Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 211626
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1226 PM EDT Mon Aug 21 2017

.SYNOPSIS...
High pressure over the region moves offshore today and tonight.
A cold front approaches from the west Tuesday and passes through
Tuesday night into Wednesday morning. High pressure then builds
in thereafter through the end of the week with a much drier and
cooler airmass.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Forecast still mainly on track with just slight adjustments to
temperatures and dewpoints to better match observed trends.

Weak quasi-zonal flow aloft with main upper level jet stream
well northwest of the region.

Surface high pressure moves across the region this morning and
offshore this afternoon. Expecting a mainly dry day with just a
slight chance of showers and thunderstorms for far western
Orange County late this afternoon. 850mb temperatures forecast
to reach near 15-16 degrees C. Surface temperatures forecast to
reach several degrees warmer than yesterday. Mid 80s to near 90
degrees F for much of the region with mostly sunny conditions
for most locations.

For sky cover, the western edge of a cirrus shield should be
east of the forks region and SE CT by 200 PM. Another area of
translucent cirrus moving through northern PA would appear to
shift through primarily north of the city in the timeframe of
the partial solar eclipse, which runs about 120 PM to 400 PM in
NYC with a peak at 244 PM. Cirrus may however develop and pass
through the city and Long Island during this period as well,
especially if any convection pops up to our west. HRRR
indicates this convective potential, but may happen too late to
be of much significance. Finally, some cumulus development along
sea breezes this afternoon may cause some obstruction within
about 10 miles of south-facing coasts. Thinking is that any
cumulus would be no more that scattered in nature for most spots
that see it.

Like previous forecast, a look at the HRRRX conveys a slight
decrease during maximum obscuration of sun during eclipse, so
adjusted temperature a degree downward at 19Z (3PM local time).

There is a low risk of rip currents today, becoming moderate
late today at Atlantic beaches.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
Rest of the forecast shows high pressure moving farther offshore
and a cold front gradually approaching from the west. Upper
levels convey an upper level trough with its upper level low based
in Ontario approaching the region. Continually more warm and
humid conditions are expected. Forecast has warmer temperatures
Tuesday, getting hot and humid for quite a few locations. Could
see heat indices up to 100 degrees in and around NYC.

Precip forecast remains near or below 30 percent for showers and
thunderstorms. Not much forcing but increasing instability and
possible lee trough forming Tuesday could provide focus for
convergence. Models are pretty minimal with forecast rainfall
amounts overall tonight through Tuesday. Weak trough evident in
lower levels late tonight into early Tuesday will lead to pops
more in low end chance for showers and thunderstorms and then
expecting much of Tuesday to be dry except for interior
locations which will have relatively higher chances for showers
and thunderstorms. These locations will be closer to lee trough
as well.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
A cold front approaches the region Tuesday night and pushes across
the forecast area on Wednesday. Expect cloud cover to increase and
showers and thunderstorms to develop and move across the region
through this time frame. By Wednesday evening, skies will begin to
clear and a much cooler airmass will be arriving.

Canadian high pressure builds into the region Thursday through the
weekend, providing dry and sunny conditions. Temperatures will
remain below normal as highs only reach the 70s to near 80 each day.

The dry and cooler conditions are expected to continue into
Monday.

&&

.AVIATION /16Z MONDAY THROUGH FRIDAY/...
VFR through the TAF period as high pressure remains in control.

An isolated shower or tstm possible late day near KSWF, and
early evening for KHPN and the NYC metros. Given earlier
upstream activity over western NY, which has died down but
should refire this afternoon, have enough confidence to mention
VCTS at KSWF.

Sea breezes are in at KBDR/KGON, and while direction at most
other terminals continues to vary between SW and W. A more S-SW
sea breeze should set in this afternoon at KJFK/KISP and reach
KLGA late, and KEWR/KTEB could be on the edge of a harbor breeze
late as well. Gusts 15-18 kt likely.

S-SW winds diminish to less than 10 kt this evening.

There is also low potential for development of low clouds/fog
late tonight with MVFR or lower flight cat, mainly at
KJFK/KISP/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: Occasional G20KT possible during the early
evening push. Low chance of a shower or tstm after 01Z.
Afternoon haze potential forecast is GREEN, which implies
slant range visibility 7SM or greater outside of cloud.

KLGA TAF Comments: Occasional G20KT possible for the late
afternoon/early evening push. Low chance of a shower or tstm
after 01Z. Afternoon haze potential forecast is GREEN, which
implies slant range visibility 7SM or greater outside of cloud.

KEWR TAF Comments: Low chance of a shower or tstm after 01Z.
Afternoon haze potential forecast is GREEN, which implies slant
range visibility 7SM or greater outside of cloud.

KTEB TAF Comments: Low chance of a shower or tstm after 01Z.
Afternoon haze potential forecast is GREEN, which implies
slant range visibility 7SM or greater outside of cloud.

KHPN TAF Comments: Low chance of a shower or tstm after 00Z.

KISP TAF Comments: Occasional G20KT possible late this
afternoon.

.OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY...
.Tuesday...Mainly VFR. Isolated afternoon shower/tstm possible.
SW winds G15-20KT in the afternoon.
.Tuesday Night...Better chance for showers/tstms with MVFR or
flight cat.
.Wednesday...Lingering showers/tstms possible early, then
becoming VFR. NW winds G15-20KT.
.Wednesday Night-Friday...VFR.

&&

.MARINE...
Starting off with quiet conditions on the waters well below SCA
thresholds with the high pressure area building in. The high
traverses over the waters this morning and moves offshore this
afternoon. The increasing return southerly flow will lead to
building seas late with ocean seas according to NWPS reaching
near 3 ft by the end of today. Winds gusts maximize near 20 kt
late today into early this evening. Ocean seas remain mostly 3
ft tonight into early Tuesday with winds slightly subsiding and
then these both increase Tuesday afternoon with SCA conditions
coming into place by mid to late afternoon on the ocean. The
southerly fetch by that timeframe builds the oceans seas up to
near 5 ft.

Small Craft Conditions continue Tuesday night into Wednesday as
winds and seas remain high with the approach and passage of a cold
front. For now, a Small Craft advisory is in effect for the ocean
waters through Tuesday night. it is likely the SCA will  need to be
expanded to the non-ocean waters. Also, SCA conditions will likely
continue into Wednesday.

Conditions fall below SCA levels late Wednesday into Wednesday
night. Winds and seas are then forecast to remain, in the absence of
any increased swell, below SCA levels through the weekend.

&&

.HYDROLOGY...
No widespread hydrologic impacts are forecast through the week.

&&

.TIDES/COASTAL FLOODING...
Tides are running high astronomically. For the South Shore
Bays, there is the potential for water levels to just reach the
minor coastal flooding benchmarks with this evening`s high tide.
Thinking is that it`s more likely that all areas fall just short
of flooding with at most only a spot or two perhaps touching
minor flooding benchmarks. Will therefore not issue a statement
at this time. With a stronger onshore flow on Tuesday, there is
a better chance for some spots along the South Shore Bays to
reach minor flooding. Too soon to issue any products for this,
so will allow subsequent shifts to assess trends and issue any
statements or advisories as needed. .

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 3 PM Tuesday to 6 AM EDT Wednesday
     for ANZ350-353-355.

&&

$$
SYNOPSIS...BC/JM
NEAR TERM...JC/JM
SHORT TERM...JM
LONG TERM...BC
AVIATION...Goodman/NV
MARINE...BC/JM
HYDROLOGY...BC/JM
TIDES/COASTAL FLOODING...


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