Area Forecast Discussion
Issued by NWS Upton, NY-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KOKX 270827
Area Forecast Discussion
National Weather Service New York NY
427 AM EDT WED JUL 27 2016
Weak high pressure will remain through tonight, then weaken on
Thursday. A weak cold front will approach Thursday night, and
remain nearby into the weekend as a few waves of low pressure
pass nearby. High pressure will return early next week.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Expect sunny skies to start, then high clouds mainly this
afternoon as a mid level shortwave approaches in zonal flow
aloft. High temps should be a shade hotter this afternoon than
those of yesterday inland, still mostly lower 90s, while coastal
sea breezes cap temps in the upper 80s along the south shore of
Long Island and SE CT. Heat indices should be close to ambient
temps for the most part via lower dewpoints in the lower 60s, but
afternoon sea breezes bringing in more humid marine air with
dewpoints in the upper 60s could boost heat indices right along
the coast to just above ambient temps.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Expect mostly clear skies tonight as the aforementioned shortwave
passes by. GFS tries to produce some light precip in association
with this wave, but this does not look realistic as the air mass
in place should still be fairly dry and stable. Low temps will be
close to or slightly warmer than those expected for early this
morning, in the 70s invof NYC and across western Long Island,
and in the 60s elsewhere.
Thu looks like another hot and increasingly humid day, with high
temps in the lower 90s for NYC metro and inland sections, and upper
80s near south facing shores. Dewpoints increasing to the upper
60s to near 70 from NYC metro east should push heat index values
into the mid/upper 90s in those areas, with lower 90s elsewhere.
Zonal flow aloft turns a little more SW through the day on Thu,
and the combo of an approaching mid level shortwave and
convergence invof a weak inland thermal trough and along sea
breeze boundaries should spark at least isold convection. The 00Z
SBU NAM/GFS WRF and the NCAR ensemble are all signaling more
focused development along the sea breeze in NYC metro and across
Long Island where greater instability will also reside, as
increasing dewpoints push MLCAPE to 1000-1500 J/kg across Long
Island and 500-1000 J/kg most elsewhere, so have scattered PoP for
those areas in the afternoon.
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
A low pressure system will move from the Mid-Atlantic northeastward
Thursday night into Friday night, resulting in showers and
thunderstorms across the area. There is the potential for locally
heavy rainfall with precipitable water values in excess of 2 inches.
As the wave of low pressure departs, there may be a break in the
precipitation Saturday, but isolated to widely scattered showers
cannot be ruled out. More unsettled conditions are possible Saturday
night into Sunday, as another potential short wave moves through.
Will continue mention of chance pops due to model differences at
this time. High pressure builds in from Canada early next week.
Temperatures look to be near seasonable levels Friday into early
.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
High pressure builds in from the west today and then east
VFR through the period.
Light northerly winds back to the W/WSW in the late morning/early
afternoon...except likely holding ne at KLGA.
Southerly sea breeze development expected at coastal terminals in
early afternoon...at KLGA/KHPN by late afternoon...with moderate
potential of SE sea breeze at KEWR/KTEB in the late afternoon.
Winds diminish to light S/SW flow tonight.
.OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY...
.Thursday...Mainly VFR. Isolated/sct showers/tstms possible in the
.Thursday Night-Sunday...MVFR or lower possible with a chance of
showers and thunderstorms. The best chance looks to be on Friday.
Sub-SCA conditions will prevail through the weekend.
There is potential for significant rainfall from late Thursday
night into Friday night. Locally heavy rainfall is possible, which
could cause flooding. It is still too early for specifics.