000
FXUS61 KOKX 202009
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
409 PM EDT Wed Mar 20 2024
.SYNOPSIS...
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A cold front moves across into early this evening. Low pressure
moves from Northern New England into the Canadian Maritimes
tonight into Thursday. High pressure will be in control Thursday
night into Friday. High pressure pushes offshore late Friday
with low pressure and its inverted trough impacting the area
Saturday into Saturday night. High pressure ridges down from the
north Sunday into Monday as low pressure slowly pushes further
offshore. A frontal system approaches from the west midweek.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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Mid level trough and vort max move across the region going
through early to the middle of this evening. The increase in
positive vorticity advection will enable for increasing lift. At
the surface, a cold front will be moving across the region late
this afternoon into early this evening. Scattered to numerous
showers move across the region going into early this evening
with a decreasing trend after 23Z.
By around 00Z, the front should be exiting southeast of the
region across the ocean waters. Central low pressure will stay
north of the region and deepen as it is expected to move into
Northern New England tonight. The increase and steepening of
the pressure gradient will drive an increasing NW flow,
increasing cold and dry air advection.
Temperatures running a little cooler than forecast so some
colder air advecting in as well as wet bulb cooling will allow
for some snow to mix in with the rain showers before all
precipitation ends. The snow showers mixing in is expected
across the interior areas with the coast staying mainly plain
rain showers. Would expect precipitation to taper off fairly
rapidly this evening as more drier air gets advected into the
region.
Slowed down the decrease of clouds late tonight that models
were conveying as there will be cyclonic flow aloft which tends
to have more clouds on average. Used a blend of NBM and MOS
consensus for lows tonight, ranging from the upper teens and low
20s across parts of the interior to upper 20s to near 30 for
much of the coastal areas.-- End Changed Discussion --
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
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Mid level ridging and negative vorticity advection on Thursday will
allow for more subsidence. Expect dry conditions with lessening
cloud coverage. The airmass over the area for Thursday and
Thursday night will be very cold for this time of year so below
normal temperatures are expected. Forecast highs and lows will
be near 5 to 10 degrees below normal.
At the surface, central low pressure will be nearly the same
strength as it moves towards and eventually into the Canadian
Maritimes Thursday into Thursday evening. High pressure will
gradually build in from the north and west but its center will be
staying more within the Great Lakes region.
Gusty NW winds will continue during the day Thursday and then
subside Thursday night with high pressure having more influence
across the area.
High temperatures forecast Thursday followed closely with the
combination of consensus of MOS and NBM, ranging from upper 30s
to near 40 across much of the interior to lower 40s along the
coastline. However, with the wind, the wind chills will be at
most in the upper 20s to mid 30s Thursday afternoon.
The lows forecast Thursday followed closely to the same blend
of guidance, with the whole area expected to be below freezing.
The range of lows is from upper teens to near 20 across much of
the interior to mid to upper 20s along much of the coast.-- End Changed Discussion --
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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Dry conditions take place to begin the period on Friday with a
strong confluence zone beginning to push out. High pressure settles
over and just north of the area early in the day. The high will then
get further east later in the day and for the evening. This is when
clouds begin to streak in from the west at first from a primary low
which starts to weaken as it moves east. Another area of low
pressure gets organized along the southeastern US coast. This will
very slowly lift northeast Friday night into Saturday. More
importantly an trough will emanate from the low in a south to north
fashion. The eastern edge of this feature will serve as the moisture
track per say for the low down to the south. The winds aloft will be
more out of the south and that should pool moisture along the trough
and lift the lower latitude air and rain into the CWA. Figure the
rain will start after 06z Friday night, and probably closer to 9z or
so for most areas, and closer to 12z Saturday for far eastern
sections. The likelihood of northern sections beginning as a mix or
wet snow has decreased a bit with the last couple of runs. By mid
morning Saturday the steadiest / heaviest rain should get into the
region, from NYC and points east. There appears to be fairly good
agreement now that the trough leans east going through the day which
should get the axis of heavier rain further east. Such that by late
in the day and into the evening much of the rain will be light for
western sections (mainly west of the Hudson River and the city),
with the steadier rain shifting into far eastern sections during
Saturday evening. From 6Z to 12z Sunday there is a chance that the
rain shuts off, or at least tapers significantly across eastern
sections as the moisture axis shifts offshore. The new ECMWF
supports this thinking. The German ICON appears to be the model that
is an outlier as it closes the low off closer to the coast, and thus
keeps significant rain across much of the CWA through much of
Saturday night. If this solution occurred then there would likely be
flooding concerns into NE NJ, the lower Hudson Valley, and NYC where
flash flood guidance is lower, compared to the higher flash flood
guidance and sandier soils across eastern most sections. WPC
maintains the Marginal risk of excessive rainfall for the majority
of the CWA (with the exception being portions of Orange and Putnam
counties) and a Slight risk to the immediate south for Central and
Southern NJ. Collaborated with WPC and thought it prudent to
maintain the current excessive rainfall outlook. However, if things
shift just a little bit west with NWP guidance and that axis of
heavier rainfall then the excessive rainfall / river flood risk
would increase where the lower FFG is. Thinking a 1 to 2 inch
rainfall, with amounts generally increasing from west-northwest to
east-southeast. See Hydrology sections for further details.
