138
FXUS61 KOKX 210249
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
949 PM EST Mon Jan 20 2025

.SYNOPSIS...
High pressure will gradually build in from the west through
midweek. The high will move over the local region Wednesday
night and then offshore on Thursday. A low pressure system then
travels offshore Thursday night into early Friday. High pressure
returns thereafter into Saturday and then moves offshore Sunday.
Low pressure approaches Sunday night into next Monday with an
accompanying cold front moving across.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Temperatures across outlying areas were a few degrees colder
than the previous forecast. With mostly clear skies (except
across eastern portions of southern CT and the Twin Forks of
Long Island) as well as a fresh snow pack, expect temperatures
to continue to fall through the night. Therefore, lowered
minimum temperatures a few degrees across the outlying areas as
well, with locations well inland seeing subzero lows tonight
(KMGJ was already down to 2 degrees at 9 pm, so there is the
potential for even colder than what is currently forecast).
Otherwise, forecast is on track.

An upper trough dominating eastern North America will result in
the coldest airmass thus far this winter season. Deepening low
pressure lifts north of the Canadian Maritimes tonight, while
arctic high pressure over the Plains bleeds eastwards across the
Mid Atlantic states. This will result in a gradually weakening
WNW flow. Some instability stratocu this evening will eventually
dissipate. While there is a snowpack and anomalously cold
airmass across the region, radiational cooling will be limited
by 5-10kt of wind. If some locations do decouple, lows could
drop to around zero across the interior and the Pine Barrens
Region of LI. For the time, expect lows in the single digits
inland and 10 to 15 along the coast.

In terms of zone averages, wind chill values are expected to
remain short of cold weather advisory criteria, which is -10
degrees F or lower for all but LI and the metro NYC, where it
is -5 degrees F or lower. Values will not be too far off.
Isolated locations could reach -10 degree to -13 degree wind
chills across parts of the interior and could reach -5 degree
to -9 degree wind chills along parts of the coast outside of
NYC. However, most wind chills expected to be around zero
degrees along the coast and from near zero to -5 degrees across
the interior.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Another piece of energy pivoting eastward through the longwave
upper trough will lift across the Northeast Tuesday night into
Wednesday. This will maintain an airmass that is about 10-15
degrees below normal with highs in the upper teens to around 20
both Tuesday and Wednesday, with lows Tuesday night near zero
inland, single digits at the coast, and around 10 for the NYC
metro. This will be another night that optimal radiational
cooling will be limited by winds staying up just a bit and a
period of cloudiness to start the night. The backing of the
upper flow ahead of the incoming upper trough will expand the
cloud shield north and west of a frontal system well offshore
during the daytime hours Tuesday. Expect partly to mostly cloudy
skies by afternoon. There is a chance that some anafrontal
precipitation offshore could work close to the east end of LI
for a low chance of light snow during the evening hours Tuesday.
This chance will be short-lived though as the clouds will work
quickly back offshore during the late evening into early morning
hours as the upper trough axis approaches. The latter of which
will send a reinforcing cold air into the region for Wednesday.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Main jet stream south of the region and mid level trough in the
Northeast will remain in the regional weather pattern Wednesday
night through Friday night. The pattern shifts thereafter to more
zonal aloft and less of a trough structure going into the weekend. A
shortwave trough approaches next Monday.

At the surface, the arctic cold airmass across the region midweek
will begin to moderate towards the end of this week. The low level
winds weaken midweek and then more of a SW flow develops.
Temperatures first get to near to above freezing for some eastern
parts of the region Thursday and then much of the region Friday.
Temperatures rise more into the 30s this weekend into next Monday,
potentially reaching lower 40s on Sunday and for next Monday.

Regarding the low temperatures, much of the region in single digits
to teens Wednesday night and Thursday night, followed by mostly in
the teens Friday night. For the nights thereafter, lows forecast are
more in the 20s for a majority of the region. While winds will be
light, wind chills still will be several degrees less than actual
temperatures. Some sub-zero wind chills in the forecast Wednesday
night across parts of the interior with otherwise single digits to
near 10 for Wednesday night, Thursday night, and Friday night for
much of the area. Wind chills mostly in the teens for the nights
thereafter during the weekend for the local region.

An area of low pressure passes offshore Thursday night. This is
expected to remain far enough offshore but some forecast models show
a closer approach, bringing a slight chance of snow along the
southeast coastal sections of the local region Thursday afternoon
into Thursday night. Mainly dry conditions are expected however.

Another surface low pressure area approaches from the west next
Monday along with an accompanying cold front. There are timing
differences between forecast models with the timing and movement of
the low pressure and front. This will allow for a another slight
chance of snow as wet bulb cooling and thicknesses show more snow
compared to rain. However, forecast models do not have much moisture
associated with the front, with some models keeping the area dry.

Max temperature forecast on Thursday, NBM/NBM50 blend, which is
slightly cooler than NBM. Otherwise, NBM followed for the
temperature forecast during the long term.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
VFR as high pressure builds from the west.

W to NW flow at 10 to 15 kt in the metro terminals through about
05Z, then 10 kt or less for the remainder of the forecast
period. An isolated gust to 20 kt is possible through this time
frame as well. Otherwise, winds will remain W to NW through the
forecast period at 10 kt or less.

 ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...

No unscheduled AMD expected.

.OUTLOOK FOR 00Z WEDNESDAY THROUGH FRIDAY...

Tuesday night through Friday: VFR.

Saturday: VFR. W winds 10-15G20kt NYC metro/coastal terminals.

Detailed information, including hourly TAF wind component
forecasts, can be found at: https:/www.weather.gov/zny/n90

&&

.MARINE...
WNW winds will gradually diminish through this evening with SCAs
only remaining for the ocean, where there are some residual
higher seas. Non-ocean zones expected to remain below SCA
thresholds tonight. The ocean SCA remains in effect through all
of tonight and into very early Tuesday. High pressure will then
continue to gradually build in with sub-SCA conditions through
midweek for all waters.

Expecting well below SCA criteria with weak pressure gradient and
high pressure moving overhead Wednesday night into Thursday for
all waters. Return SW flow develops thereafter with continued
sub-SCA conditions for all waters. Forecast has a potential
return to SCA conditions across the ocean waters for the
weekend, more probable for Sunday. Otherwise, sub-SCA conditions
will continue for non-ocean waters.

&&

.HYDROLOGY...
No hydrologic issues anticipated.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 7 AM EST Tuesday for ANZ350-353-355.

&&

$$

SYNOPSIS...JM/DW
NEAR TERM...JM/JP/DW
SHORT TERM...DW
LONG TERM...JM
AVIATION...JP
MARINE...JM/DW
HYDROLOGY...JM/DW