Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1049 am EDT Sat Mar 15 2014
a weak cold front will move across the area this morning followed by
a strong cold front by sunset. High pressure over south central Canada
will move southeast across New England through Monday. Low pressure
will pass well south of Long Island Monday followed by high pressure
Tuesday and Wednesday. A low pressure system might impact the area Thursday
into Friday with high pressure returning briefly before the next frontal
system next weekend.
Near term /through tonight/...
based on current observations including this mornings 12z local sounding
and near term forecast trends...
Increased today/S maximum temperatures and hourly temperatures by a few degrees reaching
the upper 50s across most of the metropolitan area.
The first of two cold fronts was dissipating as it approaches the
region through 10 am. A few sprinkles are possible mainly east of
NYC until around noon.
Otherwise...SW winds veer to the west with the passage of the front and
increase in speed producing another gusty afternoon with gusts of 30-40
miles per hour possible aided by day time mixing and increasing low level instability.
Stronger cold air advection sets up behind a weak trough moving
through the area late this afternoon into early this evening as
surface high pressure noses into the area and zonal flow develops
aloft. Wind gusts end this evening. However wind does not decouple
and sustained winds remain with cold advection continuing through
the night. Again used a blend of the mav and met guidance.
Short term /Sunday/...
high pressure remains anchored over the Great Lakes...gently nudging
into the northeast during the day as the area remains under the
southern extent of cyclonic flow aloft. Main concern during the day
will be the below normal highs as a shot of cold air advection in
the wake of passing front on Saturday keeps 900mb temperatures around 10
below zero. The generally cold air mass combined with increasing
clouds ahead of the approaching low should keep temperatures in the lower
to middle 30s...with some interior areas struggling to reach the 30s
Long term /Sunday night through Friday/...
the continuing focus of the long term is the progressive
flow...resulting in multiple lows and shortwaves impacting the
area throughout the coming week.
First concern to contend with...the Sunday night/Monday potential
snowstorm. The talk the past few days has been the deterministic
models handling and phasing of the northern stream energy coming
off the Pacific northwest and the energy associated with the southern stream
over the SW US. 00z model runs actually have some decent agreement
with the handling of the energy aloft and the associated surface
low that would bring the precipitation to the area late Sunday and through
Monday. However...the overall trend with the 00z model suite
continues to keep the bulk of the precipitation offshore...though close to
the coast offshore. The 00z CMC remains the go to model to bring
widespread precipitation to the area...as it drags its main energy from the
passing shortwave further to the north over the tri state
area...while the remaining models keep the best forcing south of
Long Island and thus the axis of the heaviest precipitation to the south.
The interesting to note is that comparing the model runs to
current water vapor imagery indicating where the current shortwave
energy is over the western US...there is generally decent
agreement in the placement. And even with the passage of the
shortwave over the northeast...there is not much difference in
location...but just enough that could make or break whether the
area receives significant snow or little to no snow. As for the
low at the surface...the Canadian high is looking like it may win
out in suppressing the low just far even to the south to keep most
the precipitation out. But as mentioned in previous discussions...the
models have not always been able to grasp the strength of the high
so this needs to be monitored.
So what does this all mean? It means there is still uncertainty in
the placing of the bulk of the precipitation and therefore have maintained
a similar forecast to avoid possible flip flopping in the
forecast. Did make minor changes to the probability of precipitation on Monday with growing
confidence the precipitation should be clearing the area by Monday night.
The Canadian high keeps a cold air mass in place...so despite temperatures
possibly reaching the lower 30s on Monday along the
coast...overall expecting the precipitation to remain all snow for the
period. Higher quantitative precipitation forecast/snowfall amts would be Long Island and NYC
metropolitan...with the values tapering off heading to the north.
High pressure ridge shifts to our east during Tuesday night.
Resulting onshore flow pushes some low level moisture our way. Too
difficult to tell this far out in time whether there will be
enough low level lift to squeeze out any light precipitation from
this...so will go with a dry forecast. Better chances of
precipitation begin on Wednesday as a low pressure system moves
through the Great Lakes region. Deeper moisture here and probably
some positive vorticity advection warrant slight chance/chance
probability of precipitation. Timing of best chances of precipitation in still question
with models in disagreement. They all seem to agree however that
the parent low passes to our north. Thinking is that the best
chances are during Wednesday and Wednesday night...but will continue
with a chance into Thursday due to this uncertainty. Looks like
mixed precipitation with anything that falls Wednesday
morning...then precipitation in the form of rain would be likely
High pressure influence keeps a dry forecast Friday. Introduced
slight chance probability of precipitation Saturday with both 00z GFS and European model (ecmwf) suggesting a
quick moving clipper. High temperatures Wednesday through Friday fairly close
Aviation /15z Saturday through Wednesday/...
VFR through the taf period.
As of 15z...cold front was just about to make its way through
western-most terminals. It will continue to move across the region
this morning. High pressure builds in behind the front this
afternoon and tonight.
Winds at most terminals should be west-southwest to west-northwest 15 to 20 beginning 15z
with gusts 20-30 knots developing. Eastern terminals will remain SW
through 16z-17z as the cold front will pass through later at
these locations. Gusts end 00z to 02z with wind becoming northwest.
Directions could be around 310 true through the overnight.
Outlook for 12z Sunday through Wednesday...
Sunday night-Monday...snow possible...especially New York metropolitan and Long
Island...MVFR to IFR. Little to no snow inland with VFR. NE wind
g25+ knots possible Sunday night-Monday.
Late Monday night-Tuesday...VFR. NE wind g20-25kt possible.
Wednesday...MVFR or lower possible in -ra...possibly -sn in the
a Small Craft Advisory remains in effect across Atlantic Ocean coastal
waters through 6 am Sunday based on a combination of high seas and wind
gusts to at least 25 knots.
As of 9 am...seas were ranging from 7 to 9 feet based on earlier strong
southwest winds. After a brief lull in winds this afternoon...colder
air moves in tonight with gusts again reaching small craft levels
of 25 knots. With a west to northwest flow tonight seas west of Fire
Island may subside below small craft before 10z Sunday. However
not high confidence. So have extended the small craft on the ocean
zones through 10z Sunday. Small craft conditions are not expected
on the remainder of the forecast waters. However...some gusts in
the South Shore bays may be near small craft today.
Due to uncertainty with the track of the low pressure system
Sunday night/Monday...there remains uncertainty to the strength of
the winds and how high the seas build. Confidence is increasing
for Small Craft Advisory to be reached on the ocean late Sunday as the approaching
low interacts with the high to the north. Small Craft Advisory then spread to all
waters Sunday night...then with possible gales everywhere during
the day Monday. Seas will build during this period...and while
winds will drop to below 25 kts by Monday night...expect lingering
5 feet seas through middle week on the ocean. Sub-Small Craft Advisory conditions will
persist on the remaining waters.
Possible Small Craft Advisory conditions again Thursday-Saturday with the passage
of multiple lows through the northeast.
no additional precipitation is forecast until Sunday night.
Significant precipitation in the form of snow is possible from Sunday
night through Monday night...with the higher amounts expected across
NYC metropolitan and Long Island. It is still too early to specify exact
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 until 6 am EDT Sunday for anz350-353-355.