970
FXUS61 KOKX 181105
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
605 AM EST Wed Dec 18 2024
.SYNOPSIS...
High pressure over the area this morning quickly retreats
offshore as frontal system approaches from the southwest. A
frontal wave will then move across the area this evening,
passing to the east by midnight along with the associated cold
front. High pressure briefly returns on Thursday into early
Friday before a clipper low passes to the south and an offshore
low tracks well east Friday into Saturday. High pressure then
builds late in the weekend into early next week. A weak low may
pass Christmas Eve into Christmas Day.
&&
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Temperatures have radiated quite well with mainly clear skies
and light winds. Outlying areas ranged from the upper 20s to mid
30s. However, the NYC metro was in the lower 40s. Temperatures
have been updated based on latest obs.
Otherwise, a n active pattern will continue as Pac jet energy
interacts with energy in the northern branch of the polar jet.
With no blocking over the North Atlantic, these features
continue to be progressive. The next system will be a frontal
wave over the Tennessee and Ohio Valleys today that tracks
northeast and into the area early this evening. Overrunning
rains out ahead will break out late this afternoon into early
this evening. Much of the guidance takes the low over or just
south of LI. This will make it tricky with wind direction and
whether or not coastal locations briefly get into the warm
sector. The latter of which could impact temperatures.
Instability is weak though, so not expecting any thunderstorms
if we do indeed warm sector. Due to the winds slackening this
evening with the frontal wave, expect a period of fog.
Rain will be moderate at times, but will get swept quickly
east with a cold frontal passage by midnight. Rainfall amounts
of 0.25-0.50" can be expected. Guidance has generally backed
off the last 24h with a little less amplification of the northern
branch shortwave. However, some of the guidance is pointing
toward a post-frontal band with the upper jet. This may add a
bit more rainfall. Thus, have maintained rain chances after
midnight.
As for temperatures, went with the warmer deterministic NBM for
highs today in the upper 40s to lower 50s, but then at or just
above for lows tonight due to the gusty NW flow and cloud
cover. Lows tonight will range from lower to mid 30s inland, to
the upper 30s to around 40 at the coast.-- End Changed Discussion --
&&
.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
Behind the cold front, expect a gusty NW flow of 15 to 25 mph,
which will gradually weaken heading into Thursday afternoon as
high pressure builds in from the west. The next amplifying upper
trough will send a clipper low into the Ohio Valley Thursday
night. Cloud cover will likely begin to work into the area with
the upper trough as well as some strengthening low-level warm
advection. However, expect it to remain dry at this time.
Temperatures Thursday and Thursday night will return to normal
levels.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
* A light rain snow mix Friday into early Saturday.
* 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.
* Christmas Eve (Tue) and Christmas Day (Wed) likely to stay dry
with more cloud cover and somewhat moderated temperatures,
though still below average. There is a possibility of a light
rain-snow mix.
Model guidance appears to be in good agreement on a solution for the
Friday-Saturday system we have been highlighting for the last
several days.
An Alberta Clipper low will be approaching the area early Thursday,
but is expected to rapidly weaken before arriving as its energy get
caught up in a deepening trough and transfers to a strengthening
offshore low which will pass to our southeast on Friday then
northeast into the Canadian Maritimes by early Saturday.
Light precip is possible with the approaching clipper system on
Friday. Nothing significant is expected due to the weak nature of
the clipper low. In fact, its entirely possible we could be mainly
dry on Friday with only isolated chances for showers. It will depend
on how weak the clipper low gets on its approach to the region.
Friday night into early Saturday, light precip is expected to remain
as we get impacted by the outskirts of the offshore low as it
passes. Most of the upper-level energy is expected to be offshore,
so not expecting much. The event will likely end up being a rain-
snow mix. Rain for coastal areas, with snow inland through the day
on Friday. Friday night rain will transition to snow along coastal
areas as cold air filters in behind the low as it exits to our
northeast and also aided by a deepening longwave trough over the
northeastern US. Precip will quickly end Saturday morning/midday as
dry air gets more entrenched as the low moves farther and farther
away. Only a few tenths of an inch worth of liquid QPF are expected
for the Friday-Saturday system. SNow accumulations may total a few
inches for far interior areas while coastal areas may only see a few
tenths accumulate, due to the rain transitioning to snow later
Friday night and the precip quickly ending.
