449
FXUS61 KOKX 212359
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
659 PM EST Tue Jan 21 2025
.SYNOPSIS...
High pressure continues to build in from the west through
Wednesday, and will be in control for late this week as low
pressure passes well offshore on Thursday, and again late Friday
and Friday night. A weak cold front is expected to pass through
late in the weekend as another low develops offshore and tracks
well east of the region early next week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
-- Changed Discussion --
No significant adjustments with this update as mosaic / radar
reflectivity returns mainly aloft nearby. Trajectory continues
ENE so holding line with current PoPs with perhaps the eastern
tip of LI getting grazed with light precip for an hour or so
later tonight.
High pressure will be in place at the sfc, however the flow
aloft is backing some and turning cyclonic for the mid to late
evening as a shortwave embedded in the 500mb longwave trough
pivots through the region. At the same time, we`ll be in the
right- entrance quadrant of a strong upper jet streak, enhancing
lift. So although an area of low pressure will be centered
hundreds of miles to our south tonight, models show the northern
edge of snowfall brushing the vicinity of Long Island and SE CT
due to upper divergence with just enough moisture in the
atmospheric column. Given that about half of the global and
regional/hi-res models show snow reaching our land zones, PoPs
over our land zones have been capped at 50%. Should any snow
fall, accumulations would be very light and under an inch.
Regarding the cold, part of the challenge of forecasting low
temperatures and wind chills will be the northern extent of cirrus
associated with the potential snowfall near the coast. Areas
northwest of NYC would have the best shot at radiational cooling
with the better chances of a clear or mostly clear sky, light to
calm winds, and an existing snow pack. Have gone below guidance for
low temperatures here based on what occurred last night, but didn`t
want to stray significantly due to the cirrus uncertainty. This
yields minimum wind chills/apparent temperatures right around the
advisory threshold (-10) for mainly NW portions of Orange County,
but not enough coverage across the entire county for a Cold Weather
Advisory. Elsewhere, wind chills drop to 0 to 5 below for the
most part - short of advisory criteria.-- End Changed Discussion --
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
High pressure continues to build in, with its ridge shifting through
during Wednesday evening. Winds will slowly diminish in the
afternoon and become light and variable at times during the night.
Highs still well below normal in the upper teens to lower 20s. Cloud
cover once again adds some uncertainty regarding low temperatures
and minimum wind chills/apparent temperatures for Wednesday night.
Thinking clouds will have a little more impact on the temps this
time around, and with slight temperature moderation regardless of
clouds, wind chills will fall short of advisory thresholds once
again. Western Orange County would again be closest to reaching
advisory levels.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
With respect to the longwave pattern across North America, a mean
ridge position centered just off or right along the west coast and a
mean trough centered in the East is progged to prevail through early
next week. The mean trough should lift some to the north and be
centered more across the Mid Atlantic and Northeast for the weekend
and into the start of next week.There is excellent agreement for the
most part among the global deterministic suites of the GFS, ICON,
CMC, and ECMWF at 500 mb regarding longwave positioning, along with
the more specific shortwave features.
With regard to the details, high pressure should prevail at the sfc
to begin the period on Thursday despite shortwave energy pivoting
through the region. The energy will be sheared as the trough will be
somewhat positively tilted which has been a recurring theme much of
this winter season thus far. Any positive vorticity advection should
be short lived and should progress quickly offshore, thus the
offshore development of low pressure Thursday afternoon and night
with just some mid or high level clouds expected. A similar
occurrence repeats into Friday and Friday night with a second strung
out shortwave, this one from a more southern source. Kept PoPs
minimal as the confidence remains higher than average for things to
remain primarily dry as the models keep energy locked up in a more
less closed off feature in the southern branch of the jet stream
over the SW US. If the models are handling this poorly then perhaps
any of these offshore systems could theoretically track further west
and closer to the coast, however this seems very unlikely given
model / ensemble consistency and spread.
A reinforcing shot of cold air arrives early next week with a cold
frontal passage. This front will have little to no moisture to work
with as it will be northern branch based. Thus have kept PoPs
minimal to slight chance PoPs for late Sunday into early Monday.
Otherwise dry, with temperatures continuing to average mainly below
normal. Temperatures do try to recover closer to the seasonal
averages Saturday night through Tuesday, however there is increasing
uncertainty around temperatures late in the period as the northern
branch may dive further south than some of the deterministic guidance
is indicating, along with some northern shortwave timing
differences.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
High pressure builds in, moving overhead late Wednesday.
VFR. W to WNW flow shifting to the NW this evening and
overnight persisting through much of Wednesday. Winds speeds
will be 10 kt or less through the forecast period and may
become light and variable late day as the high moves overhead.
Some high and mid level clouds before clear overnight.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
No unscheduled AMD expected.
.OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY...
Wednesday night through Friday: VFR.
Saturday: VFR. W winds 10-15G20kt NYC metro/coastal terminals.
Sunday: VFR. W gusts 20 kt.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
A shortwave passing through and subsequent cold air advection
tonight may kick up wind gusts for a few hours. Most of the night is
expected to feature winds below advisory criteria, but there may be
a few hours where gusts may occasionally reach 25kt on the ocean.
Will mention this in the forecast, but hold off on putting up an
advisory. Winds slowly diminish through the day Wednesday and may
become light and variable for a time during Wednesday night as a
ridge of high pressure pushes into the region.
A period of marginal small craft gusts are possible on the ocean
waters towards Thursday night, otherwise conditions should remain
below small craft criteria for the first half of Saturday on all
waters. For the second half of the weekend the likelihood of small
craft conditions begins to increase.
&&
.HYDROLOGY...
No hydrologic issues are anticipated throughout the entirety of the
forecast.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...JC/JE
NEAR TERM...JC/JE
SHORT TERM...JC
LONG TERM...JE
AVIATION...JP
MARINE...JC/JE
HYDROLOGY...JC/JE