825
FXUS61 KOKX 040021
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
721 PM EST Fri Jan 3 2025
.SYNOPSIS...
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Low pressure continues to weaken across eastern Canada tonight.
Meanwhile, another low rapidly develops well south and east of
the region tonight, moving towards the Canadian Maritimes this
weekend. High pressure will remain south and west of the region
this weekend. A quick moving low pressure system passes through
the Mid Atlantic on Monday and offshore Monday night. Behind it,
strong Canadian high pressure builds in from the west through mid
next week.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Longwave troughing continues to be anchored by a large scale
closed upper low over Quebec tonight. The latter of which well
send a northern stream shortwave across the area tonight. At
the surface, a cold front will pass through this evening, with
surface low development taking place well south and east of the
region.
There remains a potential for a few flurries/isolated snow
showers, with shortwave trough/cold frontal passage this
evening. Localized dusting possible with any snow shower
activity.
Otherwise, after a brief weakening of the pressure gradient
this evening, breezy conditions (occasional gusts 25 to 30 mph)
redevelop late tonight with tightening pressure gradient and
shot of CAA in wake of shortwave/cold frontal passage and with
rapid deepening of departing low pressure.-- End Changed Discussion --
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY NIGHT/...
* Light snowfall (Coating to 2") possible Monday, particularly
for southern portions of the region (40-60% prob), as low
pressure passes to the south. Travel impacts possible to the
Monday AM and Monday afternoon commute.
* Small deviations in track would increase/decrease snowfall
amounts by a few inches.
Good model agreement in longwave troughing continuing across
the NE US Saturday, anchored by deep closed low over Quebec.
This then gets sheared by developing intense closed low heading
towards NewFoundland Sunday. The evolution of the NewFoundland
closed low and interaction with original closed low Sunday Night
into Monday will play high sensitivity to track/intensity of a
vigorous shortwave (and downstream ridging) ejecting into the
Central Plains Sunday and to the Mid Atlantic coast by Monday.
Before then, deep NW/W flow between Canadian Maritimes low and
high pressure well to the SW through the weekend. CAA continues
on Saturday in wake of the cold front (NW gusts 25 to 35 mph,
peak 40 mph) with temps about 5 degrees below seasonable (lower
to mid 30s). CAA neutralizes on Sunday with winds similar to or
just slightly weaker than Sat. Continued westerly flow and
shallower mixing will have highs once again 5 degrees below
seasonable (lower to mid 30s). Dry conditions through the
weekend, but some snow flurries possible Sat aft/eve with weak
shortwave energy moving through and brief extension of lake
effect streamers.
As mentioned above, the forecast sensitivity for potential snow
on Monday lies with the complex interactions between multiple
upper level features. This in turn will be the determining
factor to the track, timing, intensity of secondary low pressure
developing along southern Mid Atlantic coast Monday and then
tracking southeast of the region Monday Night. Deterministic
med range models and their ensembles are in good agreement with
low pressure tracking well south (50 to 250 miles) of the 40/70
lat/lon benchmark, which typically keeps significant
accumulating snowfall south of the region. In addition, a good
signal for moderately strong frontogenetic forcing to the north
of the low, which will make for a sharp northern gradient
between few to several inches of accumulating snow and little to
no snowfall. Central agreement is for this banding to occur
from southern NJ down to the Mid Atlantic, with spread as far
north as central NJ. Probability at this time of this heavy snow
banding to working into southern portions of the local region is
at less than 10%.
With that said, the primary New Foundland closed upper low that
will be a driver for the Monday system does not really get
going until the next 18 to 24 hrs. WPC/CSTAR ensemble
sensitivity analysis indicating a farther east Newfoundland low
would allow for greater downstream ridging across the NE and a
further north track. This is a low probability solution (15-20%
ensemble membership at this point), but only represents a
northward track shift of 50 miles. Similarly a further west or
deeper New Foundland low would result in a further south track
to low pressure (60% ensemble membership at this point), with
little if any snow accum locally. This should be better sampled
and resolved by model guidance over the next 24-48 hrs.
