Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 161341
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
941 AM EDT Wed Aug 16 2017

.SYNOPSIS...
High pressure builds in today and moves offshore on Thursday. A
warm front, associated with low pressure over the Great Lakes,
will then approach Thursday night, and move through on Friday. A
slow moving cold front will approach from the west on Friday,
and move across on Saturday. High pressure will then build in
the region for the start of the new work week, and pass off the
coast on Tuesday as a cold front approaches from the northwest.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Fog has burned off across the area. Expect quiet conditions
across the area. Minor update to temperatures and dewpoints to
reflect current conditions otherwise, no significant changes to
the forecast.

Looking at a mostly sunny day with a drying downslope NW flow,
though immediate south facing coastal areas may still see a late
day sea breeze. GFS/NAM differ on depth of mixing for today,
but taking a compromise and adding 2-3 degrees this afternoon
for downslope flow, expect high temps around 90 just west of
NYC, upper 80s in the rest of the city and immediate suburbs,
and mid 80s elsewhere. Afternoon dewpoints falling off to 60-65
should keep max heat index values just below 90.

A high rip current risk will continue today for the ocean
beaches as the largest swells from distant Hurricane Gert
arrive. For details on Gert, please refer to National Hurricane
Center products.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
A dry and tranquil night is in store for tonight with high
pressure remaining in control. Lows will be in the 60s in most
coastal locations, and mid/upper 50s inland and in the Long
Island Pine Barrens region.

Have sided with a slower model trend with an approaching frontal
system, with upper ridging still to the west even by late day
Thu. Have therefore kept daytime Thu mostly sunny and dry, with
highs 80-85.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
With upper ridging remaining to the west of the region early
Thursday night, an upper shortwave and surface warm front will
be slower to affect the area, and as a result have delayed the
onset of precipitation until after 00Z Friday, and then with
only slight chance probabilities coming into the far western
zones. Also, with the surface low remaining well to the west,
then warm front will remains well to the southwest with little
forcing across the region through 06Z Friday. And with little
CAPE will have mention of showers but not thunder.

Portions of the area become warm sectored Saturday, mainly inland,
as the warm front moves through the region during the day. A
supporting shortwave rotates through a longwave trough to the west
and north during Friday into Friday night, and the surface low
tracks north of the Great Lakes. Probabilities for precip
increase as the cold front moves into the warm and unstable
air mass later Friday and Friday, with likely probabilities. At
this time CAPE is several hundred J/KG and will mention a chance
of thunder.

The surface cold front moves east 09Z to 15Z Saturday. However,
there will be another shortwave rotating into the longwave
trough, and the probability of precipitation remains until
toward 12Z Sunday.

On Sunday the upper flow becomes more zonal as weak ridging
builds. The northern stream remains progressive and the next
shortwave approaches for late Tuesday and Tuesday night.

&&

.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
High pressure builds in today with VFR.

NW winds increasing to around 10 kt. Winds should prevail north
of 310 magnetic most of the day. Occasional gusts to mid teens
possible this afternoon. Afternoon sea breezes expected for
KJFK/KISP/KBDR/KGON.

     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 sea breeze shift may be off 1-2
hours.

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


KLGA TAF Comments: Chance that sea breeze moves through and
shifts winds SW near 22-23z.

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


KEWR TAF Comments: Slight chance that winds back SW-S for a few
hours starting near 22-23z.

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


KTEB TAF Comments: Tempo 5sm vsby thru 13z might not occur with
VFR prevailing instead. Slight chance that winds back SW-S for
a few hours starting at around 23z.


KHPN TAF Comments: No unscheduled amendments expected.

KISP TAF Comments: Timing of sea breeze may be off 1-2 hours.
Also a chance that sea breeze doesn`t pass through with winds
remaining NW all day.

.OUTLOOK FOR 12Z THURSDAY THROUGH SUNDAY...
.Thursday...VFR. Afternoon sea breezes.
.Thursday night through Saturday night...MVFR or lower flight
cat possible in showers/tstms.
.Sunday...VFR.

&&

.MARINE...
Long period southerly swells from Hurricane Gert should peak at
5-7 ft today, then slowly subside tonight into Thu as the
hurricane races out into the open Atlantic per NHC forecast.
Have extended the ocean SCA for hazardous seas until 2 AM Thu
west, and 8 AM east.

Thursday night winds and seas will remain below advisory levels
as a cold front approaches from the west. A southerly flow
ahead of the front will increase during Friday, and wind gusts
along the Jersey shore to west of Fire Island Inlet may reach
advisory levels late in the day into Friday evening. Seas should
remain below small craft levels.

Once a cold front crosses the waters Saturday winds shift to the
west and northwest as high pressure builds over the waters.
Winds and seas will remain below small craft levels Saturday
and Sunday.

&&

.HYDROLOGY...
A slow-moving frontal system may bring periods of heavy rainfall
Friday into Saturday, with 1/2 to 3/4 inch QPF. Hydrologic
impacts are not expected at this time.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Rip Current Risk until 9 PM EDT this evening for NYZ075-
     080-081-178-179.
NJ...None.
MARINE...Small Craft Advisory for hazardous seas until 2 AM EDT
     Thursday for ANZ353-355.
     Small Craft Advisory for hazardous seas until 8 AM EDT
     Thursday for ANZ350.

&&

$$



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