000
FXUS61 KOKX 100941
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
541 AM EDT Thu Aug 10 2023
.SYNOPSIS...
A low pressure system impacts the region this afternoon and tonight.
High pressure follows for Friday and should last into at least part
of Saturday. A frontal system will then move across the area late
Saturday into early Sunday. High pressure briefly settles in again
before another frontal system moves in late Monday. High pressure
returns for mid-week.
&&
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
The forecast is mainly on track. Just some minor adjustments
made to some of the hourly grids to capture the latest trends.
Weak low pressure approaches from the west today. The center is
still progged to pass through or nearby the forecast area late in
the day today into this evening. This appears to be the case based
on radar so far, but another low center could be passing to our
south off the Mid-Atlantic Coast. Rain expected this afternoon and
evening - shifting east of the forecast area by around midnight.
One concern with this system will be the potential of heavy
rainfall. PWATs increase to 1.75-2.00 inches late today as the warm
sector of this system shifts into the area. Upward forcing in the
vicinity of the low center plus perhaps some upper level divergence
courtesy of a jet streak nearly overhead would help enhance
rainfall. The main limiting factor for flooding potential will be
the progressive forward motion of the system. Also notable is that
just about all of the 00z Weds global and hi-res regional models
have trended downward with rainfall amounts from their 12z and 18z
Tuesday counterparts. NBM shows a less than 25% chance of an inch of
rainfall in a 6-hour period. HREF chances of an inch of rain in a 1-
hour period are under 25% as well. In addition, WPC has
downgraded just about the entire area from a slight to a
marginal risk of excessive rainfall. So while a there is still a
potential for flash flooding to occur, thinking is that the
chances of a widespread enough occurrence are too low to warrant
a flood watch. Most of any flooding would be of the
minor/nuisance type.
Another concern will be the threat of severe weather. Winds
aloft in the mid levels are expected to increase to around 35kt
mid-afternoon into the evening. This will provide some speed
shear along with directional shear in place with a veering wind
profile with height. Enhanced directional shear/low-level
helicity will be enhanced in the vicinity of the warm front -
more likely over eastern portions of the forecast area. SPC
continues to keep eastern LI and SE CT under a marginal risk for
severe wx for this reason in spite of modest CAPEs. Main threat
would be strong wind gusts - which is a low threat, and even
lower threat for a tornado. Really can`t rule out the threat of
a strong to severe wind gust anywhere in the forecast area given
the winds aloft.-- End Changed Discussion --
&&
.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
The flow aloft transitions from zonal to slightly anticyclonic
Friday into Friday night. This will allow for weak high pressure to
build in at the surface. Sunny and less humid with the help of a WNW
wind flow. Blended the 75th and 90th percentile NBM for high
temperatures given the sunny conditions with a downsloping wind and
13-14C at 850mb. Remaining dry Friday night with lows ranging mostly
from the lower 60s to around 70, but some spots along the northern
fringe of the forecast area may drop into the upper 50s.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Not much change in the long term and stuck close to the NBM
guidance.
Saturday morning is expected to remain dry as high pressure slides
east. By afternoon, mid level troughing develops out ahead of an
approaching cold front. Expecting just a chance of a shower or
thunderstorm during the afternoon. Those POPS increase as we get
into Saturday night and the first part of Sunday as the front moves
across the region. Mainly drier conditions are expected for later
Sunday into the first half of Monday, however another frontal system
will bring unsettled conditions back to the region for Monday
afternoon into Tuesday. High pressure then returns for mid-week.
Temperatures will be near normal for this time of year through the
long term...generally in the 80s for highs.
&&
.AVIATION /10Z THURSDAY THROUGH MONDAY/...
Low pressure approaches from the west early this morning,
passing over, or just south of the terminals during the
afternoon.
VFR to start, with showers developing late in the morning.
Conditions lower to MVFR this afternoon (around 17z or so), and
possibly to IFR, especially in heavier showers and thunderstorms.
There is uncertainty with the areal coverage and strength of the
thunderstorms and this is dependent on the track and depth of low
pressure, along with the placement and timing of a warm front.
Westerly winds become light and more southerly early this
morning. For later today, there is a high degree of uncertainty
with the wind directions, strength, and timing of wind shifts,
and gusts. This is all due to uncertainty with the track and
strength of low pressure. For now, will go with more of a
southerly wind until the wind shift to the W-NW later tonight.
Conditions improve between 00z-06z tonight with VFR conditions
returning.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Low confidence and high uncertainty with the winds and potential
gusts today, due to uncertainty with the track and strength of
low pressure. Also, the timing and strength of thunderstorms
depends on the low and a warm front moving toward the area
this afternoon.
OUTLOOK FOR 06Z FRIDAY THROUGH MONDAY...
Thursday Night-Friday: Showers end early Thursday night,
becoming VFR.
Saturday-Sunday: Mainly VFR. Chance of showers, possibly
thunderstorms, late Saturday into Sunday.
Monday: VFR early, then a chance of MVFR with a chance of
showers and thunderstorms.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
SW-W winds increase this afternoon with the approach of storm
system. There is a chance that SCA conds could be briefly met on the
ocean waters late in the day into the evening. Have decided to not
issue an advisory due to the short duration of the this possibility.
Offshore winds then follow for late tonight through Friday night.
Sub-SCA conditions are expected to persist Saturday into Monday.
Seas will increase to near SCA levels late Monday night into Tuesday
behind a cold frontal passage.
&&
.HYDROLOGY...
A basin average of 0.50 to 1.50 inches of rainfall with the
potential of locally higher amounts is forecast for this afternoon
into evening. The heaviest rainfall is expected to occur from the
second half of the afternoon into the evening. Mainly minor/nuisance
flooding is expected with this system but flash flooding cannot be
completely ruled out. Should flash flooding occur, the most likely
area to see it would be in NE NJ and NYC where it`s typically more
prone to flooding.
&&
.TIDES/COASTAL FLOODING...
There is a moderate risk for rip currents on ocean beaches today
through Saturday.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...BC/JC
NEAR TERM...JC
SHORT TERM...JC
LONG TERM...BC
AVIATION...BC
MARINE...BC/JC
HYDROLOGY...BC/JC
TIDES/COASTAL FLOODING...