Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1245 am EST Thursday Dec 12 2013
a cold front moves across the region during the overnight...and
then high pressure builds east. Another cold front crosses the
area Friday afternoon followed by Canadian high pressure building
to our north through the weekend. Meanwhile...low pressure
develops over the southeastern states on Saturday...and emerges
off the middle Atlantic coast Saturday night...then tracks northeast
into the Canadian maritime provinces through Sunday night.
Canadian high pressure then builds in through Tuesday.
Near term /until 6 am this morning/...
forecast on track...no significant changes.
Generally quiet conditions in store for the region tonight. A cold
airmass remains in place...and with the passing of a cold
front...another shot of cold air advection will push 850mb temperatures
down to around -15 degrees celsius...resulting in overnight lows a
good 10-15 degrees below normal. Light winds will minimize wind
chills...with wind chill values reaching the single digits over
interior regions...and in the teens along the coast.
With the frontal passage...included isolated flurries across the
area. Soundings indicate minimal moisture in the vertical...but the
combination of weak convergence with the front and lift aloft with a
passing middle level shortwave could trigger an isolated snow flurry. Did
include slight chance probability of precipitation well offshore where a better moisture feed
could trigger isolated showers with the front late in the night.
Short term /6 am this morning through 6 PM Friday/...
unseasonably cold temperatures remain the main story through
Thursday night as high pressure building in from the west keeps
generally dry and quiet conditions across the area. A shot of cold
air in the wake of the cold front will keep 850mb temperatures down around
-15 degrees through Thursday...resulting in the coldest day of the
week...with highs expected to be below freezing across the board.
Went with a blend of met/mav guidance with the numbers fairly
consistent. Despite the models hinting at slightly increasing temperatures
tomorrow night...clearing of the skies with building subsidence
aloft for a part of tomorrow night should lead to temperatures being able
to drop even a few degrees cooler than tonight. Combined with
slightly more elevated winds than tonight as well...could see wind
chill values drop to the single digits everywhere...and even
approach the zero degree mark over interior regions.
Maintained a dry forecast for all land areas. Could see a shower pop
up over the waters as a decent middle level shortwave dips down during
the day Thursday into Thursday night...with the best forcing
remaining well offshore though.
Long term /Friday night through Wednesday/...
on Friday...a cold front will push across the region during the
afternoon...bringing a re-enforcing shot of cold air to the region.
With lack of moisture with this front...expect dry conditions...with
just some clouds. Behind this cold front...Canadian high pressure
will build north of the region. Temperatures on Friday will struggle
to reach the freezing mark across the New York City metropolitan and
coastal locations. Elsewhere...highs will only reach the upper 20s.
All eyes then turn to a developing storm system moving out of the
southeastern states. All the 11/12z models guidance are in agreement
with the low moving out of the southeastern states...taking a track
off the middle Atlantic coast...and traveling northeast...passing
southeast of Long Island. Model guidance differs however on
timing...speed...and strength of the low. In addition...models are
also not in complete agreement with the strength and exact position
of a high pressure system...north of the County Warning Area...which will be a major
player in this event.
Knowing this...did not make too many changes to the forecast knowing
that the next couple of model runs will continue to show different
scenarios on how this event will play out.
So...for now...thinking that snow overspread the region during the
day on Saturday. This snow will continue into the evening...with a
change over to a mix and/or rain along the coast Saturday night. Across
the interior...we are expecting an all snow event...however
depending on the exact track of the low...a wintry mix may occur.
The low moves north and east of the region Sunday afternoon with
clearing expected late in the day.
It is too early and there is not enough confidence to give snowfall
amounts. As expected with there are differences with the
models...expect the forecast to change a few more times...between
now and the weekend.
Behind this low...mostly dry conditions are expected with high
pressure over the region. The only exception will be on Tuesday and
Tuesday night as a shortwave moves over the region...which could
bring some snow showers.
Aviation /06z Thursday through Monday/...
a cold front will slide offshore early this morning...followed by
high pressure building into our southwest into tonight.
Winds will veer to out of the northwest overnight and then back to the west
Thursday afternoon. There may be some gusts around 20 knots...in
particular towards daybreak...with gusts diminishing by middle to late
morning. There is the potential for a gusty west/SW flow Thursday night
as well...but confidence in this is not high at this time.
Outlook for 06z Friday through Monday...
Friday night...MVFR or lower possible late.
Saturday-Saturday night...IFR in wintry precipitation. Snow likely...with a
changeover to rain possible at the coast late. East/NE winds 15-25 knots.
Sunday...lingering snow and/or rain early....becoming VFR by afternoon.
Small Craft Advisory continues on the ocean and eastern waters through the
overnight to account for gusts between 25 and 30 kts...and seas on
the ocean reaching 5 feet. Possible Small Craft Advisory gusts on the remaining
waters...but with such a marginal chance...have decided against
issuing a Small Craft Advisory for these areas for now.
The Small Craft Advisory will remain up on the ocean waters through the day
Thursday. Do expect winds and seas to drop to sub-Small Craft Advisory conditions
at some point in the afternoon...but with the potential to
increase again tomorrow night...went ahead and just carried
through the day. Expecting sub-Small Craft Advisory conditions on the remaining
waters through the day Thursday...with all waters reaching 25 kts
by tomorrow night.
Some lingering Small Craft Advisory conditions are likely on the coastal ocean waters
on Friday...and possibly into Friday evening east of Fire Island
All waters should experience sub-Small Craft Advisory conditions Saturday
morning...winds then increase with the approach/passing of a strong
coastal low Saturday night/Sunday. Gale gusts are possible on all
waters by late Saturday night and could persist through Sunday.
Will highlight this potential in the severe weather potential statement. There is a small chance
for storm force winds late Saturday night/Sunday over mainly the
coastal ocean waters depending ont he exact track/strength of the
storm - but this potential is to low to mention in the severe weather potential statement at this
there is the potential for significant precipitation this weekend
in association with a coastal low pressure system.
the New York City National oceanic and atmospheric administration all hazards weather radio station kwo35 has
been returned to service. However...if issues arise again due to
interference with the U.S. Coast Guard emergency broadcast
channel...the transmitter may need to be taken out of service. If this
does occur...a notice will be made to the public notifying them of
Marine...Small Craft Advisory until 6 PM EST this evening for anz350-
Small Craft Advisory until 6 am EST early this morning for
long term...British Columbia