Area Forecast Discussion
Issued by NWS Upton, NY-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KOKX 301751
Area Forecast Discussion
National Weather Service New York NY
151 PM EDT SAT JUL 30 2016
High pressure moves off the New England coast today as low
pressure slowly approaches from the Ohio Valley. This low tracks
along a frontal boundary to the south into early next week. An
upper level disturbance passes through on Tuesday with high
pressure then returning through Friday.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Regional radar mosaic shows increasing coverage of showers and a
few thunderstorms to the west of the area. Sea breeze that is
moving across Long Island and southern portions of the NYC metro
has also started to develop a few showers along it, mainly from
the Western Long Island through near Newark. These sea breeze
showers should be brief with better shower/storm development
expected by mid afternoon from the city west as better lift with
approaching shortwave and increasing warm advection begins to move
Instability has been on the increase across southern portions of
the area with CAPE values ranging from around 750-1200 per latest
LAPS. Higher CAPE resides across southern Jersey, and expect this
trend to continue into the afternoon. With a moist atmosphere and
potential for precip loading with stronger updrafts, an isolated
strong wind gusts are possible in heavier showers/storms. Locally
heavy rainfall is the main threat today.
As the activity translates eastward into this evening, there
should be a downward trend in intensity as the precipitation
encounters a more stable airmass and the surface high just to the
Highs will be in the lower to middle 80s.
.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
As deep layered ridging strengthens across the plains and SW
US and a cutoff low pressure system tracks across western
Canada...the downstream H5 flow will amplify. Unsettled weather
continues through into early next week as the amplifying upper
level trough approaches. However...the shortwave and LFQ of jet
stream are progged to lift through western New York State late
tonight and Sunday. Divergence aloft will pass through western
portions of the local area Sun aftn with additional showers and
tstms expected. With abundant moisture still present through the
column...some storms could produce heavy rainfall.
Sfc low pres approaching from the west slowly passes S of Long
Island Sunday night through Monday night...followed by the upper
trough axis on Tue. Sct showers/tstms remain a possibility with
locally heavy rainfall.
.LONG TERM /TUESDAY THROUGH FRIDAY/...
Drier weather builds into the area Tuesday through Friday. A few
isolated showers will be possible on Tuesday right behind the
Temperatures remain at or slightly below normal through Tuesday.
Then, an increase in heat and humidity start to return.
.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
-- Changed Discussion --SHRA/TSRA developing over NJ and lifting to the east. Activity
will become more widespread going into this afternoon, and impacts
to KNYC terminals are expected to develop between 19-21Z. Over
Long Island, some SHRA/embedded TSRA developed along the sea
breeze, and those should taper off in the next hour or so.
Expecting SHRA/TSRA for many of the terminals through this
evening, and then there should be a lull from around 04-06Z
through 08-10Z. SHRA develop again towards Sunday morning, and
will persist through the day. Conds will drop to MVFR with local
Persistent onshore, SE flow expected into Sunday. For outlying
terminals, winds will go LGT/VRB tonight.
.OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY...
.Sunday afternoon...MVFR or lower in SHRA.
.Sunday night-Monday Night...Chance of showers and possibly a
tstm. MVFR or lower conditions possible.
.Tuesday...Mainly VFR, although isolated showers are possible.
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A frontal boundary will remain south of the waters through early
next week until low pressure passes to the east Monday night into
early Tuesday. This will result in a mainly E/SE flow which will
be strongest Sunday afternoon/evening, with possible gusts up to
20 kt on the ocean waters. High pressure will then follow for the
mid week. Sub-sca conditions are forecast during the period.
A large range of rainfall is expected across the area this
weekend. Average QPF from this afternoon through Sunday evening is
expected to be from around 1/3 of and inch to 1 inch east of NYC
and 1 to 1 3/4 inches N and W of NYC. Locally higher amounts are
possible in any heavier showers. Minor urban flooding would be
the main hydrologic impact in any heavier shower/thunderstorm.