Highs on Friday will be in the mid-30s in the northern interior, and
low.mid-40s for the remainder of the CWA. Temperatures will be
dropping Friday night, as low as the low-20s to near 30.
A strong Canadian high builds in from the Great Lakes region through
the weekend with a longwave trough aloft, that doesn`t make its exit
until Sunday night. Mainly dry weather and sunshine is expected
during this period with a very cold air mass in place. Highs on
Saturday will peak between 25 and 36 degrees north to south.
Saturday night is when the cold air will really begin to be felt
with lows dipping into the single digits in the northern interior.
The remainder of the CWA will drop into the teens. Given 5-10 mph NW
winds, wind chills Saturday night could drop near or below zero.
SUnday will be the coldest afternoon with highs in the mid/low-20s
area-wide. Lows Sunday night will again be in the teens to single
digits. Some areas of the interior of Orange county may near zero.
Surface high pressure centers over New England on Monday as heights
rise aloft under a mostly flat ridge. Highs on Monday will nudge
slightly warmer as a result in the mid-20s to low-30s. Monday night
lows will be in the teens to low-20s.
A weak low and associated mid-level shortwave approaches and passes
Tuesday (Christmas Eve) into Wednesday (Christmas Day). Most model
guidance either has a weak low passing or has high pressure stamping
out the low before it makes it here. Timing and strength of the
system still varies among the available 00Z global guidance. For
now, best guess is that we may see a mainly dry Christmas Eve and
Christmas Day with extra cloud cover. But the chance for light
precip remains. Model guidance also varies on temperatures so either
rain or snow or a rain-snow mix is still possible. But for now,
still looking to be on the lighter side of things. However, this far
out in the forecast, look for things to still change some.-- End Changed Discussion --
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
Weak high pressure briefly settles in this morning followed by a low
that traverses over the area this afternoon into tonight, exiting
northeast tomorrow with high pressure building in again from the
west.
VFR. Becoming MVFR toward 22Z with light rain developing, then
lowering to IFR by 02Z, with the NYC metro terminals remaining MVFR,
with a chance of IFR. Returning to VFR after 8Z tomorrow.
Winds are currently light and variable. A light southerly flow
develops by midday, and then as the low approaches late Wednesday
afternoon winds shift to the east to southeast. Depending on the
track of low pressure, winds may briefly become light and variable
this evening. Then with the low passing to the east, winds become
northwest. Winds increase as the rain ends 10-15 kts with gusts
around 20 kts possible early tomorrow morning into early tomorrow
afternoon.
...NY Metro (KEWR/KLGA/KJFK/KTEB)TAF Uncertainty...
No unscheduled amendments until late this afternoon and evening with
the onset of rain and lowering flight categories.
OUTLOOK FOR 12Z THURSDAY THROUGH SUNDAY...
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-- End Changed Discussion --
&&
.MARINE...
An approaching frontal wave today will bring a period of marginal
SCA conditions to the ocean waters tonight, both in the pre-
frontal SW flow and post-frontal NW flow. However, it does look
to be short-lived and should end by late Thursday morning. High
pressure will then build in from the west.
SCA conditions will not be met Friday. An offshore low passes
east of 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.
&&
.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 from 10 PM this evening to 10 AM EST
Thursday for ANZ350-353.
Small Craft Advisory from 1 AM to 10 AM EST Thursday for
ANZ355.
&&
$$
SYNOPSIS...BR/DW
NEAR TERM...DW
SHORT TERM...DW
LONG TERM...BR
AVIATION...BR
MARINE...BR/DW
HYDROLOGY...BR/DW