Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service New York New York
202 PM EDT Tuesday Jun 30 2015

high pressure slides east today...with a weak frontal system
approaching tonight and moving through on Wednesday. A cold front
will slowly move across the area Wednesday night into Thursday
with Canadian high pressure building into the northeast in its
wake. Waves of low pressure will traverse the stationary boundary
to our south through the weekend. A warm front will lift through
the region on Monday with a cold front approaching Monday night.


Near term /until 6 PM this evening/...
forecast updated to include Severe Thunderstorm Watch effect until 8
PM for Orange and Passaic counties. Cluster of storms in eastern PA
has already prompted warnings...and may do the same in our far
western reaches as partial clearing works its way into these areas and
quickly destabilizes the air mass ahead of the storms.
Some concern for an isolated tornado as well given proximity of warm
front and resultant low level veering of winds.

Showers and thunderstorms expected to remain mainly in the watch area this
afternoon...thus kept increased pop from previous short term forecast and
lowered them to none for east of the Hudson. Hrrr and Storm Prediction Center
convection-allowing models /cams/ support the forecast for
convection remaining west of the Hudson through this afternoon.

Other change was to sky cover...which is clear east. Some clouds
should spill into Long Island and CT...but still a mostly sunny
day there. NYC is expect to become cloudy.

Otherwise...upper trough sharpens into the Ohio Valley
today...with western Atlantic ridging remaining firm. At the
surface...a resultant weak low pressure system drifts east across the
Great Lakes...with its warm front making slow progress through
eastern PA and into northwest New Jersey/southeast New York this afternoon.

Cloud cover across NYC metropolitan and points n&w...and gusty S-southeast flow
will keep temperatures in the upper 70s/lower 80s in most places.

A moderate rip current risk continues this afternoon with onshore
flow and lingering 2-feet S swells.


Short term /6 PM this evening through 6 PM Wednesday/...
upper trough slides slowly eastward tonight and then pivots NE
through the region on Wednesday. At the surface...the warm front
makes slow progress towards the region tonight...but likely not
lifting north till Wednesday morning ahead of approaching cold
front. Possibility of a weak triple pt wave to develop and move
across the region Wednesday morning/early after as well.

Forcing and instability gradually increase across west/SW portions of
the tri-state overnight as warm front and potential developing
triple pt wave approach the region. This should pose an increasing
potential for showers and scattered thunderstorms from SW to NE late tonight into
Wednesday morning. Best coverage of showers and thunderstorm looks to be Wednesday
morning into early afternoon as shortwave trough approaches and warm
front/wave lifts through.

In wake of warm front/triple point moisture axis
appears to slide east of the region. So uncertainty for afternoon
convection in terms of amount destabilization before afternoon
shortwave passage. Scattered convection possible ahead of cold
front northwest & west of NYC...or along any thermal or lingering pre-
frontal trough.

With decent shear profiles and low level jet...cannot rule out an isolated
strong to severe storm with even some weak rotation along warm
front/developing triple pt wave. Potential is low overall...but
should increase through the morning into early afternoon with
building instability. Conditional potential for a few strong to
severe storms in the early to middle afternoon as shortwave is coming
through...along cold front and any lingering boundary.

Setup does not look favorable for widespread convection late in the
afternoon into evening as shortwave axis looks to be pivoting east
of the region. Coverage may be more isolated along the lagging cold
front as it passes through...with a diminished severe threat due to
subsidence and a drying air mass.

Highs near seasonable.


Long term /Wednesday night through Monday/...
00z deterministic solutions...with the exception of the CMC...have come
into better agreement with the 500 mb pattern across noam through the
weekend. However...issues with timing and amplitude of the northern
stream flow begin to become apparent on Sat with large differences
developing by early next week...especially out west.

