-- Discussion containing changed information from previous version are highlighted. --
498
FXUS61 KOKX 272200
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
600 PM EDT Thu Jul 27 2017

.SYNOPSIS...
A weak cold front moves across the region from central New York
overnight before stalling just south of Long Island on Friday.
Waves of low pressure develop along the front Friday night into
early next week. By mid next week, the low pressure area moves
farther offshore with weak high pressure building in from the
west. Weak high pressure remains over the area until Thursday
next week when a cold front approaches from the northwest.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Light showers over the region with weak warm advection. Much of
this is east of the region by 22Z.

The next round of showers over upstate NY, which appear more
associated with the weak front passes mainly over eastern
section as the HRRR continues to insist upon.

We do have a slight chance for Thunder overnight as HRRR
soundings indicate LI`s of -2 C and up to a 1000 J/KG on MU
CAPE. Not very confident in this as there been zero lightning so
far today.

There will be a moderate risk of rip currents at area beaches.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/...
The front settles just south of Long Island on Friday and have
gone with a dry, but cloudy, forecast. Over running sets up
Friday evening as cyclogenesis begins as shortwave over the
Great Lakes closes off. This cause rapid deepening of the
surface low over the DelMarVa. The upper dynamics cause the
surface low to sag south as wave "spin off" to the east.

Main potential hazard is heavy rain. Having looked at a lot of
guidance, we have sided with the idea that the heaviest rain
stays south of our region and will not issue a flood watch - at
least not yet. In fact just saw the 15Z SREF and amounts are
down.

HWO (Hazardous Weather Outlook) continue to highlight for the
potential for flooding - but the potential is still in the low
chance level.

See Hydro section to see rainfall forecast amounts.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
The upper level trough remains over much of the Eastern U.S. for the
remainder of the weekend. The trough axis will slowly move east
during this time but will still be west of the local region. The
local region will be near the inflection point of this trough. The
upper level jet stream affiliated with the trough will be situated
generally from the western Atlantic waters not that far offshore
northeast through Nova Scotia. This will help sustain the low
pressure along the stalled front at the surface. The region will
remain in a northeast flow as a result. The pressure gradient will
still be relatively tight Saturday night, making for gusty winds
mostly between 30 and 40 mph. Winds decrease Sunday into Sunday
night as low pressure becomes weaker south of Long Island, hence
weakening the pressure gradient. The winds finally switch in
direction mid to late next week. More typical southwest flow will
come into place during this timeframe.

In terms of weather, cooler than normal temperatures and rain will
still be in the forecast Saturday night and Sunday, albeit mostly
light rain. Higher chances for the light rain will be across Long
Island and offshore while lower chances will be farther north. Rain
could even linger especially across Long Island going into Monday
and Tuesday of next week as some models convey a retrograding
movement back to the west of the offshore low. There are even some
slight increases in elevated instability, making for a slight chance
of thunderstorms on the East End of Long Island Monday night into
early Tuesday. Drier conditions and temperatures closer to normal
return Tuesday and more so for mid to late next week.

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --
A weakening cold front slowly crosses the area into Friday
morning. Low pressure begins to develop over the central
Appalachians by early Friday afternoon.

City terminals will see conditions vary between MVFR and VFR
into this evening, then ceilings lift to around 20,000 FT
overnight.

Elsewhere mainly MVFR conditions (with pockets of VFR) become
MVFR throughout by midnight. IFR conditions are probable at
CT/Long Island terminals and KHPN overnight. Conditions improve
to VFR everywhere by around 12Z Friday.

Winds become light and variable throughout this evening. 5 to
10 kt this afternoon become light and variable overnight. NE-E
winds at under 10kt develop at eastern terminals and possibly
KLGA/KJFK by mid Friday morning.

     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 MVFR ceilings are possible into
this evening.

KLGA TAF Comments: Occasional MVFR ceilings are possible into
this evening.

KEWR TAF Comments: Occasional MVFR ceilings are possible into
this evening.

KTEB TAF Comments: Occasional MVFR ceilings are possible into
this evening.

KHPN TAF Comments: Occasional VFR ceilings are possible into
this evening.

KISP TAF Comments: Occasional VFR ceilings are possible into
this evening.

.OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY...
.Friday Afternoon...VFR.
.Friday night-Saturday...MVFR or lower with heavy rain and
possibly a tstm. NE winds G25-35kt on Saturday, mainly at the
coastal terminals.
.Saturday night-Tuesday...VFR.
-- End Changed Discussion --

&&

.MARINE...
Gale watch in effect for Saturday.  Tranquil though Friday
afternoon, then low pressure to the south increase NE winds with
gales forces gusts likely on Saturday. As a result, seas build
rapidly on all waters.

Active time period to start Saturday night with gales probable
across the waters due to a relatively tight pressure gradient. The
gales could even extend on the ocean into Sunday with otherwise SCA
winds Sunday morning. The SCA winds are forecast for most waters
Sunday afternoon and evening. Then for non-ocean waters, there will
be sub SCA conditions. For the ocean, both winds and seas are
forecast to be in SCA range late Sunday night through Monday
evening. Thereafter though, ocean seas are forecast to still be
meeting low end SCA with 5-6 ft values.

&&

.HYDROLOGY...
There is the potential for a heavy rainfall event Friday night
through Saturday, especially across portions of northeastern New
Jersey, New York City and Long Island. From Friday night through
Saturday night rainfall is expected to range from around 1/2 to
3/4 of an inch across the Lower Hudson Valley and interior
southern Connecticut to 1 to 2 inches across northeastern New
Jersey and across Long Island.

There is though the potential for significantly higher amounts
if the pattern moves heavier rainfall from central and southern

&&

.TIDES/COASTAL FLOODING...
Despite the expected strong Northeast winds on Saturday, only
minor coastal flooding appears possible on the south shore bays
of western Long Island at this time.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Gale Watch from Saturday morning through late Saturday night
     for ANZ330-335-338-340-345-350-353-355.

&&

$$
SYNOPSIS...Tongue
NEAR TERM...Tongue
SHORT TERM...Tongue
LONG TERM...JM
AVIATION...Maloit/DW
MARINE...JM/Tongue
HYDROLOGY...Tongue
TIDES/COASTAL FLOODING...