000
FXUS61 KOKX 111912
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
312 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 from
Thursday into the weekend.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
-- Changed Discussion --
Subsidence under ridging aloft suppressing most Cu development,
with only sct coverage at best in the metro area and along the
sea breeze across Long Island. Temps should reach 90 in NE NJ,
parts of NYC and along the north shore of Nassau, with mid/upper
80s elsewhere, and lower 80s at immediate south facing
shorelines.
Skies should remain 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/...
-- Changed Discussion --
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.
Thursday into Thursday night, more instability and more forcing
in general. A frontal system approaches the area Thursday
night with a pre-frontal trough likely developing Thursday.
Showers and thunderstorms chances increase during the day across
Lower Hudson Valley, NE New Jersey, NYC, and SW Connecticut.
They spread across the remainder of the area at night. The
thunderstorms will be capable of producing locally heavy
downpours. Some thunderstorms could be possibly strong to severe
Thursday afternoon into early Thursday evening with the highest
instability and potentially up to 35-40 kt of bulk 0-6km AGL
bulk shear.
Temps on Thu should be slightly cooler, with upper 80s/lower
90s. Heat index values could still touch 95 in isolated spots in
NE NJ and across Long Island.-- End Changed Discussion --
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Ensemble means depict a closed upper low situated over eastern
Manitoba that slowly works south and east into Ontario though
the period. This results in a mean southwest flow aloft, with
multiple shortwaves passing through the northeast, with
generally unsettled weather, expected into early next week.
For Friday, a frontal system approaches the region from the
northwest along with a mid level shortwave rounding the base of
the upper low. Some uncertainty as to how far south/east the
upper low and shortwave will make it, and whether we`ll have
enough upper level support for organized afternoon convection.
Nonetheless, the air mass in place is moist and marginally
unstable and so thunderstorm chances increase by Friday
afternoon across the CWA. Model soundings are showing 1500-2000
J/kg of MUCAPE, decent mid level lapse rates, but weak bulk
shear of only 20-30 kt. This would suggest some isolated severe
thunderstorms are possible especially north and west of NYC on
Friday afternoon. CSU-MLP does have a wide swath of 5% across
much of the area through 12Z Saturday. In addition, PW of
1.4-1.8" raise the potential of heavy rainfall with any storm.
However, steering flow looks to be near 15-20 kt at this point,
so any cells should be moving. In addition, 1- and 3- hr FFG is
low (1.5-2.5" in three hours) across parts of the Lower Hudson
Valley where excessive rainfall occurred this past weekend.
Thus, WPC has maintained a marginal risk of excessive rainfall
for the area Friday, with the SLGT risk just to the north.
The front looks to stall to our east on Saturday into Sunday as
another shortwave in the mid levels rotates through the area. A
surface low pressure then looks to approach from the southwest
on Saturday afternoon into Sunday. Some deterministic model
disagreement here as to whether the low stays south of the area
or heads directly overhead. NBM (and thus its global ensemble
inputs) keeps the bulk of precipitation to the south, so for now
have kept slight chance/chance PoPs in, along with a thunder
chance for Saturday afternoon into Sunday with the moderately
unstable airmass remaining in place.
Shower chances lower by Sunday evening and on Monday, which
look to be a bit drier with the local between systems. The
warmest days of the period look to be Saturday and Sunday, with
highs in the upper 80s to near 90. With dewpoints in the low
70s, maximum apparent temperatures/heat indices will be just a
few degrees warmer, but short of any head headline criteria at
this point.
&&
.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
VFR as weak high pressure builds to the south and west through
tonight. A weak cold front begins to approach from the northwest
Wednesday afternoon.
Winds generally SW 10-15kt, becoming more southerly at KJFK as a
sea breeze increases. Winds become light and variable tonight
outside of the NYC metro terminals, and SW less than 10kt at the
metro terminals. Winds become WSW Wednesday.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Timing of winds becoming more southerly, 180 to 190, at KJFK
may be off by 1-2 hours. The sea breeze could make it to KLGA
late afternoon/early evening.
OUTLOOK FOR 18Z WEDNESDAY THROUGH SUNDAY...
Wednesday: VFR. There is a chance of afternoon thunderstorms,
mainly at KSWF, possibly reaching KHPN and KTEB.
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 and Sunday: MVFR or lower possible Saturday morning,
otherwise VFR with a chance of showers/thunderstorms with a
chance of MVFR.
Detailed information, including hourly TAF wind component
forecasts, can be found at: https:/www.weather.gov/zny/n90
&&
.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 1.0-1.5 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 maintains a slight risk of excessive rainfall for areas just
north of the CWA during this time frame.
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/JM
NEAR TERM...BG
SHORT TERM...BG
LONG TERM...DBR
AVIATION...MET
MARINE...BG/JM
HYDROLOGY...BG/JM/DBR
TIDES/COASTAL FLOODING...