FXUS61 KOKX 271445

Area Forecast Discussion
National Weather Service New York NY
1045 AM EDT Sun Sep 27 2020

A weak area of low pressure off the Mid Atlantic coast this
morning will track slowly northward today, washing out as it
nears the area this evening. A slow moving frontal system will
then approach from the Ohio Valley to start the week, moving
into the area late Tuesday into Wednesday. Waves of low pressure
ride along the front before it pushes east by Thursday. A series
of reinforcing cold fronts will then follow at the end of the


Minor adjustments were made with this update to account for
latest observations and trends, mainly hourly temperatures and
cloud cover.

A weak area of low pressure along the Mid Atlantic coast will
work northward toward the area today. Aloft, a shortwave ridge
passes to the east by this evening. While not much lift and
instability, guidance is all in pretty good agreement for
widely scattered showers working in from the southeast across
eastern Long Island and gradually working westward toward the
NYC metro/Lower Hudson Valley late in the day. This will be
another day of hit and miss activity with little if any

Low clouds will be slow to lift and dissipate today with the
onshore E/SE flow and a weakening subsidence inversion. Eastern
Long Island and southeast CT will likely stay mostly cloudy
throughout the day with locations to the west becoming partly
sunny as the afternoon progresses.

It will be another warm, humid day with highs into the 70s with
a few spots around the NYC metro and north and west touching
the 80-degree mark.

A moderate risk of rip currents at the Atlantic Ocean beaches
will continue today due to a continued E-SE swell and E-SE


Scattered showers will expand across the area early this evening
as weak low pressure washes out near NYC. For the second half
of the night patchy fog and drizzle can be expected with a second
area of showers emerging from the southwest as a shortwave trough
approaches from the Mid Atlantic. The latter of which is being
steered by a deepening upper trough over the Mississippi Valley.
The associated frontal system will then work slowly eastward
across the Ohio Valley on Monday, approaching the area on
Tuesday. Showers will remain widely scattered Monday into
Monday night with a deep-layered southerly flow and weak lift.
There will also be a continuation of low clouds and patchy fog
this evening and again Monday night.

There is reasonably good agreement amongst the global models
with a piece of energy separating from the main parent upper
vortex over the Great Lakes Monday night, digging it southward
across the Tennessee Valley and Southeast on Tuesday. This will
likely slow the progression of the cold front as it approaches
the area on Tuesday. This is a complicated interaction and the
amount of separation with the main upper trough will determine
the progression of the boundary and where it may eventually

The threat of showers will increase form west to east on Tuesday
as a deep-layered southerly (warm advection) set up bands of
showers out ahead of the front. There may even be enough
instability for embedded thunderstorms. Anomalously high
precipitable water values near 2 inches will also be present.
These values exceed the 90th percentile with the all-time high
for Tuesday being 2 inches. Thus, any convection will be
capable of heavy rains, especially as we get late in the day as
the better lift associated with the upper trough and front

Warm, humid conditions will continue during this time with highs
in the mid to upper 70s and lows in the 60s. These values are
well above normal by about 5 to 10 degrees for highs and more
than 10 degrees for lows.

A moderate to possibly high risk of rip currents at the Atlantic
Ocean beaches on Monday due to a building southerly swell and
strengthening onshore winds.


The cold front pushes east into the area but then looks to
stall somewhere in the vicinity Wednesday. This will allow for
disturbances to ride along the front from southwest to northeast
allowing for periods of moderate to heavy rain into Thursday.
The key will be where the front stalls and where the southern
branch vortex tracks.


A weak low passes offshore today, but on the larger scale the
region remains on the western side of a weak high pressure area
based in the Western Atlantic.

E to ESE winds of 10 kts or less are expected through the TAF

MVFR this morning with VFR expected at the NYC arpts by 18Z.
Conditions elsewhere are expected to stay mainly MVFR. All
areas are expected to drop to IFR tonight from a combination of
low ceilings and patchy fog.

A few sprinkles or shwrs possible today, especially ern

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

Low ceilings possible again tonight. Timing may require

The John F. Kennedy International and La Guardia afternoon haze
forecast for today is MODERATE (YELLOW).

.Monday...Chance of IFR/MVFR conditions. Chance of showers,
mainly during the day.
.Tuesday...Chance of IFR/MVFR conditions. A chance of showers. A
slight chance of thunderstorms. S-SW wind gusts around 20 kt.
.Wednesday...IFR/MVFR with showers likely. SW wind gusts
15-20kt day into early evening.
.Thursday...Chance of MVFR. Chance of showers. SW wind gusts
15-20kt day into early evening.

Detailed information, including hourly TAF wind component
forecasts, can be found at:


The combination of weak low pressure tracking northward along
the Mid Atlantic coast today and a building southerly swell
will allow seas on the ocean to average around 3-4 ft today
into Monday.

Winds on the ocean approach SCA criteria ahead of a cold front
on Tuesday night and seas rise above SCA criteria by Wednesday.
SCA conditions on the ocean waters are forecast from Tuesday
night through Thursday.


A frontal boundary may stall close to the area midweek, increasing
the chance for a significant rainfall event.





NWS OKX Office Area Forecast Discussion