000
FXUS61 KOKX 012201
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
601 PM EDT Sat Jul 1 2023
.SYNOPSIS...
A warm front approaches tonight and passes north late Sunday. This
will be followed by the approach of a dissipating cold front on
Monday, which likely washes out across the area on Tuesday. Weak
high pressure will then build in for the middle of the week.
Another frontal system may impact the area late in the week into
next weekend.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --
For this update, removed the mention of showers areas north and
west of NYC until around midnight, otherwise changes were
small.
A warm front southwest of the area will slowly move toward the
region tonight, possibly being situated just south of Long
Island by daybreak Sunday. Meanwhile, the associated surface
low, cold front, and upper level trough slowly move west over
the center of the country.
This warm front will provide the needed lift for the development of
these showers and thunderstorms. PWATs surge into the 2 to 3 inches
range with an increasingly more humid air mass developing. Many of
the mesoscale models show a round of showers and thunderstorms
entering western sections of the forecast area around midnight or
thereafter. However, lapse rates and surface based CAPE do not look
impressive overnight. So, strong/severe storms do not look to
develop overnight. Brief, heavy rain may be associated with
these storms, possibly causing some minor urban and poor
drainage flooding.
Warmer overnight lows expected with an increase in humidity and
cloud cover.-- End Changed Discussion --
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
The warm front will be slow to move through during the day Sunday,
and with it still in the vicinity, it will continue to provide lift
needed for continued storm development. Once in the warm sector, a
pre-frontal trough will continue this chance overnight. Better
instability in the form of surface based CAPE for Sunday. Models
show 1000-15000 J/kg of either surface based or elevated CAPE,
though lapse rates still do not look too impressive. With that said,
there is a threat for strong to possibly severe thunderstorms Sunday
afternoon. It all depends on how much clearing, heating, and thus
how much we destabilize. If storms do develop, bowing thunderstorms
are possible (bulk shear of 30-40+ kt noted in models, and modeled
reflectivity shows bowing) again, mainly north and west of New York
City. The main threat therefore would be damaging winds. Hail cannot
be ruled out either, but this seems to be a lower threat as CAPE in
the hail growth zone looks to be in the few hundred J/kg range.
A possible factor against strong to sever storms is the smoke.
Although this is expected to improve, if there is still enough on
Sunday to inhibit some solar radiation, it could decrease the threat
for severe storms by decreasing surface instability. This may also
be why lapse rates are so low as the smoke may be increasing
temperatures aloft.
With unidirectional flow leading to possible training, slow moving
storms, and PWATs remaining in the 2-3 inch range, especially north
and west of New York City, flash flooding is also a possibility. It
seems to be the same areas hit with heavy rain about a week ago. 1
hour flash flood guidance for the non urbanized areas of northeast
New Jersey are around 1" to just over 1.50".
Showers and thunderstorms continue Sunday night, with the pre-
frontal trough moving in after the warm front lifts north. However,
with the loss of instability, storms will weaken just after sunset,
with little if, any activity left for the second half of the
night.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
We will be heading into the warmest part of the summer thus far
early in the season. There is the potential for 3 to 4
consecutive days around 90 for portions of the NYC metro, from
Monday through Thursday. Before then though, a weakening cold
front approaches from the west Monday, likely dissipating as it
moves through the area on Tuesday. The best chance for any
convection will be Monday afternoon/early evening with the
approach of an upper trough and pre-frontal trough. Ingredients
are marginal with the airmass drying out some. Any severe
weather threat looks to be isolated at this time. With the
weakening cold front on Tuesday, chances are low and confined to
the interior. Heights begin to build with the departure of the
upper trough and ridging building in from the west(strengthening
the mid level cap).
For the mid week period, mid level ridging and 85h temps around
18C, will result in surface temps 5-8 degrees above normal.
This places much of the area, with the exception of the immediate
south shore of LI and the twin forks well into the 80s and
likely around 90 for NYC metro and points north and west.
Airmass looks to dry out enough with a W/SW flow to keep heat
indices close to the ambient temperature. So at this time, the
threat for heat advisory criteria is low. However, the NBM box
ands whisker plots shows the median temps several degrees
warmer than the deterministic. In some cases, the deterministic
is below the 25th percentile. Thus, the potential is there for
higher temperatures.
For the end of the week, heights fall with the approach of
another upper trough. Temperatures will be cooler in the 80s,
largely due to an increase in cloud cover and chances for
convection and onshore flow.
&&
.AVIATION /22Z SATURDAY THROUGH THURSDAY/...
Weak high pressure will slowly move east as a warm front approaches
the terminals from the south.
VFR for most terminals thorough this evening. Vsbys have improved to
VFR now everywhere except KGON/KSWF, that are still hanging onto 4SM
with haze. Expecting this to diminish this evening/overnight as the
front approaches.
Southeast flow 10-15kts, with occasional gusts at KEWR and KTEB.
Winds become fairly light and vrb tonight with increasing clouds and
the chance of showers and thunderstorms after 06z Sunday and likely
to impact the morning push. TSRA chance diminishes late morning,
and return again Sunday afternoon.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
AMD possible for the timing of early am convection, which remains
uncertain and may be off by an hour or two.
OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY...
Sunday: Showers possible and chance of tstms early with brief MVFR
likely, IFR possible. Then a break with MVFR cigs with a second
round of thunderstorms possible later in the afternoon. Timing
remains a bit uncertain but it appears to be after 18-20z.
Monday and Tuesday: Chance of afternoon/evening showers/tstms,
otherwise VFR.
Wednesday: Mainly VFR.
Thursday: Chance of afternoon/evening showers/tstm.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
Winds and seas are expected to generally be below SCA levels
through the upcoming week. Waves on the eastern ocean zone may
approach 5 ft Sunday night into Monday with a southerly flow
gusting up to 20 kt.
&&
.HYDROLOGY...
With unidirectional flow leading to possible training, slow moving
storms, and PWATs remaining in the 2-2 1/2 inch range, especially
north and west of New York City, flash flooding is a possibility.
It seems to be the same areas hit with heavy rain about a week
ago. 1 hour flash flood guidance for the non urbanized areas of
northeast New Jersey are around 1" to just over 1.50". The
Weather Prediction Center has placed the entire area in a
marginal risk for excessive rainfall, with a small portion of
the northern Lower Hudson Valley in a slight risk.
No hydrologic issues are expected Monday through Saturday.
&&
.TIDES/COASTAL FLOODING...
A moderate risk of rip currents is expected through Sunday.
With astronomical tides increasing this weekend with the
approach of a full moon on Monday, minor coastal flooding looks
possible tonight for southern Nassau, but becomes more likely
for the Sunday night into Monday evening high tide cycles. A
statement remains in effect for southern Nassau this evening,
which will be the area most likely to experience any minor
coastal flooding into Monday. Elsewhere, the water levels may
approach or just touch Sunday and Monday evenings, mainly across
the south shore back bays of western LI and western LI sound.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...JP/DW
NEAR TERM...JP/DW
SHORT TERM...JP
LONG TERM...DW
AVIATION...DBR
MARINE...JP/DW
HYDROLOGY...JP/DW
TIDES/COASTAL FLOODING...