discussion on 2023-08-31

000
FXUS61 KOKX 312029
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
429 PM EDT Thu Aug 31 2023

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

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
-- Changed Discussion --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.-- End Changed Discussion --

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/...
-- Changed Discussion --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.-- End Changed Discussion --

.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 over top the high amplitude
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 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 /20Z THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --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 evening. N wind continues
overnight and into early Friday morning. For most outlying
terminals the winds will diminish closer to 5 kt or less
overnight. The winds then become more NE towards midday Friday.
Afternoon sea breeze is expected for coastal terminals in the
afternoon.

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

No amendments are expected.

OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY...

Friday afternoon: VFR.
Saturday-Tuesday: VFR.

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

.MARINE...
-- Changed Discussion --Southeasterly swell from tropical cyclone Franklin that had
been affecting the eastern Long Island Sound have subsided and
the small craft advisory has been cancelled. 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...
-- Changed Discussion --
No hydrologic impacts are expected through next week.-- End Changed Discussion --

.TIDES/COASTAL FLOODING...
-- Changed Discussion --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. Thus, the high surf advisory has been cancelled.
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.-- End Changed Discussion --

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...None.
NY...High Risk for Rip Currents through Friday evening for NYZ075-080-
081-178-179.
Coastal Flood Advisory from 8 PM to 11 PM EDT this evening for
NYZ178-179.
NJ...None.
MARINE...Small Craft Advisory until noon EDT Friday for ANZ350-353-355.-- End Changed Discussion --

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