Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
938 PM EST sun Nov 23 2014
a period of stormy weather will kick off late tonight as low pressure
rapidly deepens over the Great Lakes and draws a warm front through
the tri-state region. A cold front will follow on Monday night. A weak
cold front passes through on Tuesday...with high pressure briefly
building into the the region Tuesday night. Coastal low pressure
impacts the region Wednesday into Wednesday night...departing into
the Canadian Maritimes on Thursday. High pressure then builds in
from the west into Friday...with a Alberta clipper system possible
to impact the area Saturday.
Near term /through Monday/...
will adjust hourly temperatures based on latest surface observation. Temperatures dropped
off a bit...but with clouds approaching...can expect temperatures to hold
steady and slowly rise after midnight.
Rain moves in after midnight tonight and through Monday morning...with
mainly a few showers thereafter for most of Monday. Precipitation amts around an
inch. An embedded thunderstorm is possible across southern portions of the
tri- state late tonight into early Monday morning as a tongue of
elevated instability accompanies low level jet in the morning.
The heaviest rain does look to fall near the morning rush so impacts
should be expected.
By 12z Monday...the County Warning Area will be sandwiched between a 970s low over
the upper Great Lakes...and a 1030s high over the Atlantic. This
will translate into strong southerly flow. The GFS has h975 winds over
50kt for most of Li...which is concerning. Have mixed down 80
percent of this for the forecast and issued a Wind Advisory for all of
Li...including Brooklyn and Queens. There is the potential that
the advisory may need to be expanded northward into coastal CT if deeper mixing
The core of the strongest winds aloft shift eastward through the day...so
only kept the western portion of the advisory through the morning. Some
uncertainty on whether Wind Advisory gusts will continue in
Suffolk County into the afternoon...but will let midshift re-
Otherwise...gusts to 40 miles per hour possible across NE New Jersey and lower Hudson
Valley and higher elevations in the afternoon with any breaks of
sun and deeper mixed layer.
Record high temperatures still possible.
Short term /Monday night/...
the associated cold front comes through overnight. This Ushers the more
humid airmass offshore. The pressure gradient still stays up so it will
remain windy through the night. Speeds however will remain blw advisory
criteria with the low approaching Labrador. A few showers are
possible with the frontal passage. The NAM has been very consistent with
this suggestion. As a result...maintained low chances for showers for
With the cold air lagging behind and winds keeping the llvls
mixed...low temperatures expected to be a solid 10 degrees or more above
Long term /Tuesday through Sunday/...
tranquil and near seasonable temperatures on Tuesday as a weak cold front
passes through the region and high pressure briefly builds in its
wake Tuesday night.
Potential continues to increase for a coastal storm with snow...rain
and wind to impact the region Wednesday/Wednesday night...but spread remains
moderate in terms of exact track of this system.
Forecast sensitivity based on sbu cstar analysis for this system
lies in development of trough over the epac over the next 48
hours...and resultant downstream strength of West Coast ridging and
ultimately strength of East Coast troughing for midweek.
Operational/ensemble model analysis reveal middle/upper level model
fields in good agreement over the next 48 hours initially with
phasing northern stream and Pacific energy diving down the backside of
deep central US troughing...with this energy then swinging up the
coast Wednesday and interacting with yet another piece of northern
stream shortwave energy diving through the middle-Mississippi River
valley. It is with this second interaction...after 48 hours...that
models diverge enough to affect strength and orientation of the
phased shortwave energies as they pivot through the NE Wednesday
night/early Thursday. This is resulting in minor timing differences
with the coastal low...but mainly track differences. The range of
operational solutions on track of coastal low are...the 12z European model (ecmwf)
continuing to trend west and tracking across Li Wednesday night...to the
12z NAM/CMC trending west and projecting well east of
benchmark...and 12z GFS consistently near the 40/70 lat/Lon.
With this spread have continued to play a middle of the Road track
between CMC/gefs/ECMWF ensemble means...which would track low
pressure near to just inside the 40/70 latitude/Lon benchmark Wednesday night.