So at this point, forecast aligns with NBM/WPC ensemble means,
with central forecast of 1 to 2 inches across NE NJ/NY metro and
W/C LI, and dusting to an inch for Low hud and S CT. Reasonable
high end forecast (10th percentile) of 3 to 5" for southern
areas (less to the north) and reasonable low end (90th
percentile) of no snow. Snowier solutions present potential for
light snow to develop for the Mon AM commute for NYC/NJ metro
and surroundings and likely tapering off before evening commute.
Again, monitor forecasts through the weekend for the latest.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
Key Points:
* Dry, cold and windy conditions are expected through the entire
long term period.
Low pressure continues to pull away Tuesday to the northeast. This
low looks to interact with another low in eastern Canada and then
remain in place through the end of the week. Meanwhile, high
pressure will be in place to our west and southwest. This puts the
area in a tight pressure gradient and will result in a persistent
gusty northwest flow. Blended in the NBM 90th percentile winds
and wind gusts to bump up and better match global guidance. For
now, it looks like a period of widespread 20 to 30 mph gusts,
but this could trend up a bit.
For temperatures, the NBM deterministic temperature guidance was
closer to the NBM 90th percentile temperatures. Went with a
blend of the 50th and 75th as well as raw model data to bump
temperatures down a few degrees. Highs Tuesday through Thursday
look to be in the upper 20s to low 30s. Lows each night look to
be in the mid teens to low 20s. Given the winds though, wind
chill values likely don`t get out of the teens Tuesday through
Thursday and could be as low as below 0 Wednesday night (mainly
across the interior).
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
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A cold front pushes through this evening. A sprawling area of low
pressure remains centered well to the north providing a W to NW flow.
VFR through the TAF period.
Winds veer more towards the NW tonight with winds redeveloping
to 15g25kt. Winds and gusts increase Saturday morning, and
toward 18Z some peak gusts may be as high as 35-39kt.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Gusts redevelop late tonight 05Z/06Z and may begin an hour or two
later than forecast.
Occasional gusts up to 40kt possible Saturday afternoon.
OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY...
Saturday night: VFR. W winds 7-15kt, gusts 20-25kt at times,
especially along the coast.
Sunday: VFR. W gusts 20-25kt. MVFR with a chance of light snow at
the NYC metro terminals toward Monday morning.
Monday: IFR at the NYC metro terminals and KISP with snow. MVFR, IFR
possible, with light snow at the other terminals.
Tuesday: VFR. WNW winds 15-20kt, gusts 25-30kt.
Wednesday: VFR. W gusts 20-25kt.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
SCA conditions expected all waters through Sunday, outside of a
brief lull in SCA cond for nearshore waters this evening with
passage of a weak cold front.
SCA conditions should briefly abate on the ocean Sunday night
and Monday as low pressure track well to the south, before
returning Monday night or early Tuesday as NW flow increases
with persistent cold advection.
Small Craft Advisory conditions expected Tuesday through the end of
next week for all waters. There could even be some periods of gale
force gusts in there, but it is too far out to narrow down a time
window for that. Given the consistent northwesterly flow, seas on
the ocean likely rise to 7 to 8 feet by mid to late week. Waves on
the LI Sound may also reach 5 to 6 feet, especially closer to the
Suffolk County coast.
&&
.HYDROLOGY...
No significant hydrologic issues anticipated through the end of
next week.
&&
.TIDES/COASTAL FLOODING...
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Low probability for water levels to approach minor flood
thresholds for vulnerable coastal communities with the Monday
Night high tide. This will be contingent on further north
solution with a low pressure passage.-- End Changed Discussion --
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 7 PM EST Sunday for ANZ331-332-335-
338-340-345-350-353-355.
&&
$$
SYNOPSIS...JT/NV/DW
NEAR TERM...NV/DW
SHORT TERM...NV
LONG TERM...JT
AVIATION...JE
MARINE...JT/NV
HYDROLOGY...JT/NV
TIDES/COASTAL FLOODING...