okx-afd on 2025-01-18

094
FXUS61 KOKX 190032
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
732 PM EST Sat Jan 18 2025

.SYNOPSIS...
-- Changed Discussion --Low pressure will move across the area this evening, then slide
east tonight. Another wave of low pressure develops the Mid
Atlantic coast on Sunday and pushes northeast into Sunday night.
Arctic airmass builds in early into middle of next week with
high pressure building in from the west. A low pressure system
passes well offshore mid and late in the week. High pressure
will be more offshore towards the end of next week.-- End Changed Discussion --

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --Low pressure and associated cold front move across the region
this evening, then slide eastward overnight.

Forecast overall on track, but added some patchy fog with minor
adjustments to POPs for rain. Rain will continue across the
eastern portions of the forecast area across Southern
Connecticut and Long Island early this evening, then gradually
taper off mid to late this evening. Some patchy fog can be
expected, reducing visibilities down to around 2 miles in some
places this evening. This is expected until overnight when more
of a northerly flow develops and allows for some drying of the
low levels.

Behind the front, drier conditions are then expected as winds
back to the west and eventually northwest late. Lows tonight
will range from the middle 20s to lower 30s.-- End Changed Discussion --

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
*Winter storm Warnings and advisories are in effect.

Main focus will turn to a developing low pressure system over the
Mid-Atlantic on Sunday. As the low pressure system gradually
strengthens Sunday afternoon, moisture overruns the northern side of
the low and precipitation blossoms over the area. This will be aided
by large scale synoptic forcing over the area.

Despite confidence continuing to increase that a quick moving winter
storm will impact the region, there still remains questions to the
exact track of the low. Subtle changes to the track this system will
take, will also have impacts on the amount of snow we see.

Most of the 12z forecast guidance now has the low passing south and
east of Long Island. All the 12z GEFS members, which were closer to
the coast, shifted a bit south and east and the 12z NAM, which had
previously been further offshore, did shift a bit closer to the
area.

Overall, expecting precipitation to overspread the region as early
as late morning/early afternoon, with likely POPs by mid to late
afternoon through midnight. After midnight, the snow begins to taper
off and come to an end.

QPF amounts are generally going to range from 0.40 to 0.60. Expect a
swath of 5 to 7 inches, with locally higher amounts possible across
the interior. Closer to the coast, amounts will range 3 to 5 inches,
with locally higher amounts up to 6 possible. As a result, have
converted most of the winter storm watch to a warning. The only
exception was eastern Bergen County. Anywhere there was no watch and
eastern Bergen county, a Winter Weather Advisory is now in effect.
These headlines will start at 1pm Sunday and end at 4am Monday.

One area of concern was across the coastal locations, specifically
Long Island and portions of coastal Connecticut, where I felt
temperatures may have been too warm. I did lower temperatures here a
bit mainly to account for wet bulbing. If temperatures are
warmer than forecast, we may see more mixing or a slightly
longer period of rain before a change over to all snow occurs.

The low departs the area Sunday night with strong high pressure
building into the area.

.LONG TERM /MONDAY THROUGH SATURDAY/...
-- Changed Discussion --Main points

* Arctic cold airmass across the region with temperatures not
getting to freezing until Friday for most locations and not above
freezing for until next Saturday for most locations.

* Coldest high temperatures forecast for Tuesday and Wednesday when
highs only reaching upper teens to lower 20s.

* Coldest low temperatures forecast Tuesday night and Wednesday
night when lows plummet to single digits to lower teens for much
of the area. Some locations get to sub-zero low temperatures.

* Sub-zero wind chills forecast for Monday night, Tuesday night, and
most locations north and west of NYC for Wednesday night.
Wednesday night, along coast mostly a few degrees above zero for
wind chills.

Main jet stream stays south of the region much of the next week.
Northerly flow in the low to mid levels will help establish an
arctic airmass building in through much of the week. Highly
amplified trough stays in the Northeast. Potential moderation of
this airmass by Friday into start of next weekend with potential
upper level pattern shift with flattening trough in Northeast.

The core of this arctic airmass with coldest temperatures and wind
chills occurs in the early to mid part of the week. Forecast model
850mb temperatures down to near -20 to -23 degrees C Monday
through Wednesday. The forecast models show an increase in 850mb
temperatures Thursday near -5 to -10 degrees C.

ESAT from NAEFS shows standard deviations of -2 to -3 with the 850
to 500mb temperatures within the Monday through Wednesday timeframe
for the Northeast.

