000
FXUS61 KOKX 131449
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1049 AM EDT Thu Jul 13 2023
.SYNOPSIS...
-- Changed Discussion --
A cold front and associated pre-frontal trough approach from the
north and west through this evening. The front then settles over
the area tonight and remains nearby into Friday night.
Unsettled weather is expected much of the time from Saturday
through Thursday as a series of frontal boundaries move across
the area.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
The forecast remains on track early this morning.
Main concern for this afternoon/early evening is potential
convection along/ahead of a pre-frontal trough. The associated
cold front will also be approaching. Convection is expected to
initiate to the NW this afternoon along the pre-frontal trough,
and then drop south and east towards the interior late afternoon
and evening.
Most of the CAMs show afternoon moving in across locations
mainly to the north and west of NYC. Model forecast of bulk
shear 0-6 km AGL indicates 25-30 kt so combined with the
instability, there could be some strong to severe thunderstorms
with potential for hail and strong wind gusts. This threat
appears limited to the interior of the Lower Hudson Valley. If
a pulse storm can initiate a bit further east this afternoon,
there could be a strong gust as well. There is a substantial
amount of CAPE between -10C and -30C, so hail cannot be ruled
out. Locally heavy rainfall is possible in any shower/storm. The
threat is limited further east this afternoon due to a bit more
CIN and dry air aloft.
The forecast highs range from the upper 80s to lower 90s with
heat indices in the lower 90s with some mid to upper 90s. Since
yesterday featured max heat indices were only in the lower 90s,
there will not be two consecutive days of 95 to 99 degree heat
indices. Forecast heat indices today are expected to remain
below 100.-- End Changed Discussion --
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
The cold front will begin to enter into the region tonight. Forecast
models indicate frontal entrance towards Lower Hudson Valley late in
the evening and then slowly moving southeast through overnight into
the more coastal sections of the region. There is a wave of low
pressure the models are also resolving to form and move along the
front. The low pressure wave will slow down the front and will help
enhance rainfall. More waves of low pressure develop along the
front move northeastward Friday into Friday night. Enhancing
lift will be a departing upper level jet streak early Friday
with its right rear quadrant near the region.
There are model differences with the timing of individual low
pressure waves, the cold front and therefore differences with the
timing of groups of showers and thunderstorms. The NAM Nest
convection depicts a line of showers and thunderstorms moving in
late evening to the north and then moving southward into the local
region for overnight whereas other CAMs keep the convective line
north of the forecast region.
With a majority of the CAMs indicating not much of any convection,
lowered the POPs for tonight with a south to north gradient to the
POPs. The northern half of the forecast region will have a higher
chance for showers and thunderstorms compared to the southern half.
Again, model bulk shear 0-6 km AGL indicates around 30 kt so
combined with the CAPE, again there could be some strong to severe
thunderstorms with potential for hail and strong wind gusts,
tonight into Friday night.
Layer precipitable water increases to near 2 inches late tonight
through Friday night. This will be an indication of the airmass
becoming very humid to allow for any thunderstorm to produce
torrential downpours.
The showers and thunderstorms continue at times Friday through
Saturday. There will likely be lulls in the activity so it will
not rain the entire time. Heavy rain will become primary threat
without too much change in CAPE. With nearly parallel flow from
lower to upper levels, there will be training of showers and
thunderstorms where showers and thunderstorms develop and move
across the same area. This will increase the flood threat. Still
not nearly high enough confidence to go with any flood watch
however.
The CAMs have much variety in their reflectivity forecasts so
the forecast confidence on the timing of showers and
thunderstorms and where the heavy rain will occur is low.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Stuck fairly close to the NBM through the long term period
overnight, with unsettled conditions continuing through much of the
time frame.
Saturday night and Sunday, yet another upper level shortwave and
surface trough/low pressure approach the region and move across the
area. Once again, with a rather humid airmass in place, PWATS values
over 2.25 inches, heavy rainfall will be possible. WPC continues to
keep a large portion of the CWA in the day 4 ERO outlook (Slight
Risk).
Additional rounds of rainfall continue into the middle of next week,
and with antecedent moisture at least a nuisance flood risk will
remain.
Conditions remain warm and humid through much of next week, with
highs in the 80s and lower 90s.
&&
.AVIATION /14Z THURSDAY THROUGH MONDAY/...
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A weak frontal boundary will remain north of the terminals
today. A cold front then approaches tonight into Friday.
Generally VFR and dry for most terminals through 00z. Forecast
becomes a bit tricky with placement of any showers and
thunderstorms. Latest CAMS keep most of the shower and
thunderstorm activity north of the NYC terminals, however there
are still a few models showing some thunder at the NYC terminals
after 00z. With so much uncertainty will only carry a PROB30 at
KSWF where the highest confidence of thunder occurring is
expected. The timing of the PROB30 may have to be adjusted by an
hour or two. Otherwise, will leave the NYC terminals dry for
now, based on low confidence on timing and placement for any
storms.
Light and variable winds this morning become SW-S 12-16 kt, on
average, with gusts 18-25kt by midday with additional sea
breeze enhancements developing by afternoon. Winds become light
once again tonight.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
AMD possible for start time of gusts this afternoon.
Low confidence of any shower activity in and around the NYC
metro terminals tonight into Friday morning.
OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY...
Friday: Showers/thunderstorms likely with MVFR, IFR possible at
times in the afternoon.
Friday night: Chance of evening showers/thunderstorms, then MVFR or
lower conditions possible.
Saturday: MVFR or lower possible in the morning, otherwise VFR with
a chance of showers/thunderstorms in the afternoon and evening.
Sunday and Monday: Chance of showers/thunderstorms with MVFR or
lower.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
-- Changed Discussion --
Sub-SCA conditions expected through Saturday night. Brief 25 kt
gusts on ocean western Long Island late this afternoon are
forecast, but only occasional.
Sunday into the first part of next week, conditions are expected to
remain below SCA levels.-- End Changed Discussion --
&&
.HYDROLOGY...
Multiple rounds of showers and thunderstorms are expected
through Friday night. Moderate to heavy rain will be possible
especially tonight through Friday. The Weather Prediction Center
has placed the forecast area in a marginal risk for flash
flooding today into tonight and a slight risk for flash
flooding Friday into Friday night. Smaller streams and fast
responding rivers may flood, along with urban and poor drainage
areas.
Additional rounds of moderate to heavy rain will be possible
Saturday and Sunday, and the threat of flash flooding and
nuisance and minor flooding of poor drainage areas remains.
&&
.TIDES/COASTAL FLOODING...
There is a moderate risk of rip current development at all the
ocean beaches today through Friday.
Southerly winds with southerly swells of 2-3 ft will be in place
across the ocean beaches during this time period.
If winds trend higher than forecast however, a high risk of rip
current development would occur at the ocean beaches.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...BC/JM
NEAR TERM...JM/DS
SHORT TERM...JM
LONG TERM...BC
AVIATION...BC/DW
MARINE...BC/JM
HYDROLOGY...BC/JM
TIDES/COASTAL FLOODING...