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Area forecast discussion 
National Weather Service New York New York
738 am EST Monday Mar 2 2015

Synopsis...
low pressure tracks into the Canadian Maritimes today...allowing
high pressure to quickly build in tonight. The high drifts over
then east of the region on Tuesday. Low pressure will track well
north of the area Tuesday night and Wednesday...with a warm front
lifting towards the area Tuesday night...followed by a cold front
Wednesday. Another wave of low pressure may affect the region
Wednesday night into Thursday. High pressure will then build in
for the remainder of the week.

&&

Near term /through tonight/...
northwest flow will begin to pick up today as low pressure deepens over the
Maritimes and high pressure builds into the Ohio Valley. Despite the
cold airmass...the northwest flow will allow for deep mixing. NAM and GFS
bufr soundings indicate mixing to about 800 mb...which yields highs
right around freezing interior to just above at the coast.
Normally...a few degrees could be added to this with the March
sun angle. With fresh snow cover this should be limited
however...especially outside the city. As a result...went with
temperatures a little blw guidance for today.

Increasing subsidence by early afternoon should help to erode the
residual cloud cover across the area. A period of clear skies this
evening...then middle and high clouds ahead of the next system begin to
filter in late tonight.

Temperatures a blend of guidance tonight. Winds this evening may limit the
initial drop off after dark...particularly coasts and city. As winds
diminish overnight...the increasing middle clouds are expected at this time
to keep temperatures from completely bottoming out.

&&

Short term /Tuesday/...
the Gulf begins to open up and hi pressure over the County Warning Area drifts
offshore. Result is increasing Theta-E over the region with snow
developing from SW to NE after 18z. The NAM/GFS/ECMWF all have
similar timing. Temperature profiles indicate the column is generally cold
enough for all snow through 00z. The NAM does warm things slightly
faster aloft...so some sleet mixing in would be possible across
Staten Island into New Jersey in the 22-00z time period should this faster
solution verify.

With a locally MDT burst of snow at the onset...will forecast around
an inch of snow western zones for late in the afternoon.

Temperatures blw climatology with a blend of guidance used. The onshore southerly
flow will keep temperatures nearly steady as the day ends.

&&

Long term /Tuesday night through Sunday/...
main focus will be prolonged period of unsettled weather Tuesday
night through Thursday.

Models in decent agreement with a couple of northern stream
shortwaves phasing and digging down the Front Range of The Rockies
into northern plains early this week...phasing with a SW US low...and
then gradually lifting across the US to East Coast by end of the
week.

The phased streams will have a moist SW flow from the subtropical Pacific
developing all the way into the northeast US by Tuesday night with
several disturbances riding along it through midweek.

The first piece of phased energy will have strong low pressure
tracking from central Ontario into central Quebec Tuesday/Tuesday
night...with its warm front...and an absorbed Central Plains low...
approaching the region during this time. Strong warm air advection as described
above will allow for precipitation to overspread the area late Tuesday afternoon as
snow...but with mentioned subtropical Pacific
connection...expecting temperatures aloft to warm fairly rapidly Tuesday
evening/night with snow changing to mixed precipitation then rain from S to north. A
quick 1 to 2 inches of snow city/coast and 2 to 4 interior are
possible before changeover.

Due to the primary low tracking well to the northwest of the region...deep
snow pack and cold water temperatures...the surface warm front will likely
have trouble lifting north Tuesday night into Wednesday. A brief period of
freezing rain with a trace to few hundredths of an inch of ice
possible along the city/coast Tuesday evening before changeover to
rain...but interior portions of the tri-state may struggle to get
above freezing until after daybreak. 1 to 2 tenths of an inch of ice
possible here. With some of the 1/2 to 1 inch of precipitation falling in
frozen form and temperatures not expected to get much above the middle to
upper 30s through Wednesday morning...not expecting a great amount of
snowmelt...so just expecting some nuisance flooding issues across
the coastal plain.

Best lift moves east Wednesday morning with a weak cold frontal passage.
Just some residual shower activity in wake of front.

