855
FXUS61 KOKX 092024
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
424 PM EDT Fri Aug 9 2024
.SYNOPSIS...
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A cold front moves through late tonight into early Saturday
morning. High pressure off to the west builds in for Saturday
into Saturday night. A weak front moves offshore on Sunday,
allowing high pressure to build in west of the area through next
week.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Tornado Watch 617 which includes Orange County, Rockland,
Putnam, and Westchester in New York, and Essex, Union, Bergen,
and Passaic counties in NJ, remains in effect until 10 pm
tonight.
Main line of showers and thunderstorms will continue to push
through the forecast area tonight in association with a cold
front. The cold front is expected to move offshore around
daybreak Saturday or a couple of hours thereafter. South to
north warm conveyor belt bands of tropical showers continue to
develop across the area the Lower Hudson Valley, NE NJ, and
southern CT. However, these are expected to push eastward
through the night, again as the cold front pushes through. With
moderate instability, and high helicity, this could result in
mini supercells this evening. Best chance is across the watch
area across NE NJ and the Lower Hudson Valley.
The trend of a faster system and less rainfall continues. We
are now looking at about a quarter to a half inch across NYC
and LI, with amounts of 1 to possibly 1.5 inches to the north
and west. Western portions of Orange County NY and western
Passaic could see amounts closer to 1.5 inches. Thus, localized
higher amounts are possible, but storms will track quickly
south to north along the front and pre-frontal trough, which
will also be steadily moving east. WPC has areas north and west
of NYC in slight risk for excessive rainfall, with a marginal
risk to the east. But again, the quick moving nature of these
storms will likely preclude scattered instances flash flooding.
While the most likely result will be urban and poor drainage
flooding, isolated instances of flash flooding cannot be ruled
out.
As for the severe weather threat, this is very much a tropical
airmass with skinny CAPE (mainly 500-1000 J/KG) and increasing
deep-layer shear. Hodographs across the area show helicity
values increasing to 200-300+ m2/s2 early this evening across
the Lower Hudson Valley and NE NJ, with lower values to the east
(mainly due to weaker shear vectors and smaller hodographs
areas). Thus, there is a local threat for brief tornadoes with
mini supercell development (low-topped convection). Latest CAMs
do show weakening of the convection as it works toward coastal
area tonight, partly due to the weaker shear and decreasing
instability.
There Wind Advisory continues across coastal and SW CT, NYC,
Long Island, northeast NJ, and the Lower Hudson Valley. With
mixed layer winds showing the potential of mixing down 40 kt (46
mph) gusts to the surface this afternoon into this evening.
This is mainly due to scattered reports of downed trees across
these areas, likely in association with the higher winds aloft
being brought down with convection over areas where the soil is
saturated. The ending time for Wind Advisory for the coastal
areas has been shortened to 2 am as the LLJ is expected to push
east by around this time.
It will be warm and muggy with temperatures in the upper 70s to
lower 80s with dew points well into the 70s. In fact, there
are heat indices around 90 at the coast this afternoon.
Overnight lows will be in the upper 60s to lower 70s with some
drier air arriving behind the front late.-- End Changed Discussion --
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
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A westerly flow on Saturday will bring in a significantly drier
air mass into the region. Cold advection lags behind the front
and the airmass should heat up nicely into the lower and mid
80s. Dew points will be falling through the 60s. Dry conditions
with seasonable temperatures will be on tap for Saturday night.
Lows Saturday night will be near normal, ranging from the upper
50s inland, to the upper 60s along the coast and into NYC. Dew
points should fall into the upper 50s to lower 60s, possibly
lower as models typically do not handle the influx of drier air
too well.-- End Changed Discussion --
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
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A weak boundary over the region will pass out to sea on Sun as an
upr low reaches QC. The airmass will be moisture starved, so no pcpn
is expected on Sun.
The upr trof will leave suppressed heights across the region thru the
week. Moisture remains limited however, so only some isold aftn
shwrs/tstms modeled across the interior at times. Pops were kept at
slight chance, with the NBM timing followed.
Return flow from the ocean on Fri may add some upslope component and
allow for better coverage of shwrs, but this far out the prob
remains low at only 20-25 percent.
