Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1238 am EST Friday Jan 30 2015
low pressure and an associated cold front approach from the west
tonight with the cold front passing through late tonight into
early Friday morning. An Arctic cold front will follow Friday
afternoon as the low deepens off the northeast coast. High
pressure builds in Friday night and Saturday.
A wintry pattern will persist through the middle of next
week...with frigid cold on Saturday and chances for snow Sunday
night into Monday...and again around Wednesday.
Near term /until 6 am this morning/...
clipper system approaches from the west tonight. A shortwave
embedded in a digging upper trough will provide lift for periods
of light snow through the overnight. Warm advection ahead of the
low is raising boundary layer temperatures...however...profile
still looks cold enough for all snow on land. Warm air over the
waters will allow for rain and snow and a slight chance that
enough warm air may move in across the very far eastern zones for
a mix of rain and snow. Temperatures will hold nearly steady or
only fall a few degrees tonight.
Adjusted probability of precipitation slightly overnight based on latest trends and
guidance. None of the guidance is capturing the rise in surface temperatures
well...but would expect them to level off and hold steady or even
slightly fall due to evap cooling.
Short term /6 am this morning through 6 PM Saturday/...
the clipper low move through during the morning with an associated
cold front. Meanwhile the upper trough continues to dig and become
negatively tilted. A strong vorticity maximum rounds the base of the trough
Friday afternoon allowing for the low to rapidly deepen off the
northeast coast. An Arctic front moves through Friday afternoon as
the low deepens. Northwest wind will increase and become gusty as
Arctic air flows in. Late Friday afternoon and Friday night
sustained wind and gusts are expected to fall just below advisory
levels...with the highest wind along the coast. The combination of
cold air and gusty wind will produce wind chills well below zero
Friday night...with wind chills at advisory levels by late Friday
night. Being late third period into fourth period will hold off on
a Wind Chill Advisory.
Long term /Saturday night through Thursday/...
980s low spinning near Nova Scotia will keep gusty northwest flow locked in
on Sat...producing wind chills mainly at or below zero for most of the day.
As winds slacken late...wind chills will likely rise into the single
digits. 850 mb winds in the GFS are around 55-60kt at 12z Sat...so
there is the potential for Wind Advisory early with gusts in the 45-50
miles per hour range. Subsidence on the western fringe of the system should aid in the
gust potential...while at the same time clearing out the skies.
Weak hi pressure ridge Sat night so much lighter winds into sun.
Models lining up with the next system for Sun night and Monday. The 12z GFS
and European model (ecmwf) are virtually the same with respect to the track and intensity. At 18z
Monday the low centers were approximately 60 miles apart and about 130
miles S of the benchmark. Most of the GFS ensemble members were
clustered on this solution.
Extensive area of middle level moisture with the system...so with high slr/S
at least light-MDT accums possible. Based on the progressive
nature...it looks like a 4-8 inch potential at this time. This of course can
change...in fact a southern track could leave the County Warning Area with just flurries.
As an aside...the 12z mex has Cat 8 snowfall for all sites.
Hi pressure Monday night and Tuesday. Sunny on Tuesday as a result.
The Gulf opens up midweek potentially in tandem with another northern
stream upper trough. European model (ecmwf) forecasts low pressure heading towards Cape Cod. This
reflects the idea of low pressure exhibited in the 00z run. The GFS is
less organized. Included 30 probability of precipitation for precipitation Wednesday.
Aviation /06z Friday through Tuesday/...
low pressure approaches from the west early this morning...
crossing the area...then exits to the east as it deepens this
MVFR/IFR in periods of light snow early this morning. Steady
period snow likely between 11z and 16z for city and eastern
terminals with IFR conds. Snow may be briefly moderate with LIFR
Generally expecting 1-2 inch snowfall with highest amounts across
Conditions gradually improve to MVFR from late morning to early
afternoon...and then VFR late afternoon. Isolated snow
showers/flurries possible in the afternoon.
S winds with a brief period of occasional S gusts to 20 knots
possible at coastal terminals will shift SW-W-NW later this
morning...with northwest wind gusts to 25-35 knots afternoon. VFR in the
evening...northwest winds g30-35 knots likely. A few 40 knots gusts possible.
Outlook for 06z Friday night through Tuesday...
late Friday night-Saturday...VFR. Northwest winds g30-35 knots likely. A
few 40 knots gusts possible.
Saturday night...VFR. Northwest wind g 20-30kt possible early.
Sunday...VFR. Northwest wind g15-20kt possible.
Sunday night-Monday..chance of snow with IFR conditions. NE-north
wind g25-35kt possible.
Monday night...becoming VFR from west to east as any snow comes to an
end. North-northwest wind g20-25kt possible.
low pressure approaches from the west tonight with an increasing
southerly flow allowing for seas on the ocean to build to small
craft levels overnight. In addition some southerly wind
gusts...mainly over the outer forecast waters...may reach small
craft levels. As low pressure passes through the waters late
tonight into early Friday the wind will diminish and will likely
fall below small craft for a few hours. Then as the low and
associated cold front move through wind shifts to the northwest
and increase as the low deepens. An Arctic cold front crosses
Friday afternoon. The deepening low and strong cold advection will
allow the wind over the waters to gust to gale force Friday
afternoon into Saturday. The Small Craft Advisory remains as
posted...and the Gale Warning was extended through Saturday.
Gales will wind down Sat night as low pressure passes north of Nova Scotia.
Seas may be close to 5 feet on the extreme eastern ocean sun...elsewhere
winds and waves will be blw Small Craft Advisory levels. Small Craft Advisory winds likely Monday as low
pressure deepens east of the waters. Improving conditions on Tuesday as hi pressure
builds over the region.
one to two tenths of an inch of liquid equivalent is expected from
late tonight into Friday afternoon with the precipitation falling
Low pressure Sun night and Monday will bring the potential for less than an
inch of liquid equivalent. Precipitation likely to be all snow.
Marine...Gale Warning from 1 PM this afternoon to 6 PM EST Saturday for
Small Craft Advisory until 1 PM EST this afternoon for anz350-