discussion on 2023-08-05

000
FXUS61 KOKX 052044
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
444 PM EDT Sat Aug 5 2023

.SYNOPSIS...
High pressure remains in control through Sunday and then gives way
to a frontal system that impacts the area Sunday night into
Tuesday. The warm front will move through Monday night with the
attendant cold front moving through on Tuesday. Weak high
pressure will then build in through midweek. Another frontal
system approaches from the west Thursday and lingers in the
vicinity of the region Friday.

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
High pressure continues to slide down from the Great Lakes
remaining in control overnight tonight. Aloft, the flow will be
mostly zonal, with slight height increases.

Mid and high level clouds can be seen spilling into the area from
the west in association with an MCV near Illinois/Indiana. Filtered
sunshine will continue through the afternoon. Current sea
breeze boundaries along the Long Island and CT coast remain near
the shore battling the northerly flow.

Lows tonight will be around normal. The greatest uncertainty is
across the interior. With slightly drier air being advected in from
the north, and light winds overnight, there is potential for some
areas to drop into the mid 50s. However, this will depend on cloud
cover. Thinking there can be a few hours of mostly clear skies just
before daybreak for upper 50s readings.

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
Conditions on Sunday should be similar to Saturday. Shortwave wave
ridging moves in aloft as high pressure remains in control at
the surface. Highs will be in the 80s across the whole area.

Sunday afternoon the high shifts offshore and a return flow sets up
that will begin to advect in a more humid airmass. The shortwave
ridge axis passes overhead Sunday night and an amplifying shortwave
trough approaches. There is potential for several rounds of heavy
showers and thunderstorms early Monday morning through Monday night
as multiple embedded pieces of energy move through aloft. An
associated broad surface low will be approaching, trekking
through the Great Lakes on Monday. Its fronts will remain out of
the area through Monday.

The first rounds of rain looks to reach the area late Sunday night
into Monday morning with strong warm advection ongoing. While
overall forcing is not too impressive, any showers will be capable
of producing heavy downpours as pwats are modeled to be around 2
inches. According to SPC`s Sounding Climatology Page, this value is
over the 90% moving average for the 8/7 12z sounding. Flooding
is not expected with this first round, but it could saturate the
ground and make flooding easier during later rounds. Being
ahead of the warm front early Monday morning, forecast soundings
do not look all that impressive for thunder given very low, if
any, CAPE. Left mention in the forecast for now because can not
completely rule it out, but thinking this will be more
widespread showers.

From hints in the QPF fields of the global guidance, and whats
available of the CAMs this far out, it looks like another round of
showers and thunderstorms will move through sometime late
Monday. There looks to be better forcing as well as more
instability to work with. There is potential for heavy rain to
move over the same areas that see the first batch of rain. If
this is the case, scattered flash flooding is possible. The WPC
now has the NYC north and west in a slight risk of excessive
rainfall. Also, given veering profiles and moderate shear, any
storms can be strong to severe.

.LONG TERM /TUESDAY THROUGH SATURDAY/...
By Monday night, the warm front lifts through the region, with rain
chances continuing overnight into Tuesday as the warm sector moves
over the region and a 30 to 40 kt LLJ develops at 925 mb. The
attendant cold front tracks east through the region during the day
on Tuesday, with the potential for scattered showers and
thunderstorms continuing prior to the fropa. Thunderstorm potential
will depend on timing and how much the environment can destabilize,
but given BUFKIT soundings and shear profiles can`t rule out a few
strong to severe thunderstorms into the early afternoon.

The H5 trough axis slides overhead late Tuesday, shifting east
Tuesday night with heights beginning to climb. Weak surface high
pressure moves in as the low pressure system exits into the Canadian
Maritimes for Wednesday. The high pressure remains in the area
through Wednesday night before moving offshore Thursday. Another
frontal system then approaches Thursday night into Friday bringing
the next chance of showers and thunderstorms.

Temperatures will remain relatively seasonable through the period,
with highs generally in the low to mid 80s, and perhaps the upper
80s in the urban metro. Dew pts drop behind the frontal passage
Tuesday, allowing for a bit lower humidity on Wednesday, before
increasing once again late week. Primarily followed the national
blend of model guidance for this update.

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
High pressure builds in from the northwest through Sunday morning
and moves offshore Sunday afternoon.

VFR.

Light N-NW flow with coastal S to SW sea breezes. The sea breeze may
briefly move into KISP late this afternoon, and most likely will not
reach KLGA. Flow becomes light northerly with sea breezes ending
this evening, with a few locations becoming light and variable
tonight. Flow becomes S/SW Sunday morning with sea breeze
enhancement.

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

There is a low chance that the sea breeze reaches KLGA late
afternoon and then diminishes, 20Z to 22Z.

Timing of winds shifting to the south Sunday is uncertain, and may
be earlier than forecast.

OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY...

Sunday afternoon through Sunday night: VFR. A chance of MVFR
ceilings, with a chance of showers and isolated thunderstorms late
Sunday night, mainly west of KBDR and KISP.

Monday through Monday night: Showers likely with a chance of
thunderstorms with MVFR or lower conditions.

Tuesday: A chance of showers and thunderstorms with MVFR or lower
conditions, ending late Tuesday night with conditions improving.

Wednesday: VFR. NW gusts 20-25kt.

Thursday: VFR. A chance of late day showers and thunderstorms at the
NYC metro terminals and west.

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

.MARINE...
Winds and waves will remain below SCA criteria as high pressure
remains in control this weekend. An increasing southerly flow ahead
of a frontal system Monday may produce marginal SCA wind gusts and
seas on the ocean late in the day.

Wind and seas increase behind a frontal passage on Tuesday, with SCA
conds developing late Tuesday into Tuesday night on the ocean
waters. Occasional gusts to 25 kt are possible on all other waters.
Winds subside Wednesday, but ocean seas may remain elevated around 5
ft through Wednesday evening before lowering.

Elsewhere, largely sub-SCA conds expected into late week.

.HYDROLOGY...
Multiple rounds of showers and thunderstorms are possible early
Monday morning through early Tuesday. If the heaviest rainfall moves
over the same area, scattered flash flooding is possible later in
the day on Monday. The WPC has placed the area in a slight risk of
excessive rainfall.

At this time, there are no significant hydrologic concerns from
Wednesday through late week.

.TIDES/COASTAL FLOODING...
-- Changed Discussion --There is a moderate risk of rip current development along Atlantic-
facing beaches Sunday and again Monday due to a ~3 ft S swell
at 8-9 sec.-- End Changed Discussion --

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

$$
SYNOPSIS...DR/JT
NEAR TERM...JT
SHORT TERM...JT
LONG TERM...DR
AVIATION...MET
MARINE...DR/JT
HYDROLOGY...DR/JT
TIDES/COASTAL FLOODING...