Scientific Forecaster Discussion
fxus61 kokx 241201
Area forecast discussion
National Weather Service New York New York
801 am EDT Mon Jul 24 2017
a frontal boundary will remain south of the area through Tuesday.
High pressure builds over the northeast late Tuesday through
Wednesday, then drifts off the coast Wednesday night. Another
wave of low pressure follows for Thursday into Saturday. High
pressure returns Sunday.
Near term /until 6 PM this evening/...
main area of showers moving across the area. Thunder possible
near the coast and over the ocean waters where best instability
exists, but an thunder will be isolated.
Once area of showers in eastern PA pivot through, activity will
be scattered to isolated this afternoon.
High temperatures today will be in the mid to upper 70s.
There is a high risk for the development of rip currents at
ocean beaches today.
Short term /6 PM this evening through 6 PM Tuesday/...
showers continue through late tonight as an upper level trough
remains over the area. Low temperatures tonight will be in the
low to mid 60s along the coast and in the upper 50s inland.
Other than an isolated shower, dry conditions return on Tuesday
as high pressure builds over the area. High temperatures will
be in the low to mid 70s.
Long term /Tuesday night through Sunday/...
the extended forecast mainly remains consistent with the
previous forecast with the exception that precipitation is
expected remain into Saturday as was hinted at by the European model (ecmwf) late
Saturday, as an upper trough is slower to move east.
The northern stream flow along the US/Canadian border remains
nearly zonal and progressive with embedded shortwaves moving
through the flow.
One shortwave will be exiting the northeastern coast, along
with the accompanying surface low, Tuesday. Cape and instability
remain limited so will continue with showers.
A weak ridge axis builds into southern Canada from the southern
ridge over the southwest and moving into the plain states mid
Another shortwave was coming onshore of the Canadian Pacific
coast as seem on the upper level water vapor loop. And these
system has been picked up by the models. This shortwave open and
tracks quickly across southern Canada then digs and large trough
along the eastern United States late in the week into the weekend
as a western North Atlantic ridge builds and blocks the eastern
trough. This will keep waves of low pressure tracking along a
frontal boundary Thursday into Saturday before the last one exits
later Saturday. So now have chances of precipitation through
Friday into Saturday.
The upper trough weakens Sunday as surface high pressure builds
to the north resulting in a dry Sunday.
Temperatures through the extended period will be near seasonal
normals, except for being below normal Tuesday.
Aviation /12z Monday through Friday/...
a frontal boundary will remain south of the area through
Showers with widespread MVFR/local IFR conditions will continue
until around 16z-17z NYC Metro/lower Hudson Valley, and until
18z-20z east. After showers end, MVFR cigs should linger much of
the day, though think there will be enough drying aloft to allow
for a period of VFR conditions late today into early this
evening mainly for the NYC Metro terminals.
East-NE winds gusting over 20 kt will continue through the day at
kbdr/kgon. Farther west, winds should slowly diminish and back
north-NE this afternoon.
With the front remaining just south and a lighter NE flow
continuing, MVFR conditions should return to all terminals
tonight. There is a chance that cigs could lower to IFR late
tonight especially at kisp/kgon.
..NY Metro enhanced aviation weather support...
Detailed information, including hourly taf wind component fcsts,
can be found at http:/www.Weather.Gov/zny/n90
Kjfk taf comments: unscheduled amend likely to fine tune changes
in flight category. The kjfk afternoon haze potential forecast
is red, which implies slant range visibility less than 4sm
outside of cloud.
Klga taf comments: unscheduled amend likely to fine tune changes
in flight category. The LGA afternoon haze potential forecast is
red, which implies slant range visibility less than 4sm outside
Kewr taf comments: unscheduled amend likely to fine tune changes
in flight category. The kewr afternoon haze potential forecast is
red, which implies slant range visibility less than 4sm
outside of cloud.
Kteb taf comments: unscheduled amend likely to fine tune changes
in flight category.
Khpn taf comments: unscheduled amend likely to fine tune changes
in flight category.
Kisp taf comments: unscheduled amend likely to fine tune changes
in flight category.
Outlook for 12z Tuesday through Thursday...
Tuesday...MVFR in the morning, then VFR. NE winds 10-15 kt.
Tuesday night...patchy fog with MVFR vsby possible late at kswf,
Wednesday and Wednesday night...VFR.
Thursday...chance of showers and possibly a tstm with MVFR or
lower conds northwest of the NYC metros in the afternoon, otherwise
Thursday night and Friday...MVFR or lower conditions possible, with
chance of showers/tstms.
gusty winds ahead of a wave of low pressure riding along a front can
be expected this morning. By afternoon, the low and front track
across the ocean waters, just south of Long Island. This wave of low
pressure moves east tonight, with another low along the front
passing to the south. High pressure then builds to the north of the
waters Tuesday and Wednesday.
Small Craft Advisory has been posted for most waters this morning, except New York Harbor
and South Shore bays of Li. Winds diminish this afternoon. Across
the eastern waters, a few gusts in excess of 30 kt are possible
Ocean seas remain rather rough today, and tonight. Will extend the
Small Craft Advisory for the ocean waters through tonight for now, but it likely
will need to extend into Tuesday as well.
The easterly flow continues into Wednesday and then gradually
diminishes and becomes southeasterly as high pressure moves well
east of the forecast waters. Ocean seas are expected to subside
below 5 feet by mid week. Then winds and seas remain below small
craft levels Wednesday night into Friday.
widespread rainfall is moving across the area early this
morning, but rainfall rates have generally been less than a half
an inch per hour. Scattered showers will move through later this
morning, but do not foresee flash flooding, so will cancel the
Flash Flood Watch.
Additional rainfall is possible Thursday through Friday night.
Hydrologic impacts are not expected at this time.
with the new moon that occurred early yesterday morning, tides are
running astronomically high. Tidal departures of 1 1/2 to 2 ft are
needed for minor flooding during daytime high tide. Only 1/2 to 1 ft
departures are needed at night.
With easterly winds, will issue a coastal flood statement for the
South Shore back bays of Nassau, Queens and Kings, and across the
western Li sound as tides approach minor benchmarks. Elsewhere, feel
tides remain below minor benchmarks.
For tonight, coastal flood advisories may NE needed, but will wait
on another run of guidance to determine potential headlines for
this subsequent high tide cycle.
New York...high rip current risk through this evening for nyz075-080-081-
Marine...Small Craft Advisory until 6 PM EDT this evening for anz330-
Small Craft Advisory until 2 PM EDT this afternoon for anz335.
Small Craft Advisory until 6 am EDT Tuesday for anz350-353-355.