Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
829 PM EDT Tuesday Jul 7 2015
a cold front approaches from the northwest tonight...and then
crosses the area on Wednesday. The front stalls to our south
Wednesday night into Thursday. Waves of low pressure riding along
the front through Thursday night. Weak high pressure builds in
Friday through Saturday...then slowly slides offshore Sunday. A
warm front slowly approaches from the west Sunday night and
Monday. A cold front approaches Monday night into Tuesday.
Near term /until 6 am Wednesday morning/...
showers and thunderstorms across southwestern CT in associated
with a shortwave moving through produced heavy rainfall across
these areas over the past couple of hours. Outflow boundary noted
on radar will mean gusty winds as these showers move through...but
should also put an end to the activity as the evening
progresses...especially with the loss of daytime heating.
Mainly dry conditions are expected overnight. There may be a
passing shower or thunderstorm for northwestern Orange County as a
cold front approaches late tonight. Patchy fog is possible
overnight in moisture rich low level air mass. Dense fog is
possible in some locations across Long Island and southeast CT...but not
enough confidence for any advisory at this point.
There is a moderate risk of the meteorological enhancement of rip
current development at area Atlantic beaches today..
Short term /6 am Wednesday morning through Wednesday night/...
a cold front approaches from the northwest Wednesday morning.
Clouds will be on the increase as well as chances for showers and
thunderstorms throughout the day. Several factors bring
uncertainty to the forecast for coverage of showers/storms during
the day on Wednesday. A shortwave is forecast by the models to
move across during the morning hours...and this could lead to less
in the way of support for widespread convection with negative
vorticity advection behind it. Another potentially limiting factor
is how much we destabilize. With the front nearby...clouds may
limit the overall amount of heating. With this in mind...have
capped probability of precipitation off at 50 percent. There should be enough low level
convergence for scattered showers/storms to develop along and near the
front in the afternoon and evening. Any of these showers/storms
has the potential to produce torrential rain with precipitable waters around 2
inches. Severe weather threat appears limited due to overall weak
shear as 0-6 km bulk shear is around 20 kts.
The front should stall near or just south of the region Wednesday
night. Another shortwave is forecast to approach from the west
Wednesday night...and this could act on the front to enhance
coverage of convection. Have continued with high chance during the
first part of the evening...tapering to low chance late in the
night. The main threat from any storms that linger into the night
continues to be locally heavy rainfall.
Highs on Wednesday are a bit uncertain due to amount of cloud cover
and precipitation...but temperatures in the low to middle 80s look likely.
Heat index values will reach the upper 80s to near 90
degrees...especially in the NYC metropolitan. Lows Wednesday night will be in the
middle to upper 60s.
Long term /Thursday through Tuesday/...
agreement in the models with the overall set up early in this
period. Zonal flow aloft with a stalled frontal boundary in the
vicinity for Thursday into Thursday night. A couple of disturbance
will develop along the frontal boundary...one in the early morning
to early afternoon hours...and another in the evening to overnight
time period. The 12z GFS...12z Canadian...and 00z European model (ecmwf) all show
these disturbances moving through the region...along with low spread
in the naefs and gefs. Zonal flow will mean these disturbances will
move through rather quickly. However...uncertainty lies in the
amount of quantitative precipitation forecast. Stability during this time period is not impressive
with little...if any cape present over the area and showalter
indices generally greater than 0.
High pressure builds in for Friday...bringing with it dry conditions
through Saturday night. The high will push offshore
Sunday...allowing for a warm front to approach late Sunday into
Monday morning. A cold front approaches the region late Monday into
Tuesday. This front may stall in the vicinity through the middle-week
period as an Omega block looks to develop across North America early
to late next week.
Aviation /00z Wednesday through Sunday/...
a cold front over the Ohio Valley approaches tonight and passes slowly
during the day Wednesday.
Last of the thunderstorms now in CT should not impact any taf sites this
evening. Kgon could be impacted if there is additional development
ahead of the complex.
VFR most areas tonight. Kgon will likely have IFR most of the
night. Redevelopment of IFR is possible at kisp if SW flow does not
Showers and thunderstorms likely develop after 13z Wednesday from northwest to southeast. With
the slow movement of the front...activity may impact the area for
most of the day. Thunderstorms in the vicinity included in the tafs for this. MVFR or even
lower possible in vicinity of the thunderstorms Wednesday.
Flow weakens tonight with a general westerly flow on Wednesday. Winds shift to
the northwest behind the front late Wednesday afternoon into Wednesday evening.
New York 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: winds may shift to around 230 true with
gusts up to around 20kt through 2z.
Klga fcster comments: occasional gusts possible after 01z.
Kewr fcster comments: occasional gusts possible after 01z.
Kteb fcster comments: gusts may only be occasional this evening.
Khpn fcster comments: winds may shift to around 230 true before
becoming vrb tonight.
Kisp fcster comments: low probability of IFR tonight.
Outlook for 00z Thursday through sun...
Wednesday night-Thursday evening...shra/tstms possible with MVFR or lower
conditions at times.
Late Thursday night-sun...VFR.
visibilities across the waters have risen to above 1 nm. While
dense fog may be possible again tonight...at this time it looks
to be patchy rather than widespread.
Otherwise...seas will be around 2-3 feet through the first portion of
tonight and then could build further to 4 feet into Wednesday...but
are expected remain below 5 feet. Winds could gust to around 20 knots
this evening on the ocean...but will also remain below Small Craft Advisory levels
through Wednesday night.
Lack of a strong pressure gradient in the long term will mean winds
and wave below Small Craft Advisory criteria.
localized urban and poor drainage flooding is possible
in heavier showers through this evening and then again on Wednesday
into Wednesday night. Training of storms is also possible...with a
low probability of flash flooding.
There is the potential for a heavy rainfall event Thursday into
Thursday night. However...there is large uncertainty in where the
axis of heavy rainfall will occur as two disturbances move