449
FXUS61 KOKX 190224
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
924 PM EST Wed Dec 18 2024
.SYNOPSIS...
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A frontal wave just south of Long Island passes to the east
after midnight. High pressure briefly returns on Thursday. A
clipper system will then pass across the region Friday as low
pressure develops well offshore Friday afternoon into Saturday
morning. High pressure builds late Saturday through the rest of
the weekend and will remain in control early next week. A weak
frontal system may approach by Christmas.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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The main low has developed just south of Long Island at 02Z, and
will move east of the region by late tonight. Rain continues
across the region. There may be a brief lull across portions of
Long Island as the low passes to the south and over eastern
portions late this evening. The rain should then fill back in
behind the low due to passage of an upper jet to our north
putting the region in the favored right entrance region. The
rain will quickly exist from west to east after midnight with
dry conditions expected before day break. Rainfall amounts range
from one quarter to one half inch.
Some colder air may try to filter in as the system exits, but
think the moisture will push east before it is cold enough for
any west snow across the NW interior. Have therefore removed any
mention of snow. Fog potential is limited and visibility
reduction is more likely from the rain itself. Winds will go NW
once the weak low passes east, which will also limit fog
development overnight after the rain ends.-- End Changed Discussion --
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
For Thursday, winds will initially be gusty from the NW around
15 to 25 mph as the cold front departs and high pressure builds
in from the west. Temperatures will be cooler than the previous
few days in a cold advection regime, but still a few degrees
above climatological normals in the low to mid 40s.
By Thursday night another trough begins to move through the
Great Lakes, coincident with a weak southern stream wave that
will remain offshore. Developing warm advection and onshore
flow between the two systems will allow an increase in cloud
cover overnight, with the possibility of some light rain and/or
snow closer to the coast by daybreak.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Unsettled conditions Friday into Saturday will transition to
the coldest air mass of Dec 2024 the rest of the weekend into
early next week.
Key Points:
* Minimal impacts are anticipated from offshore low pressure and a
Clipper system Friday into Saturday. There is a continued chance
of light snow, or a light rain/snow mix at the coast, Friday. Any
precip that falls Friday night into Saturday morning will be in
the form of light snow.
* Snowfall accumulations look light with potential of a coating down
to the coast late Friday night into Saturday morning. Across the
interior 1-2 inches possible across the duration of the event.
* An arctic airmass 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.
Guidance continues to be in good agreement overall regarding Friday
into Saturday with the main low pressure passing far enough
offshore, with minimal impacts to the area. There will also be a
clipper low that approaches on Friday, but likely gets absorbed by
the offshore low by Friday night. This transfer of energy may leave
a relative minimum in precipitation coverage over the area on
Friday. There is enough mid level energy to warrant the potential of
some light precip during the day into Friday night. Some of the
guidance has hinted at an inverted trough extending towards the
coast with the main upper trough still to the west into Friday
night. It is always difficult to pinpoint where this may occur, but
the latest guidance has hinted it may remain to our south with
potential of an extension into the Lower Hudson Valley.
Any precip that develops on Friday will be in the form of light snow
inland and rain, or a mixture of rain/snow, closer to the coast due
to slightly warmer air. Amounts will be light and it should be noted
there is potential that very little precip occurs across the area
during the daylight hours. Highs Friday range from the middle 30s
inland to the low 40s at the coast.
Precip chances gradually increase Friday night into Saturday morning
due to trailing middle level energy and a secondary trough axis.
Global guidance is in decent agreement with the placement and timing
of this feature. There appears to be a window with increased PVA,
which should support a band of light snow to sweep across the region
late Friday night into Saturday night. Amounts will be light with
this feature as well, but potential exists for a coating down to the
coast as colder air begins to move into the area.
Total snow accumulation from Friday into Saturday morning of an inch
or two well NW of the NYC metro with mainly a coating to under an
inch elsewhere. This potential light snow should quickly diminish in
coverage by afternoon with dry conditions following the rest of the
weekend.
