939
FXUS61 KOKX 191229
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
729 AM EST Thu Dec 19 2024
.SYNOPSIS...
High pressure briefly moves in today. A clipper system will then
pass across the region Friday as low pressure develops well offshore
Friday afternoon into Saturday morning. High pressure builds in
from the west late Saturday through early next week. A weak frontal
system may approach by Christmas.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Rainfall has come to an end as a frontal wave departs to the
east early this morning. Behind the frontal passage, a brisk NW
flow is anticipated this morning. As a surface high pressure
system builds in and slides north of the area into the
afternoon, skies will become clear and the wind will relax as
the pressure gradient weakens. High temperatures will be
seasonable today with temperatures in the low to middle 40s for
much of the area.
High pressure remains overhead tonight with cloud cover once again
increasing as upper level moisture from an approaching clipper
system brings in high clouds into the area. Lows tonight will be in
the middle 20s to low 30s.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
Guidance continues to be in fairly good agreement as to how the next
system develops. A large digging trough with an embedded vorticity
maximum approaches the East Coast early Friday. This will force a
surface coastal low development off the Carolina coast that will
move up the Eastern Seaboard, but well offshore. A clipper-
type system that approaches the coast at the same time from the
Ohio Valley likely gets absorbed into the developing coastal low
into Friday night. This may result in a minimum area of
precipitation over our CWA as the transfer of energy occurs.
Regarding sensible weather, scattered showers may develop ahead of
the coastal low over the area as early as Friday morning. These
would be in the form of rain along the coast and possible light snow
showers inland if they develop at all. As the low continues to
strengthen and move SE of the area Friday afternoon into the
evening, a more pronounced area of steadier precipitation may
develop and approach the extreme eastern portion of the CWA, namely
the Twin Forks of Long Island. Depending on the intensity of the
precipitation, the timing of any precipitation, and the
temperature, will depend on if it falls in the form of rain,
snow, or a mix of both. Regardless, the low quickly moves NE of
the area into Friday night and most precipitation should exit
with it.
Another piece of mid-level energy moves overhead in the passing
trough which may force a few more snow showers Saturday. All
precipitation looks to end by Saturday evening with a strong N flow
advecting frigid air into the area. Overall, less than an inch of
snow is expected over much of the CWA with the exception of some
interior areas should more persistent snow showers develop in higher
elevations or areas to the north where upwards of 2 inches may be
possible. Highs on Saturday will likely only be in the low to middle
30s, with lows Saturday night in the teens and possibly single
digits for the coldest spots in the interior.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Key Points:
* An arctic airmass settles over the area Sunday into Monday.
Some inland locations may not get above freezing until Christmas
Day.
* Potential for a light wintry precipitation event heading toward
Christmas.
There is generally good agreement with the global models in building
strong Canadian high pressure out of eastern Canada Sunday and into
the Northeast early next week. Thus, closely followed the NBM with a
few noted exceptions detailed below. Where there are differences,
which could impact ptype heading toward Christmas Day, is with the
progression of the high and the amount of cold air damming along the
lee side of the Appalachians. The 00Z GFS is much more progressive
with the high, kicking it out in the western Atlantic by 00Z
Tuesday, while the ECMWF, Canadian, GEPS, and EPS are all
maintaining stronger high pressure over eastern Canada and into the
Northeast through the middle of next week. While the arctic air at
the onset of the period lifts out to the northeast Tuesday into
Wednesday, the consensus forecast approach would maintain a
marginally cold enough airmass for some light wintry precipitation
Christmas Eve (Tue night) into Christmas Day (Wednesday) with weak
frontal system. However, there are no indications of this being a
significant storm system.
More importantly, will be the very cold airmass across the area
Sunday into Monday with highs 15 to 18 degrees below normal. In
fact, with high pressure over the area Sunday night through Monday
night, opted to go colder using the NBM 50th percentile for
overnight lows. Much of the area by daybreak Monday will be in the
single digits to lower teens. Some of the normally colder sports
could even approach zero. Fortunately, winds will be light at this
time and apparent temperatures do not look cold enough for a Cold
Weather Advisory. The airmass will then gradually warmup close to
normal levels by midweek.
&&
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
Low pressure will continue to track away from the area today,
while high pressure builds in from the west. The center of the
high passes to the north tonight, while a clipper low tracks
into the Ohio Valley and another forms off the Carolinas.
VFR today with chance of MVFR developing after 12Z Friday.
Chance of light rain or snow on Friday. Best chance is after
18Z. Confidence is low and for the time will keep the mention
out of the 30h TAFs.
NW winds G20-25kt to start, but diminish toward late morning.
Winds will then gradually veer this afternoon into tonight,
becoming NE-ENE at less than 10 kt.
...NY Metro (KEWR/KLGA/KJFK/KTEB)TAF Uncertainty...
Occasional gusts may linger into the first half of this
afternoon.
OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY...
Friday: VFR, becoming MVFR, IFR at times, afternoon into night.
A chance of rain and/or snow during afternoon. A chance of snow at
night. NE wind gusts 15-20 kt, strongest at the coastal
terminals
Saturday: Chance of MVFR/IFR in snow during the morning into
early afternoon. NW gusts 20-25 kt.
Sunday - Monday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
Brief SCA conditions on the ocean waters are expected this morning
with gusts near 25 kt and seas near 5 feet. Sub-SCA conditions are
then expected late this morning and through tonight on all waters.
An offshore low will bring increasing winds and rising wave heights
to the ocean waters late Friday such that SCA are likely afternoon
with gusts 25-30 kt and waves 5-6 feet. Strong northerly flow
behind the departing system will likely allow for SCA conditions to
continue on the ocean and possibly spread to the non-ocean waters
during the day Saturday with gusts near 25 kt.
High pressure builds across the waters Sunday into Monday. Winds and
seas will subside during this time, however, 5 ft seas may linger on
the ocean waters Sunday.
&&
.HYDROLOGY...
There are no hydrologic concerns through the middle of next
week.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 10 AM EST this morning for ANZ350-
353-355.
&&
$$
SYNOPSIS...DW/MW
NEAR TERM...MW
SHORT TERM...MW
LONG TERM...DW
AVIATION...DW
MARINE...DW/MW
HYDROLOGY...DW/MW