FXUS61 KOKX 190800

Area Forecast Discussion
National Weather Service New York NY
400 AM EDT Mon Aug 19 2019

A cold front will approach the region today and then weaken as
it slowly moves across Long Island this evening. The weakening
front will move farther south of Long Island late tonight into
Tuesday. A wave of low pressure develops late Tuesday and
approaches Tuesday night. A cold front approaches Wednesday and
pushes through the region by Thursday. High pressure builds in
through the weekend.


Main 500mb shortwave energy stays well north of the region
through tonight. Going into today, area on southern edge of
shortwave extending from Central to Southeast Canada. Net mid
level flow across local area is quasi zonal.

Coherency in model guidance depicting an axis of positive
vorticity advection at 500mb moving in 18-00Z across CWA. This
is associated with a shortwave axis. This will provide enhanced

Negative vorticity advection behind it will quell convection mid to
late this evening and into overnight. Slight rises in height
fields are evident in the model fields at 500mb for tonight.

At the surface, a cold front approaches the region today and
moves in late this afternoon into early this evening. Front
slowly moves slowly eastward, lingering into the evening and
weakening across Long Island, eventually moving south of Long
Island overnight. The NAM depicts a little more accurately with
precip with 00Z runs compared to ECMWF and Canadian models. 00Z
GFS has too much precipitation for overnight.

With high heat and humidity in place for today, heat advisory
remains as is with exception of Eastern Long Island. Heat
indices of 95-100 can be expected where advisory remains in
effect and it remains in effect until 8PM this evening. This
will also allow for high instability and with enhanced lift in
the afternoon would expect scattered showers and thunderstorms.
Gusty winds and heavy rain can be expected with these with some
relatively higher shear late in the day. Showers and
thunderstorms continue into start of evening and then diminish
with loss of synoptic forcing and instability.

Moderate risk of rip currents at ocean beaches today.


Mainly dry conditions expected with the front well south of Long
Island with exception being any convergence along developing sea
breeze circulations in the afternoon. More northerly surface
wind flow will allow for lower dewpoints. 850mb temperatures are
a few degrees cooler behind the cold front. This translates to
surface temperatures being a few degrees cooler than the
previous day.

There will be an increase in POPs for showers and thunderstorms
to the north and west of NYC late in the day as a wave of low
pressure approaches.


Unsettled weather along with heat and humidity will continue on
Wednesday as the region remains on the western side of a Bermuda
High. A vigorous upper trough will approach out of the Great Lakes
region into Thursday. Smaller scale features within the upper trough
still remain uncertain which will affect the timing and progression
of an approaching cold front. The front will be the focus for any
convection Wednesday night into Thursday. However, a weak pre
frontal trough could be enough to spark some showers and storms
during the day on Wednesday. Therefore, maintaining a chance PoPs
through through the afternoon.

With the approach of the cold front Wednesday night and Thursday,
there is a better chance of convection. There is a possibility for
severe weather, but uncertainty remains due to the eastward
progression of the cold front. If the front is slower to approach,
and later at night, the environment may not be as favorable. It
still looks like the front won`t fully clear the area until sometime
on Thursday so decided to keep chance PoPs through much of the day.

Following the front, a cooler and more comfortable airmass
overspreads the region. Generally, a dry weekend is forecast with
high pressure building to the north.

Temperatures will be above normal Wednesday and Thursday before
falling a few degree below normal Friday and through the


Low pressure passes to the south and east through tonight.

Mainly dry conditions tonight, however can not rule out a brief
isolated shower or thunderstorm. Any shower that develops could
briefly reduce visibilities. Stratus and fog are once again
expected, mainly east of the NYC terminals, and possible patchy
fog at HPN and SWF. Once the stratus and fog burn off, VFR once
again Monday morning.

NW flow from earlier outflow will settle back to the south and
remain light overnight.

Southwest winds Monday morning back to the south and increase to
10-15 kt. Included PROB30 groups for thunder for late in the
day due to expected afternoon thunderstorms.

...NY Metro Enhanced Aviation Weather Support...

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

KJFK TAF Comments: Timing of afternoon showers and thunderstorms may
be off by an hour or two.

The afternoon KJFK haze potential forecast is YELLOW...which implies
slant range visibility 4-6SM outside of cloud.

KLGA TAF Comments: Timing of afternoon showers and thunderstorms may
be off by an hour or two.

The afternoon KLGA haze potential forecast is YELLOW...which implies
slant range visibility 4-6SM outside of cloud.

KEWR TAF Comments: Timing of afternoon showers and thunderstorms may
be off by an hour or two.

The afternoon KEWR haze potential forecast is GREEN...which implies
slant range visibility 7SM or greater outside of cloud.

KTEB TAF Comments: Timing of afternoon showers and thunderstorms may
be off by an hour or two.

KHPN TAF Comments: Timing of afternoon showers and thunderstorms may
be off by an hour or two.

KISP TAF Comments: Amendments likely this morning for changing
flight categories. Low chance of an late afternoon/evening
showers or thunderstorm.

.Monday night...Mainly VFR, but MVFR is possible in any showers
or thunderstorms.
.Tuesday-Thursday...Mainly VFR, but sub-VFR possible in showers or
.Thursday night-Friday...VFR.


Conditions are expected to remain below SCA criteria for the
waters through the short term forecast period (through Tuesday).

Sub small craft conditions are expected through the long term
period (Tuesday night through Sunday) as well outside of any
thunderstorms. Gusts may approach 25 kts on Wednesday night with
seas building to 5 feet into Thursday.


Could have some minor urban poor drainage flooding with
relatively stronger thunderstorms this afternoon into early this

No hydrologic impacts are expected at this time through the long
term forecast period.


NYC NOAA Weather Radio Station KWO35 (162.55 MHz) remains off
the air.


CT...Heat Advisory until 8 PM EDT this evening for CTZ005>012.
NY...Heat Advisory until 8 PM EDT this evening for NYZ067>075-078-
NJ...Heat Advisory until 8 PM EDT this evening for NJZ002-004-006-



NWS OKX Office Area Forecast Discussion