The NBM seemed reasonable for temps thru the extended, with some
cooler temps possible on Fri due to the onshore flow. In general,
low humidity thru the period, with an uptick on Fri.-- End Changed Discussion --
&&
.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
A strong cold approaches this afternoon and moves across later this
evening northwest and passes east early Saturday morning.
MVFR ceilings across the region may briefly be IFR, especially
along the coast and later this afternoon., however, low
confidence in flight categories and timing. As a line of
showers and thunderstorms move into the terminals late afternoon
into this evening with IFR conditions likely. After the main
band of showers and thunderstorms a few shower may in in the
area into late tonight with mainly MVFR, and possibly becoming
VFR before the showers end. Gradual improving conditions are
expected late tonight into early Saturday morning as the showers
end. Then VFR Saturday.
S to SE winds 15-25 kt with gusts 30-40 kt, strongest near the
coast, a few occasional gusts 40-45 kt. Winds should begin
weakening this evening once the front passes and wind direction
shifts to the SW to W. The timing of this shift and weakening
may be off by 1-3 hours in the TAF. Winds become W-WNW early
Saturday morning.
LLWS 45 to 55kt into early this evening ends quickly west to
east late evening into the overnight.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Low confidence flight category forecast into this evening with
amendments expected, with ceilings mostly MVFR.
Moderate confidence with the timing of main band of showers and
embedded thunderstorms late afternoon into this evening.
Peak gusts 40-45 kt possible 18-00Z.
OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY...
Saturday-Wednesday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
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Gales are up for all waters today into tonight. Gales could
come down sooner tonight with an inversion setting up and the
LLJ passing to the east. Seas on the ocean will build to 8 to
10 ft by this evening, with 3 to 6 ft across Long Island Sound.
Seas diminish late tonight but should remain above 5 ft on the
ocean waters for much of Saturday morning, then slowly diminish
to below 5 ft through Saturday night. Once the Gale Warning
ends Small Craft Advisories will likely be needed late tonight
on the non ocean waters, and on the ocean into Saturday night as
seas remain elevated.
Winds and seas are expected to subside blw sca lvls on Sun, and
remain blw criteria through at least Thu with high pres W of the
waters.-- End Changed Discussion --
&&
.HYDROLOGY...
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Isolated flash flooding will be possible tonight. Rainfall
rates of 1 inch per hour during the heaviest rain is likely,
with rates as high as 1.5 inches per hour in localized areas.
The best chance to see these higher hourly rates will be across
the Lower Hudson Valley. Rapid responding small stream flooding
and urban/poor drainage flooding will the likely outcome given antecedent
rains/saturated grounds. The overall chances for flooding is
lower across the entire forecast area, but the highest chances
are across New Jersey, into the lower Hudson Valley where WPC
maintains a slight risk of flash flooding. The remainder of the
area is in a marginal risk for flash flooding Rainfall amounts
will range from around a quarter to half an inch across LI and
the NYC metro (downward trend), to 1 to 1.5 inches north and
west.
There are no hydrologic concerns from Sun-Fri.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
There is a high risk for rip currents today through Saturday
evening as breaking surf builds to 5 to 11 feet by mid to late
afternoon and remains at least 7 feet into midday Saturday. A
high surf advisory remains in effect from noon EDT today through
noon EDT Saturday.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...Wind Advisory until 11 PM EDT this evening for CTZ005.
Wind Advisory until 2 AM EDT Saturday for CTZ009>012.
NY...Wind Advisory until 11 PM EDT this evening for NYZ067>075-176-
178.
Wind Advisory until 2 AM EDT Saturday for NYZ078>081-177-179.
High Risk for Rip Currents through Saturday evening for NYZ075-080-
081-178-179.
High Surf Advisory until noon EDT Saturday for NYZ075-080-081-
178-179.
NJ...Wind Advisory until 11 PM EDT this evening for NJZ002-004-006-
103>108.
MARINE...Gale Warning until 6 AM EDT Saturday for ANZ331-332-335-340-
345-350-353-355.
Gale Warning until 2 AM EDT Saturday for ANZ338.-- End Changed Discussion --
&&
$$
SYNOPSIS...JMC/JP
NEAR TERM...JP
SHORT TERM...JP
LONG TERM...JMC
AVIATION...MET
MARINE...JMC/JP
HYDROLOGY...JMC/JP
TIDES/COASTAL FLOODING...