Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service New York New York
628 am EDT sun Oct 4 2015

high pressure builds down from southeastern Canada through
Monday...then retreats to the northeast Monday night. Another high
builds in from south central Canada through the middle of the
week...then slides offshore Thursday night. A storm system
approaches from the west on Friday...then slowly lifts to the
northeast into Saturday.


Near term /until 6 PM this evening/...
made minor changes this update to reflect the latest trends in
observations and guidance. The forecast appears on track.

A weak tracked using 300 hpa potential vorticity
approaches from the south today. This will act with abundant low
level moisture trapped under an inversion with a base around 875
hpa. The result will be a slight chance to chance of light rain or
drizzle for mainly the southeast 1/4 of the County Warning Area. It should be mainly dry
elsewhere...however...cannot completely rule out some patchy
drizzle...especially in higher elevations experiencing upslope
flow. The other influence of this shortwave will be to reduce the
chances of any breaks in the clouds today...the best chance for
any peaks of sunshine will be over the northwest 1/2 of the County Warning Area.

Winds continue to be gusty out of the NE...with gusts of 20-35
miles per hour...except gusts up to around 40 miles per hour along the South Shore of
Long Island/NYC.

For highs today used a blend of ecs/mav/met guidance with NAM
2-meter temperatures and a mix down from 900 hpa per BUFKIT
soundings. Highs should be 5-10 degrees below normal.


Short term /6 PM this evening through Tuesday night/...
the aforementioned shortwave pushes into the area
tonight...bringing a chance to slight chance of light rain or
drizzle across mainly the southeast 1/2 of the County Warning Area. Once again cannot
completely rule out spotty drizzle over the northwest 1/2 of the
County Warning Area...especially in areas experiencing upslope flow. Winds
start to diminish tonight...with gusts of 20-30 miles per hour...mainly over
coastal regions. For lows tonight...used a blend of mav/met/ecs
guidance and NAM 2-meter temperatures...with values near to
slightly below normal.

A weak 700-500 hpa trough crosses the area Monday...with its main
impact being to mainly slow the rate of clearing over the southeast 1/2
of the County Warning Area. Low levels will begin to dry out as 850 hpa ridging
builds in...and low level downslope flow begins to set up in the
afternoon. Winds continue to diminish on Monday. For highs
Monday...used a blend of NAM 2-meter temperatures...a mix down
from 925-900 hpa per BUFKIT soundings...and a mixture of
mav/ecs/met guidance. Highs should be around 5 degrees below

Weak northern stream ridging begins to build in at 500 hpa Monday
night...along with negative vorticity advection at 700 hpa. So
expect some clearing Monday night. The wind also continues to depending on exactly how much clearing
occurs...could end up with some radiational cooling...especially
over areas north/west of NYC. As a result...have shaded lows towards the
cooler of mav/met/ecs guidance...and under cut slightly for
normally colder areas north/west of NYC. Lows Monday night should be near

West-northwest-northwest flow aloft Tuesday-Tuesday night should keep things dry
with partly cloudy-mostly clear sky conditions. For highs
Tuesday...a blend of ecs/mav/met guidance...NAM 2-meter
temperatures and a mix down from 925 hpa per BUFKIT soundings was
used. Highs should be within a couple degrees of either side of
normal. A blend of mex/men/ekd/ece/ecm/wpc guidance was used for
lows Tuesday night...and adjusted downward slightly over usually
cooler locations...readings should be slightly above normal.


Long term /Wednesday through Saturday/...
a northern stream shortwave passes to the north Wednesday. Not
much lift is expected...with the best dynamics up near the
Canadian border. Moisture will also be very limited with
precipitable waters falling to between 0.5 and 0.75 inches.
Temperatures Wednesday will be able to rise into the upper 60s and
lower 70s.Weak northern stream ridging builds in from Wednesday
night into Thursday. Highs will return to near seasonable levels
for Thursday.

