Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1041 PM EDT Wednesday Oct 1 2014
a slow moving upper low will pass to the east through Thursday...
while high pressure briefly follows for Thursday night into
Friday. A cold front will pass on Saturday. A series of frontal
systems may then impact the region during the beginning of next
Near term /until 6 am Thursday morning/...
forecast remains on track.
Upper low moving across the area combined with drying middle levels
will result in a chance of light rain/drizzle through the
overnight...mainly to the east of NYC metropolitan/lower Hudson Valley/NE
New Jersey. There is a chance for a more significant rainfall event after
midnight tonight across southeast CT and the eastern half of Li. Strong
frontogenetic banding with offshore low pressure and a
strengthening easterly low level jet will send the rain band west-southwest
tonight. This activity was beginning to track westward and some
of this activity may get as far west as the lower Hudson Valley/NE
New Jersey...but the forcing looks to weaken with lighter rainfall
amounts. The 18z GFS and 02/00z NAM are not as aggressive across
eastern Li and southeast CT...with a quarter to a third of an inch
possible. The sref and gefs support the operations runs...but are
not as far west with the rain shield.
The cloud cover...northerly flow...and rain/drizzle will keep lows
several degrees above normal with readings in the lower to middle 50s.
Short term /6 am Thursday morning through Thursday night/...
a dissipating rain band is forecast to push south of Li during the
morning with perhaps some drizzle lingering into the early evening.
A north/NE flow will maintain low-level moisture with weak warm advection.
Expect overcast conditions for most of the day with some partial
clearing late at night. Gusty NE winds of 20 to 35 miles per hour are expected
near the coast as low pressure over the western Atlantic retrogrades
briefly westward Thursday morning in response to the aforementioned
High pressure builds in both aloft and at the surface Thursday night with
some drier air filtering in from the NE.
Highs will top out in the middle to upper 60s Thursday with overnight lows
Thursday night dropping into the middle 40s inland to the middle 50s at the
coast. This is close to seasonable levels.
Long term /Friday through Wednesday/...
a hipres ridge over the eastern Seaboard will keep the weather dry on Friday.
Weighted temperatures towards the cooler nam12 and met guidance to the the
influence of the maritime airmass. Upper low currently over northern ab
will draw a cold front through Sat. Models remain consistent. Rain ahead of
the front with around an inch likely...with strong moisture
transport building precipitable water/S to around 1.5 inches. Precipitable water/S drop to blw a
half inch sun and 850 mb temperatures fall 10c. Dry...breezy and cooler is
therefore the forecast. Convective temperature in the upper 50s...so scattered fair weather
cumulus possible despite the subsidence. SW flow aloft develops Monday and
Tuesday with a 520s dam 500 mb low setting up over western on. The models have
been hinting at low rain chance with this...so retained a 20-30 pop.
Best chance will be with the associated cold front...which looks to be
around Tue-Wed. Temperatures sun-Wednesday a blend of the gmos/mex/men and 00z
European model (ecmwf) ensemble guidance.
Aviation /03z Thursday through Monday/...
an upper level low overhead tonight will gradually sink southeast of the
A moist low level north/NE flow overnight will maintain IFR/MVFR
conditions through Thursday morning. Gradual improvement to VFR
likely from northwest to southeast Thursday after/evening as low pressure departs.
Bands of -ra dz will continue over Long Island and southern CT
into Thursday morning...occasionally affecting western terminals
between midnight and 12z. Conds will likely drop to MVFR/IFR in any
of this activity.
High confidence in the persistent north-northeast surface flow
through the period...but will likely vary across the 040 mag
direction through Thursday morning for metropolitan terminals. Winds increase on
Thursday with gusts into the upper teens and lower 20s for coastal
Outlook for 00z Friday through Monday...
Thursday night...improvement to VFR. NE winds 10-15 knots...occasional
gusts to 20kt in the evening.
Friday...VFR. Light southeast wind.
Sat...rain - MVFR or lower at times. Southeast wind 15-20 knots.
small craft conditions on the ocean waters remain with seas up to
5 to 7 feet at 02z. The Small Craft Advisory continues on all waters...with the
ocean waters in effect through Thursday night. The sound and
surrounding Li bays will be in effect for Thursday. A prolonged period
of north/NE flow with high pressure building across New England and
low pressure over the western Atlantic will build seas of 7 to 10
feet on the ocean and gusts up to 30 knots. Highest winds and seas will
be Thursday morning into the aft, conditions begin to gradually improve
Thursday night as high pressure builds in from the from the north. Even
then seas on the ocean will remain above 5 feet with a lingering
On the ocean...Small Craft Advisory conditions can be expected Friday 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.
rainfall totals tonight into Thursday across eastern Li and southeast CT will
range from a quarter of an inch to one inch. The highest amounts
look to be across New London County CT late tonight. Areas to the
west will generally be a tenth of an inch or less.
Around an inch of rain possible on Sat. A few tenths possible
during the beginning of next week.
Marine...Small Craft Advisory from 6 am to 6 PM EDT Thursday for anz330-
Small Craft Advisory until 6 am EDT Friday for anz350-353-355.