921
FXUS61 KOKX 182248
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
548 PM EST Tue Feb 18 2025
.SYNOPSIS...
-- Changed Discussion --
High pressure builds to the southwest of the region through
Wednesday. Deepening low pressure along the Mid Atlantic coast
Thursday will pass well south and east of the area through Thursday
night. High pressure will then continue to dominate through the
weekend. Weak low pressure approaching from the Great Lakes may
then affect the region Monday night into Tuesday.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
-- Changed Discussion --
The forecast is mainly on track. Only minor adjustments to
hourly temperatures and dewpoints were made with this update.
Confluent zonal upper flow aloft across the region, with broad
sheared polar trough extending from the northern plains to
northern New england. At the surface, the tight pressure
gradient slowly relents as high pressure builds towards the Mid
Atlantic and large Canadian Maritimes low pressure lifts towards
Greenland.
Pressure gradient will gradually weaken tonight as a result, with
gusts falling back into the 15 to 25 mph range. Low temperatures
will fall into the single digits far interior, to teens along
the coast, with min windchills in the single digits city/coast
and single digits degrees below zero across the interior.-- End Changed Discussion --
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
* Model consensus continues to point towards deepening low
pressure tracking well south and east of the region Thursday,
with a light dusting of snowfall the most likely scenario in
response to approaching vigorous closed upper low.
Confluent and zonal upper flow gradually amplifies Wed into Wed
night ahead of a deepening northern stream closed low digging
through the upper Mississippi River Valley and into the Ohio Valley.
Good agreement on this vigorous closed low sliding just south
of the region late Thursday into Thursday Night. Meanwhile a
southern stream shortwave across the Lower Mississippi River
Valley Wed AM (bringing snow to the southern plains and Mid
Mississippi River Valley today) races towards the Mid Atlantic
coast by Wed eve, with a second southern stream shortwave racing
around the digging northern stream closed low to the southern
Mid Atlantic coast by Thu AM.
As has been the case over the last 48 hours, overwhelming
deterministic/ensemble model consensus is that the two streams
never partially or completely phase until they are both well
east of the region. The result is very good agreement in
southern surface low pressure tracking to the SE US coast late
Wednesday, and then intensifying as it tracks northeast and
offshore Thursday into Thursday Night, 300- 450 miles se of Long
Island. The result being that most if not all the precip shield
with the offshore low remains to the SE of the region (perhaps
clipping SE LI THU AM). The potential for a period of light snow
or snow shower activity will be more-so coincident with the
approach/passage of the vigorous upper low and some moisture
convergence along weak inverted troughing Thu aft/eve.
The few exceptions to this consensus are the 12z 32/12km NAM
deterministic runs, which although fairly similar in upper
dynamics through daybreak Thu AM, rapidly develop surface low
pressure with an abrupt jog about 150 miles close to the coast
THU AM compared to rest of model guidance. Interestingly this
is not seen in the high- res 3km NAM CAM. A possible reason for
the outlier NAM 12km/32km NAM surface solutions may be the
convective parameterization schemes used in these runs (and not
the 3km NAM) firing off abundant convection as the 150kt+ upper
jet streak overspread the gulf stream and general low position.
The 12z 32/12km NAM solutions, for reference bring close 1/4"
to 1/2" liquid to the coast (around 4 to 7" snowfall), but for
the above mentioned reason and lack of support this scenario is
considered an outlier.
The 18z NAM has trended further south and less intense with the
surface low, but still indicating potential for a widespread
1/10th to 1/4" qpf along the coast. This downward trend, in
line with consensus guidance, is anticipated to continue over
the next 24 hrs, but it is worth noting that this solution falls
in line with other reasonable worst case scenarios. The source
of enhanced snowfall appears to be coming from enhanced lift
from the left front exit region of a more cyclonically curved
jet streak and NW enhancement of offshore low pressure precip
shield. Outside of the 18z NAM 12km/32KM, a few 12z SREF NMMB,
GEFS, and ECE members indicate some snowfall solutions in the 3
to 5" range for eastern LI and extreme SE CT, in line with a
reasonable worst case scenario.
