141
FXUS61 KOKX 120908 CCA
AFDOKX
Area Forecast Discussion...CORRECTED
National Weather Service New York NY
408 AM EST Thu Dec 12 2024
.SYNOPSIS...
High pressure will gradually build Thursday 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/...
-- Changed Discussion --
Cold advection well underway early this morning with the cold
front off the New England coast. Temperatures have fallen into
the mid and upper 30s across the area. Most locations will remain
above freezing for the morning commute. However, the interior of
the Lower Hudson Valley and potentially SW CT could see
temperatures drop to around freezing by day break.
An anomalously deep upper trough and closed low will dominate
the weather pattern over the northeast through tonight. The
Tri-State will lie between building high pressure across the
Plains down to the southeast and strong low pressure over
southeastern Canada. Cold advection will continue through the
day along with a fairly tight pressure gradient. This will lead
to westerly winds around 15-20 mph gusting 25 to 35 mph. The
strongest winds will most likely occur early this morning and
then again this afternoon. Partly cloudy skies are expected with
highs in the upper 30s to lower 40s.
The pressure gradient relaxes as the high pressure builds towards
the area tonight. Winds will be much weaker, but it may 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 in the upper teens to the lower
and middle 20s elsewhere.-- End Changed Discussion --
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
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.-- End Changed Discussion --
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As a longwave upper ridge slides across the eastern CONUS
Sunday into Monday, a 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 /09Z THURSDAY THROUGH MONDAY/...
VFR as strong low pressure moves north across eastern
Canada, and high pressure builds eastward from the Plains
states.
W-WNW winds will continue overnight with some gusts 25-30 kt.
Winds should shift more to the W-WSW daytime Thursday and
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 diminish Thu evening.
...NY Metro (KEWR/KLGA/KJFK/KTEB)TAF Uncertainty...
No unscheduled AMD expected.
OUTLOOK FOR 06Z FRIDAY THROUGH MONDAY...
Late tonight through Saturday: VFR.
Sunday: MVFR or lower cond possible with light rain and low
clouds, especially late.
Monday: MVFR cond possible in showers.
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 until 6 pm. An occasional gale
is possible on the Sound, Bays, and Harbor, but peak gusts
should average around 30 kt. Have converted the Gale Warning
here to an SCA, which runs through 10 pm when winds are most
likely to fall below 25 kt. Seas will remain high today, 8-13 ft
on the ocean, and 4 to 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.
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. However, no hydrologic
impacts are anticipated through the middle of next week.
&&
.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