Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
443 am 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/...
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 central PA and middle Atlantic
during the day.
Increasing high and middle cloud cover across western portions of the
tri-state this morning...gradually spreading eastward through the
afternoon in SW flow aloft. Potential for late day rain showers/thunderstorms and rain
activity drifting NE from eastern PA...into areas well west and northwest
Considerable cloud cover across NYC metropolitan and points n&w...and
S/southeast flow will keep temperatures in the upper 70s/lower 80s across much
of the region.
A moderate rip current risk exists today with onshore flow and
lingering 3 feet S swells. The rip risk may be a marginal high risk
across eastern Li beaches early this morning with 4 feet S swells
and onshore flow...but should drop to moderate after daybreak.
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 wave...best 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-
With decent shear profiles and low level jet...cant 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 in vicinity of any 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 airmass.
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 /09z Tuesday through Saturday/...
hi pressure drifts over the Atlantic today. A warm front approaches from
the S tonight and lifts through Wednesday morning.
Mainly VFR through at least 4z Wednesday. There could be some pockets of
fog at the outlying arpts through 12z...but the probability remains too low
to include in the tafs. Chance for showers mainly after 8z Wednesday in the
extended tafs...but there could also be some stratus during the
same period in vicinity of the front.
Light winds through 12-14z with some variability in
direction...although in general prevailing around 220-180 true.
Winds back to the southeast during the day and further to the east-southeast tonight.
..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: no unscheduled amendments expected.
Klga fcster comments: no unscheduled amendments expected.
Kewr fcster comments: no unscheduled amendments expected.
The afternoon kewr haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.
Kteb fcster comments: no unscheduled amendments expected.
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: no unscheduled amendments expected.
Outlook for 06z Wednesday through Saturday...
Tuesday night-Saturday...MVFR or lower possible at times through
the period in rain showers and possible thunderstorms and rain.
sub Small Craft Advisory conditions today with weak high pressure. 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 below 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+ 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