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Area forecast discussion 
National Weather Service New York New York
430 am EST Wednesday Mar 4 2015

Synopsis...
deepening low pressure tracks across eastern Canada today with a
cold frontal boundary approaching as a wave of low pressure
develops along it southwest of the region. The cold front slides to
the southeast tonight...with waves of low pressure tracking along
it into Thursday. Canadian high pressure then builds in through
Thursday night...then slides to our south through Friday night. A
series of weak cold fronts cross the region this weekend into
early next week.

&&

Near term /until 6 PM this evening/...
a west-southwest flow remains across the region through the day today. Pretty
much a steady state environment with temperatures only rising a few
degrees and intermittent light rain.

The upper level jet streak of around 200 knots will be approaching
through the day. Temperatures remain generally in the middle to upper 30s to
keep precipitation in the form of plain rain. The intensity will
be rather light due to the area not being in a favorable region of
lift relative to the jet streak placement but increased divergence
aloft should allow for rain field to expand.

Temperatures used were a combination of gmos...nam12 and gfs40.

&&

Short term /6 PM this evening through Friday/...
models in good agreement with northern stream energy digging down
the Front Range of The Rockies into northern plains/upper Great
Lakes today...interacting with a SW US low...and then gradually
lifting across the US to East Coast by Thursday night.

Have stayed close to ensemble means...with a reinforcing cold front
moving south of the region this evening with falling temperatures tonight. A
series of waves will develop along a stationary front to the south
..tracking NE through the middle Atlantic...Ahead of approaching upper
trough axis and as the region falls under favorable entrance region
of a 175-200kt upper jet.

Biggest uncertainty exists in quantitative precipitation forecast...with models wobbling back and
forth from run to run on northern extent of heavier quantitative precipitation forecast axis.
Relying on a ensemble approach to quantitative precipitation forecast...with 1/4 to 3/4 inch of quantitative precipitation forecast
across the region as the synoptic setup taps into a moist SW flow
all the way from the subtropical Pacific. Ensemble indicating highest
probability of .5 inches or greater after transition for southern portions
of NYC/New Jersey metropolitan and Li.

Models in general agreement with thermal profiles cooling through
the overnight...with a changeover of precipitation from rain in the early
evening to wintry mix then snow from northwest to southeast. All areas appear to be
mainly snow by 06z. Modest frontogenetic forcing appears to be across
southern zones...with potetnial for snow to be heavy at times late
tonight through Thursday morning there...coupled with strong jet
dynamics. Snow should gradually taper off in intensity and coverage
from northwest to southeast Thursday afternoon as shortwave trough approaches and
offshore stationary front slides well offshore.

Highest confidence in 6+ inch amounts is for Li and southern
portions of NYC/New Jersey metropolitan. Will upgrade to warning in this area after
collab with phi and box. Potential for 3 to 6 inches for coastal
southern CT...the rest of NE New Jersey...and southern portions of lower
Hudson Valley. Will leave watch in these areas with potential for 6"
but higher likelihood of advisory level. With a sharp gradient in
precipitation across areas far n&w of NYC...between 1 to 4 inches...
not enough confidence for an advisory at this time.

Drying conditions Thursday night...with temperatures dropping into the
single digits...lower teens NYC metropolitan...on gusty northwest winds.
Windchills likely dropping to around zero to 5 below zero for much
of the region by Friday morning.

&&

Long term /Friday night through Tuesday/...
thereafter...mean troughing continues into early next week.
Unseasonably cold conds (about 20 degrees below seasonable) continue
Thursday night into Friday night as Canadian high pressure builds into the
region.

Then a series of weak shortwave/cold fronts move through the
region this weekend into early next week...with temperatures moderating but
still remaining several degrees below seasonable. Some light rain/snow
shower activity possible with any of these disturbances.

&&

Aviation /09z Wednesday through Sunday/...
low pressure tracks across eastern Canada today...with its trailing
cold front crossing the area late tonight into Thursday morning.

Precipitation has ended for the moment at all terminals except kgon...which
will follow suit over the next 1-2 hours as well. Hi res models are
all over the place with timing precipitation today...but expecting at least
2-3 hours of dry weather. Watching next area over central
PA...although the leading edge of this has been drying out as it
advances eastward. This area is currently timed to reach western
terminals around 10-11z...but will need to watch radar trends to see
if this will materialize. All terminals are now above the freezing
mark...so expect plain rain everywhere.