So, current thinking is potential for a period of light snow or
snow showers Thu afternoon into Thursday evening in response to
the deepening closed low and weak inverted trough in vicinity.
Snow accumulation generally less than an inch areawide, with
potential for an inch or so for extreme SE portions of the area
where fringe of offshore snow shield may glance. Reasonable
worst case WPC WSE and NBM (1 in 10 chance of occurrence),
capturing 18z NAM 12/32km and other outlier ensemble members,
would be a 2-5" snowfall across eastern LI and SE CT.
Remaining cold, region largely sub freezing with highs in the mid
20s interior and upper 20s to around 30 city/coast on Wed and Thu.
Winds are expected to be lighter than previous days with the high
more established and a relaxed pressure gradient in response.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
Remaining somewhat breezy on Friday as high pressure continues to
build in from the west. Dry conditions with high temperatures 5-10
degrees below normal - in the lower and middle 30s. The high
pressure ridge is expected to reach the east coast on Saturday.
Winds will be light and shift west to southwest, allowing for milder
high temperatures, but still a little below normal.
A weak trough aloft shifts through the region late Saturday night
into Sunday with perhaps some weak surface reflection. Moisture is
lacking, and will go with a dry forecast for this period, however a
sprinkle or flurry isn`t completely out of the question. High
temperatures on Sunday finally returning to normal at 40-45.
Weakening low pressure shifts east from the Great Lakes Region,
likely passing to our north at some point Monday night into Tuesday.
A leading warm front and trailing cold front may support enough lift
to bring us some precip. Capped PoPs at slight chance for the time
being. Precip would be mainly rain for coastal areas and a mix of
rain and snow inland.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Strong high pressure gradually builds in from the west through
Wednesday.
Winds will be W to WNW around 20 kt with gusts 30-35 kt this evening
before gradually diminish tonight. Gusts to around 20 kt may then
briefly be possible after sunrise Wednesday morning before gradually
subsiding into the afternoon.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
No unscheduled AMD expected.
.OUTLOOK FOR 21Z WEDNESDAY THROUGH SUNDAY...
Wednesday night: VFR.
Thursday: Mainly VFR. Chance MVFR or lower in light snow, mainly for
the terminals east of NYC. NW winds G20-25kt at night.
Friday: VFR. NW winds G20-25 kt.
Saturday: VFR.
Sunday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
-- Changed Discussion --
Winds expected to fall below Gale across eastern ocean waters
later this evening, with conditions falling below SCA late
tonight on nearshore water and Wed AM for the ocean waters.
Ocean seas (NW Wind wave dominated) expected to follow suit and
fall below SCA Wed AM as well.
Light freezing spray possible everywhere through Wednesday
morning as well, but not anticipating it to be heavy enough to
necessitate an advisory.
Next chance of SCA conditions late Thursday into Friday in wake of
rapidly deepening offshore low pressure as it tracks northeast up
into the North Atlantic.
Advisory conditions continue through Friday for all waters,
then will be limited to mainly the ocean through Friday night.
Sub advisory conditions then prevail through the upcoming
weekend with a weaker pressure gradient as a high pressure ridge
is followed by a weak trough.-- End Changed Discussion --
&&
.HYDROLOGY...
No hydrologic impacts are expected through the week.
&&
.TIDES/COASTAL FLOODING...
Low water conditions expected to improve for the evening low tide (
1 to 1.5 ft below MLLW) as offshore winds weaken a bit. Further
improvement expected with Wed high tides with continued
weakening of winds and rising of astro low tides.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 7 AM EST Wednesday for ANZ331-335-
338-345.
Small Craft Advisory until 10 AM EST Wednesday for ANZ332-340.
Gale Warning until 10 PM EST this evening for ANZ350.
Small Craft Advisory until 1 PM EST Wednesday for ANZ353-355.
&&
$$
SYNOPSIS...JC/NV
NEAR TERM...NV
SHORT TERM...NV
LONG TERM...JC
AVIATION...MD
MARINE...JC/NV
HYDROLOGY...JC/NV
TIDES/COASTAL FLOODING...