discussion on 2023-12-21

000
FXUS61 KOKX 211109
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
609 AM EST Thu Dec 21 2023

.SYNOPSIS...
High pressure anchored north of the area will be in control for the
remainder of the week. Departing high pressure Saturday gives way to
a decaying low pressure wave Saturday night into Sunday. High
pressure then reestablishes itself for Sunday night into early next
week but will remain centered well offshore. A frontal system
approaches for the middle part of next week.

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --Forecast remains on track as the cold front is now pressing
through. In the wake of the cold front passing to the south a
north wind ushers in one of the coldest air masses of the season
thus far with a 1040+ mb high building from SE Canada. With
that said, temperatures will be close to normal, perhaps
averaging a couple of degrees below normal. A north wind with
gusts of 20 to 25 mph closer to the coast will make it feel
about 10 degrees colder with wind chills mainly in the lower 30s
despite an abundance of sunshine.

The pressure gradient weakens tonight as the southern periphery of
the high begins to settle over the area. A lighter north wind means
temperatures fall into the 20s widespread across the area, with even
a few upper teens across northern and northwestern interior
sections. Used a consensus blend in putting together forecast.-- End Changed Discussion --

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
Look for the drier stretch of weather to continue with high pressure
spreading down into New England. After plenty of sunshine, some high
clouds begin to streak during the afternoon and evening as the 500
mb ridge axis moves over the area. Temperatures will struggle to get
out of the 30s, despite sunshine.

Clouds begin to increase Friday night, especially late in advance of
an approaching mid level shortwave. The timing of the advance of mid
level clouds will ultimately determine how much radiational cooling
takes place, and thus how low temperatures ultimately get. Either
way, a seasonably cold night takes place with consensus guidance
utilized with lows in the 20s to lower 30s. Used a consensus
blend in putting together forecast.

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
*Key Points*

- Mainly dry conditions expected this weekend through Christmas Day.

- Gradual warming trend forecast this weekend through first half of
next week.

- Probabilities are increasing for widespread rain event Tuesday
through the middle of next week. A lot of uncertainty on rainfall
amounts.

Looking at the consensus of large scale numerical weather prediction
models, 250mb height and winds depict strong westerly jet across
Mexico and Gulf Coast intensifying early next week. The
models depict this subtropical jet to be relatively the strongest
for next Tuesday and potentially brushing into the local area for
the middle part of next week.

Meanwhile for Saturday through Tuesday, the local region stays in
between the subtropical and polar jet. The 250mb height pattern does
not get too amplified across the local area. In the mid levels, the
local area will transition from a ridge pattern to more of a trough
pattern this weekend. The shortwave does not appear to be too deep
and will move across with highest positive vorticity advection late
Saturday night into Sunday. The shortwave then departs southeast of
the region Sunday night, with ridging returning going into early
next week.

The large scale numerical weather prediction models indicate at the
surface about the same central pressure but with the center of the
high moving farther southeast out into the Atlantic Saturday. A weak
low pressure system from the Great Lakes will be approaching
Saturday night and moving across the local region Sunday, weakening
as it does so. With all the westerly flow in the atmosphere,
moisture will be very limited.

Not expecting widespread precipitation this weekend, just slight
chance to low end chance, near 15 percent to near 25 percent
Saturday. Would expect much of the weekend will remain dry.
Concerning the precipitation type, for parts of the interior
Saturday night, a wintry mix will be possible. Forecast model
soundings indicate a lack of ice nuclei aloft with the NAM and
the GFS even showing showing warm layer of above the ground,
allowing for some snowfall to melt and for some locations,
potentially allow for some freezing rain. Other locations in the
region are forecast to just have plain rain. Precipitation amounts
shown by the large scale forecast models are very small, only a few
hundredths of an inch or less.

High pressure then builds southward Sunday night but will quickly
make its way out into the Atlantic for early next week. A larger
frontal system to the southwest of the local area then approaches
towards the middle of next week. This will bring the next widespread
rainfall event to the area. Ambient temperatures will allow for this
event to be plain rain for all forecast locations. Precipitable
waters could reach near or a little above 1 inch towards middle of
next week so rain could be heavy at times. Much uncertainty on
timing, longevity of the rain and therefore the rainfall
amounts.

.AVIATION /11Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --A cold front approaches from the north and moves across early today.
High pressure builds in from the north thereafter.

VFR conditions through the TAF period.

Winds will be out of the north today. Wind speeds will be generally
near 10-12 kt into this morning. Winds will be more in the 10-15 kt
range for the late morning and afternoon, along with gusts near 20
kt for all terminals. Some locally higher gusts will be possible.

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

Gust may end a few hours earlier than indicated by TAFs late today.

OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY...

Friday through Saturday: VFR.
Saturday night-Sunday: VFR, with possible MVFR at times.
Monday: VFR.

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

.MARINE...
Small craft advisories are in effect for the eastern most nearshore
waters through midday, and the ocean waters through Thursday night.
Small craft conditions may continue due to 5 ft ocean seas through
Friday morning. High pressure settles across the Eastern New England
later on Friday with the pressure gradient becoming rather weak.
For weekend and into Monday, the pressure gradient remains
relatively weak, allowing for conditions to remain below SCA
thresholds.

.HYDROLOGY...
-- Changed Discussion --
No hydrologic impacts are expected at this time.-- End Changed Discussion --

.TIDES/COASTAL FLOODING...
A long period E swell has prevented water levels from falling
further. However, total water level guidance has trended lower and
thus at this time it appears that minor coastal flood benchmarks by
and large will not be met with the early Friday morning high tide
cycle. A couple of locations in the south shore bays of Nassau may
approach minor benchmarks, but at this time it appears statements
and advisories will not be needed.

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until noon EST today for ANZ331-332-340.
Small Craft Advisory until noon EST Friday for ANZ350-353-355.

SYNOPSIS...JE
NEAR TERM...JE
SHORT TERM...JE
LONG TERM...JM
AVIATION...JM
MARINE...JE/JM
HYDROLOGY...JE/JM
TIDES/COASTAL FLOODING...