The main weather story late Saturday through early next week will be
a very cold air mass settling over the area. A strong, Canadian high
pressure over the Great Lakes Saturday will build towards the
northeast on Sunday and then remain over the area next Monday.
Temperatures on Saturday look to reach the low and mid 30s, highest
near the coast. Cold advection increase Saturday night under modest
northerly flow around 10 mph gusting 15 to 20 mph. 850 mb
temperatures will also drop to -14C to -18C across the region and
even lower, closer to -20C, further north across New England. This
will allow temperatures to drop into the teens across the entire
area, with some single digits inland. Wind chills by Saturday
night/early Sunday morning fall to zero to five below inland and
single digits elsewhere. The coldest day will likely be Sunday with
highs in the lower 20s inland and middle to upper 20s closer to the
coast. The modest northerly flow will continue Sunday with potential
of 15-20 mph gusts making it feel like it is in the teens during the
day. Winds should diminish Sunday night as the high pressure settles
over the northeast. This should allow temps to fall into the single
digits inland with low and middle teens elsewhere. Light winds will
make it feel like the single digits early Monday morning.
The air mass slowly moderates by Monday with highs ranging from the
upper 20s inland to lower 30s near the coast. The high pressure
moves offshore by Monday night with guidance signaling potential for
the next frontal system to approach Tuesday or Wednesday.
Uncertainty is quite high at this time range so generally followed
the model consensus which for now is indicating low PoPs. Moderating
temperatures should bring us back to near seasonable levels by
Christmas Day.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
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Weak low pressure just to the south, and across eastern Long
Island at 02Z tracks east of the area by midnight, and then to
the northeast overnight. High pressure builds in behind the low
late tonight through Thursday.
Mainly MVFR with IFR at times as light rain continues into late
tonight. Rain ends late tonight with conditions quickly
improving to VFR.
With the low a little farther to the south, and over eastern
Long Island winds have shifted to the NW to N across most of
the terminals at 02Z. As the low tracks east and northeast winds
will shift to the NW across the region. Wind speeds remain
under 10 kt, and increase to 10-15 kt as the rain ends. Gusts to
around 20 kt are possible early tomorrow morning. Gusts may end
earlier than forecast or become more occasional before ending
by early afternoon. And by late day winds become more northerly
and gradually diminish.
...NY Metro (KEWR/KLGA/KJFK/KTEB)TAF Uncertainty...
Amendments likely through the overnight for changing flight
categories with light rain ending overnight.
Gusts on Wednesday may be more occasional at times, especially
by late morning. Can not rule out a few gusts higher than
forecast.
OUTLOOK FOR 00Z FRIDAY THROUGH MONDAY...
Thursday night: VFR.
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 - Monday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
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Made minor adjustments to the winds as low pressure was just
south and over eastern Long Island, as winds have become NW
across most of the forecast waters.
A frontal wave will bring a period of SCA conditions to the
ocean waters tonight, both in the pre-frontal SW flow and post-
frontal NW flow. These conditions will be short-lived as high
pressure builds in from the west on Thursday, allowing winds and
seas to subside.
An offshore low will bring increasing winds and seas Friday with
potential for marginal SCA conditions on the ocean late in the day.
SCA looks more likely on the ocean Friday night into Saturday as the
system departs and increases northerly flow behind it. Ocean seas
then look to remain elevated Saturday night into Sunday, but should
end up below 5 ft by Sunday night. Conditions will then remain below
SCA levels on Monday.-- End Changed Discussion --
&&
.HYDROLOGY...
There are no hydrologic concerns through the middle of next
week.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 10 AM EST Thursday for ANZ350-353.
Small Craft Advisory from 1 AM to 10 AM EST Thursday for
ANZ355.-- End Changed Discussion --
&&
$$
SYNOPSIS...MD/DS
NEAR TERM...MD/DS/MET
SHORT TERM...MD
LONG TERM...DS
AVIATION...MET
MARINE...MD/DS/MET
HYDROLOGY...MD/DS