Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 221938
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
338 PM EDT FRI JUL 22 2016

.SYNOPSIS...
High pressure builds further offshore today as a weak cold front
approaches and moves through early Saturday. High pressure over
the area this weekend moves offshore early in the new week, and
then a cold front approaches on Monday and passes through the area
Monday night. High pressure returns for Tuesday through Thursday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Things remain quiet on the radar so far today. Given the strength
of the surface winds and the general synoptic scale of them, I
have trimmed back POPs and the intensity of convection across the
area for the early part of this afternoon, especially across Long
Island. This does not look a favorable environment with the
gradient winds we are seeing for convection to pop up.

The NAM WRF seems to have the best handle on convection trends
for this evening as it shows some activity developing now near the
Finger Lakes which is supported by general composite
reflectively trends on radar. It looks like any activity won`t
work into our area or pop up in the higher terrain of Orange,
Putnum and Upper Passaic Counties until later this afternoon with
activity then advecting toward The City and coast this evening
(maybe after 9 PM). Thus adjusted POPs and weather wording to
match this. Activity should weaken as it drops toward the coast
into a less favorable environment with more showers than
thunderstorms for central and eastern areas of Long Island. The
inverted V signature showing up in soundings supports gusty winds
as the main threat in and near storms this evening. SPC continues
a slight risk for the much of the area mainly from western Long
Island on north and west.

Otherwise the big concern this afternoon/evening will be Heat in
The City and in northeast New Jersey and the Heat Advisory still
looks justified given expected heat index values between 95 and
100 this afternoon and early evening.

A high risk for rip current development at ocean beaches will be
also be developing this morning and continuing to be high through
the evening due to southerly wind waves increasing to 3 to 5 ft
and a residual 2 ft se swell.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Models are also in good agreement that the best dynamics from the
shortwave and jet streak approaching tonight will be closest to
eastern CT/LI with areas N of here in the sweet spot. Models are
still indicating moderate instability into the overnight hours as
a cold front approaches and while severe wx typically doesn`t
occur at night here...this could be an exception...especially
during the first half of the night.

Showers and thunderstorms taper off late tonight with the passage
of the cold front early Saturday.

Another hot day Saturday but relatively drier with the westerly
flow. This should allow for more vertical mixing and lower
dewpoints. Although the dewpoints are expected to be
lower...temperatures will be higher with heat indices well into
the 90s once again. The heat advsy continues for NYC on Sat and
may also be needed again in NE NJ with values near 100...but the
uncertainty in mixing down lower dewpoint air from the top of the
mixed layer could preclude this and keep it just below.
Therefore...do not have the confidence to extend NE NJ attm.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
High pressure builds back into the area from the west Saturday night
through Sunday. High temps on Sunday will top off in the upper 80s
to low 90s for most areas, but will be in the low to mid 90s for
NYC, portions of NE NJ, and southern portions of the Lower Hudson
Valley. With a W-NW flow, dewpoints should not be as high as
Saturday, generally in the upper 50s to low 60s. This results in
heat indices below 95 degrees.

The high moves offshore Sunday night, and return flow develops on
the back side of the high. Dewpoints will creep up into the mid and
upper 60s Sunday night through Monday as S flow increases ahead of
approaching cold front. Highs on Monday will top off in the low to
mid 90s, and heat indices will top off in the mid to upper 90s.

As cold front approaches on Monday, scattered showers and
thunderstorms will develop over western areas, and those storms will
continue to develop and spread east as that front advances and
pushes through the region Monday night. With deep S to SW flow, low
level moisture will increase throughout the region, and a very warm
and humid night on tap with lows near 80 in/around NYC, and in the
low to mid 70s elsewhere. Surface dewpoints will will be in the low
70s, resulting in overnight heat indices in the 80s for NYC and
urbanized portions of NE NJ. Areas of fog are likely as well.

