okx-afd on 2024-12-17

635
FXUS61 KOKX 171939
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
239 PM EST Tue Dec 17 2024

.SYNOPSIS...
-- Changed Discussion --High pressure passes over the area tonight and early Wednesday.
Another frontal system will approach on Wednesday and move
across the area Wednesday night. High pressure briefly returns
on Thursday into early Friday before a clipper system passes
along with an offshore low pressure late Friday into Saturday.
High pressure then builds late in the weekend into early next
week.-- End Changed Discussion --

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --A cold front will continue to move east of the area this evening.
Behind the front, high pressure builds into the area with light
winds and clear skies expected. Good radiational cooling will allow
temperatures to drop into the 30s for most locations, with a few
upper 20s possible in the normally colder spots.-- End Changed Discussion --

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
-- Changed Discussion --Surface high pressure moves offshore Wednesday morning.

Meanwhile, another shortwave trough will drop across the Great Lakes
sending another frontal system toward the area. The associated warm
front and cold front pass through quickly during the first half of
Wednesday night with a quick shot of rainfall. Rain is expected to
overspread the area from SW to NE Wednesday afternoon/evening, and
should end across eastern sections before daybreak Thursday.
Temperatures remain warm enough for just plain rain this event with
the cold air advection lagging behind the cold front.

Highs on Wednesday will remain above normal, topping out in the mid
40s to lower 50s, with lows dropping into the 30s for most locations
by daybreak Thursday.-- End Changed Discussion --

.LONG TERM /THURSDAY THROUGH MONDAY/...
-- Changed Discussion --Confidence continues to increase on minimal impacts from a passing
clipper system Friday into Friday night and offshore low pressure
Friday into early Saturday. Confidence has also increased on the
coldest air mass of December 2024 this weekend into the start of
next week.

Key Points:

*A clipper system passing across the northeast on Friday into Friday
night may interact with an offshore low Friday night into early
Saturday to bring some light snow and/or light snow/rain mix near
coast.

*An arctic air mass likely follows the rest of the weekend into next
Monday with potential for several areas, especially inland, not
rising above freezing for at least 3 consecutive days. Temperatures
may begin moderating next Tuesday.

Brief high pressure on Thursday will lead to dry conditions with
temperatures near normal in the lower and middle 40s. Attention
quickly turns to an amplifying upper trough over the eastern states
and developing offshore low pressure on Friday. There will also be a
vortmax off the southeast coast that will induce low pressure
development early Friday. There will be multiple areas of energy
within the trough with the lead vort energy helping keep the
developing low off the coast, which prevents any direct impacts over
the area. However, the guidance has been inconsistent on any precip
from the trailing energy/clipper and if a inverted trough develops
somewhere over the area. The inverted trough and lingering upper
trough axis may be enough to support an area of light precip
somewhere over the area, but confidence in its location and
occurrence is low at this time. Have capped PoPs off at chance given
the aforementioned uncertainty and with the consensus of the latest
guidance keeping the low far enough offshore. If there is any light
precip development, it would mainly be in the form of light snow
although some light rain could mix in at the coast. Surface
temperatures Friday afternoon/evening look marginal near the coast,
but wet bulb cooling supports the mix becoming all light snow Friday
evening into Friday. A light accumulation is possible if this
scenario were to verify, but there is equal chances of conditions
remaining mostly dry as well. Highs on Friday look to range from the
middle 30s inland to around 40 near the coast.

The upper trough axis swings to the east on Saturday allowing precip
chances to decrease through the day. Conditions should trend dry and
cold the second half of Saturday as a cold, high pressure starts
building towards the region. Highs on Saturday range from lower to
middle 30s.

The high pressure continues to build in Saturday night through
Sunday bringing arctic air to the Tri-State. This air mass looks
colder than the one that occurred this past weekend with 850 mb
temperatures across the northeast -17C to -21C. Have gone closer to
the NBM 50th percentile during this time period as the NBM
deterministic appears too warm, especially near the coast where it
lies above the 75th percentile. Strong cold advection under
northerly flow will bring temperatures down into the teens for most
spots with around 20 in the NYC metro by Sunday morning. Breezy
conditions (N winds 10 mph with gusts 15-20 mph) will make it feel
like it is in the single digits early Sunday morning. For Sunday,
highs will only be in the middle to upper 20s with wind chills
largely in the teens. It looks even colder Sunday night with lows in
the single digits inland and teens near the coast. Winds look
lighter Sunday night as the high pressure settles over the
northeast, but any breeze may make it feel like the single digits.
The high pressure remains over the area Monday with temperatures
ranging from the upper 20s inland and low 30s near the coast.
Conditions may begin to moderate on Tuesday, but highs still will be
below normal.-- End Changed Discussion --

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
A cold front moves through the area this afternoon. High
pressure follows.

VFR expected through Wednesday afternoon.

SW/W winds will be sustained 10-15 kts this afternoon. There
remains uncertainty regarding whether we will see gusts this
afternoon. Have left out of TAFs due to low confidence.
However, for your awareness, if we see gusts, they will likely
not be higher than 20-25 kts. Winds drop below 10kts this
evening and become light and variable tonight into Wednesday.

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

20 to 25 kt gusts are possible this afternoon, but will likely
be occasional if at all.

OUTLOOK FOR 18Z WEDNESDAY THROUGH SUNDAY...

Wednesday Afternoon-Wednesday night: Becoming MVFR-IFR during
the late afternoon with rain developing and continuing into the
night. NW gusts 15-20 kt late Wednesday night.

Thursday: VFR. NW gusts 15-20kt.

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. NW gusts late at night 15-20 kt.

Saturday: MVFR to IFR with a slight chance of snow, ending late in
the afternoon. NW gusts 20-25 kt.

Sunday: VFR.

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

.MARINE...
-- Changed Discussion --Winds and seas continue to diminish on the area waters. Have gone
ahead and cancelled the Small craft for the western ocean waters.
The small craft advisories remain in effect through 1am for the
central and eastern ocean waters as seas continue to gradually
diminish as high pressure builds into the region. There is a chance
that seas could fall faster than forecast.

We should see a lull in the SCA condition through much of the day
Wednesday then winds and seas increase once again Wednesday night
with the passage of a cold front.

SCA conditions, mainly in seas, will continue Thursday morning.
These conditions should subside by evening with sub SCA winds and
seas Thursday night into Friday. An offshore low passes the waters
Friday night into Saturday bringing the next chance of SCA
conditions, especially on the ocean. Winds look marginal, but ocean
seas should build to 5-6 ft. The marginal SCA winds may continue on
Sunday with seas near 5 ft.-- End Changed Discussion --

.HYDROLOGY...
There are no hydrologic concerns through the beginning of next
week.

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 1 AM EST Wednesday for ANZ350-353.-- End Changed Discussion --

SYNOPSIS...BC/DS
NEAR TERM...BC
SHORT TERM...BC
LONG TERM...DS
AVIATION...JT
MARINE...BC/DS
HYDROLOGY...BC/DS