Sunday through Monday remains a difficult forecast. The models
continue to handle the mid / upper level feature differently in terms
of the details. The difficulty lies in forecasting PoPs and how much
shower activity will be left over with the low as it attempts to
close off and be more of a drifter and non-progressive. It could
remain predominantly dry and mostly cloudy. Maintained a good deal
of clouds through Sunday with a chance to slight chance of showers.
Some guidance also hints at showers attempting to linger for a
portion of Sunday night into early Mon AM, more so for eastern
sections. This is where low end chance to slight chance PoPs are
maintained for now. Due to the pressure gradient remaining tight
with high pressure building across Southern Canada and offshore low
pressure look for brisk conditions, and windy conditions for eastern
coastal sections.
The upper level ridge axis draws closer Monday into Tuesday. This
should lead to a decrease in clouds and more in the way of sun
potentially by Monday afternoon. This will depend on how far west
any influence of the offshore / upper low low gets. The northeast
wind will continue to be felt. The winds decrease gradually over
time and should be noticeably less into Tue PM. The next frontal
system will approach late Tue night or Wed. With the upper level
height field increasing into Tue this may delay the next system from
getting any closer until Wed as differences in timing show up in the
various NWP suites. Night time temperatures through the period
should average close to normal, with daytime temperatures likely
remaining a few degrees below normal.-- End Changed Discussion --
&&
.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
A cold front passes across the terminals this afternoon.
VFR with scattered showers ending 21-00z. SW-W winds around 10 kt
increase as they veer towards 21-00z with a shift into WNW shortly
thereafter and increasing with gusts 30-35kt until around 06z. Winds
diminish at little overnight before picking up again towards the end
of the Thursday morning push.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Winds may be stronger by around 5 kt than forecast before 21-23z and
may be veered by 20-30 degrees than forecast at times. Gusts 30kt+
may end a few hours before 06z. Chance of showers may continue
around an hour longer than forecast in TEMPO group.
OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY...
Thursday PM: VFR. WNW gusts 25-30kt, diminishing to around 20kt by
midnight
Friday: VFR.
Friday night: MVFR or lower developing after midnight with rain near
the coast and rain/snow inland.
Saturday: IFR and rain. SE wind gusts 20-25kt during the day with
LLWS possible city east, becoming N all areas with gusts around 30kt
at night.
Sunday: VFR. N-NE wind gusts around 25kt.
Monday: VFR. NE gusts 20-25kt.
Detailed information, including hourly TAF wind component
forecasts, can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
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Winds expected to rapidly increase behind a cold front this
evening as the pressure gradient tightens. Associated low
pressure will strengthen as it heads into Northern New England
tonight and then will remain nearly the same strength as it
moves into the Canadian Maritimes Thursday.
SCA conditions expected going into early this evening on the
ocean with perhaps some occasional 25 kt gusts on non-ocean
waters. Then as the evening progresses, gale force wind gusts
are expected to develop on all waters, continuing through the
rest of tonight. The gales continue into Thursday morning for
most of the waters before winds decrease more into SCA range
Thursday afternoon into Thursday night.
A relaxed pressure gradient will result in quieter conditions to
begin Friday, however an onshore flow increases late in the day and
into Friday night. Small craft conditions will develop by Saturday
morning out on the ocean, and by the afternoon for the eastern
nearshore waters. A prolonged period of gales is looking likely late
Saturday night and through at least the first half of Monday for
much of the coastal waters. This period of gales may last longer and
into Monday night, especially out on the ocean and eastern most near
shore waters.-- End Changed Discussion --
&&
.HYDROLOGY...
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Total precipitation of less than a quarter inch through tonight
(mostly in the form of rain) will not present any hydrologic
issues.
Rain on the order of 1 to 2 inches on average is expected late
Friday night through Saturday, and into a portion of Saturday night
mainly for eastern sections. Some minor nuisance urban flooding is
expected where the axis of heavier rain sets up. Flash flood
guidance has recovered some over the past week from previous rain
events, but there remains some elevated pockets of soil moisture.
However, the coverage of elevated soil moisture has decreased. As of
now the axis of steadier, heavier rainfall would be over the eastern
half of the area where flash flood guidance is relatively higher,
but if this axis shifts further west where flash flood guidance is
lower then at least minor river flooding would be brought into play
for NE NJ and perhaps even the Lower Hudson Valley. WPC maintains
the Marginal risk of excessive rainfall across the majority of the
CWA, but overall the flood risk remains limited at this time.
However confidence remains lower than ideal, thus this could change
in subsequent forecast releases.-- End Changed Discussion --
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None.
NY...None.
NJ...None.
MARINE...Gale Warning until 10 AM EDT Thursday for ANZ331-332-335-340-
345.
Gale Warning until 6 AM EDT Thursday for ANZ338.
Small Craft Advisory until 6 PM EDT this evening for ANZ350-
353-355.
Gale Warning until noon EDT Thursday for ANZ350-353-355.-- End Changed Discussion --
&&
$$
SYNOPSIS...JM
NEAR TERM...JM
SHORT TERM...JM
LONG TERM...JE
AVIATION...JC
MARINE...JE/JM
HYDROLOGY...JE/JM