Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
547 PM EDT Friday Jul 29 2016
low pressure moves south and east of the region through this
evening. High pressure then briefly builds into the region tonight
into the first half of Saturday. This high shift towards the New
England coast for remainder of the weekend as low pressure slowly
approaches from the Ohio Valley. This low slowly moves along a
frontal boundary to the south into early next week. High pressure
then returns for the middle of the week.
Near term /until 6 am Saturday morning/...
drier air in the middle and upper atmosphere as seen on water vapor
continues to move over the area behind the departing low.
This has allowed for clearing skies with a fair weather cumulus
field developing as solar heating increases.
Main forecast challenge in the near term is with temperatures as
significant heating has taken place across much of the region behind
the departing low. Temps from the city north and west have warmed
well into the 80s, with some upper 80s in the lower Hudson Valley.
Highs for the day east of the city may occur late this afternoon, in
the lower and middle 80s. It will remain muggy with dew points in
the upper 60s and lower 70s.
Mrms regional radar mosaic shows some isolated showers developing
across New England and upstate New York. Some of these may advance
into the interior this evening before loss of daytime heating.
With dry air aloft, do not think these will be anything more than
isolated and brief with no thunder mentioned.
Weak ridging builds aloft tonight. Scattered clouds are likely to
continue with some lingering low level moisture indicated on
BUFKIT soundings. Dry and muggy conditions forecast with the
potential for patchy fog towards daybreak across east Li and southeast CT.
Short term /6 am Saturday morning through Saturday night/...
weak ridging flattens aloft on Saturday as a broad shortwave
trough approaches from the Midwest/Ohio Valley. The weak surface
high will move off the New England coast in the afternoon with low
pressure across the Ohio Valley associated with the shortwave
Instability is not impressive on Saturday, with the highest cape
confided to western portions of the area. As has been the case
with the last several systems, the models are struggling with the
placement of precipitation and convection. However, there appears
to be good agreement that the best coverage will be west of the
Hudson River. The high resolution 4-km NAM and sbu-WRF also agree
with this idea and have lowest pops across Long Island and southeast CT
increasing to high chance from the city north and west. Steering
flow is weak so will need to keep an eye on any slow moving
showers and isolated thunderstorms for locally heavy rainfall as
pwats approach 2 inches.
Instability diminishes overnight, but lift may improve across the
interior so will show likely pops here tapering to chance across
the far east end. The 12z GFS may be overdone with its depiction
of widespread precipitation for the whole area overnight and have
elected to follow a blend of the NAM and European model (ecmwf) as well as the
Stony Brook WRF.
Long term /Sunday through Friday/...
a frontal boundary will remain in the vicinity of the tri-state area
Sunday through Monday. A few weak waves of low pressure develop
along the boundry and move near the region. Will continue to keep
chance pops in through this period. An upper trough approaches
Monday and moves through Monday night with additional scattered
showers and thunderstorms.
Drier weather builds into the area Tuesday through Friday. A few
isolated showers will be possible on Tuesday right behind the upper
Temperatures remain at or slightly below normal Sunday through
Tuesday. Then, an increase in heat and humidity start to return.
Aviation /22z Friday through Wednesday/...
lows pressure departs as high pressure departs.
VFR conditions expected. Exception would be for terminals away from
New York Metro, mainly khpn/kisp/kgon, where visibility reductions to MVFR
or lower in br, is possible late tonight through Saturday morning.
Weak low pressure approaches Saturday afternoon. For now, will
carry prob30 groups for 30 hour taf sits of kewr/kswf, as precip
should hold off until after 18z, and not confident enough that
precip would reach kjfk prior to 00z Sunday to have a prob30 group
in kjfk taf at this time.
... 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: south winds due to seabreeze will
lighten this evening.
Klga taf comments: winds turn to the south due to seabreeze.
Kewr taf comments: south winds due to seabreeze will lighten this
Kteb taf comments: south winds due to seabreeze will lighten
Khpn taf comments: south winds due to seabreeze will lighten
Kisp taf comments: winds may turn to the south by 00z as
Outlook for 18z Saturday through Wednesday...
Saturday afternoon...scattered showers possible, mainly for
western terminals, late in the afternoon. VFR otherwise.
Saturday night into Sunday...chance of showers and possibly a
tstm. MVFR or lower conditions possible.
Sunday night-Monday night...chance of showers. MVFR conditions
winds on the ocean have been diminishing as low pressure moves
further offshore. However, a few gusts around 25 kt are possible
east of Moriches Inlet through the rest of the afternoon.
Winds diminish tonight as high pressure builds across the waters.
This high will move off the New England coast Saturday afternoon
as low pressure slowly approaches from the Ohio Valley through
Saturday night. Winds and seas are expected to remain below Small Craft Advisory
levels during this time period.
A fairly light pressure gradient will continue on the area waters
resulting in conditions remaining below small craft conditions
Sunday through Thursday.
the next chance for organized rainfall Saturday into Sunday. Less
than an inch is expected with the highest amounts north and west
of New York City. Locally higher amounts are possible in any
heavier showers. Minor urban flooding would be the main hydrologic
impact in any heavier shower/isolated thunderstorm.
long term...British Columbia