Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
713 am EDT Tuesday Oct 13 2015
weak low pressure tracks from southeast of Long Island into the
Gulf of Maine this morning. A cold front then crosses the tri-
state this afternoon and evening. A secondary cold front
approaches late tonight...then crosses the area Wednesday morning.
High pressure then builds in from the west through Thursday. A
frontal system approaches Thursday night from the west...and
crosses the tri-state on Friday. Another cold front moves through
on Saturday followed by Canadian high pressure building in Sunday
Near term /until 6 PM this evening/...
weak wave of low pressure and associated middle level energy have
tracked a little closer to the southeast coast of Long Island
than originally forecast. This is in association with the left
front quadrant of an 75+ knots 300 hpa jet streak. Convection has
remained over the water south and east of Long Island...with
showers mainly east of the William Floyd Parkway. A few isolated-scattered
light showers have also developed in vicinity of of the NYC metropolitan...but
most of this appears to not be reaching the ground. All shower
activity early this morning will continue tracking to the NE and
end 12-13z. Have updated probability of precipitation and weather grids to better reflect the
latest radar trends.
Patchy fog will dissipate shortly after sunrise.
Focus then turns to potential for scattered to numerous showers
ahead of 700 and 500 hpa shortwaves this afternoon. There is also
a very low chance for a rumble of thunder this afternoon as
well...but confidence is not high enough to place in the forecast
at this time.
Short term /6 PM this evening through 6 PM Wednesday/...
probability of precipitation linger into this evening...mainly across S CT and western
portions of the lower Hudson Valley...with passage of main 700-500
hpa shortwave...then should see some clearing after midnight. Lows
tonight are based on a blend of ecs/met/mav guidance and should be
around 5-10 degrees above normal.
700-500 hpa long wave trough axis builds into the region
Wednesday...however...drying low levels will serve to limit
precipitation to most likely at most spotty sprinkles.
However...do have slight chance probability of precipitation across far northern portions
of the northwest quadrant of the County Warning Area. Highs on Wednesday were based on a
blend of met/ecs/mav guidance...NAM 2-meter temperatures...and
mixing down from 875-825 hpa per BUFKIT soundings. Highs should be
a few degrees above normal.
Long term /Wednesday night through Monday/...
the synoptic pattern throughout much of the long term period will be
characterized by troughing over the eastern states and ridging over
the western states. Several shortwaves will rotate through the
trough over the east which will in turn send several cold fronts
across the region. Surface high pressure will build in from the
south Wednesday night into Thursday...with the core of the high
passing across the southern middle Atlantic and offshore Thursday
night. Dry conditions expected through Thursday night with
temperatures slightly below seasonal norms.
A potent middle level shortwave digging into Great Lakes Thursday night
will aid in deepening a longwave upper trough over eastern Canada
down into the Middle Atlantic States Friday that will continue into
the weekend. This shortwave will send a frontal system across the
tri-state on Friday. Minor model differences are noted between the
deterministic and ensemble guidance with the timing of the front
with the latest 00z European model (ecmwf) a bit slower than the GFS/gefs/CMC. This
front will bring a chance of showers Friday morning into Friday
afternoon before moving offshore Friday evening. Temperatures on
Friday will continue slightly below seasonal norms.
Much cooler air follows behind the frontal passage for Saturday.
Another cold front crosses the region late Saturday which will bring
an even colder air mass behind its passage. Weak shortwave energy
will move across as the upper level jet sinks south of the area on
Saturday. With some lingering moisture and weak lift with this
shortwave energy...the possibility exists for a brief shower
Saturday. 850 hpa temperatures are forecast to fall to between -6c
and -9c on both the GFS and European model (ecmwf) Saturday night into Sunday. This
may be a bit too low as models can have a slight cold bias at this
time range. However...it is not out of the question to see these
values verify with 500 hpa height anomalies near 2 South Dakota below normal
for this time of year. Canadian high pressure builds over the region
Sunday into Monday.
Temperatures Saturday through Monday are likely to average around 10
to possibly 15 degrees below seasonal normals. Forecast highs on
Saturday will be in the 50s...and on Sunday are in the upper 40s and
lower 50s. Slight moderation occurs on Monday as the core of the
coldest air moves east. The first freeze of the season is also
looking likely to occur Saturday night across the interior as lows
bottom out in the lower 30s. Lows elsewhere are forecast in the
middle and upper 30s. Similar values are forecast Sunday night.
Aviation /11z Tuesday through Saturday/...
low pressure passes southeast of the region this morning. A cold
front moves from west to east across the area terminals this
afternoon and evening.
Generally looking at VFR conditions...except across the far
eastern sections where some MVFR ceilings have developed. Thinking
conditions wont change too much today.
Any sub-VFR conditions improve back to VFR after 14z or so...however
there will still be a chance for MVFR during the rest of the day in
any showers that develop with the cold frontal passage this
The winds overall will be S-SW at near 10 knots for city terminals
and less elsewhere. The S-SW flow increases Tuesday to 10-15 knots
with some gusts to near 20 knots. Winds lower and become more
westerly Tuesday night.
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: amendments may be needed today for any
flight category changes.
Klga fcster comments: amendments may be needed today for any flight
Kewr fcster comments: amendments may be needed today for any flight
The afternoon kewr haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.
Kteb fcster comments: amendments may be needed today for any flight
Khpn fcster comments: amendments may be needed today for any flight
Kisp fcster comments: amendments may be needed today for any flight
Outlook for 12z Wednesday through Saturday...
Wednesday-Thursday night...mainly VFR. West/northwest winds with gusts to near 20 knots
during the day Wednesday.
Friday-Friday evening...low chance of MVFR with any showers.
Late Friday night-Sat...VFR. Northwest winds...gusts near 20 knots.
patchy fog is possible early this morning...especially near
shore...with visibilities possibly falling to around 1 nm or maybe
even less at times.
Winds should be 10 knots or less over all waters this morning. Winds
increase this afternoon over the coastal ocean waters...with gusts
up to 20 knots likely...there is a small chance for gusts up to 25 knots
by late afternoon. Noting wavewatch often is to fast to bring in
flow with a southerly component...have opted to delay onset of 5
feet seas on the coastal ocean waters until tonight. Given
uncertainty on wind gusts and sea height...did not have confidence
to issue a Small Craft Advisory for the coastal ocean waters with
Winds increase tonight...with gusts to 20 knots possible on the non-
ocean zones and to up to 25 knots possible on the coastal ocean
zones. Winds increase a tad more with cold advection on
Wednesday...with Small Craft Advisory gusts possible on all waters...with the best
chance on the coastal ocean waters. A persistent southeast swell likely
will bring seas on the coastal ocean waters tonight...with these
seas persisting on Wednesday.
Other than the possibility of lingering 5 feet seas on mainly the
eastern ocean waters Wednesday night...sub Small Craft Advisory conditions are
forecast Wednesday night through Thursday night. A cold front
approaches Friday with increasing SW flow. This will likely bring
wind gusts near 25 knots on most waters...except maybe the western
sound. Ocean seas may also build to between 5 and 7 feet. These seas
subside Friday night behind the frontal passage...but wind gusts to
25 knots remain possible on mainly the ocean waters on Saturday.
occasional light rainfall is probable from into this evening...with
less than 1/4 of an inch expected County Warning Area wide...and all but far
eastern portions receiving less than 1/10th of an inch.
No significant precipitation is then expected into early next