Main chance of snow Tuesday night into Wednesday along the coast
with peripheral precipitation from low moving well offshore.
This is accompanied with an area of mid level positive vorticity
advection. Would expect mainly dry conditions to prevail
however, considering how far away the low is. Another slight
chance of snow late in the week, Thursday night into Friday time
period with another low pressure area potentially tracking
nearby offshore.

Surface winds become lighter for mid to late week, allowing for wind
chills to become less of a factor. Eventual moderation of the
airmass is forecast as forecast high temperatures Thursday reach for
majority of region into the low to upper 20s, much of the region
near 30 for Friday, and then low to mid 30s for next Saturday.-- End Changed Discussion --

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
A weak frontal wave and/or warm front approaches from the
southwest into early this evening. A cold front then passes
through later tonight (03Z-06Z). Low pressure develops along
the Mid Atlantic coast on Sunday, passing to the southeast of
the area Sunday night.

MVFR/IFR with patchy VFR as rain exits the area. Widespread VFR
returns from about 02Z to 04Z after cold frontal passage with
W/NW flow less than 10 kt.

For Sunday, ceilings will lower to IFR/LIFR in snow during the
afternoon, persisting into Sunday evening. Winds will be N/NW
around 10kt with gusts developing in the afternoon at 15-20kt.

Expected Snowfall Accumulations:

NYC terminals and BDR: 4-6"
ISP: 3-5"
HPN/SWF: 5-7"

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

Timing of changing flight categories will likely vary +/- 1-2
hours.

.OUTLOOK FOR 00Z MONDAY THROUGH THURSDAY...

Sunday Night: IFR/MVFR becoming VFR. NE-N wind gusts 15-20kt in
the evening, becoming NW 20-25kt overnight.

Monday: VFR. NW wind gusts 20-25 kt.

Tuesday: VFR. W wind gusts around 20 kt.

Wednesday: Chance of MVFR or lower in -SN, particularly coastal
terminals.

Thursday: VFR.

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

.MARINE...
-- Changed Discussion --Waves have significantly increased at Buoy 44097 with winds
increasing in the vicinity there as well. Buoy 44025 has also
held with its seas around 5 ft early this evening. These
observations have been much better captured by the Wavewatch
compared to the NWPS. Updated waves through Sunday with
Wavewatch.

As a result, expecting much of the timeframe of tonight through
Sunday to have SCA levels seas for the ocean east of Fire Island
Inlet. Started SCA earlier and this is currently in effect for
the ocean east of Fire Island Inlet with the same end time of
6PM Monday. The rest of the marine zones are expected to remain
below SCA thresholds tonight through Sunday.

Winds and seas then increase Sunday night across all forecast
waters as the low pressure passes nearby. As the low pulls away
Sunday night, SCA conditions should prevail across all waters
with a gusty WNW behind another cold front. There will be a low
end chance for some gale gusts.

Monday, widespread SCA conditions expected for all waters due to
wind gusts, for ocean both wind gusts and seas. Decreasing trend to
winds and seas Monday night, but ocean will probably still have SCA
conditions much of the night. Non-ocean waters stay below SCA for
Monday night. The ocean could have some lingering SCA conditions
Tuesday morning with otherwise below SCA conditions for the waters.
For Tuesday afternoon through Thursday, sub-SCA conditions
forecast for all waters.

Also, would expect some light freezing spray for Sunday night
through early next week for parts of the waters.-- End Changed Discussion --

.HYDROLOGY...
No hydrologic issues are anticipated through Saturday.

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...Winter Storm Warning from 1 PM Sunday to 4 AM EST Monday for
CTZ005>007.
Winter Weather Advisory from 1 PM Sunday to 4 AM EST Monday
for CTZ008>012.
NY...Winter Storm Warning from 1 PM Sunday to 4 AM EST Monday for
NYZ067>070.
Winter Weather Advisory from 1 PM Sunday to 4 AM EST Monday
for NYZ071>075-078>081-176>179.
NJ...Winter Storm Warning from 1 PM Sunday to 4 AM EST Monday for
NJZ002-004-103-105-107.
Winter Weather Advisory from 1 PM Sunday to 4 AM EST Monday
for NJZ006-104-106-108.
MARINE...Small Craft Advisory from 6 PM Sunday to 6 PM EST Monday for
ANZ331-332-335-338-340-345-355.
Small Craft Advisory until 6 PM EST Monday for ANZ350-353.-- End Changed Discussion --

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