000
FXUS61 KOKX 102130
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
530 PM EDT Tue Oct 10 2023
.SYNOPSIS...
Weakening low pressure north of Great Lakes will track slowly
east across eastern Canada through Thursday. At the same time,
weak high pressure will be centered over the central Appalachians.
High pressure will then briefly build across the area Friday
before a frontal system impacts the area over the weekend.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
-- Changed Discussion --
Minor adjustments were made based on current observations.
Otherwise, the forecast remains on track.
A large upper vortex centered just north of the Great Lakes will
gradually fill over the next couple of days, while working east
in tandem with its weakening surface low across eastern Canada.
To the south of it, there will be a progressive upper flow and
weak surface high centered over the central Appalachians. This
will keep the area under a weak WSW-SW surface flow with
seasonable temperatures.
In addition, like last night, there could be a few showers
and/or sprinkles overnight as another shortwave ejects out of
the Ohio Valley and into the area. While moisture is very
limited, these features have been able to squeeze some of it
out. The best chance based on latest CAMs would appear to be
across LI and SE CT. This is a low chance with sprinkles
elsewhere.
Lows tonight will be in the 40s with the exception of lower/mid
50s across the NYC metro. There is a bit of uncertainty as to
how much the area radiates with potential clouds associated
with the approaching disturbance.-- End Changed Discussion --
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/...
Once again weakening low pressure will track across eastern
Canada with weak high pressure to the SW. This will keep the
area generally dry and seasonable.
Another large upper vortex over the Pac NW and northern
intermountain region will be a player for another wet weekend.
This system emerges across the northern and central Plains
Thursday with the possibility of some warm advection well out
ahead of it sending mid level clouds into the area. Any light
rain at this time looks to stay to the south and west of the
area.
Highs Wednesday and Thursday will be in the mid to upper 60s
with even a 70 degree reading not out of the question. Lows
will be in the 40s with the exception of the lower 50s across
the NYC metro. This is pretty close to normal.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Ridging builds aloft on Friday between a departing low over the
Canadian Maritimes and a low over the Central Great Plains allowing
for high pressure building in at the surface on Friday from Canada.
Some mid-level moisture may spill over the ridge but, this likely
won`t be enough for any showers. Highs slightly below normal.
The ridge is pushed offshore by an strong mid-level low approaching
from the Great Plains. It is progged to track over the region late
Saturday with an associated surface frontal system with it, possibly
enhanced by a weak low tracking up the east coast. Rain will
likely start ahead of its arrival midday Saturday with the
heaviest and most widespread rainfall late Saturday into early
Sunday. PWATs will generally be between 1.2 and 1.35" which is
around 90% of the average moving mean and about 0.5" above
average. NBM`s probability for greater than 1" in 6 hours
remains low around 15-25%, so will likely be a long rainfall
event with only minor flooding issues being isolated. In total,
1.5-2.5 inches is possible across the entire CWA. NBM`s 25th
percentile gives us 0.75-1" while the 75th percentile gives us
2.5-3.25". This spread is still pretty large indicating
uncertainty in rain amounts, but it should arrive over a long
period, with light rain continuing into the day on Sunday as the
system departs. Deterministic models show large amounts of
positive vorticity advection at 500mb and strong warm air
advection at 850mb Saturday night into Sunday morning as the
frontal system passes over us. This may enhance the rainfall
enough to allow for periods of moderate rainfall. Afternoon
temperatures with this system will also be cooler due to
rainfall and cloud cover in the mid-50s, with some low-60s still
possible for some coastal areas on Saturday. Highs Sunday
should remain around the mid-50s for most. An increasing
pressure gradient late Saturday and through the day on Sunday
should allow for breezy conditions to develop.
A large mid-level trough flattens and lingers overhead on Monday
likely allowing for scattered to isolated POPs to continue and for
cooler temperatures to remain.
&&
.AVIATION /22Z TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --
Low pressure will continue to meander across southeastern Canada as
it gradually weakens through midweek.
VFR. SW to SSW this evening to around 10 kt with gusts 15-19kt
become light and variable later this evening and overnight.
A brief pop-up shower cannot be ruled out over the next couple of
hours. There are no expected impacts to vsby or cigs with these
showers.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Gusts might be only occasional, or may not occur at all. Chance that
winds turn more S this afternoon/early this evening for all
terminals.
OUTLOOK FOR 18Z TUESDAY THROUGH SUNDAY...
Tuesday Night-Wednesday: VFR.
Thursday: VFR.
Friday: VFR during the day. Chances for rain and MVFR or lower
at night.
Saturday-Sunday: MVFR/IFR in rain. ENE wind G15-20kt.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
A relatively weak pressure gradient over the waters Wednesday
through Thursday night will lead to winds remaining below SCA
levels. Ocean seas will continue to subside to 2 to 3 ft by
Thursday.
Sub-SCA conditions continue into Friday with an offshore flow.
Low pressure then approaches the Mid-Atlantic coast on Saturday
with winds veering ENE and increasing through the day and night
as a frontal system approaches us from the west. This will help
push wave heights above 5 feet over the ocean Saturday night,
with wind gusts around 25-30 kts across all waters.
&&
.HYDROLOGY...
No hydrologic impacts are expected through Friday.
Low pressure this weekend may bring 1.50 to 2.50 inches of rain
with locally higher totals possible. Since this would occur
over a relatively long duration of time, the overall chances of
flash flooding are low at this time. There is still some
uncertainty regarding potential rain amounts which leaves the
possibility of flash flooding open, but impacts would more
likely be minor/poor drainage flooding as well as some of the
quicker responding rivers and streams.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...BR/DW
NEAR TERM...BR/DW
SHORT TERM...DW
LONG TERM...BR
AVIATION...JP
MARINE...BR/DW
HYDROLOGY...BR/DW