635
FXUS61 KOKX 121809
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
109 PM 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/...
-- Changed Discussion --
Dewpoints running several degrees lower than forecast. Winds
have also picked up the last few hours. Increased gusts this
afternoon. Feel any gusts to near 45 mph would be infrequent
with most peak gusts in the 35 to 40 mph range.
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 30-40 mph with some downward
trend late this afternoon into this evening. 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.-- End Changed Discussion --
&&
.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 /18Z THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --
High pressure builds eastward from the Plains states into
eastern Canada and New England.
VFR through the TAF period.
W winds 20-25 kt with gusts to near 35 kt into the early evening.
Winds gradually diminish this evening to 10-15 kt tonight. Winds
increasing again Friday with gusts 15-20kt by midday before
diminishing again by evening. Some backing of the wind possible
Friday afternoon to more northerly.
...NY Metro (KEWR/KLGA/KJFK/KTEB)TAF Uncertainty...
No unscheduled AMD expected. Occasional gusts to 40 kt possible
until evening.
OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY...
18Z Friday: VFR.
Saturday: VFR.
Sunday: BKN MVFR cigs possible along the coast in the afternoon.
Sunday night: Chance of MFR or lower conditions 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.
Tuesday...IFR or lower possible in a chance of rain.
Detailed information, including hourly TAF wind component
forecasts, can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
-- Changed Discussion --
Forecast mainly on track. Some 35 kt gusts have been observed on
non-ocean waters. These are just expected to be occasional in
frequency this afternoon before further decreasing tonight.
Gales will continue on the ocean through this afternoon and
here the gale warning is in effect until 6 PM. SCA remains in
effect for the non ocean waters for prevailing gusts up to 30
kt, and occasional gale force gusts 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.-- End Changed Discussion --
&&
.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/JM
SHORT TERM...DS
LONG TERM...BG
AVIATION...IRD
MARINE...JM/BG/DS
HYDROLOGY...BG/DS