000
FXUS61 KOKX 112313
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
713 PM EDT Tue Jul 11 2023
.SYNOPSIS...
-- Changed Discussion --
Weak high pressure will pass east on Wednesday. A weak frontal
boundary will approach parts of the area late Wednesday. A
series of stronger frontal boundaries will approach and move
through from Thursday into early next week.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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No changes to thinking through tonight, forecast remains on
track with subtle adjustments for current observations. Mostly
clear skies persist with weak high pressure in place and
subsidence aloft. Previous discussion follows.
Subsidence under ridging aloft has suppressed most cu
development, with only sct coverage at best in the metro area
and along the sea breeze across Long Island. Skies should be
mostly clear tonight as subsidence continues, while winds become
light. Low temps just a shade below GFS/NAM MOS tonight, from
70-75 in/around NYC to the 60s elsewhere.-- End Changed Discussion --
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
For Wednesday, the weak high will slide to the east, with WSW
flow continuing to advect in a warmer air mass. Expect high
temps to reach the mid 90s in urban NE NJ, lower 90s across a
good portion of the rest of the CWA, and mid/upper 80s in the
higher elevations and along the immediate south shore of Long
Island and SE CT. Max heat index values will be close to actual
temps in most places, but could top out right at 95 in parts of
the NYC metro area, also across parts of Long Island and S CT
where sfc dewpoints will be a little higher than area to the
west.
Instability will build in the afternoon, but with ridging aloft
and a capping inversion inhibiting convective development in
most places except well NW of NYC, where an approaching mid
level shortwave trough and weak boundary sagging southward may
both help weaken the cap enough to allow isolated to scattered
convection by mid to late afternoon. Any storms that develop
could produce gusty winds given presence of mid level dry air,
dry sub-cloud air and steep low level lapse rates. Activity
should quickly die down after sunset, with only leftover slight
chance PoP at night.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
A relatively active summer pattern sets up as ensemble means depict
a closed upper low situated over Hudson Bay slowly working south and
east into Ontario though early next week as blocking over the North
Atlantic begins to weaken. This results in a general southwest flow
aloft, with multiple shortwaves passing through.
Forcing increases as a frontal system approaches the area Thursday
night with a pre-frontal trough ahead of it. Scattered showers and
thunderstorms should develop during the day across the lower Hudson
Valley, NE NJ, NYC, and SW CT, spreading across the remainder of the
area into the overnight. Any thunderstorm will be capable of
producing locally heavy downpours. WPC has expanded the slight risk
of excessive rainfall to include the lower Hudson Valley, with
recent rains having lowered FFG values here. In addition, a few
thunderstorms could become strong to severe Thursday afternoon
through the evening. BUFKIT soundings indicate surface-based
instability of 1000-2000 J/kg, along with potentially up to 30-35 kt
of bulk 0-6 km AGL bulk shear. SPC has a marginal risk outlined for
all except SE CT and eastern Long Island, with the primary hazard
being isolated damaging wind gusts. This convective activity likely
continues overnight into Friday as the main shortwave energy moves
through.
Friday, a second mid level shortwave rounds the base of the upper
low and approaches from the west. With the moist and marginally
unstable air mass in place, thunderstorm chances increase once again
by the afternoon. With similar parameters to Thursday, isolated
strong or severe thunderstorms are possible once again. CSU-MLP has
a swath of 5% across the entire area through 12Z Saturday.
Fortunately, with steering flow a bit more progressive than earlier
this week, threat for training convection is lower. Still, given the
antecedent conditions, FFG is low (1.5-2.5" in three hours) across
parts of the lower Hudson Valley and NE NJ, it won`t take much to
produce nuisance flooding or worse. Accordingly, WPC has kept a
marginal risk of excessive rainfall for the area Friday, with the
SLGT risk just to the north in New England.
Additional wet weather is likely this weekend as another shortwave
approaches and moves through late Saturday into Sunday, leading to
increased chances for a few showers and thunderstorms. Rain chances
lower by Sunday evening and on Monday, with a brief respite in
between systems.
Hot and humid through the period. Highs generally top out in the mid
to upper 80s, to around 90 in the urban metro. With the moist air
mass in place, dew points in the 70s, heat indices will likely get
into the low to mid 90s for much of the region this weekend. Heat
headlines may be needed, though confidence is not high on this given
marginal conditions and coverage. National blended guidance was
largely followed for this update.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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VFR as weak high pressure builds to the south and west through
tonight. A weak frontal boundary begins to approach from the
northwest Wednesday afternoon and evening.
Winds will begin to diminish this evening, gradually becoming
light and/or variable outside of the NYC metro terminals. NYC
terminals will likely be SW around 5-7 kt. The flow may briefly
veer towards the W or WNW around 12z before becoming WSW-SW into
the afternoon. Afternoon sea breeze enhancements are likely at
KJFK, KISP, KBDR, and KGON.
A shower or thunderstorm is possible at KSWF late Wednesday
afternoon and evening. Any of this activity is expected to stay
well NW of the NYC metro terminals.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Low chance winds at KLGA could go S towards sunset this evening.
Similarly, the sea breeze could reach KLGA in the late
afternoon/early evening on Wednesday.
An occasional gust 15-18 kt is possible at KEWR on Wednesday
afternoon.
OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY...
Wednesday Night: Mainly VFR. Low chance for a shower/thunderstorm
at KSWF early.
Thursday: Chance of afternoon showers/thunderstorms with MVFR.
Thursday night and Friday: Showers/thunderstorms likely with MVFR,
IFR possible at times.
Friday night: Chance of evening showers/thunderstorms, then MVFR or
lower conditions possible.
Saturday: MVFR or lower possible in the morning, otherwise VFR with
a chance of showers/thunderstorms in the afternoon and evening.
Sunday: Chance of afternoon/evening showers/thunderstorms with MVFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
Minimal SCA conditions are possible on the ocean from Thu night
into Fri night, with seas up to 5 ft and wind gusts up to 25
kt.
&&
.HYDROLOGY...
Basin avg rainfall of 1-2 inches expected mainly from late Thu
night into daytime Fri across the lower Hudson Valley and S CT,
with about 3/4 inch for NE NJ, NYC, and Long Island. Local amts
of over 2 inches possible inland, especially over S CT. WPC has
expanded the slight risk for excessive rainfall on Thursday to
now include the lower Hudson Valley, with the remainder of the
region in marginal.
Additional rounds of showers/tstms expected this weekend. Basin
avg QPF mainly 1/4 to 1/2 inch over most of the area Sat
afternoon/eve, and NW of NYC Sunday afternoon/eve.
&&
.TIDES/COASTAL FLOODING...
There is a moderate risk of rip current development at all the
ocean beaches through Wednesday. More SW winds with southerly
swells of 2-3 ft will be in place across the ocean beaches
during this time period.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...BG/DR
NEAR TERM...BG/DR
SHORT TERM...BG
LONG TERM...DR
AVIATION...DS
MARINE...BG/DR
HYDROLOGY...BG/DR
TIDES/COASTAL FLOODING...