Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
501 am EST Sat Dec 7 2013
high pressure will build towards the region today...and drift into
northern New England on Sunday. Low pressure will approach Sunday
night and impact the northeast through the first half of next
week. High pressure will build in for the second half of the week.
Near term /until 6 PM this evening/...
main band of precipitation is now offshore per radar and satellite. Have
cancelled the Winter Weather Advisory as a result. Only some residual
pockets of light rain and snow showing up on radar and verified by
observation. Snow has been reported down to kfrg and kisp on Li.
Followed the hrrr until 11z for the residual light precipitation this morning.
Otherwise...clearing skies and northerly flow today. Edge of the cloud
shield was in vicinity of Port Jervis...and advecting eastward...at 330 am.
Short term /6 PM this evening through 6 PM Sunday/...
modifying Arctic hi will build over the County Warning Area tonight. Msas analysis at
8z placed the 1044 center of the hi over eastern Montana. This will produce
cold temperatures with widespread teens expected across the interior and
Pine barrens. Strong subsidence but a few high clouds are likely
to filter in from the SW.
An increasing high overcast can be expected on sun with backing middle and
upper level flow. Clouds will lower and thicken in the afternoon. GFS time
heights show lift is fairly robust after 18z...so it will just be a
matter of how long it takes for saturation and precipitation...which based
on the 00z suite of data will be all snow with perhaps some rain
mixed in on Li and in the city. Forecast has been sped up with most
spots with chances for snow by dark. Based on the current timing of
the system...less than an inch of snow is expected by 5 PM.
Long term /Sunday night through Friday/...
a wintry mix expected to start the week and then an Arctic airmass
for middle to late week.
Weather through this time period will be controlled by the polar
vortex over Hudson Bay...which will rotate a series of shortwaves
through the northern US. Models in decent agreement with one of these
shortwaves phasing with a shortwave ejecting out of the western
US...resulting in a developing low pressure system affecting the
region with a wintry mix of precipitation Sunday night into Monday
morning. Based on closley clustered consensus track of a double
barreled coastal low...a transition to rain would be expected
along the coast by Monday morning. Across interior
areas...particularly northwest zones...a few inches of snow and sleet are
possible with even a brief transition to freezing rain. Sref
plumes indicating a mean of 3 to 4 inches across far northwest
zones...with generally an inch or less for city coast. This could
make for a wintry morning commute for interior areas...while at
the city/coast roads should mainly be wet with rain and rising
Models are in decent agreement with a trailing cold front pushing
through the region with drying conditions late Monday...but the
front lingers close enough to the region Monday night into Tuesday
for additional waves of low pressure to possibly brush the region
with light wintry precipitation. Have maintained slight chance/chance probability of precipitation
through this time based on model spread.
Then for the middle to late week period...model indicating several
pieces of an Arctic airmass over Canada spilling into the northern
US. Currently have trended temperatures to stay below freezing from
Wednesday through Friday based on anomalously cold airmass...with
potential for temperatures to struggle to reach the upper teen/lower 20s
for highs late week if polar vortex drops into northern New
England/southeast Canada as depicted by some model guidance. Stay tuned.
Aviation /10z Saturday through Wednesday/...
a weak wave of low pressure will continue to push well offshore this
morning with high pressure building into the region this afternoon
Main precipitation shield has pushed offshore...with mainly just drizzle
and isolated light rasn showers expected through around 10-12z. With
temperatures at freezing at kswf potetnial exists for -fzdz through around
IFR/MVFR conds are expected to gradually improve from west to east after
11-13z...with VFR should return to all terminals by 15z.
Moderate confidence in wind forecast. Isolated gusts around 20 knots
possible at klga/kewr through early morning. Winds/gusts diminish
Outlook for 06z Sunday through Wednesday...
tonight and sun...VFR.
Sun night...IFR. Snow...then snow/sleet/rain near the coast and
snow/sleet across interior.
Monday...IFR. Rain. Wintry mix across interior early...then rain.
Southeast winds 10-15 knots...becoming northwest late.
Monday night...wintry mix possible. West winds at or below 10 knots.
Tuesday...VFR. West winds at or below 10 knots.
Wednesday...VFR. West wind 15-25 knots.
northerly flow will result in Small Craft Advisory conditions on the ocean today. Winds
and seas will linger a bit longer off Montauk...so the Small Craft Advisory has
been extended through the evening for the eastern most ocean zone. Winds and
seas will remain blw Small Craft Advisory levels on sun with hipres over the waters.
Small Craft Advisory conditions likely to return Sunday night into Monday morning
onthe ocean and Li sound waters...possible elsewhere...ahead of an
approaching low pressure system. Winds should diminish by Monday
afternoon as the complex low pressure system works through the
region...but ocean seas should remain at Small Craft Advisory levels. Marginal Small Craft Advisory
winds are possible in the wake of the low Monday night/early
Tuesday...mainly on the ocean. The next time of concern will be
Tuesday night through Wednesday with gale conditions possible as
an Arctic front crosses the waters.
widespread significant precipitation is not expected through the day on sun.
A storm system could bring around half inch to an inch liquid
equivalent to the hydrologic service area...from late Sunday
afternoon through Monday night.
due to interference issues with the U.S. Coast Guard
emergency broadcast channel...the New York City National oceanic and atmospheric administration all hazards
weather radio station kwo35 remains out of service. The National
Weather Service is working with several U.S. Government agencies
to isolate and resolve this technical problem.
During this time...the transmitter may be returned to service
intermittently for use of the National oceanic and atmospheric administration all hazards weather radio
during potentially dangerous weather situations...for routine
weekly tests of the warning system...and to determine if the
interference issue has been resolved.
Marine...Small Craft Advisory until 1 PM EST this afternoon for anz353-
Small Craft Advisory until midnight EST tonight for anz350.