355
FXUS61 KOKX 172300
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
600 PM EST Fri Jan 17 2025
.SYNOPSIS...
High pressure slides offshore tonight, followed by a frontal
boundary towards late Saturday into Saturday night. A wave of low
pressure develops along the Mid Atlantic coast on Sunday and pushes
northeast into Sunday night. Low pressure departs to the northeast
on Monday with a strong arctic high pressure system building into
the area through the middle of next week. Another low pressure
system may approach late in the week.
&&
.NEAR TERM /THROUGH SATURDAY/...
-- Changed Discussion --
No major changes to the forecast with this update as it`s mainly
on track. Only bumped up cloud cover for the next few hours
based on satellite trends.
A high pressure ridge nosing up from the south begins to get east
tonight. This gets the region on the western side of the ridge axis
later tonight with a weak return flow setting up out of the WSW.
Initially at the start skies should be fair to mostly clear.
Temperatures will fall some this evening, especially in more
sheltered location where the winds will be lighter to calm and less
cloud cover for the first half of the night. However, with a milder
airmass in place compared to the previous few days there will be a
lid sort to speak on how much temperatures can fall as dew points
only bottom out in the 20s. Therefore look for temperatures to only
fall to around freezing in the metro locations, with mainly middle
and upper 20s in most outlying locations. Upper and mid level clouds
will begin to filter in later at night.
For Saturday look for mostly cloudy skies for the morning, but it
should be dry for a good portion of the day. PoPs will begin to
increase in the afternoon as cold front off to the west begins to
draw closer. Any lift initially will be driven by some moderate PVA.
A milder southerly flow increases during the day which should get
temperatures well into the 40s closer to the coast, and closer to 40
for the northwestern interior sections. NWP is suggestive that the
main batch of precipitation breaks out ahead of the cold frontal
boundary for the afternoon and evening bringing showers into the
region. Temperatures will be warm enough for all precip to be in the
liquid form.-- End Changed Discussion --
&&
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
A winter storm is likely to impact the region Sunday into
Sunday night. A winter storm watch has been issued for much of
the northern and northwestern interior portions of the area.
Any PVA shuts off with NVA ensuing towards and after 0z.
Therefore any light rain should end by the mid to late evening
as thermal advection will be weak. PoPs thus lower as the night
progresses as the region gets in-between 2 systems. The front
appears to go through some frontolysis / weakening as it is
projected to cross through the area late Saturday night. Thus a
milder SW flow should persist through the evening hours. A
mostly cloudy night is expected, however some breaks may develop
later at night. Colder air is expected to gradually bleed into
the region from the west towards early Sunday morning.
Temperatures will fall back to seasonable levels with middle 20s
to lower 30s.
Then all eyes turn to a wave of low pressure moving across the lower
Appalachians Sunday morning, then ENE to the Mid Atlantic coast
later Sunday. Uncertainty remains high with mid level and the sfc
low track / position, and thus high uncertainty around location
specific temperature profiles. And this leads to high uncertainty
around the derived liquid and frozen precip amounts. One big
question right off the bat is how much sfc cold air can get all the
way into the coastal plain for late Sunday morning as the wave of
low pressure to our south begins to spin up. Therefore some light
rain or a light wintry mix at onset towards mid day / early
afternoon for at least the eastern 1/3, maybe even the eastern 1/2
of the region. Further west profiles look cold enough for mainly all
snow, even at the onset. The higher PoPs and steadiest precip looks
to take place for the late afternoon and into the evening. The
system overall is quite progressive and this will keep liquid
equivalent amounts / QPF in check overall. However, at least half
inch liquid precip amounts are suggested by the majority of the high
res guidance, mainly from 18z Sun to 06z Mon. Thus a complicated
situation with the higher res guidance and even the global guidance
now having more precip over the colder mid level baroclinic zone
with arctic air attempting to press in from the west. The 500 mb
vorticity track is suggestive of a wintry mix and climatologically
speaking when you have the 500 mb vort bisect the region you often
don`t have an all snow scenario for the coast. However, the system
will be quite progressive and that offsets things some as the region
looks to be completely on the cold side of the upper level jet
dynamics. How much the cold air gets in determines precip type
across eastern most areas and snow ratios further inland. This
ultimately will determines liquid and subsequent snowfall totals.
With all this said a Winter Storm Watch has been hoisted for most
northern and northwester potions of the area. Thinking warning
criteria snow is looking more likely across NW portions of the area,
especially into most of the Hudson Valley and interior NE NJ, and
across northern sections of Fairfield, New Haven, and Middlesex
counties in CT for the potential for 5 to 8 inches of snow through
Sunday evening. Elsewhere there is the potential for advisory level
snow, and held off with any watches further east and southeast
across the area with an increasing threat of mixing with rain, or
perhaps just plain rain at the onset before a changeover to snow
towards evening.
