Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
754 PM EDT Friday Sep 19 2014
high pressure to our north moves east over the Atlantic on Saturday.
A cold front crosses the area Sunday night. High pressure returns
on Monday and remains in control through the end of the week.
Near term /until 6 am Saturday morning/...
high pressure over the Gulf of Maine resulting in southeast surface flow.
With the flow going southeast this evening...believe the stratus
expands to the northwest. This idea is supported in the simulated
10.3-3.9 um NSSL arw WRF imagery and in the narre time lag.
Uncertainty remains on the timing and extent of the stratus...but
believe this should focus in the western half of the County Warning Area with the
eastern portion mostly clear to partly cloudy.
With water temperatures near 70...do not believe fog is an issue...but
would not be surprised by some spotty drizzle over the lower
Temperatures will be affected by the stratus and its timing. Have stayed
close to MOS and previous forecast due to uncertainty with the clouds.
Think Long Island Pine barrens should have no problem radiating.
Short term /6 am Saturday morning through Saturday night/...
southerly flow through the period with positive low level moisture
advection. Morning clouds give way to sun by afternoon.
Uncertainty though in the maximum temperatures with NAM MOS a good 5 degrees
higher than GFS. With uncertainty in amount of sun...have stayed
close to previous forecast which is basically a compromise of the
NAM and GFS MOS.
Expect widespread stratus Saturday night and potentially some fog
along the coast. With ocean temperatures still near 70 though...did not
include the fog in the forecast. While some deterministic 12z runs
(nam, CMC gem) suggest measurable precipitation...measurable quantitative precipitation forecast in the
sref is only around 10 percent. Thus used slight probability of precipitation (light rain)
for the eastern half of the County Warning Area...but did go with drizzle (all
areas) as nwp profiles suggest moisture to 700 hpa as subsidence
There will be a moderate risk of rip currents at Atlantic Ocean
facing beaches Saturday.
Long term /Sunday through Friday/...
potential for unsettled weather Sunday through Sunday night
Model guidance is in fairly good agreement with forecasts of the
mass fields Sunday through Sunday night. They Show Low pressure
developing off the southeast coast then moving NE as it is picked up by the
approaching digging and amplifying upper level short wave. There are
differences in the amplification and timing of this short wave which
will impact the position and intensity of this offshore low. At this
time...it appears that Long Island and southern CT will be most
vulnerable with the highest chances for rain.
Additionally...scattered showers and thunderstorms are possible ahead of the
approaching cold front. If adequate instability develops...a few
storms could produce gusty winds west and north of NYC late in the
Monday through Friday will be dominated by a cool Canadian high
pressure with temperatures averaging at least 5 degrees below
normal. No rain is forecast during this time as drying continues.
Aviation /00z Saturday through Wednesday/...
high pressure moves eastward off the coast of New England tonight
and into the Atlantic Ocean through the rest of the taf period.
Southeast flow around 5-10 knots tonight become more southerly and
increases a few kts Saturday.
The winds will help bring in some lower MVFR stratus overnight
into Saturday. There is uncertainty with this and start/end times
will vary for individual sites with occasional fluctuation between
MVFR and VFR quite possible as well. The clouds are forecast to
scatter out Saturday afternoon.
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: start/end time of MVFR could vary 1-3 hours
Klga fcster comments: start/end time of MVFR could vary 1-3 hours
Kewr fcster comments: start/end time of MVFR could vary 1-3 hours
Kteb fcster comments: start/end time of MVFR could vary 1-3 hours
Khpn fcster comments: start/end time of MVFR could vary 1-3 hours
Kisp fcster comments: start/end time of MVFR could vary 1-3 hours
Outlook for 00z Sunday through Wednesday...
Saturday night-Sunday...VFR lowering to MVFR in
fog/clouds...possibly locally IFR after 04z with drizzle.
Conditions improve to VFR in the morning with areas of MVFR in
showers and isolated thunderstorms.
Sunday night...showers ending with conditions improving to VFR.
wind gusts have subsided to below 25 knots on the ocean...but seas are
still at 5 feet at 44017 and 44025. Thus the Small Craft Advisory remains in effect
until around 10 PM. Southeast winds tonight into Saturday as seas slowly subside
on the ocean.
Winds increase slightly late Saturday with gusts to around 20 knots.
Sunday night through Monday night...winds will increase causing seas
to build...approaching Small Craft Advisory levels of 25 knots and 5
feet across the Atlantic coastal waters. SW winds 15-20 knots Sunday
night will shift from the northwest by sunrise Monday and continue
through Monday evening. Seas will build to 3 to 5 feet.
Otherwise...winds and seas will be tranquil through Tuesday night.
Increasing east winds will develop by Wednesday as seas gradually build as
strong high pressure moves across northern New England.
less than 1/4 inch of rain is forecast Sunday through Sunday night
as a low moves offshore followed by a cold front Sunday night.
Otherwise...dry weather is forecast.
Marine...Small Craft Advisory until 10 PM EDT this evening for anz350-