Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 210240
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1040 PM EDT WED JUL 20 2016

.SYNOPSIS...
An area of high pressure which extends east from the Ohio Valley
to off the Mid Atlantic Coast will slowly work offshore through
Thursday night. A cold front approaches the region on Friday and
moves through late at night into Saturday morning. High pressure
then follows Saturday afternoon through Sunday. Another cold front
approaches on Monday and passes through Monday night.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
A departing upper trough will continue to work offshore into the
western Atlantic as anomalously warm heights associated with a
ridge over the mid section of the country expand east. This will
result in increasingly warmer and more humid conditions through
the end of the week.

At the surface, a large area of high pressure, extending from the
Ohio Valley to off the Mid Atlantic coast, will slowly work east.
This will keep the area dry with a weak return SW flow and nearly
seasonable lows.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Heights will continue to build aloft as the upper ridge over the
mid section of the country expands east. Airmass will remain
capped with no convection forecast. It will be several degrees
warmer than Wednesday as a westerly flow aloft transports warmer
air from the upper Midwest and Great Lakes into the region. An
increase in humidity will also become more noticeable Thursday
night as dew points climb through the 60s due to a strengthening
SW flow. Gradient wind tightens due to the offshore high and an
approaching frontal system over the upper Great Lakes. Gusts up to
20 mph are possible across the NYC metro and LI Thursday
afternoon/early evening, but of a lesser magnitude to the north.

Highs on Thursday will range from the lower 80s along the coast,
to around 90 in the interior. Lows Thursday night will range from
the mid 60s inland, to the lower 70s along the coast. These
readings are about 3 to 5 degrees above normal.

There is a moderate risk for rip current development at ocean
beaches Thursday afternoon into evening due to the combination of
2 ft long period se swell and increasing southerly wind waves.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
A cold front approaches on Friday and passes through late at night
into early Saturday morning. With increasing CAPE and a shortwave
contributing to shear, particularly across the NE portion of the
CWA, showers and thunderstorms, some possibly strong to severe will
be possible. Best chances of this will be in the afternoon and
evening hours. By Saturday morning, perhaps a lingering shower or
storm possible over the eastern zones early on, otherwise dry
behind the cold front.

A high risk for rip current development at ocean beaches is likely
for Friday afternoon due to southerly wind waves increasing to 3
to 5 ft and a residual 2 ft se swell.

Regarding the heat, both days are progged to have 18-19C
temperatures at 850MB. Saturday, with lower boundary layer dewpoints
and a better chance of mostly sunny conditions, is currently
forecast to be slightly warmer than Friday. But since surface
dewpoints will probably have a harder time mixing out during Friday,
heat index values will be higher on Friday. There is potential that
a heat advisory will be needed across the city for this period,
however Saturday`s heat indices are currently forecast to barely
meet the criteria. The rest of the forecast area should remain below
advisory criteria.

Sunday will feature dry and mostly sunny conditions with weak high
pressure over the area. Temperatures aloft drop a little, and
surface dewpoints should be able to mix out again, so heat indices
should be below 95 for just about everywhere.

Another cold front approaches on Monday, but a warm front pushes
through first. This will bring higher dewpoints across the area, and
with 850MB temperatures forecast to be 19-20C, heat indices of 95-
100 could be widespread. Just like on Friday, there is some
uncertainty for high temperatures due to potential thunderstorm
activity and related cloud cover.

850MB temperatures don`t look to drop off all that much, if at all
on Tuesday. Surface dewpoints will probably be lower, but heat
advisory criteria could be met once again in the city for the Monday-
Tuesday period.

High pressure looks to continue the dry weather pattern on
Wednesday. High temps and heat indices are forecast to be below
95.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
High pressure centered over western Pennsylvania into West Virginia
drifts east overnight, and moves off the Mid-Atlantic coast early
Thursday morning. The high remains offshore into Thursday night.

VFR through the TAF period.

Southwest winds under 10 KTS at the metro terminals overnight, with
outlying terminals light and variable. SW winds increase Thursday
morning with sea breezes developing in the afternoon.


.OUTLOOK FOR 00Z Friday through Monday...
.Thursday night through Friday morning...VFR.
.Friday afternoon through Friday night...MVFR or lower possible in
SCT TSRA. S-SW winds 15-20 KT with 25 KT gusts across NYC and Long
Island.
.Saturday through Sunday...VFR.
.Monday...MVFR or lower possible in SCT TSRA.

&&

.MARINE...
High pressure builds slowly east of the waters through Thursday
night with a frontal system dropping SE across the Great Lakes.
Southerly flow strengthens Thursday afternoon/night with gusts up
to 20 kt possible on the ocean waters with seas building to
around 4 ft. At this time, expect winds and seas to remain below
SCA.

A tightening pressure gradient ahead of a cold front will probably
bring winds and seas to advisory criteria levels on the ocean waters
Friday afternoon into Saturday morning. For the other waters,
meeting criteria during this period appears to be more marginal, but
currently have 25 KT gusts in the forecast for the eastern sound
Friday afternoon and night. Sub-sca conditions then prevail across
all waters for the rest of the forecast period.

&&

.HYDROLOGY...
No adverse hydrologic impacts are anticipated with scattered
showers and thunderstorms Friday/Friday night and Monday/Monday
night.

&&

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

&&

$$
SYNOPSIS...JC/DW
NEAR TERM...NV/DW
SHORT TERM...DW
LONG TERM...JC
AVIATION...MET
MARINE...JC/NV/DW
HYDROLOGY...JC


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