Area Forecast Discussion
Issued by NWS Upton, NY

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230
FXUS61 KOKX 201344
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
944 AM EDT Tue Aug 20 2019

.SYNOPSIS...
High pressure will build over the region today. A warm front will
move north of the area on Wednesday followed by a cold front
passage late Thursday into Friday. Canadian high pressure to
build in for the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
The forecast is on track this morning. Just minor update to
temperatures and dew points to reflect current observation
trends. Otherwise, high pressure will briefly build to the
north across the region today. While temperatures are forecast
to be in the 80s to around 90, northerly flow will keep
dewpoints a few degrees lower therefore, heat index values will
be close to the actual air temperature.

There is a low risk of rip current development at ocean beaches
today.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
A warm front will approach from the south overnight into Wednesday
morning ushering in a very humid airmass. Dewpoints will once again
rise into the lower 70s with southerly flow. A weak shortwave will
interact with the warm front as it lifts north, which could spark a
few morning showers and thunderstorms. Given the moist airmass, any
shower will be capable of heavy downpours.

The best chance for thunderstorms will be Wednesday afternoon as an
upper trough over the Great Lakes pushes a cold front towards the
region. Upper level jet support combined with mid level shortwave
energy will initiate convective development during the afternoon.
Forecast soundings showing >2000 J/kg of CAPE into the afternoon
along with increasing shear with the incoming trough. With a
favorable storm environment, the Storm Prediction Center is
maintaining a marginal risk over the region with the exception
of northern Orange and Putnam Counties which has been upgraded
to a slight risk. Southwesterly flow will advect in precipitable
water of near 2 inches, therefore heavy downpours are likely in
any storm.

Temperatures will rise into the upper 80s to lower 90s. The
combination of heat and rising dewpoints will result in heat
indices between 95 and 99 for most locations with the exception
of eastern Long Island and southeastern coastal Connecticut.

There is a moderate risk of rip current development at ocean
beaches for Wednesday.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
A cold front will slowly approach the area Wed night, and not
pass until some time Thu night or early Fri. This will produce
somewhat swampy weather, with periods of showers and
thunderstorms, until the front passes offshore. Probabilities
for rain are therefore in the forecast Wed night through Thu
night. Some minimal chances have been included for Fri with the
frontal timing uncertain this far out. The 00Z GFS and ECMWF are
both mainly dry for the day however. A shot of much cooler air
settles in for the weekend. A backdoor cold front on Sat could
produce a sprinkle, but the probability was too low to include
in the forecast. Some marine stratus may attempt to build in by
late Sun or Mon as the flow veers to the east.

The NBM was used for temperatures for all but Sat night. With good
model agreement on the position of the Canadian high, low
temperatures were adjusted significantly downward from the guidance
Sat night.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
High pressure will build in today before another frontal system
approaches tonight into Wednesday.

VFR conditions are expected through much of the TAF period. Only
exceptions would be brief reductions to MVFR or possibly lower
in any showers/thunderstorms or within any fog/low stratus.
There is a slight chance of showers and thunderstorms this
evening with higher chances overnight into early Wednesday.
With the uncertainty in timing and location for showers and
thunderstorms, these were mentioned mostly as vicinity.

Winds remain light under 10 kts through the TAF period,
initially more northerly before sea breeze circulations develop
in the afternoon with a switch to more S-SE flow. Timing of
wind shifts for terminals may vary 1-2 hours from forecast.

     NY Metro Enhanced Aviation Weather Support...

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

KJFK TAF Comments: Amendments possible for timing of sea breeze.

The afternoon KJFK haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KLGA TAF Comments: Amendments possible for timing of sea breeze.

The afternoon KLGA haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KEWR TAF Comments: Amendments possible for timing of sea breeze.

The afternoon KEWR haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KTEB TAF Comments: Amendments possible for timing of sea breeze.

KHPN TAF Comments: Amendments possible for timing of sea breeze.

KISP TAF Comments: Amendments possible for timing of sea breeze.

.OUTLOOK FOR 06Z WEDNESDAY THROUGH SATURDAY...
.Tonight-Thursday night...Mainly VFR, but MVFR or lower
possible in showers or thunderstorms. Patchy fog with MVFR or
lower possible late tonight.
.Friday-Saturday...VFR.

&&

.MARINE...
Winds and seas will remain below SCA criteria through Wednesday.

Marginal Small Craft Advisory conditions on the ocean
Wed night and Thu ahead of a cold frontal passage. Seas are
often overdone on southwest flow, so confidence is too low to go
with an advisory at this point. All areas are expected to
remain below advisory levels through the weekend, although
increasing east flow will build seas on the ocean late Sun and
Mon.

&&

.HYDROLOGY...
Locally heavy rainfall is possible with thunderstorms that
develop Wednesday, which may result in localized flooding for
urban and poor drainage areas.

&&

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

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$



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