FXUS61 KOKX 182335

Area Forecast Discussion
National Weather Service New York NY
735 PM EDT Tue May 18 2021

High pressure remains in control through Thursday, but a cold
front will move west through the region Wednesday afternoon and
night before stalling just off to our west. This stationary
front will remain just west of us through Friday night before
moving northeast as a warm front Saturday. A cold front
approaches Sunday and moves through Sunday night. A warm front
approaches Tuesday.


Forecast is on track with only minor changes needed to reflect
current conditions

High pressure brings us mostly clear conditions tonight. Following a
day with high temperatures well above normal, lows tonight are
expected to end up about 5-10 degrees above normal.


Deep-layered ridging occurs through the period as an upper ridge
axis slowly shifts east through the Eastern Great Lakes. The surface
high will be centered near the Mid-Atlantic Coast. Models continue
to agree that a back door cold front begins to move through the
forecast area from the east starting in the middle of the afternoon.
Even eastern zones will be able to warm up to well above normal
levels before this occurs. Afternoon 850mb temps are progged at 13-
14C, and with a mostly sunny sky and offshore winds to start, highs
are expected to climb to near 90 in the normally warmest spots in
the NYC metro area. Expect mid and upper 80s for most other
locations, and upper 70s to around 80 for coastal SE CT and the the
Twin Forks. These temperatures will however fall short of daily

Lift provided by the front, coupled with a passing shortwave and
some CAPE could trigger isolated to scattered late day/early
evening showers and thunderstorms across SE CT and eastern LI.

Another night of mostly clear conditions and above normal
temperatures for most spots follows for Wednesday night along with
patchy fog in the suburbs.


The long term will be characterized by an omega block at 500 hPa,
with a 500 hPa low over the western U.S., while another will remain
over the western Atlantic through Saturday. The 500 hPa ridge
associated with the block will be over the Northeast through Friday
night, and will break down Saturday as a shortwave approaches.

At the surface, a cold front will remain to the west of the Hudson
River, or over western portions of the forecast area through Friday
night, then push northeast as a warm front on Saturday. A cold front
will approach on Sunday and move through on Sunday night. High
pressure then builds in from southern Canada for the beginning of
next week, with a warm front approaching from the southwest on
Tuesday. There will be some uncertainty as to exactly where the
front will be from Thursday through Saturday, which will lead to
uncertainty in where exactly the showers and thunderstorms set up.

The stationary front will provide the lift and will be the focus for
showers and thunderstorms from Thursday through Saturday. Daytime
heating through this period will provide some instability for the
development of showers. Given a few hundred J/kg of CAPE on Thursday
inland, these areas could see some isolated thunderstorms. Less in
the way of CAPE is seen on Friday, with slightly cooler temperatures
possibly due to cloud cover, so would expect less in the way of
thunderstorms, but a passing thunderstorm is still not out of the
question inland. Similar instability for Saturday, but more in the
way of CAPE is expected on Sunday as the cold front approaches and
moves through. As for moisture, it will be on the increase from
Thursday into Saturday as PWAT values increase all the models.
Similar PWAT values on Sunday as Saturday.

The stationary moves northeast as a warm front Saturday, and warmer
conditions are expected for Sunday. As previously mentioned, this
will lead to a more unstable airmass. Better chances for
thunderstorms exist for Sunday as the cold front approaches and
moves through Sunday night.

Dry conditions return Sunday night and into the beginning of the
work week as Canadian high pressure builds in from southern Canada.

Thereafter, the old frontal boundary to our southwest approaches
again as a warm front on Tuesday, bringing more chances for showers
and thunderstorms.

With deep layered ridging and higher than normal heights over the
Northeast, temperatures are expected to run above normal until the
cold front moves through on Sunday night.


High pressure remains centered to the west of the terminals into
Wednesday morning. A cold front moves in from the east Wednesday


Sea breezes weaken early this evening, and winds become westerly
less than 10 kt, and NW toward Wednesday morning. Afternoon sea
breezes are expected to develop Wednesday afternoon. Across the
eastern terminals winds shift to the southeast in the afternoon
with the passage of a cold front.

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

Amendments possible Wednesday afternoon for sea breeze timing.

.Wednesday night-Thursday...VFR.
.Thursday night-Saturday...Mainly VFR. Low chance for showers
and isolated thunderstorms.
.Sunday...MVFR possible with a chance of isolated thunderstorms.

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


With high pressure over the area, winds and seas will remain
below SCA thresholds through at least Friday night. An approaching
cold front will allow waves on the ocean to build to 5 ft on
Saturday. However, this may only occur for the outer waters of
the ocean zones. Waves fall below 5 ft Sunday night.


No hydrologic impacts are expected.





NWS OKX Office Area Forecast Discussion