Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service New York New York
637 PM EDT Thursday Oct 30 2014

Synopsis...
high pressure will build in tonight. Low pressure develops off
the middle Atlantic coast Friday and tracks northeast. A secondary
low forming off the middle Atlantic coast on Saturday will intensify
and head northeast to the Canadian Maritimes by Sunday evening.
High pressure will builds in behind this storm from Monday into
Tuesday. A warm front will pass to the north on Tuesday...
followed by a series of fast moving cold fronts Wednesday into
Thursday.

&&

Near term /until 6 am Friday morning/...
with the loss of daytime heating most of the inland strato cumulus was
dissipating. Drier air was flowing in on a northwest wind.
Adjusted temperatures and dew points for current trends.

In the upper levels...vigorous shortwave and positive vorticity advection dives across the
upper Midwest/western Great Lakes region southward. Another
shortwave tracks across the Gulf states...moving east tonight.

At the surface...weak high pressure builds in and moves quickly
northeast ahead of this trough. Diurnal scattered to broken cumulus
clouds should give way to clearing overnight...although do expect
few to scattered lower clouds through the night.

Low temperatures tonight should be near or slightly below normal per MOS
blend.

&&

Short term /6 am Friday morning through Friday night/...
shortwave and weak positive vorticity advection tracks off the middle Atlantic coast...with surface
low pressure developing off the Carolinas. More potent shortwave
carves out low pressure Friday night as it rounds the base of the
main trough over the southeast states.

Weak inverted trough extends northwest from the western Atlantic low later
Friday and Friday night. With some support aloft...and a moistening
column due to increasing east/northeast flow below 800 mb hpa...expect
light rain to develop Friday afternoon. Rain chances increase
Friday night...with the better chance across the eastern zones.

Temperatures are expected to average slightly below normal due to
increasing clouds and NE flow. Near normal readings anticipated
Friday night. Followed a MOS blend.

&&

Long term /Saturday through Thursday/...
guidance remains mostly consistent on the evolution of a storm
developing off the coast this weekend. First...low pressure moving
along an offshore front will bring mostly light rain to the
area...especially over eastern Long Island/southeast CT with Cat pop...with
likely pop as far back as NYC metropolitan. There are differences in
timing and rainfall amts during the day Sat between the latest
runs of the model guidance...with the latest GFS sooner and a
little farther east...and the European model (ecmwf) wetter and later out
east...have smoothed out these differences for now with a general
all day event.

Focus of rain should gradually shift to the east Sat night...with
decreasing pop as this first low lifts to the NE. Precipitation could
briefly end as some snow or a rain/snow mix in the highest
elevations well north/west. As a stronger low forms near Cape
Hatteras and then tracks outside the 40n/70w benchmark by daybreak
Sunday...its rainfall should remain offshore as it fails to phase
with the upper trough to its west. Its more important impacts will
be and cooler conds on Sunday...with a brisk north flow as as the low
intensifies and the pressure gradient tightens around between it
and building high pressure to the west. There should also be
plenty of instability stratocu as an upper trough moves across.
Highs will only barely reach 50 in NYC metropolitan and Long Island...and
remain in the 40s inland.

Winds will diminish somewhat Sunday night under mostly clear
skies...but remain strong enough to prevent the boundary layer from
completely decoupling in most places. Asa result stuck close to
guidance lows for Sunday night and did not undercut...with lows
25-30 well inland...lower 30s most elsewhere...and middle 30s for NYC.

After one more cool day on Monday with highs again in the upper 40s and
lower 50s...temperatures should moderate back to near normal for the middle
week period as a warm front passes to the north and high pressure
passes to the east. Should then see a series of weak...fast moving
cold fronts passing through in fast quasi-zonal flow...with chance
pop for rain showers north/west of NYC on Wednesday...and throughout the
area Wednesday night into Thursday.

&&

Aviation /20z Friday through Tuesday/...
hi pressure slides north and east of the terminals through
tonight...with low pressure begins to develop S of the region Friday.

Mainly VFR through taf period. Broken 4-5 kft strato cumulus this
afternoon...becoming scattered tonight. Increasing likelihood for broken
strato-cumulus 3.5-4 kft to develop Friday morning. Ceilings gradually lower to
MVFR late Friday/Friday evening across metropolitan terminals with -ra developing.

Winds will continue to generally run between 310 and 350 degrees
magnetic into this evening. Diurnal instability will occasionally
increase this range of wind direction variability by 20 degrees on
either side with occasional gusts to 20 knots through around 22z for
metropolitan terminals. Winds continue to veer to the north overnight and NE on
Friday.

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: winds generally right of 310 magnetic through
this evening...but will occasionally vary between 290 and 360
magnetic with gusts to 20kt through around 22z.

Klga fcster comments: winds generally right of 310 magnetic through
this evening...but will occasionally vary between 290 and 360
magnetic with gusts to 20kt through around 22z.

Kewr fcster comments: winds generally right of 310 magnetic through
this evening...but will occasionally vary between 290 and 360
magnetic with gusts to 20kt through around 22z.

Kteb fcster comments: winds generally right of 310 magnetic
through this evening.

Khpn fcster comments: no unscheduled amendments expected.

Kisp fcster comments: no unscheduled amendments expected.

Outlook for 18z Friday through Tuesday...
Friday after...ceilings lower through the after with MVFR possible late.
Friday night-Sat night...MVFR or lower. Precipitation mainly rain...but snow may
mix in across the interior Sun night. NE-north winds 15-20g25-35kt.
Sunday...mainly VFR. After strato-cumulus with isolated
flurries/sprinkles. Northwest winds 20-25g30-35kt.
Monday...VFR. West winds 5-10 knots.
Tuesday...VFR.

&&

Marine...
northwest wind 10 to 15 knots has allowed for seas on the ocean to
subside to 2 to 3 feet...so have adjusted wave heights downward up to
a foot through much of tonight as wind will gradually turn to the
north and diminish a few knots.

As high pressure builds then moves northeastward...northwest winds will
turn toward the north tonight. The winds then turn to the NE and
increase later in the day as low pressure approaches from the
south. These east/NE winds increase Friday night...likely to Small Craft Advisory
thresholds.

Relatively tranquil seas build late Friday and Friday night as the
winds increase. Small Craft Advisory conds are likely by Sat...but it is still
uncertain whether gales will develop that early due to timing
uncertainty of an initial low passing to the southeast. Gales appear more
likely late Sat night into Sunday as stronger low pressure
develops and passes to the southeast...with cold air advection over still relatively
mild waters and a tightening pressure gradient.

After some lingering gales on the eastern ocean waters Sunday
evening...Small Craft Advisory conds should otherwise follow for Sunday night into
Monday for most waters. Then quiet conds should return to all waters
by Monday night. Increasing SW flow ahead of a cold front could bring
a return of Small Craft Advisory conds to the eastern ocean waters late Tuesday night-Wed.

&&

Hydrology...
rainfall from Friday night through Sat night should remain under a
half inch...with the higher amounts generally across eastern Long
Island and southeast CT. No significant hydrologic impact expected.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory from 6 PM Friday to 6 am EDT Saturday for
anz330-335-338-340-345-350-353-355.

&&

$$
Synopsis...Goodman/pw
near term...met/pw
short term...precipitable water
long term...Goodman
aviation...Nevada
marine...Goodman/met/pw
hydrology...Goodman/pw

National Weather Service Glossary of Abbreviations