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000
FXUS61 KOKX 150346
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1146 PM EDT Mon Aug 14 2017

.SYNOPSIS...
A frontal boundary south of Long Island will slowly move northward
tonight into Tuesday. Meanwhile a weak cold front will also be
approaching the region from Southeast Canada Tuesday and will move
across Tuesday night. High pressure builds across the area
Wednesday then moves offshore by Thursday. A warm front moves
northward Thursday night, while a slow-moving cold front
approaches from the west through the latter part of the week.
The front finally passes to the east by the weekend with high
pressure building in its wake.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Forecast is generally on track, although have made some minor
adjustments to the database this evening. Showers across central
NJ will move across the NYC metro between 04z and 06z and
continue across Long Island through the overnight hours as a
weak upper level shortwave and accompanying entrance region of
an upper level jet moves through the region. Coverage has been
decreasing somewhat over the past hour, but expect some increase
as the jet streak moves into the area. Also lowered lows a few
degrees, mainly inland as some locations had already hit their
forecasted low.

Otherwise...synoptic map shows a frontal boundary extending
from Virginia through the Delmarva and into the Western
Atlantic. High pressure is well offshore and weakening. A weak
frontal system will be moving through the Great Lakes.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
The region will still be under the right entrance region of the jet
streak Tuesday. Upper level low pushes farther southward through
Quebec. Mid levels show an approaching trough from the west during
the day, moving across at night.

At the surface, the frontal boundary across the Western Atlantic
slightly moves farther northward, closer to the local region.
Tropical cyclone Gert will be south of this front moving
northeast far away well out into the Atlantic. However, long
period swells will be emanating out from the center of Gert,
starting to arrive late Tuesday. To the west across the Great
Lakes, the frontal system and its associated cold front will
slowly approach the region during the day. The cold front will
move across Tuesday night.

Rain shower chances will be higher earlier in the day with more SE
low level flow to keep moisture levels higher near the ground. Rain
showers chances lower thereafter and by the afternoon, there will
still be a slight chance of showers and thunderstorms as well,
mainly across the western half of the region. In the mid levels, the
local region is conveyed to be in between the shortwaves. The system
to the west is weakening and the forecast models show a negative
vorticity advection trend.

Therefore, the cold front looks to move through dry Tuesday night.
The jet streak is exiting northeast of the region. Outside of a
slight chance of showers and thunderstorms across northern extremes
of the Lower Hudson Valley, the forecast is dry.

Thunderstorms are a slight chance and are being introduced into the
forecast Tuesday into early Tuesday night because instability is
expected to be a little more due to daytime heating.

For temperatures, MAV/MET blend was used for high temperatures as
both solutions had relatively similar temperatures. The temperatures
reach the upper 70s to lower 80s for highs, slightly cooler than the
previous day. A combination of MAV/MET/NAM12/GMOS was used for lows
at night Tuesday night, ranging from the low 60s to near 70.

A high risk of rip currents continues at Suffolk County ocean
beaches on Tuesday. A moderate risk of rip currents for ocean
beaches in Nassau and NYC should prevail Tuesday morning, but
long period swells from tropical cyclone Gert are expected to
begin impacting the ocean waters Tuesday afternoon which should
result in a high risk during the afternoon and evening hours.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
The primary concern for mid week will be at ocean beaches as
southerly to southeasterly swell continues to the north of Tropical
Cyclone Gert. This may create hazardous conditions with an enhanced
risk of rip currents.

Apart from the dangerous surf, high pressure will build across the
area Wednesday into Thursday. Initially the offshore flow on
Wednesday will lead to subtle downsloping, aiding in above normal
temperatures across the area. As the high continues to build
southeastward overnight, lower dew points will advect into the area
allowing temperatures to fall close to or slightly below normal
values in favorable radiational cooling. By Thursday the high begins
to shift offshore leading to a return flow and increasing humidity
from south to north once again. Aloft, a short wave of low pressure
will slowly approach from the west which may gradually increase
shower and thunderstorm chances by evening, continuing into Friday
as multiple disturbances rotate around the low. The attendant cold
front finally reaches the area on Saturday with shower and
thunderstorm chances gradually ending from west to east as the front
moves through late in the day. Humidity will decrease into the early
week as high pressure builds back into the area.

&&

.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
A series of weak waves of low pressure will track east, along a
warm front to the south of the region, tonight through Tuesday.

Latest high-res model guidance indicating showers across
southeastern PA working into the NYC/NJ terminals after
midnight, and working east through the terminals through Tue
morning. Additional shower activity possible Tue aft.

Increasing likelihood for MVFR stratus late tonight into Tue
morning, with IFR potential for eastern terminals. MVFR cigs
possible to remain through the day, especially for eastern
terminals.

Light and variable winds overnight, becoming SE under 10 kt
Tuesday morning.

.OUTLOOK FOR 00Z WEDNESDAY THROUGH SATURDAY...
.Tuesday night...MVFR or lower conds possible in stratus/fog,
particularly for eastern terminals.
.Wednesday and Wednesday night...VFR.
.Thursday...MVFR conds possible from NYC metro west, with chance
of showers.
.Thursday night through Saturday...MVFR or lower flight cat
possible, with chance of showers and tstms. Best chance for
tstms in the afternoon.

&&

.MARINE...
Sub SCA conditions are forecast tonight with a weak pressure
gradient remaining in place. However, Tuesday while starting likely
below SCA with a weak pressure gradient, the long period swells from
distant far offshore tropical cyclone Gert will allow for
building seas up to near 4 ft. There is a chance ocean seas
could reach 5 ft by late Tuesday afternoon. SCA chances are
higher Tuesday night when modeled long period swell comes more
into the waters. Due to uncertainty in start time and 5-6 ft
seas being mostly in the 3rd period, did not issue SCA at this
time.

Swells from tropical cyclone Gert will maintain SCA level seas
through mid week. The official NHC forecast places the system well
east of the area by Thursday, which combined with a weakening
pressure gradient as high pressure builds in should allow seas to
slowly subside Thursday. Despite a frontal system approaching late
week, the pressure gradient will remain weak keeping sub-SCA
conditions on the waters through the weekend.

&&

.HYDROLOGY...
No hydrologic problems are anticipated through Tuesday night.
Rainfall expected to be less than a quarter inch.

A slow moving-frontal system may bring periods of heavy rainfall
towards late week.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Rip Current Risk through Tuesday evening for NYZ080-081.
NJ...None.
MARINE...None.

&&

$$