discussion on 2023-07-06

000
FXUS61 KOKX 061950
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
350 PM EDT Thu Jul 6 2023

.SYNOPSIS...
-- Changed Discussion --High pressure remains offshore as a weak cold front approaches on
Friday. The front stalls over or near the area through the
weekend. Weak low pressure may then move through the region on
Monday followed by high pressure into the middle of next week.-- End Changed Discussion --

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
-- Changed Discussion --A few showers and thunderstorms have been able to get going in the
Lower Hudson Valley. A moist southerly flow over terrain in a
moderate CAPE/very low shear environment has allowed for pulse
thunderstorms and downpours. This activity will slow down heading
into late afternoon and evening as instability is expected to
decrease.

The mid and upper level shortwave ridge is now just east of the area
as surface high pressure slowly continues to shift east offshore. A
moist, light southerly flow will continue tonight. Guidance shows
fog and low stratus returning across much of the area. Dense fog is
possible, but thinking it will be more patchy.

Lows tonight will be in the upper 60s to mid 70s, a few degrees
warmer than normal for early July.-- End Changed Discussion --

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
-- Changed Discussion --On Friday, a digging upper trough and weak cold front approach
the area. Afternoon showers and thunderstorms are possible
again, mainly north and west of NYC. Instability will be the
greatest across far western Orange County (about 2000-2500 J/kg
of SBCAPE, similar to today) with a pretty sharp gradient
heading south and east across the rest of the area. Shear will
also be very weak. Severe thunderstorms are not expected,
however, pwats 1.75-2.00 inches and a weak steering flow will
allow for heavy downpours. Widespread hydrologic issues are not
expected, but localized flash flooding is possible. The WPC has
shifted the marginal risk a bit farther west, which matches
trends in latest guidance. Far western Orange County is likely
the only area with a localized flash flooding threat.

The cold front likely makes it about halfway through the area by
late Friday night, before stalling. Low stratus and fog could make
a return to the area Friday night, but for the eastern half of
the area.

Highs Friday will be in the mid to upper 80s, with lows similar
to Thursday night.-- End Changed Discussion --

.LONG TERM /SATURDAY THROUGH THURSDAY/...
-- Changed Discussion --There has not been much change to the forecast thinking for the
extended period. The long term appears somewhat unsettled into the
weekend as mean mid and upper level troughing and attendant
shortwaves impact the area into early next week. Ensemble means
continue to advertise a mean ridge over the northeast on Saturday
shifting offshore with a closed upper low over central Ontario
slowly working east and weakening into mid next week. This feature
will send a series of shortwaves and frontal systems through the
region during the period providing chances of locally heavy
precipitation and thunderstorms each day.

For Saturday, the area will reside on the back side of a surface
cold front. Deep southwesterly flow aloft continues as the front
looks to stall nearby or just to the south of the CWA. This will
provide focus for additional rounds of showers and thunderstorms
during the afternoon as the airmass destabilizes. Model soundings
again are showing some modest SBCAPE near 2000 J/kg on Saturday
afternoon, but shear remains weak so multicells look to be possible.
Some additional focus for the convective forecast will come into
better view over the next 12 hours as the timeframe enters the CAM
window.

The Canadian upper low looks to edge to the southeast on Sunday and
another frontal system and low pressure approaches from the
southwest for Sunday. The forcing aloft looks a bit better than on
Saturday with a shortwave rounding the base of the low. One change
from the previous forecast is the better forcing looks to now be
just west of the CWA, across southcentral NY/PA. BUFKIT soundings
showing PWATs increasing to nearly or just over 2" (which is near
the max value for date per SPC sounding climo) by Sunday afternoon,
which would raise the heavy rainfall potential with any
showers/thunderstorms that do develop. NBM probabilities of >1" in 6
hours is still relatively low, 5-15%, with the highest values across
the Lower Hudson Valley and SW CT, and the trend remains similar
from previous NBM cycles. WPC has maintained the northwestern
portions of the area in a slight risk of excessive rainfall on
Sunday.

The low pressure system and frontal system then looks to then slowly
move out of the area on Monday. High pressure then looks to build
back in by Tuesday and into Wednesday, with a slight warming trend
toward the end of the week.

Given the pattern, high temperates will remain near or slightly
below normal for the period in the low to mid 80s.-- End Changed Discussion --

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
Weak high pressure remains in place.

VFR this evening with a few notable exceptions...KEWR is
experiencing MVFR with some smoke some over part of the runway
due to a nearby cargo ship fire. It is unknown how long that
smoke may last at the airport. Also...patchy stratus has been
persistent along the south coast of Long Island... it may move
slightly inland during the next few hours allowing for MVFR or
IFR to re-develop sooner at KJFK and KISP especially toward
00z. Otherwise...Sub-VFR conditions should develop under low
stratus and patchy fog tonight and into Friday morning. Chance
of showers and thunderstorms north and west of NYC terminals
this evening and then again Friday afternoon. With the exception
of KSWF...probability not high enough to include in TAFs.

Southerly winds around 10kt this evening and Friday with light
and variable winds tonight into Friday.

...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...

Extent of smoke in time and placement at KEWR is unknown.
Offshore fog should stay at the immediate coast. Timing of
lowering categories tonight may be off by a few hours.

OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY...

Friday-Saturday: Mainly VFR. Chance of showers. Chance of
thunderstorms for NYC terminals and to the north and west in the
afternoon into early evening Friday. Chance of thunderstorms
for all terminals in the afternoon into early evening Saturday.

Sunday and Monday: MVFR possible with a chance of showers. A chance
of thunderstorms, mainly afternoon into early evening.

Tuesday... Becoming VFR.

Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90

.MARINE...
-- Changed Discussion --There is potential for dense fog overnight tonight on all waters and
for the eastern nearshore and ocean waters on Friday night.
Otherwise, Conditions remain below SCA criteria through the
weekend with a weak pressure gradient over the area.-- End Changed Discussion --

.HYDROLOGY...
-- Changed Discussion --No widespread hydrologic issues are expected. The localized flash
flood threat for Friday has been shifted farther west as latest
guidance has trended slower with bringing showers and thunderstorms
to our area. The localized threat is now likely confined to far
western Orange County.

No widespread hydrologic issues are expected Saturday and after
Sunday. A localized threat of nuisance/poor draining flooding
is possible on Sunday, mainly north and west of NYC, with any
stronger or slow moving thunderstorms.-- End Changed Discussion --

.TIDES/COASTAL FLOODING...
For today and Friday, there is a low risk of rip current
development for all ocean beaches. However, latest wavewatch
guidance does show a 2 ft 9-10s SE swell moving in late Friday
that could increase the rip current risk to moderate.

In terms of coastal flooding, astronomical tides associated with a
full moon will gradually lower through the week. Generally,
localized minor coastal flood impacts are on tap again for
tonight`s high tide cycle for southern Westchester, southern
Fairfield, southern Queens, and areas adjacent to Lower NY
Harbor, with more widespread minor flooding (up to 1 ft of
inundation) for Southern Nassau. The threat is expected to
diminish moving into Friday.

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Coastal Flood Advisory from 10 PM this evening to 3 AM EDT
Friday for NYZ179.
NJ...None.
MARINE...None.

$$
SYNOPSIS...DBR/JT
NEAR TERM...JT
SHORT TERM...JT
LONG TERM...DBR
AVIATION...IRD
MARINE...DBR/JT
HYDROLOGY...DBR/JT
TIDES/COASTAL FLOODING...