375
FXUS61 KOKX 121153
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
653 AM EST Thu Dec 12 2024

.SYNOPSIS...
Strong high pressure will gradually build in today and settle
over the region Friday into Saturday. After the high moves
east on Sunday, a weakening frontal system will approach Sunday
night and pass through on Monday. A stronger frontal system will
move across on Tuesday, followed by high pressure on Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Cold advection well underway early this morning with
temperatures mostly in the lower and mid 30s.

An anomalously deep upper trough and closed low will dominate
the weather pattern over the Northeast through tonight. The
Tri-State area will lie between building high pressure across
the Plains down to the southeast and strong low pressure over
eastern Canada. Cold advection will continue through the day
along with a fairly tight pressure gradient. This will lead to
westerly winds 15-25 mph gusting to 30-35 mph, strongest from
late morning into the afternoon. Partly cloudy skies are
expected with highs in the upper 30s and lower 40s.

The pressure gradient relaxes tonight as the high builds toward
the area. Winds will be much weaker, but it will be difficult for
the boundary layer to completely decouple with the core of the
high still to our west. Cold advection should allow temperatures
to bottom out from the upper teens to mid 20s.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
The upper trough begins to lift northeastward on Friday with its
axis likely moving over the Canadian Maritimes Friday night. A
shortwave ridge will then build overhead Saturday into Saturday
night. This pattern allows the surface high to strengthen as it
settles over the northeast through Saturday and remaining
dominant Saturday night.

The modeling continues to signal an anomalously strong high
pressure with central pressures ranging from 1047-1050 mb
centered over the northeast. The combination of the shortwave
ridging and strong confluence left behind the departing upper
trough are some of the factors contributing to the strengthening
high pressure. The potential high sea level pressure (SLP) is
close to the highest observed across the northeast in December
and in any month based on data from WPC. The highest observed
SLP in the northeast ranges from 1052-1054 mb, which occurred on
February 13, 1981. The highest observed SLP at Central Park was
1052.5 mb, which also occurred on February 13, 1981. The
highest observed SLP in the northeast for December ranges from
around 1049-1053 mb (1051.8 mb at Central Park), which occurred
on December 25, 1949.

The result of the strong high pressure will be cold and dry
conditions Friday and Saturday. Winds continue to weaken
Friday and should be light on Saturday with the high pressure
overhead. Temperatures on Friday may struggle to rise above
freezing. The NBM deterministic lies at the top (warmest) of the
full NBM ensemble distribution. A blend of MOS is closer to the
50th percentile of the NBM distribution for most spots. This
yields highs in the lower to middle 30s, highest in the NYC
metro and near the coast. The coldest night of December so far
appears likely Friday night with nearly ideal radiational
cooling conditions. Lows bottom out in the middle and upper
teens inland and lower 20s closer to the coast. Saturday will be
a few degrees warmer, but still cold with highs in the middle
30s. Lows Saturday night range from the upper teens inland to
the lower and middle 20s elsewhere.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As a longwave upper ridge slides across the eastern CONUS
Sunday into Monday, a weakening shortwave closed low will move
through the ridge across the Great Lakes on Sunday, then
across NY into New England on Monday. The departing strong sfc
high should keep daytime Sunday dry, but skies should become
mostly cloudy as low level moisture increases in onshore flow
and as high/mid level clouds stream across from the west.

Precip chances increase Sunday night into Mon as the wave aloft
and an associated sfc warm front approach. Partial thicknesses
and fcst sfc wet-bulb temps support the idea of a period of
mixed wintry precip at the onset especially inland, changing to
all rain fairly quickly for NYC metro and coastal areas, and
inland by early Mon morning.

The warm front is unlikely to lift through until daytime Tue,
when the longwave ridge and embedded shortwave trough both
exist east, and a stronger upper trough approaches on Tue with a
light to moderate rainfall. A trailing cold front should then
move across Tue night, with high pressure sfc/aloft building in
its wake for Wed.

Temps near normal on Sunday will transition to above normal for
the rest of the fcst period especially on Tue, after a warm
frontal passage when highs could be well into the 50s for the
NYC metro and coastal areas.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
VFR as strong low pressure moves north across eastern
Canada, and high pressure builds eastward from the Plains
states.

W to WSW winds should increase to just over 20 kt with gusts
just over 30 kt at KJFK/KEWR/KLGA, and to 15-20 kt with gusts
25-30 elsewhere. Winds gradually diminish this evening, then
should settle in either side of 10 kt overnight.

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

No unscheduled AMD expected. Ocnl G35kt possible this afternoon.

OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY...

Saturday: VFR.

Sunday: BKN MVFR cigs possible along the coast in the
afternoon.

Sunday night: Chance of MFR or lower cond mainly after midnight.
Precip type snow at KSWF, a rain/snow/sleet mix at
KHPN/KBDR/KGON, and mainly rain at the NYC metros/KISP.

Monday: MVFR cond possible in light rain. Wintry mix possible at
KSWF early.

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

&&

.MARINE...
Gales will continue on the ocean through this afternoon and
have extended the gale warning there until 6 PM. SCA remains in
effect for the non ocean waters for prevailing gusts up to 30
kt, and an occasional gale force gust up to 35 kt. Seas will
remain high today, 8-13 ft on the ocean, and 4-6 ft on the
Sound. However, seas will begin subsiding more rapidly tonight
as the winds weaken considerably. It appears ocean seas will
fall below 5 ft Friday morning. A weak pressure gradient over
the waters Friday afternoon through the weekend will lead to
conditions below SCA levels.

Longer term: For the non ocean waters, sub SCA conds expected
Mon and Tue. For the ocean waters, a fairly long fetch onshore
flow increasing to 15-20 kt could build seas to 5 ft as early
as Mon afternoon, and more likely Mon night into Tue.

&&

.HYDROLOGY...
Rainfall of 1/2 to 3/4 inch is possible via a pair of frontal
systems moving across early next week. This rainfall will be
light/moderate in intensity and also beneficial, so no
hydrologic impacts anticipated.


&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ331-
     332-335-338-340-345.
     Gale Warning until 6 PM EST this evening for ANZ350-353-355.

&&

$$

SYNOPSIS...BG/DS
NEAR TERM...DS
SHORT TERM...DS
LONG TERM...BG
AVIATION...BG
MARINE...BG/DS
HYDROLOGY...BG/DS

NWS OKX Office Area Forecast Discussion