Scientific Forecaster Discussion
fxus61 kokx 251822
Area forecast discussion
National Weather Service New York New York
122 PM EST Sat Feb 25 2017
mild with showers and scattered thunderstorms with a cold
frontal passage this evening. Cool high pressure then builds
south of the area through Monday. A warming trend on Tuesday
gives way to another cold frontal passage during the middle of
Near term /through tonight/...
have adjusted back the dense fog advisory and will likely cancel
the remaining section shortly based on latest satellite imagery
and surface observations.
Will turn main focus now to convection. Cold front associated
with fine line on radar just passed Rochester and Johnstown PA.
Showers developing ahead of the front over NE PA and central New York.
While there's plenty of shear, there's limited thermodynamics
suggested in the latest hrrr sounding. Though in southeast PA, the 17z
Storm Prediction Center meso analyses shows 1000 j/kg of SBCAPE and Li's of -3 c.
Storms of interest are those over central Virginia as of 17z that are
tracking NE at 60 knots. These should continue to grow as they feed
on the instability. That would put them into the Newark area
Will add slight risk of severe west of the Hudson to the
hazardous weather outlook.
The rain ends quickly overnight and northwest winds usher in a more
Short term /Sunday through Sunday night/...
mixing temperatures down on Sunday from 850 millibars yields
upper 30s to around 40. Add a few degrees for the super
adiabatic lapse rate near the surface and this yields highs
right in the guidance ballpark, which was subsequently used for
Initially, clear skies should allow for decent radiational
cooling Sunday night. The challenge will be whether high clouds
overspread the area early enough to keep temperatures from
completely bottoming out, and how quickly the winds subside.
For now, the forecast leans milder due to these two potential
limiting factors, however the end result could play out 5
degrees or more colder.
Long term /Monday through Saturday/...
the system currently off the Pacific northwest brings some
dynamics through Monday and Tuesday. The airmass is modeled to
be very dry limiting chances for precipitation at least through
Monday. Thereafter, warm air advection aloft will increase
chances for some rain as a warm front develops and lifts north
of the tri-state region.
The GFS and European model (ecmwf) both bring a cold front through on Thursday,
so chances for rain remain until the frontal passage. The model
consensus breaks down on Friday. The GFS brings a clipper
through, with the European model (ecmwf) holding off until the weekend. No
changes have been made during this period, although the GFS
suggests colder and snowier.
Aviation /18z Saturday through Thursday/...
a cold front moves across this evening with high pressure
building in from the west thereafter. Mainly MVFR to VFR
conditions this afternoon and some isolated IFR with some
lingering low level stratus. Low level stratus will eventually
scatter out leaving MVFR/VFR stratus.
With the cold front for city terminals and terminals khpn and kswf,
expecting a brief period of showers and embedded thunderstorms
while to the east, just a brief period of showers is expected in
a general timeframe from west to east of 22z-03z. After this,
mainly VFR conditions are expected.
Winds will be southeast veering to S with wind speeds near 10 kt
gusting at times to 15-20 kt. After the cold frontal passage,
an abrupt shift in wind direction and speed is expected as winds
veer to west-west-northwest near 15 kt gusting 25-30 kt. Winds could
occasionally peak a few kts higher than forecast.
Outlook for 18z Sunday through Thursday...
Sunday...VFR. Northwest winds g20-25kt likely.
Sunday night-Monday evening...VFR. West-SW winds g15-20kt Monday.
Late Monday night-Thursday...chance of MVFR or lower at times
with any showers. West-northwest winds g20-30 knots Thursday.
a combination of swells and winds increasing from west to east will
bring seas to Small Craft Advisory levels over the two western zones this morning,
and then on the eastern most coastal ocean zone this afternoon.
Winds then increase on all waters tonight to small craft levels and
continue on Saturday in response to low level cold advection.
Looking at low level winds and they appear to generally stay below
35 kt, so do not have confidence in anything other than maybe some
isolated 35 kt gusts on the coastal ocean waters. As a result, have
converted the gale watch to a Small Craft Advisory on the coastal
ocean waters for tonight. I then extended the Small Craft Advisory
through the day on Sunday for all marine zones.
Small Craft Advisory conditions could linger into Sunday night on the coastal ocean
waters, eastern Long Island Sound and the bays of Long Island, and
maybe into Monday for the coastal ocean waters east of Moriches
The pressure gradient relaxes over the waters Monday night and
remains fairly light into Wednesday, so sub-small craft conditions
are expected from Monday night through at least Wednesday morning.
There are some indications that small craft conditions could return
to at least the coastal ocean waters by late Wednesday if the
pressure gradient tightens over the waters as currently
around a half inch of rain with locally higher amounts can be
expected through tonight. There will be chances for rain
throughout next week, however widespread heavy precipitation is
not expected at this time.
Marine...Small Craft Advisory from 6 PM this evening to 6 PM EST Sunday
Small Craft Advisory until 6 PM EST Sunday for anz350-353-355.