Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1007 PM EST Thursday Mar 6 2014
high pressure pushes through the northeast tonight...and offshore
Friday. Meanwhile...low pressure will pass to the south and east
of Long Island Friday into the weekend. A series of weak fronts will
cross the region through early next week. A storm system will
then approach from the middle section of the country during the
middle of next week.
Near term /until 6 am Friday morning/...
minor changes made to forecast database. Temperatures for most
places outside of Westhampton were increased a few degrees to
account for dense cirrus moving in overhead for remainder of
night. Lows forecast range from the single digits and lower teens
in outlying rural sections to lower 20s near New York City.
The Canadian high will push to the east overnight and eventually
offshore of New England...eventually bringing winds from the
northeast to a more easterly flow. As this occurs in the second
half of the night...BUFKIT soundings indicate moistening with the
increasing easterly flow in the lower levels...with plenty of dry
air still in place aloft with westerly winds persisting along the
near zonal flow. Little to no forcing combined with the drier air
aloft should keep any precipitation formation to a minimum and more in the
form of drizzle/freezing drizzle/snow flurries if any precipitation occurs.
This is just a chance along the southern coastlines of NYC and
Long Island as large dewpoint depressions may prevent any precipitation
from reaching the ground at all.
Regions of the atmosphere where ice nucleation takes
place...typically within the -10 to 30 degree c layer...will be
dry with a lack of ice nuclei. However...dense cirrus moving
overhead will be ice nucleated and could deposit some ice nuclei
into the lower level clouds forming...which is the seeder feeder
mechanism. This is why snow flurries will also be possible if
there is enough ice nuclei in the lower clouds...otherwise just
supercooled liquid would allow for freezing drizzle.
Increasing clouds overnight with multiple sources. High clouds
are coming from both northern stream shortwave over Great Lakes
region and potent low over the far southeast US which will begin to make
its way to the northeast tonight into Friday. As such...expecting
lows to occur in the first half of the night...then near steady
temperatures with only a 1-2 degree drop the remainder of the night.
Another night of well below normal temperatures...though with the cold air advection
finally shutting off...will not expect as cold as previous night.
Sided with the slightly cooler guidance.
Short term /6 am Friday morning through Friday night/...
any freezing drizzle/snow flurries that develop overnight
expected to taper off early Friday morning...with period of dry
weather after early Friday morning with the last bit of the high
influencing the area. As the high pushes off to the
east...attention turns to approaching low pressure from the south.
12z models in generally decent agreement with the track of the low
along the eastern Seaboard...then pushing off to the
northeast...passing well east of the 40/70 benchmark by 12z
Saturday. High confidence in minimal impact from this low...with
the main area of precipitation remaining offshore...well south of Long
Island. That being said...the 12z models so push the northern
fringe of the precipitation shield a bit more to the north...enough so that
there is now reason to include slight chance probability of precipitation in for areas of
Long Island...corresponding with weak forcing in the middle levels.
Any precipitation that does occur will be spotty and light in nature...and
looks to happen between 18z Friday and 06z Sat. A shot of warm air advection
accompanies this low...so will see temperatures reaching above
freezing...resulting in any precipitation Friday/Friday evening being light rain.
The low tracks off to the east Friday night...taking the precipitation away
from the area as well...keeping things dry for the second half of
the night...if not even sooner for Long Island. Areas north and
west of NYC metropolitan will most likely stay dry the entire period.
Temperatures attempting to return to normal with the strong push of warmer
air with the low. Highs Friday may actually reach the 40s along
the coast...just a couple of degrees below normal. The combination
of warmer air and cloud cover will keep lows Friday night right
Long term /Saturday through Thursday/...
a fast...nearly zonal flow will impact the northern half of the
country through early next week...with a series of short waves
sending weak fronts across the area. The forecast then introduces
some uncertainty as Pacific short wave energy interacts with the
northern branch of the polar jet. Deterministic 12z runs vary
significantly with the magnitude of the trough...with the European model (ecmwf)
developing a full latitude trough across the middle section of the
country by middle week...with the GFS a less amplified...colder
solution. The differences seem to arise due to different packets of
short wave energy off the Pacific and the spacing between them. Such
details at this time can hardly be realized...thus an ensemble or
model consensus approach is preferred. This scenario will take low
pressure across across the middle section of the country Tuesday...and then
across Tennessee Valley Wednesday...passing off the middle Atlantic coast Wednesday night
into Thursday morning. This is a cold scenario that would result in a
mainly snow event. However....the preference for the more
progressive solution and the associated uncertainty makes it way to
early to consider this a significant system...but something to watch
in subsequent model runs.
Expect mainly dry conditions Sat-Tue...with a low chance of snow
showers Sun morning with a cold frontal passage...and then a light
rain/snow mix Monday morning with a weak warm front. Neither of
these systems are expected to be significant. Snow is then
forecast to develop late Tuesday night with the aforementioned storm
system...winding down early Thursday. Once again there is a lot of
uncertainty this far out in time.
Temperatures will be near seasonable levels through early next week...then
drop off ahead of the storm with the passage of a polar cold front
Tuesday night. Daytime highs are forecast to drop back into the 30s for
both Wednesday and Thursday.
Aviation /03z Friday through Tuesday/...
MVFR ceilings slow to track up the coast. Do not want to remove them
from the tafs...but will delay onset for a few more hours. Once
the MVFR ceilings develop...they will persist into Friday.
Precipitation forecast...there is a slight chance of light
snow...light freezing rain and/or freezing drizzle after 06z tonight
through 18z Friday. Because of low confidence...this chance was
not included in the taf forecasts.
Wind forecast...winds will persist from the NE to east around 10 knots or
less across interior locations through 18z Friday.
Outlook for 03z Sat through Tuesday...
Friday night...MVFR. Light rain possible metropolitan NYC east.
Sunday...mainly VFR. Brief light precipitation possible in the morning.
Monday...mainly VFR. Brief light precipitation possible.
seas and winds will be on a downward trend tonight with
decreasing pressure gradient with influence of high pressure as it
However...as low pressure approaches Friday...expecting winds and
seas to increase once again...with another period of Small Craft Advisory
conditions on the ocean waters...lasting through the night. Wind
gusts on the ocean will increase up to 25 knots...mainly east of Fire
Island Inlet Friday night. Another Small Craft Advisory remains in effect for Friday
through Friday night to cover this.
Marginal Small Craft Advisory seas will linger into Sat on the ocean waters as
deepening low pressure passes well to the east. Marginal Small Craft Advisory
conditions are then possible in a northwest flow sun...otherwise sub Small Craft Advisory
conds expected into early next week with a series of weak frontal
no significant widespread precipitation expected through early
There is the potential for significant precipitation during the
middle of next week as a storm system emerges from the MS valley.
There is a lot of uncertainty in the forecast details at this time
due to the timing of the energy from the Pacific and its eventual
interaction with the northern branch of the polar jet.
the National oceanic and atmospheric administration weather radio transmitter that serves the New York City
metropolitan area remains out of service due to radio frequency
interference with the U.S Coast Guard transmitter.
For more information see the following public information
statement (all lower case):
Marine...Small Craft Advisory from 6 am Friday to 6 am EST Saturday for