The steadier precip shuts off fairly quickly towards midnight, say
(04-06z Mon) as the system moves quickly NE. Thus any precip / snow
tapers quickly for the overnight period. The shortwave feature lifts
further NE later at night and clearing should begin during the pre-
dawn hours, or at least towards daybreak from SW to NE. In any
event, the arctic air completely presses in towards the Monday
morning commute. Thus any moisture on surfaces and roadways will
freeze solid as temperatures plummet mainly into the teens and lower
20s and wind chills likely getting into the single digits to around
10 above.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
An arctic airmass filters into the region behind the departing storm
on Monday and lingers through the middle of next week with the core
of the cold air over us Monday night through Wednesday night. After
highs only in the 20s on Monday, highs will only be in the teens for
most spots Tuesday and Wednesday. Lows mostly in the single digits
for Monday night and Tuesday night, and only slightly higher for
Wednesday night. Adding to the chill will be gusty winds, which will
be the strongest during the daytime on Monday. Given the current
wind chill forecast, advisory criteria would be met for a good
portion of the forecast area Monday night with a little less
coverage for Tuesday night. Still plenty of time to see how things
trend before any headlines are issued to address this. Minimum wind
chills for both nights generally -5 to -15.
Regarding precipitation, it still appears that low pressure will be
passing well SE of the area during Wednesday. Models however show
precip stretching out well NW from the center of the storm, perhaps
owing in part to being in the right-entrance quadrant of a very
strong upper jet streak. Will leave in slight chance PoPs for snow
showers Tuesday night into Wednesday to account for this. The next
chance of precip otherwise could be as early as Friday with another
potential coastal low, which models vary regarding its track and
timing. Once again, PoPs have been limited to slight chance for the
time being. Temperatures should at least moderate Thursday and
Friday, with most of the area finally getting above the freezing
mark during Friday.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
High pressure builds in this evening from the south. Another frontal
system approaches from the west tonight and into Saturday, pass
Saturday afternoon.
VFR expected today and tonight. Ceilings begin to lower Saturday
late morning with MVFR or lower possible after 17-18Z Saturday with
rain.
Winds SW/SSW 5-10 kt through early evening. Winds become S tonight.
Speeds remain mainly at or under 10 kt through tonight time. Winds
may begin to gust 20 kt in the morning to midday tomorrow, sustained
10-15 kts. Winds then drop below 10 kts as the rain arrives around
17-18Z, remaining S.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Onset timing of MVFR ceilings and rain is around 17Z, but subject to
change by a few hours.
Potential for gusts tomorrow morning have been included in TAFs, but
its possible they could be more occasional.
.OUTLOOK FOR 21Z SATURDAY THROUGH WEDNESDAY...
Sunday: MVFR or lower with increasing chances of snow in
the afternoon and into the evening.
Monday: Mainly VFR, MVFR possible in the morning. NW wind gusts near
20 kt.
Tuesday: VFR. W wind gusts around 20 kt.
Wednesday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
A southerly wind gradually increase tonight, especially late out on
the ocean waters with small craft conditions developing. The small
craft on the ocean waters will carry through Saturday with gusts to
25 kt and seas approaching 5ft at times. More marginal small craft
conditions are expected along the south shore bays of LI. The winds
then switch to a more W direction with a cold front swinging through
Saturday night as any small crafts go away Saturday evening, and non-
advisory conditions continue through the day Sunday, although
visibilities will lower. Winds and seas begin to increase late
Sunday afternoon and evening with developing low pressure moving
closer. As the low pulls away Sunday night small craft conditions
should prevail across all waters with a gusty WNW behind another
cold front.
SCA conditions persist on all waters Monday with conditions falling
below advisory levels for most, if not all waters by Tuesday
morning. For Tuesday through Wednesday, mainly sub-SCA conditions,
however gusts on the ocean may be close to 25 kt from time to time.
Persistent winds above 15 kt with a frigid airmass in place may
result in the potential for freezing spray, especially on the ocean
where wave heights will be more elevated during Monday into Monday
night.
&&
.HYDROLOGY...
No hydrologic issues are anticipated for the weekend and into next
week through Friday.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Storm Watch from Sunday afternoon through late Sunday
night for CTZ005>007.
NY...Winter Storm Watch from Sunday afternoon through late Sunday
night for NYZ067>070.
NJ...Winter Storm Watch from Sunday afternoon through late Sunday
night for NJZ002-004-103>105-107.
MARINE...Small Craft Advisory from 4 AM to 6 PM EST Saturday for ANZ350-
353-355.
&&
$$
SYNOPSIS...JC/JE
NEAR TERM...JC/JE
SHORT TERM...JE
LONG TERM...JC
AVIATION...BR
MARINE...JC/JE
HYDROLOGY...JC/JE