Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
711 PM EST sun Dec 21 2014
high pressure remains northeast through Monday night as low pressure
approaches from the south. High pressure remains northeast
through Monday night as low pressure approaches from the south.
The wave of low pressure weakens while moving north Tuesday and
Tuesday night. A more significant storm system affects the area
Tuesday night through early Christmas day with a cold front
passing through late Wednesday night into Thursday morning. High
pressure builds in late Thursday through Friday. A weak cold front
moves through dry Saturday. Another low approaches from the south
Near term /until 6 am Monday morning/...
challenging forecast due to subtle weak features...and ample low
level moisture present.
Models are in general agreement as upper shortwave departs to the
east...with ridging expected late tonight. Surface trough over the
eastern zones lingers into tonight...and global models do output
light quantitative precipitation forecast through much of the overnight.
If precipitation does indeed occur...this may become problematic with
regard to precipitation type forecasting.
Surface temperatures are expected to hold steady or fall slightly tonight.
As mentioned...moisture is rather shallow...and there is a concern
that any precipitation later this evening and into the overnight
that does fall will be liquid. If so...scattered sprinkles/drizzle
could freeze on contact with the cold surface where temperatures fall
below the freezing mark.
Otherwise...if moisture is deep enough to support snow...very
light snow or flurries will be the result.
However...complicating things is that temperatures through 850 hpa or so
warm slightly as the night progresses. So even if moisture is deep
enough to support snow producing processes...any precipitation may
change over the rain anyway as the night wears on.
Otherwise...clouds likely linger through the night...but these low
clouds could break up somewhat as ridge builds.
Temperatures are a blend of latest MOS and forecast database.
Short term /6 am Monday morning through Monday night/...
upper ridge builds ahead of digging middle west trough. High pressure
remains anchored over the Canadian Maritimes through Monday night.
A weak area of low pressure develops along a warm front off the middle
Atlantic...drifting northward toward the area.
Weak low level lift will result in chance probability of precipitation for light rain
through the period. Do not expect real high coverage at this time.
Temperatures warm into the middle 30s Monday across the interior...with
lower to middle 40s expected near the coast. These temperatures likely
remain steady Monday night due to east flow and cloudy skies.
Long term /Tuesday through Sunday/...
weak low to the south continues to weaken Tuesday as a warm front
develops associated with a deepening low over the Midwest and lower
Mississippi River valley. All guidance does not maintain a closed
circulation as previously forecast. Otherwise there is generally
consistency with the midwestern low deepening and tracking northward
Tuesday night through Thursday morning as the full latitude upper
trough becomes negatively tilted. Only change has been a slightly
slower cold frontal passage across the region. Currently forecast to
come through just after 06z Thursday...and clear the eastern zones
just after 12z Christmas day. Also...both the GFS and European model (ecmwf) profiles
are slightly warmer than yesterday and all rain is expected for the
With a strong low level jet late Wednesday into Wednesday night and
strong lift periods of heavy rainfall can be expected. Also there
will be a deep influx of Gulf of Mexico and Atlantic moisture ahead
of the trough. Up to 2 inches will locally higher amounts will be
possible. See hydrology section.
In the colder air behind the front Thursday winds and gusts increase
but are expected to remain below advisory levels.
High pressure builds in for Friday. Then a weak cold front crosses
the region Saturday...however the passage is expected to now be dry.
A wave of low pressure develops on the front across the Gulf Coast
states later Saturday and tracks north Sunday bringing the next
chance of precipitation. The storm will be inland and the area will
be on the warm side with all liquid precipitation expected.
Aviation /00z Monday through Friday/...
weak surface trough across the area and low-level moisture trapped
beneath an inversion will result in widespread MVFR conditions
through Monday...with even some locations being IFR. Latest Sat
imagery is indicating some of slight clearing across the area...so
conds may tempo increase to VFR for a few hours this evening. They are
expected to come back down however. There is also low confidence in
the timing of conds dropping to IFR.
Pockets of light rain/drizzle/snow will possible through the evening
due to the aforementioned trough...mostly east of the NYC terminals.
A weak northerly flow at less than 10 knots gradually veers around to east/NE
by Monday after.
Outlook for 00z Monday through Friday...
Monday night...IFR possible in east flow and rain.
Tuesday-Tuesday night...IFR likely in rain. East winds 10-20 knots...becoming
Wednesday...high impact event becmg likely. IFR with +ra. S/southeast winds
15-20g20-25kt. Winds shift to the SW late Wednesday night.
Thursday...VFR conds returning by afternoon. -Shra in the morning. West winds
light northerly winds continue tonight...slowly shifting east as
high pressure remains well northeast of the waters. A weak area of
low pressure develops off the middle Atlantic coast and drifts northward
toward the waters Monday and Monday night. East winds increase
slightly but should remain below Small Craft Advisory thresholds.
Seas remain 4 feet or less over the ocean waters through Monday night.
A persistent easterly flow into Tuesday will allow for seas on the
ocean waters to build to small craft levels ahead of an approaching
warm front. Wind and gusts are expected to remain below advisory
levels Tuesday into Tuesday night.
A deepening low pressure system over the Midwest Wednesday will
result in an increasing southerly flow and wind and gusts will
increase to small craft levels across all the waters by late
Wednesday. Then Wednesday night the wind gusts on the ocean increase
to gale force.
A cold front associated with the low passes through the waters late
Wednesday night into early Thursday morning. Southerly wind shifts
to the west to northwest and becomes very gusty in the colder air.
Gale force gusts will become likely across all the waters during
Thursday and then subside to below gale force Thursday night...and
possibly below small craft during Friday as high pressure builds
A weak cold front comes through dry Saturday...and wind and sea are
likely to be below small craft level.
no significant precipitation is expected through Monday...mainly
just light amounts.
Rainfall from Monday afternoon through Thursday morning could total
1 1/2 to 2 inches with locally higher amounts. Much of the rainfall
is expected to occur Wednesday into Wednesday night. Minor urban and
poor drainage flooding is possible.
Dry weather returns Thursday afternoon through Saturday night.