Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
311 am EDT Thursday Oct 2 2014
an upper level low will slowly move east today...with high pressure
building in the wake briefly through Friday. A cold front will pass
on Saturday followed by high pressure for Sunday and Monday. A
weak area of low pressure affects the region on Tuesday with a
weak cold frontal passage late at night. High pressure returns on
Near term /until 6 PM this evening/...
upper level low slowly pivoting through the northeast is currently
producing light precipitation over portions of CT and eastern Li. Associated
vorticity maximum almost stationary over southern New England...with the 00z
models suggesting it pushing to the south this morning...then
pushing offshore to the east as the low slips to the east throughout
the day. Concerning the extent of the precipitation for today...maintaining
likely probability of precipitation initially this morning over CT then tapering back as the
main forcing moves out and drier air moves in aloft. NE flow will
keep a fairly moist lower level in place but generally thinking the
loss of forcing aloft will minimize the precipitation chances. Thus taper
probability of precipitation from northwest to southeast this morning...and only lingering
probability of precipitation in this afternoon over eastern Li.
Some uncertainty with high temperatures for tonight as weak warm air advection would
suggest temperatures could push near normal. However...cloudy skies and
persistent NE flow could keep temperatures on the slightly cooler side.
Sided more with the mav guidance to reflect this possibility.
Short term /6 PM this evening through 6 PM Friday/...
any lingering precipitation by this evening should be offshore south of
Long Island with dry weather then on tap through Friday. A sliver of
high pressure briefly builds south from Canada tonight/Friday
before retreating once again ahead of an approaching low pressure
system for the weekend. Upper level ridging builds in as well
during this time...with the ridge axis shifting through the
northeast during the day Friday. Plenty of subsidence aloft...so
should see clearing skies for a short period late tonight/Friday
morning before high level clouds begin streaming in ahead of the
low. With drier air moving in with the high as well...not
anticipating much in the form of fog development tonight.
Have more of a handle on temperatures for tonight/tomorrow...using
generally a blend of the met/mav guidance. Temperatures tonight expected
to be right around normal to slightly above. With mostly sunny
skies on Friday and warm air advection...should see highs a few degrees warmer
Long term /Friday night through Wednesday/...
all nwp guidance remains very consistent with a cold frontal passage on
Saturday. Precipitation moves in from west to east in the morning and exits in
the afternoon with clearing quickly developing by Saturday evening.
Have cut previous forecast quantitative precipitation forecast in coordination with river forecast
centers. Expecting around 1/2 inch with 3/4 inch up in the lower
Hudson Valley. No Hydro issues expected.
High pressure for Sunday and Monday. Clouds start increasing late
Monday with warm air advection. Over-running pattern continues on Tuesday with chance
probability of precipitation for light rain. Weak and diffuse cold frontal passage passage early Wednesday
morning with high pressure building in. Have made it dry on
Wednesday with timing of cold frontal passage.
Lowered temperatures and made for non-diurnal pattern on Saturday with the
precipitation. Below normal temperatures on Sunday...but we quickly return to normal
on Monday and then a bit above normal for Tuesday and Wednesday.
No hazards foreseen through Wednesday.
Aviation /07z Thursday through Monday/...
low pressure well east of Cape Cod will remain nearly
stationary...while an upper level low over the area moves to the
east...allowing high pressure to build down from New England.
A moist low level north-NE flow will maintain widespread MVFR conds at
most terminals until 20z-21z...and until 23z kisp. Occasional light
rain/drizzle likely at the CT/Long Island terminals...and kgon
could experience occasional IFR ceilings this morning until about 14z.
North-NE flow should increase closer to 15 knots at most terminals after
daybreak as the high starts to build down...with frequent gusts
just over 20 knots at kisp/kgon. Occasional gusts up to 20 knots may occur
elsewhere...and are not mentioned in taf.
As VFR conds return late this afternoon or early Thursday evening...NE
flow will gradually diminish to under 10 knots.
Outlook for 06z Friday through Monday...
Late Thursday night-Fri...VFR.
Friday night...MVFR conds possible late at the NYC metropolitan and lower
Hudson Valley terminals.
Sat...rain with IFR conds and southeast winds 15-20g25kt. Cold frontal passage
middle to late afternoon at the NYC metropolitan and lower Hudson Valley
terminals...followed by VFR conds and west wind g20kt.
Sat night...rain with IFR conds early at the CT/Long Island
terminals...then cold frontal passage with improvement to VFR. Post-frontal
west winds g25kt.
Sunday...VFR. West winds g20kt.
Small Craft Advisory remains in effect for all the waters minus New York Harbor as NE
flow increases between the low offshore and the high digging down
from the north. Gusts between 25 to 30 kts expected during the day
today...then diminishing tonight as the pressure gradient weakens
with high building further over the waters. Seas build today with
the strengthening flow...with 5-9 feet possible on the ocean waters.
Occasional gusts up to 25 kts will be possible this evening/early
overnight for the bays and Long Island Sound. Though confidence is
not enough to extend the Small Craft Advisory at this time over those waters. Still
expecting gusts to 25 kts and seas above 5 feet on the ocean...and
in fact expecting the 5 feet seas to continue so extended the Small Craft Advisory
over the ocean for Friday.
On the ocean...Small Craft Advisory conds can be expected through next Wednesday...with
perhaps a brief respite for portions of Monday. Elsewhere...25kt
winds possible Sat-sun both ahead of and behind a cold front. Otherwise
they will generally be in the 10-20kt range.
no significant precipitation is expected through the coming week
resulting in hydrologic issues. Expecting around 1/2 inch with 3/4
up in the lower Hudson Valley during the day on Saturday. Light
rain is possible for Tuesday.
Marine...Small Craft Advisory from 6 am this morning to 6 PM EDT this
evening for anz330-335-340-345.
Small Craft Advisory until 6 PM EDT Friday for anz350-353-355.