Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
748 PM EDT sun Sep 21 2014
a cold front approaches from the west this evening...and crosses
the tri-state tonight...meanwhile a coastal low tracks to the
east...then northeast of Long Island tonight. High pressure then
builds in from the west through Tuesday. The high then dominates
the weather through next Sunday.
Near term /until 6 am Monday morning/...
deepening low pressure was southeast of Long Island and moving
quickly to the northeast. Much of the precipitation with the low
was exiting the South Fork of Long Island and the ocean waters
south of the east end. Meanwhile the line of showers ahead of a
cold front continues to track east. The scattered showers ahead of
the main line have dissipated. So have adjusted probability of precipitation for current
700-500 hpa trough approaches this evening then begins to cross
the tri-state overnight. Expect the other line to weaken as it
tracks east with the loss of heating and best dynamics staying to
For lows tonight sued a blend of mav/met guidance with values
forecast to be 4 to 8 degrees above normal outside of the NYC heat
island...and near normal inside the heat island and areas to the
north/west of NYC due to the timing of the cold front.
Also have the potential for patchy fog this evening over southeast CT/the
Twin Forks ahead of the cold front. While locally dense fog cannot
be ruled out - am currently not confident enough in its potential
to issue any statements.
Short term /6 am Monday morning through Monday night/...
region remains under the base of 700-500 hpa trough Monday and
Monday night. Will have a few shortwaves round the base of the
trough - but given forecast drying in the low levels would only
expect at most some clouds as they pass. So going with a mostly
sunny to partly cloudy sky Monday and a mostly clear to clear sky
Monday night as a result.
For highs Monday used a blend of mixing down from 875 hpa...except
850 hpa over the northwest 1/4 of the County Warning Area per BUFKIT soundings...with NAM
2-meter temperatures and a blend of mav/met guidance. Expect
readings to be near to slightly below normal.
A blend of mav/met guidance was used for lows Monday night - with
readings forecast to be 5-10 degrees below normal. Lows in the upper
30s are possible in portions of Orange County.
There is a moderate risk of rip currents at Atlantic beaches
Long term /Tuesday through Sunday/...
a strong upper ridge will be building into the East Coast Tuesday
and Tuesday night...then remain nearly stationary through Sunday.
At the surface high pressure builds east from the Ohio Valley while
another surface high builds in from central Canada. The combined
high pressure center will build east from the Great Lakes and
through northern New England Tuesday into Wednesday. The high then
builds over the region Thursday and remains nearly stationary into
Sunday. Initially the air mass will be cool Tuesday into
Thursday...with slightly below seasonal normal temperatures. A
warming trend sets up for Thursday night through Sunday as the air
mass modifies. Next weekend temperatures will have rebounded to
above seasonal normals.
Aviation /00z Monday through Friday/...
a cold front across upstate New York will pass through the region overnight.
Light and vrb winds becoming SW as the front gets closer this evening.
Winds switch to the northwest behind the front. Strong northwest flow Monday with
isolated gusts to 30kt.
Mainly VFR ahead of the front...however occasional MVFR ceilings possible in
the city and IFR eastern terminals. A few -shra possible in vicinity of the
front...then VFR through the remainder of the taf period.
Outlook for 00z Tuesday through Thursday...
Monday night...VFR. Northwest winds diminishing.
Tuesday...VFR with light winds.
Wednesday...MVFR ceilings around 3000ft possible. East-northeast winds 5-15kt.
Thursday...VFR with light NE flow.
seas build to up to 5 feet on the western coastal ocean waters and
up to 8 feet on the eastern coastal ocean waters by late tonight.
With wind gusts up to 25 knots on the coastal ocean waters on Monday
- have converted Small Craft Advisory for hazardous seas to a plain Small Craft
Advisory. Small Craft Advisory wind gusts should linger over the eastern two
coastal water zones into Monday evening and Small Craft Advisory level seas through
the night in those two zones...so have extended the Small Craft Advisory for
anz-350 and 353 through 10z Tuesday as a result.
On the remainder of the coastal ocean waters sub-Small Craft Advisory conditions are
currently expected through Monday night. Wind gusts to 20 knots are
forecast on Monday - however occasional gusts to 25kt cannot be
There is a chance of lingering 5 foot seas across the extreme outer
ocean waters east of Moriches Inlet very early Tuesday morning as
seas will be subsiding as high pressure builds in.
With high pressure across the waters Tuesday into Saturday wind and
seas are expected to remain below Small Craft Advisory levels.
little if any additional rainfall is expected through tonight with
the passing of a coastal low to the east and the passage of a
Dry conditions expected from Monday through next Sunday.
Marine...Small Craft Advisory until 6 PM EDT Monday for anz355.
Small Craft Advisory until 6 am EDT Tuesday for anz350-353.