The forecast for the end of the week into the start of next weekend
becomes much more uncertain. A shortwave trough is forecast by the
models to dig into the Great Lakes on Thursday and approach on
Friday. There is decent agreement among the deterministic models and
ensembles with the occurrence of this system...but differences
exist with its associated surface low and amplitude of the
shortwave trough. The surface low would end up moving across
Friday into Saturday. With this about a week away...have only
included low chance probability of precipitation for showers for now.


Aviation /12z Sunday through Thursday/...
high pressure stays anchored north of the area through the taf
period while gradually becoming weaker. There will be a slight
chance of light rain or drizzle without much visibility
restriction along the coastal terminals. There will also be MVFR
ceilings much of the time. VFR will be more dominant for CT terminals
and kswf.

Overall...conditions could fluctuate between MVFR and VFR at
times. NE winds near 15-20 knots with gusts up to 25-30 knots will
gradually lower towards Sunday afternoon and evening.

Outlook for 06z Monday through Thursday...
late Sun night and Monday...VFR with diminishing NE winds.


made minor changes this update to reflect the latest trends in
observations and guidance. The forecast appears on track.

Have continued the Gale Warning on all waters through 5pm...and
extended on the coastal ocean waters through Sunday night. Seas of
up to 14 feet are expected on the coastal ocean waters and up to 7
feet on eastern Long Island Sound.

Small Craft Advisory conditions are likely on the non-ocean zones tonight and
possibly into/through Monday. Then sub-Small Craft Advisory conditions are expected
there Monday night-Thursday.

Gale gusts could linger on the coastal ocean waters into
Monday...with gusts to 25 knots possible there through Monday night.
Seas will probably remain at or above Small Craft Advisory levels on the coastal
ocean waters into Tuesday night or Wednesday. For appears
the coastal ocean waters should experience sub-small craft
conditions on Thursday.


other than some spotty light rain or drizzle through
should be mainly dry through at least Thursday.


Tides/coastal flooding...
the gusty NE flow continues between the high north of the region and
low well south of the region. This will continue the piling of
water. However...astronomical tides are lowering with time. The high
tide cycles for the overnight period thus far have been a little
lower than forecast.

Therefore...more confident stages will stay in minor coastal flood
for next high tide later today considering the anomalies this past
high tide cycle.

The surge forecast is approximately 1-2 feet. Adding that on top of
predicted astronomical levels gives most locations minor coastal
flooding. Thus...coastal Flood Advisory continues with just slight
adjustments of 0.1 to 0.3 feet to forecast stages.

In addition...splash over of northeast facing shorelines is

For tonight and Monday...the astronomical levels continue to lower.
The pressure gradient decreases as the high weakens to the north. As
wind decrease...water levels should remain below minor coastal
flooding thresholds during high tide cycles.

A high surf advisory for the South Shore of Long Island remains
in effect through Monday. Expect beach erosion and washover to
occur due to rough seas and battering waves...with surf as high as
10 feet in spots.


Okx watches/warnings/advisories...
CT...coastal Flood Advisory from 4 PM this afternoon to 7 PM EDT
this evening for ctz009.
New York...coastal Flood Advisory from 1 PM to 4 PM EDT this afternoon
for nyz072-074-075-178-179.
Coastal Flood Advisory from 4 PM this afternoon to 7 PM EDT
this evening for nyz071-073-078-176-177.
High surf advisory until 6 PM EDT Monday for nyz080-081-178-
Coastal Flood Advisory from 3 PM this afternoon to 6 PM EDT
this evening for nyz080.
New Jersey...coastal Flood Advisory from 1 PM to 4 PM EDT this afternoon
for njz006.
Marine...Gale Warning until 5 PM EDT this afternoon for anz330-335-338-
Gale Warning until 6 am EDT Monday for anz350-353-355.



near term...maloit
short term...maloit
long term...maloit/ds

National Weather Service Glossary of Abbreviations