Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
133 PM EDT sun Aug 30 2015
high pressure remains offshore ahead of an approaching trough
which will cross the area tonight. Low pressure then passes to the
north across eastern Canada on Monday...sending a weak back door
cold front through the area Tuesday morning. High pressure will
remain in control for the remainder of the week.
Near term /until 6 PM this evening/...
minor changes made to forecast database to better match observed
trends. Temperatures slightly increased across the interior and
temperatures elsewhere were pretty much on track. Dewpoints were
increased slightly as well across the coastal sections. Probability of precipitation were
kept at slight chance for showers and thunderstorms north of NYC.
Mesoscale models not showing much convection with hrrr model
showing relatively more convective coverage.
The trend will be for warmer and increasingly more humid
conditions heading into the new week as a high amplitude ridge
over the western U.S. Merges with the sub tropical ridge along
the eastern Seaboard. In between...a weakness across the middle
section of the country will gradually fill...while a northern
stream short wave trough passes through the area tonight. At the
surface...this will be reflected as a surface trough or warm front...
preceded by weak thermal forcing. This forcing combined with
marginal instability may be enough for an isolated shower and/or
thunderstorm this aft/eve...mainly north and west of NYC. Clouds
will also spread in from the northwest today with mostly cloudy
conditions by afternoon inland and party sunny at the coast.
Highs will range from the middle 80s near the coast...to around 90
There is a moderate risk for the development of rip currents
Short term /6 PM this evening through Tuesday night/...
aforementioned trough/warm front moves through tonight with gradual
clearing from northwest to southeast by morning. The upper level ridge begins to
expand eastward on Monday with warming temperature profiles aloft and a
gusty west/SW flow in the after. This will allow for highs a few
degrees warmer than on sun...with readings topping out in the
lower 90s inland.
A weak back door cold front then passes through Monday night as low
pressure passes well to the north and east across the Canadian
Maritimes. Not much relief though for Tuesday with perhaps a degree
or two shaved off of Monday highs. Lows will range from the lower to
middle 60s inland...to 70 to 75 NYC metropolitan. These readings are still
well above normal. It will also be muggy with dew points well into
the 60s. Heat index values look to remain below advisory criteria
at this time.
Winds briefly go northwest Tuesday morning behind the cold front...but then
return from the S by after as the front lifts northward and
dissipates nearby. Subsidence aloft will put a cap on any
convection during this time period.
Long term /Wednesday through Sunday/...
the main theme of the long term period will be the continuation of
heat and humidity across the region.
Models are in good agreement with the 500 mb pattern across North
America into the middle of the week as an upper level ridge
out west merges with the sub tropical ridge over the western
Atlantic. This will result in dry and unseasonably warm weather
through Thursday possibly Friday. This will depend on the timing of the
next cold front moving across which is currently uncertain due to
differences that develop in the 500 mb flow during the latter portion
of the week. Could see a few showers or thunderstorms with the frontal
passage which is currently slated for Friday...followed by dry
conditions and cooler but still above normal temperatures for the
Highs will generally range in the upper 80s to lower 90s across the
area through much of the week...the exception Friday/Sat with the
frontal boundaries in/through the area. Heat indices are expected
to be close to the ambient air temperature and are not currently expected
to reach 95 degrees in NYC through Wednesday.
Aviation /17z Sunday through Thursday/...
a weak trough of low pressure will cross the tri-state this
afternoon and evening...then stall out south of Long Island into
VFR through the taf period.
Seabreezes on track for all terminals except kswf/kteb and
probably kewr. Already through CT terminals/kisp/kjfk. Question
is timing for remainder of terminals. Isolated gusts to around 15
knots possible at NYC metropolitan terminals this afternoon as well.
Winds become SW at under 10 knots at city terminals tonight and
light and variable elsewhere. West-southwest- west-northwest winds at around 10 knots
develop by late Monday morning- early Monday afternoon. Wind
speeds could increase to around 15 knots at kjfk towards the end of
the taf period.
An isolated shower or thunderstorm cannot be ruled out the lower
Hudson Valley this afternoon/early this evening. Have included a
vcsh at kswf to reflect.
Outlook for 18z Monday through Friday...
Monday afternoon...VFR. West-southwest-west winds g15-20kt possible.
Monday night-Wednesday night...VFR. Afternoon seabreezes
probable each afternoon.
Thursday...most likely VFR. Isolated showers/thunderstorms
possible. Afternoon seabreezes probable.
Friday...most likely VFR. East winds g15-20kt possible. Isolated-
scattered showers/thunderstorms possible.
forecast winds and seas continue to remain on track.
A relatively quiet period with sub-Small Craft Advisory conditions will feature
late after/early evening enhancement of the SW flow from the New York bight
east along the ocean waters. These winds may gusts to around 20
knots with seas as high as 4 feet. High pressure will then build
across the waters on Tuesday with tranquil conditions through Thursday.
no significant rainfall is forecast through the upcoming week.
with a recent full moon...brief minor inundation is possible
during the times of high tide across the typically vulnerable
coastal locales into the start of the work week.