Behind the cold front, surface dewpoints fall back into the 60s. It
will take some time for cooler and dryer air to build east. Highs on
Tuesday will climb back into the low to mid 90s, and with surface
dewpoints in the 60s, heat indices will once again top off in the
mid 90s.

High pressure continues to build in from the west for the midweek
period. Temperatures will top off in the upper 80s to low 90s on
Wednesday, and then will top off in the mid to upper 80s on
Thursday.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
A weak cold front approaches tonight and moves through early
Saturday. Scattered convection is possible late this afternoon and early
evening out ahead of the front associated with a pre-frontal
trough. There are multiple limiting factors for a widespread
event, thus confidence is not high for thunderstorms at any one
location.

Generally VFR conditions expected through the TAF period, except
in any thunderstorm that develops. Patchy fog and MVFR vsbys are
possible, mainly outside NYC metro during the overnight period.

Gusty southwest winds with speeds 15 to 20 KT and gusts to around
25 KT will continue, but become less frequent after sunset. Wind
speeds will diminish overnight.

     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: Gusts up to 30 KT possible late this afternoon.
Amendments likely for possible thunderstorms late this afternoon
into early this evening.

KLGA TAF Comments: Gusts up to 30 KT possible. Amendments likely
for possible thunderstorms late this afternoon into early this
evening.

KEWR TAF Comments: Gusts up to 30 KT possible. Amendments likely
for possible thunderstorms late this afternoon into early this
evening.

KTEB TAF Comments: Gusts up to 30 KT possible. Amendments likely
for possible thunderstorms late this afternoon into early this
evening.

KHPN TAF Comments: Amendments likely for possible thunderstorms
late this afternoon into early this evening.

KISP TAF Comments: Gusts up to 30 KT possible. Amendments likely
for possible thunderstorms late this afternoon into early this
evening.

.OUTLOOK FOR 18Z Saturday through Wednesday...
.Saturday afternoon through Sunday night...VFR. W gusts up to 20
KT possible Saturday afternoon.
.Monday-Monday night...Mainly VFR, except MVFR or lower possible in
scattered late day/evening thunderstorms.
.Tuesday and Wednesday...VFR.

&&

.MARINE...
SCA remains in effect for the ocean waters and the south shore
bays of Long Island due to an increasing SW flow today. Gusts up
to 30 kt are expected...especially late this aftn and eve as low
level winds peak. Seas on the ocean will also build to advsy
levels in response to the strong winds. Only change to the
headline was to pad the timing a few hours on the south shore
bays...which now expires at 11pm. A cold front moves across early
Saturday with conditions dropping below SCA levels.

High pressure will influence the waters from Saturday night through
Monday. A cold front passes through the waters Monday night, and
then high pressure returns for the middle of next week.

Sub-SCA conditions expected for the period.

&&

.HYDROLOGY...
Boundary layer winds increase today so any thunderstorms this
aftn and tonight will be faster moving, mitigating the flood
threat. Still though, some localized minor urban and small stream
flooding will be possible.

Scattered showers and thunderstorms will impact the region Monday
afternoon and Monday night. PWATs will range from 2-2.5 inches,
resulting in the potential for locally heavy rain. Localized minor
urban and small stream flooding is possible.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Heat Advisory until 7 PM EDT Saturday for NYZ072>075-176-178.
     High Rip Current Risk until 9 PM EDT this evening for NYZ075-
     080-081-178-179.
NJ...Heat Advisory until 7 PM EDT Saturday for NJZ006-106-108.
     Heat Advisory until 7 PM EDT this evening for NJZ004-103>105-
     107.
MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ350-353-
     355.
     Small Craft Advisory until 11 PM EDT this evening for ANZ345.

&&

$$
SYNOPSIS...24/MPS
NEAR TERM...24
SHORT TERM...24
LONG TERM...MPS
AVIATION...CB/DW
MARINE...24/MPS
HYDROLOGY...24/MPS



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