Mean trough over the eastern US will remain through the end of the
week...before a split flow develops over the weekend. The degree of
downstream amplification across eastern Canada and northestern portion of the
Continental U.S. Will determine if and when the next cutoff low pressure system
traversing the Canadian provinces will impact the local area next

Any convection ahead of a cold front Wednesday evening is expected to wind
down fairly quickly due to the lack of shortwave energy and
additional upper level support. Could see a few stray thunderstorms right
along the front. NAM is the slowest with the frontal passage with parent low
pressure system cutting off aloft and surface low tracking due north Thursday night.
It is also slightly stronger than the remaining guidance. At any
rate...all solutions indicate the system cutting off and gradually
lifting north/NE Thursday/Thursday night leading to a slow frontal progression
across the area. As the upper low departs...shortwave energy
tracking through New England could trigger an isolated shower/thunderstorm
across the interior Thursday. Additionally...several pieces of shortwave
energy tracking around the base of the mean trough will result in
waves of low pressure tracking along the boundary.

Trends from the 12z guidance have shifted the frontal boundary
further S with Canadian high pressure building into the NE providing dry
and slightly cooler weather for Friday. Sat may end up being dry if the
high hangs on and keeps a frontal wave suppressed to the S. Dry
weather is then expected to continue with rising heights and warm
advection sun into Monday as a warm front lifts through.

Temperatures are expected to be near seasonable levels through the


Aviation /18z Tuesday through Sunday/...
low pressure and a warm front approach from the west tonight.

VFR most terminals into the evening. The only exception would be
possible rain showers/thunderstorm at kswf late this afternoon.

Stratus develops tonight...mainly after midnight. Low end MVFR or
even IFR conditions are possible from 6-14z. Showers are possible as

Improvement to VFR is expected Wednesday morning after 14-15z.

Gusty south to southeast winds diminish 22-00z. Winds back to the
east/southeast tonight before veering again Wednesday morning to the S.

..NY metropolitan enhanced aviation weather support...

Detailed information...including hourly taf wind component forecasts can
be found at: http:/www.Erh.NOAA.Gov/zny/n90 (lower case)

Kjfk fcster comments: occasional to frequent gusts continue 20 to 25
kts through 22z or so.

Klga fcster comments: occasional to frequent gusts continue 20 to 25
kts through 22z or so.

Kewr fcster comments: showers and thunderstorms should stay just to
the west of the Airport through 00z. Occasional to frequent gusts
continue around 20 kts through 22z or so.

Kteb fcster comments: showers and thunderstorms should stay just to
the west of the Airport through 00z. Occasional to frequent gusts
continue around 20 kts through 22z or so.

Khpn fcster comments: occasional to frequent gusts continue around
20 kts through 22z or so.

Kisp fcster comments: occasional to frequent gusts continue around
20 kts through 22z or so.

Outlook for 18z Wednesday through Saturday...
Wednesday afternoon...mainly VFR but thunderstorms are possible.
Wednesday night-Sunday...generally VFR expected. Isolated thunder
though cannot be ruled out through much of the period. As such...sub
VFR conditions remain possible from time to time.


near shore winds in the New York bight and Harbor will increase this
afternoon with gusts to the lower 20s.

Ocean seas will gradually build on Wednesday ahead of a cold front.
Potential for marginal Small Craft Advisory seas by Wednesday evening.

Winds are expected to remain blw Small Craft Advisory levels through the
period...although if the stronger NAM solution ends up verifying Thursday
night into Friday...winds could get close. Otherwise...a southerly swell may
bring seas on the ocean above 5 feet Wednesday night and continue through
Thursday evening with sub- Small Craft Advisory conds thereafter.


potential for scattered thunderstorms to produce locally heavy
rainfall late tonight into Wednesday. The forecast basin average of
rain is around a half inch but locally 1 inch or more is possible.

Main threat will be for minor urban flooding with any
convection...with a low threat of flash flooding with any
training convection along warm front/triple pt low.

No widespread significant rainfall is expected through the end of
the week.


Tides/coastal flooding...
with approaching full moon...tidal departures of only 3/4 to 1 1/2
feet are needed for minor coastal flooding benchmarks to be reached
during the late evening/night high tides the next few days. Minor
benchmarks could be touched across the most vulnerable
areas...particularly along the South Shore bays of Nassau
County and western Li sound...middle to late week.


Okx watches/warnings/advisories...
New York...none.
New Jersey...none.


near term...Goodman
short term...Nevada
long term...24
aviation...precipitable water
tides/coastal flooding...

National Weather Service Glossary of Abbreviations