Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
723 am EDT Sat Mar 15 2014
a cold front crosses the region today. High pressure builds in
tonight. High pressure builds into the region tonight into the
beginning of the week as low pressure lingers offshore. A low
pressure system will impact the area Thursday into Friday with
high pressure returning briefly before the next frontal system
Near term /through tonight/...
a shortwave moves through the area today with most of the energy
moving through upstate New York and into New England. At the surface
a cold front passes through today. 11z radar imagery showing first
line of light rain showers stretching across eastern Long Island
and Connecticut. Second line of light rain right ahead of the
front expected to pass through between 12 and 14z. With the
passing shortwave and developing westerly downslope flow will lead
to clouds quickly dissipating. Temperatures expected to climb into
the 50s across the region...and used a blend of the mav and met
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 airmass 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 havent 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 airmass 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 /12z Saturday through Wednesday/...
a cold front moves across the region this morning. High pressure
builds in behind the front this afternoon and tonight.
VFR through the taf period. Brief light showers possible until
around 15z with no impact to visibility or ceilings.
Wind SW around 10kt. The wind becomes SW to west 15 to 20 knots by 14z
with gusts 20-30 knots developing. Gusts end 00z to 02z with wind
becoming northwest. Directions could be around 310 true through the
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
forecast remains on track.
A southerly flow ahead of a cold front was producing small craft
conditions on the ocean waters with wind gusts 25 to 30 knots...and
seas 5 to 8 feet. Gusty small craft wind will continue into early this
afternoon with a brief lull...then as colder air moves in tonight
some gusts may again reach small craft levels. On the ocean waters
seas will also remain at small craft levels today and into tonight.
With a west to northwest flow tonight seas on 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.
a few hundredths of an inch of rainfall is possible today...mostly
this morning. Dry weather returns through tonight.
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.