098
FXUS61 KOKX 091819
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
219 PM EDT Fri Aug 9 2024
.SYNOPSIS...
A warm front will lift north of the area this morning, while
post-tropical depression Debby lifts north across the Appalachians,
interacting with an approaching cold front. The low will pass
well west of the area today and then to the north tonight, sending
a strong front through the area tonight into Saturday morning.
Broad low pressure will remain to the north from Saturday night
into the middle of next week, with high pressure off to the west,
and only a few weak surface troughs or cold frontal passages.
&&
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Tornado Watch 616 has been replaced with 617 and includes
Orange County, Rockland, Putnam, and Westchester in New York,
and Essex, Union, Bergen, and Passaic counties in NJ, which is
in effect until 10 pm.
Main line of showers and thunderstorms is just west of the
forecast area in western PA and south central NY as of just
after 2 pm. 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. With moderate instability, and
high helicity, this could result in mini supercells this morning
into the afternoon. Best chance is across the watch area across
NE NJ and the Lower Hudson Valley.
Warm front has lifted north across much of CT and eastern
portions of the Lower Hudson Valley and will continue to push
north this morning. Much of the shower activity is limited to
the Hudson Valley, NE NJ and inland southern CT, mainly north
of the warm front and to the south in the warm sector. Warm
precipitation processes in a tropical airmass are allowing for
heavier pockets of rain. As the morning progresses, much of the
shower activity will lift north of the area with the best
thermal forcing. However, the strengthening southerly flow to
the east of Post- tropical depression Debby will allow for
upslope and possible showers and isolated thunderstorms to
continue, but mainly across the Lower Hudson Valley. To the
east, dry air in the mid levels will keep coastal areas mainly
rain-free to start the day, barring some spotty activity.
At the same time, a large upper vortex across the Great Lakes
will send a strong cold front eastward. Moisture from Debby and
instability will allow for a band of heavy rain producing
showers and thunderstorms to work east and into far western
areas by late this afternoon, then working east through the
night, exiting far eastern LI and SE CT by daybreak. Trend over
the last few days have been for a faster system and less rainfall.
We are now looking at about half an inch across NYC and LI, with
amounts of 1 to possibly 2 inches to the north and west. Western
portions of Orange County NY and western Passaic could see amounts
closer to 2 inches. PWAT values will be at near all-time level
of around 2.50". Thus, localized higher amounts are possible,
but storms will track quickly south to north along the front and
pre-frontal trough, which will be steadily moving east. The
progressive nature of the system will spare the area much higher
rainfall amounts that looked possible earlier this week. WPC
has ares north and west of NYC in slight risk for excessive
rainfall, with a marginal risk to the east. There is a small
portion from Port Jervis west that is a moderate risk.
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 by this afternoon 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 is also a wind advisory for coastal locations with mixed
layer winds showing the potential of mixing down 40 kt (46 mph)
gusts to the surface this afternoon into this evening. 00Z HRRR
max gust potential showing about 45 kt. There is a chance that
some of these gusts push farther inland, but confidence is
lower. Wind Advisory may also need to shortened later for
eastern areas as the core of the LLJ passes to the east by early
morning.
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 /SATURDAY THROUGH SATURDAY NIGHT/...
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.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
A mainly dry period is expected, with plenty of sunshine, and near
to slightly below normal temperatures late this weekend into early
next week as a broad upper trough lingers over the Northeast. The
trough begins to pull out during mid week, with temps rising to a
little above normal by Wed-Thu.
A few surface troughs or weak cold frontal passages are possible
through the middle of next week. The current pattern will hold
tropical air south of the area, with dewpoints in the upper 50s and
lower 60s. With low moisture and weak lift, most of these surface
trough/weak cold frontal passages should be mainly dry, with no
more than 10 or 20 PoP.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
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-- End Changed Discussion --
&&
.MARINE...
Gales are up for all waters today into tonight.
As post-tropical depression Debby passes to the west today along
with an approaching cold front, southerly winds will steadily
increase this morning with gale force gusts possible by late
morning, continuing into the night. 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. Once the gale
warning ends small craft conditions linger into Saturday
morning on the non ocean waters, and on the ocean into Saturday
night as seas remain elevated. Otherwise, quiet cond should
prevail from then into Tue night, with generally light winds.
&&
.HYDROLOGY...
Isolated to scattered flash flooding will be possible later
today into early Saturday morning. Rainfall rates of 1 inch per
hour during the heaviest rain is likely, with rates as high as
2 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 be possible given antecedent rains/saturated
grounds. The overall higher chances for flooding will be across
northeastern 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 with mainly poor
drainage and urban flooding is possible. Rainfall amounts will
range from around half an inch across LI and the NYC metro
(downward trend), to 1 to 2 inches north and west.
There are no hydrologic concerns from Sat night into mid next
week.
&&
.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...
CT...Wind Advisory until 11 PM EDT this evening for CTZ005.
Wind Advisory until 6 AM EDT Saturday for CTZ009>012.
NY...Wind Advisory until 11 PM EDT this evening for NYZ067>070.
Wind Advisory until 6 AM EDT Saturday for NYZ078>081-177-179.
Wind Advisory until 11 PM EDT this evening for NYZ071>075-176-
178.
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-
103>108.
Wind Advisory until 11 PM EDT this evening for NJZ006.
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.
&&
$$
SYNOPSIS...DW
NEAR TERM...JP/DW
SHORT TERM...DW
LONG TERM...BG
AVIATION...MET
MARINE...BG/DW
HYDROLOGY...BG/DW
TIDES/COASTAL FLOODING...