Sunday may give way
to a very weak cold front or surface trough that likely pushes
through without any precipitation. High pressure then builds
back into the area from the southwest as an upper level ridge
moves back into the area by the middle of the week.

There will be a significant warmup during this period with the
warmest day possibly being early in the period on Monday. In
fact, the 12Z GFS brings plus 20C air at 85h over top the upper
ridge building east. However, the warmup is not as pronounced on
the operational 12Z GDPS (Canadian) and ECMWF. This is largely due
to TC Idalia getting cutoff across the western Atlantic, acting
like a block of the upper ridge working into the eastern part of
the country next week. In fact, the ridge builds over top of it
with surface high pressure strengthening across the Northeast and
the Canadian Maritimes. This will likely keep the area under more
of a maritime influence with an onshore surface flow for much of
the period. This is not to say it will not be hot or unseasonably
warm, but the potential is more for 5 to 10 degrees above normal
versus the record warmth forecast some 24h ago. The warmest days
at this time look to be Monday into Tuesday with highs for NYC and
points north and west in the upper 80s to lower 90s. This will
produce heat indices around or or just short of 95 for these
areas. Heat Advisory criteria at these values requires 95-99 for
two consecutive days. The remainder of the week looks to be
slightly cooler with the upper low/TC Idalia retrograding toward
the Northeast. However, there is lots uncertainty with the
interaction with a shortwave trough moving off the coast on Sunday
and how far north the system gets drawn.

Thus,looking at a period of unseasonable warmth and mainly dry
weather. There is a slight chance of showers/thunderstorms late
in the week as a weak frontal system approaches on Thursday.

For the latest official forecast information on Tropical Cyclone
Idalia, please monitor the National Hurricane Center at
https:/www.nhc.noaa.gov or https:/www.weather.gov/okx/tropical.-- End Changed Discussion --

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
A large area of high pressure centered over the Great Lakes
will build east into the area through tonight, and then settle
over the area through the remainder of the TAF period.

VFR. N winds around 10 kt into this overnight. For most
outlying terminals the winds will diminish to 5 to 10 kt. The
winds then become more NE towards mid morning Friday. Afternoon
sea breeze is expected for all terminals except KSWF.

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

No amendments are expected.

OUTLOOK FOR 00Z SATURDAY THROUGH TUESDAY...

Friday Night: VFR.
Saturday-Tuesday: VFR.

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

.MARINE...
-- Changed Discussion --On the ocean waters, seas will remain elevated at or above SCA
levels into Friday morning as southeasterly swells continue, and
the advisory was extended through 16Z Friday.

With high pressure building into the forecast waters tonight
into Friday, the pressure gradient will remain weak and once
swells subside winds and seas will remain below advisory levels.
Sub-SCA conditions are expected Saturday through Wednesday as
high pressure remains across the waters.

.HYDROLOGY...
No hydrologic impacts are expected through next week.

.TIDES/COASTAL FLOODING...
While rough conditions continue on the ocean front due to long
period swells from TC Franklin, they are diminishing and latest
observations are below the 7ft required for a high surf
advisory. However, while swell heights will be diminishing, a
high rip current risk will continue through Friday. Lingering
impacts will continue into Saturday and possibly longer as the
system remains over the western Atlantic through the upcoming
week.

In addition, the combination of the long period swells and
the recent full moon (high astro tides) will lead to minor
flood benchmarks being exceeded for the south shore back bays of
western LI with tonight`s high tide. Water levels will likely
just touch minor benchmarks across the lower NY Harbor and
coastal Fairfield County CT coast. The latest guidance still
indicates that isolated minor flooding is possible with the
high tide cycles on Friday, but it is looking less likely for
widespread minor coastal flooding Friday night across the south
shore back bays.

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Risk for Rip Currents through Friday evening for NYZ075-080-
081-178-179.
Coastal Flood Advisory until 11 PM EDT this evening for NYZ178-
179.
NJ...None.
MARINE...Small Craft Advisory until noon EDT Friday for ANZ350-353-355.

SYNOPSIS...MET/DW
NEAR TERM...MET
SHORT TERM...MET
LONG TERM...DW
AVIATION...JP
MARINE...MET/DW
HYDROLOGY...MET/DW
TIDES/COASTAL FLOODING...