Stronger cold front moves across Wednesday evening/night with falling temperatures
Wednesday night. Models are signaling potential for another period of
Post-frontal precipitation Wednesday night into Thursday...with a series of waves
developing along the cold front and ahead of approaching upper
trough axis and the region under favorable entrance region of a
175-200kt upper jet. Potential for much of this to be in the form of
snow...with several inches possible. Have trended forecast in this
direction...but will have to monitor next few models runs for
increased confidence in snow threat.

Another shot of Arctic air infiltrates the area Thursday into Friday.

Strong Canadian high pressure then builds towards the area into the
weekend with dry weather. Temperatures will rebound around 5 degrees below
normal next weekend with warm air advection developing.

&&

Aviation /13z Monday through Friday/...
high pressure gradually builds from the west through Tuesday
morning. Isolated MVFR early today but overall VFR conditions are
expected through the taf period. West winds 5-10 knots become northwest 10-20
knots with gusts 25-30 knots late this morning through the afternoon.
Winds and gusts diminish this evening.



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: moderate confidence forecast. MVFR and gust
timing could be off 1-2 hours from forecast.

Klga fcster comments: moderate confidence forecast. MVFR and gust
timing could be off 1-3 hours from forecast.

Kewr fcster comments: moderate confidence forecast. MVFR and gust
timing could be off 1-3 hours from forecast.

The afternoon kewr haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.

Kteb fcster comments: moderate confidence forecast. MVFR and gust
timing could be off 1-3 hours from forecast.

Khpn fcster comments: moderate confidence forecast. MVFR and gust
timing could be off 1-2 hours from forecast.

Kisp fcster comments: moderate confidence forecast. MVFR and gust
timing could be off 1-3 hours from forecast.

Outlook for 12z Tuesday through Friday...
Tuesday morning...VFR.
Tuesday afternoon...chance MVFR or lower in snow.
Tuesday night...IFR or lower likely. Snow...changing to a wintry
mix late evening...and then rain at all terminals except kswf and
possibly CT terminals overnight. Low level wind shear likely.
Wednesday...IFR or lower possible in any rain - with a brief period
of freezing rain possible in the morning at kswf. Low level wind shear possible in the morning.
Wednesday night-Thursday...MVFR or lower possible in any
precipitation...otherwise VFR. If there is precipitation...should
change to all snow Wednesday night into Thursday and possibly
continues Thursday afternoon. Northwest winds g15-20kt possible.
Thursday night-Friday...VFR. Northwest winds g15-20kt possible Thursday
night.

&&

Marine...
northwest winds will pick up to Small Craft Advisory levels today as low pressure deepens over
the North Atlantic. Winds and seas will begin to subside tonight as hi pressure
quickly builds over the waters. Conditions blw Small Craft Advisory levels on Tuesday. Small Craft Advisory
wind gusts possible on the ocean Tuesday night ahead of approaching
cold front...with accompanying Small Craft Advisory seas developing. Winds likely
drop below Small Craft Advisory on Wednesday...but seas should remain Small Craft Advisory. Small Craft Advisory conditions could
continue into Thursday behind the passage of two cold fronts...with a
tight pressure gradient. Sub-advisory conds for the end of the week as the
pressure gradient weakens with another building high.

&&

Hydrology...
between 1/2 to 1 inch of liquid equivalent precipitation is likely late
Tuesday through Wednesday morning. Some of this will fall as plain
rain...therefore the combination of this and some melting snow
pack could cause nuisance urban flooding issues across the metropolitan
and coastal plain Tuesday night into Wednesday morning.

Between 2 to 4 inches of liquid equivalent exists in the snowpack
across the area. With temperatures rising several degrees above
freezing on Wednesday...some melting of snowpack can be
expected...but only enough for nuisance flooding.

Some minor increases in streamflow are possible across primarily the
northeastern New Jersey river basins due to rain and snowmelt late
Tuesday night into Wednesday evening. The probability of ice
movement and ice jam flooding appears low at this time.

Another 1/2+ inch of liquid equivalent precipitation is possible
Wednesday night into Thursday. This will mainly be frozen.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory until midnight EST tonight for anz330-335-
338-340-345.
Small Craft Advisory until 6 am EST Tuesday for anz350-353-355.

&&

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

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