On and off light rain is then expected through the day.

IFR should prevail through the morning...although conditions may
bounce around to LIFR and MVFR at times. IFR or MVFR likely through
the rest of the day...although stratus may scatter...especially
across the interior. If that does occur...VFR conditions are
possible for a time.

SW winds 10 kts or less shift to the SW-W. Low level wind shear through 11z or so.

..NY 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: exact timing of rain through the day is
uncertain. Flight category may vary between IFR and MVFR this
morning...and MVFR and VFR this afternoon.

Klga fcster comments: exact timing of rain through the day is
uncertain. Flight category may vary between IFR and MVFR this
morning...and MVFR and VFR this afternoon.

Kewr fcster comments: exact timing of rain through the day is
uncertain. Flight category may vary between IFR and MVFR this
morning...and MVFR and VFR this afternoon.

The afternoon kewr haze potential forecast is moderate...which
implies slant range visibility 4-6sm outside of cloud.

Kteb fcster comments: exact timing of rain through the day is
uncertain. Flight category may vary between IFR and MVFR this
morning...and MVFR and VFR this afternoon.

Khpn fcster comments: exact timing of rain through the day is
uncertain. Flight category may vary between IFR and MVFR this
morning...and MVFR and VFR this afternoon.

Kisp fcster comments: exact timing of rain through the day is
uncertain. Flight category may vary between IFR and MVFR this
morning...and MVFR and VFR this afternoon.

Outlook for 06z Thursday through Sunday...
tonight-Thursday...becoming IFR with a transition back to snow
around midnight. Chance north gusts to 20 knots on Thursday.
Thursday night-Friday...improving to VFR Thursday night. Northwest gusts
15-20kt possible Thursday night.
Sat/sun...VFR.

&&

Marine...
Small Craft Advisory conditions are expected to continue across the ocean with
other waters remaining below Small Craft Advisory. The Small Craft Advisory event will be more of a
marginal one but any rainfall will be help transport momentum
down and give some higher gusts that would reach Small Craft Advisory thresholds.
Water temperatures are a few degrees warmer on the ocean relative to
other waters so it will be relatively easier for higher gusts to
be achieved on the ocean.

Small Craft Advisory conditions are likely on the coastal ocean
waters into Thursday morning as a series of low pressure waves
tracks to the south of the waters. Some uncertainty if Small Craft Advisory conds
continue into Thursday afternoon...with higher confidence of
re-occurrence Thursday night. So for now have only run Small Craft Advisory until Thursday
morning.

Sub Small Craft Advisory conds return Friday as high pressure builds over the waters.

A series of weak cold fronts will move through the waters this
weekend into early next week...one Saturday night into Sunday
morning and another Monday night. Winds approach Small Craft Advisory criteria
Saturday into Saturday night and then again Monday night into
Tuesday on the ocean waters...but as of right now...they should
remain below. Waves remain below Small Craft Advisory criteria through the period.



&&

Hydrology...
around a quarter of an inch or less is expected with the remaining
rainfall today. Low potential for flooding although some ponding
of water is expected with steady moderate rain that falls due to
excess runoff from melting snowpack.

1/4 to 3/4 inch liquid equivalent precipitation is likely Wednesday
night into Thursday. Most of this will be frozen...so hydrologic
impacts are not expected.

&&

Okx watches/warnings/advisories...
CT...Winter Storm Watch from this evening through Thursday evening
for ctz008>012.
New York...Winter Storm Warning from 7 PM this evening to 7 PM EST
Thursday for nyz074-075-078>081-176>179.
Winter Storm Watch from this evening through Thursday evening
for nyz071>073.
New Jersey...Winter Storm Warning from 7 PM this evening to 7 PM EST
Thursday for njz107-108.
Winter Storm Watch from this evening through Thursday evening
for njz002-004-006-103>106.
Marine...Small Craft Advisory until noon EST Thursday for anz350-353-
355.

&&

$$
Synopsis...jm/NV
near term...jm
short term...Nevada
long term...Nevada
aviation...24
marine...jm/NV
hydrology...jm/NV

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