With only a marginally cold airmass to start...this track would
bring mainly rain to Li/southeast CT...rain/snow mix for NYC/New Jersey metropolitan and
SW CT...and mainly snow well n&w of NYC...changing to all snow Wednesday
night for most if not all of the region as the low deepens and track
north. This meshes fairly well with wpc...with a low probability of
seeing warning level snow relegated to interior portions of NE
New Jersey...lower Hudson Valley..and SW CT...and advisory level snow
possible into NYC metropolitan and coastal SW CT Sun night. Confidence in
these values is low to moderate at this point based on above
mentioned spread. Predictability too low with this day 4 event for a
deterministic storm total snow forecast.
Zonal flow builds in behind the system for Friday into the weekend with
generally quiet and temperatures a few degrees seasonable. A weak Alberta
clipper may pass to the north on Saturday with a few rain/snow
Aviation /03z Monday through Friday/...
high pressure departs to the east as a warm front approaches
VFR through 05-06z tonight. Rain with IFR ceilings/visibility develops
shortly thereafter. LIFR at times in rain possible 9-14z. Cannot
rule out thunder around this time frame as well...especially east
of NYC metropolitan.
IFR conditions likely linger through the morning Monday...although
the moderate/heavy rain will taper off to light isolated showers.
Light S winds into the evening turn toward the southeast.
Low level wind shear is likely late tonight into early Monday
morning with winds at 2000ft ranging from 50-65 knots.
Surface winds turn back to the south/southwest by 10-13z. Speeds
increase quickly to 15 to 25kt with gusts 25 to 35 knots. A few coastal
gusts could reach 40 knots.
Outlook for 00z Tuesday through Friday...
Monday night...VFR. Winds shift to the west at 10-15 knots.
Tuesday...VFR. West-southwest winds 15-20 knots with 20-30 knots gusts.
Tuesday night...diminishing winds. Sub-VFR ceilings possible late.
Wednesday-Wednesday night...low to moderate confidence forecast
with passage of coastal low. Accumulating snow threat possible for
the interior...but accumulating snow could occur closer to the coast
during Wednesday night based on track of low. Strong winds possible
depending on track of low as well.
Thursday...becoming VFR. Lingering rain/snow showers possible early.
Gusty winds possible as well.
Friday...VFR with gusty northwest winds.
strong pressure gradient sets up late tonight allowing for southerly flow through Monday
night. Gales develop late tonight and continue through Monday. Winds diminish
late Monday night from west to east. The gale was extended for the eastern
waters...and may need to be extended for the remaining waters
based on the exact timing and strength of the system.
Small Craft Advisory conditions continue through Tuesday with a tight west-northwest
gradient...followed by a relatively brief period of sub-Small Craft Advisory
conditions likely Tuesday night through Wednesday morning as high
pressure nose in.
Small Craft Advisory conditions then likely Wednesday after through Thursday as a coastal storm
affects the waters. Potential exists for marginal gale conds on the
eastern waters Wednesday night as low pressure makes its closest approach
to the region. Small Craft Advisory conds possible on the ocean waters through Friday
due to residual swells and tight offshore gradient.
around an inch of rain is expected late tonight into Monday. Minor urban
flooding will be possible...with impacts likely around the time
of the morning commute.
Increasing potential exists for 1/2 to 1 inch of precipitation Wednesday
into Wednesday night. Some portion of this should fall in the form of
snow...particularly across areas n&w of the NYC metropolitan.
some of the most vulnerable spots along the South Shore of western
Li...NYC...and southwestern CT could see minor inundation during
the Monday morning cycle. Some minor beach erosion is also possible on
the Atlantic coast with surf in the 6-8ft range.
record high temperatures for Monday 24 November...
* also occurred in previous years
New York...Wind Advisory from 4 am to 11 am EST Monday for nyz075-176>179.
Wind Advisory from 4 am to 6 PM EST Monday for nyz078>081.
Marine...Gale Warning from 1 am to 6 PM EST Monday for anz330-335-338-
Gale Warning from 1 am Monday to 6 am EST Tuesday for anz350-