Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
713 PM EDT Wednesday Apr 1 2015
high pressure builds over the area tonight and moves offshore on
Thursday. A cold front then approaches Thursday night and
Friday...then pass through late Friday night into Saturday
morning. Another cold front follows on Sunday.
Near term /until 6 am Thursday morning/...
good mixing with daytime heating and weak pressure gradient from
high building in from the west and offshore low have continued
breezy conditions this evening. Gusts to 20 miles per hour are possible until
around sunset when winds should diminish rapidly.
With deep layered ridging building overhead tonight...mostly
clear skies are forecast. Excellent radiational cooling conditions
are expected for much of the night. After 06z...warm advection in
the middle levels as well as some moisture spilling over the ridge
may produce some clouds to limit cooling. Temperatures may level off or
not fall as drastically as they could.
Blended in the latest guidance for lows tonight...which gives in
the middle/upper 30s for NYC and nearby suburbs...and in the 20s in
outlying areas...but these temperatures are highly dependent on the
degree of clouds after 06z.
Short term /6 am Thursday morning through Thursday night/...
the center of the high drops south of Long Island by midday
Thursday. Any clouds associated with that middle-level warming will
dissipate during the morning...giving way to to mostly sunny
Meanwhile...low pressure tracking across southern Canada will
drag a cold front into the Great Lakes. The pressure gradient will
tighten during the day...and with a 40-50 knots low level jet approaching from
the west...can expect strong SW winds to develop with 30-35 knots
gusts for NYC/coastal portions of NE New Jersey/western Long Island and
20-25 knots gusts elsewhere. Strong warm air advection and downsloping effects will
push maximum temperatures into the low to middle 60s for NYC and urbanized
portions of NE New Jersey...while most of the County Warning Area will top off in the middle
to upper 50s. Only exception will be Long Island and coastal
CT...where the flow coming off the cold waters will keep highs
only in the low 50s.
High pressure south of Long Island departs Thursday evening and cold
front continues to approach from the west. This will produce
showers across the area starting after midnight Thursday night.
Since lows Thursday night will be in the middle 40s...precipitation will be
Long term /Friday through Wednesday/...
showers likely on Friday with the cold front approaching...and
enough elevated instability for a mention of thunder. For
highs...blended in cooler NAM 2m temperatures with mav/NAM MOS...figuring
on rain/clouds/and wind flow off the waters for areas for some
Low level jet keeps periods of rain/showers for Friday night with
still a threat of a thunderstorm. Relatively higher dewpoint air
moving over the cold waters probably produces patchy/areas of fog
Friday and Friday night.
Cold front should be through most of the County Warning Area by 12z Saturday...so
outside of low chances of showers early on...dry weather with
clouds diminishing. Highs a little below normal with a gusty northwest
The flow aloft Sunday through Wednesday is forecast to be
generally zonal. This will weaken a cold front dropping down from
the north on Sunday. Models disagree where this front eventually
stalls before lifting back north. This has implications on precipitation
chances as well as temperatures. Best guess considering a zonal
flow is that should the front pass completely through the County Warning Area...it
will stall just offshore to our south. European model (ecmwf) is appearing to trend
this way...which is towards the GFS and ggem. Given the
uncertainty...have gone with a prolonged period of slight chance to
chance probability of precipitation Sunday afternoon through Wednesday. Much of the time should be
dry...but the threat of rain should remain. Might even be able to
eventually remove probability of precipitation for Monday. Precipitation type will be rain...except
late Sunday night into early Monday morning north of the city
where a mix of rain and snow will be possible.
Aviation /00z Thursday through Monday/...
high pressure builds tonight. The high tracks to the east as a
warm front moves through Thursday morning.
VFR through the taf period. Isolated -shra possible across northern
terminals early Thursday morning.
Gusty northwest winds will lighten tonight and become S/SW by
morning. S/SW winds increase on Thursday...peaking at 15 to 25 knots
with gusts 25 to 30 late Thursday after. Winds subside a bit after 00z.
... 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: sustained southerly winds of 25-30 knots
possible between 19z and 23z.
Klga fcster comments: southerly gusts around 35kt possible between
19z and 23z.
Kewr fcster comments: southerly gusts around 35kt possible between
19z and 23z.
Kteb fcster comments: southerly gusts around 35kt possible between
19z and 23z.
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: no unscheduled amendments expected.
Outlook for 00z Friday through Monday...
Thursday night...developing rain showers...with MVFR conds late.
Southerly winds of 15 to 20 knots with higher gusts.
Friday-Friday night...MVFR or lower in rain showers. Wind forecast
uncertain as front remains nearby.
Saturday...sub-VFR possible in showers early...then VFR. Gusty
northwest winds 20 to 30 kts.
Sunday night-Monday...mainly VFR...but cannot rule out sub VFR at
times in possible showers.
tranquil conds through Thursday morning as high pressure builds
overhead tonight and drops south of Long Island by Thursday
A cold front slowly approaches from the west...and Small Craft
Advisory conds develop on all waters by Thursday afternoon as the
pressure gradient tightens over the waters. A few gale force gusts are
possible over the western Atlantic waters as well Thursday
afternoon and evening.
Small Craft Advisory conds will continue on the ocean waters through at least
Saturday evening before a brief period of sub-Small Craft Advisory conds late at
night into Sunday morning. Gusts to near gale force are also
possible during Saturday afternoon/early evening. Otherwise...
winds will then pick up again Sunday afternoon...returning Small Craft Advisory
conds as a cold front slowly drops down from the north and
tightens the pressure gradient. This looks to be short-lived as
winds diminish Sunday night...and remain below advisory criteria
For the other waters...a cold front passage will bring gusts over
25kt on Saturday...possibly lingering into the evening.
Otherwise...sub-sca conds for the long term period.
relative humidities Thursday afternoon fall to 30-35 percent over
areas mainly west of the Hudson...and winds Thursday afternoon
there likely will gust to 20-25 miles per hour with peak gusts of 30-35 miles per hour
possible. At the minimum these conditions could promote rapid
growth/spread of any fires which occur Thursday afternoon.
around an inch of rain is expected late Thursday night through
Friday night. Minor urban flooding is possible...but just a low
Increased river/stream flow across the lower Hudson Valley and
southern Connecticut late week into this weekend will continue
local and upstream ice breakup and movement. Isolated ice jams
are possible...which if they occur...could result in localized
flooding. Since ice jam flooding is unpredictable and
sudden...interests along ice covered rivers should monitor National Weather Service
forecasts for the latest information.
For details on specific area rivers and lakes...including
observed and forecast river stages and lake elevations...please
visit the advanced hydrologic prediction service /ahps/ graphs on
our web site.
Marine...Small Craft Advisory from 2 PM Thursday to 6 am EDT Friday for