000
FXUS61 KOKX 270022
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
822 PM EDT Wed Jul 26 2023
.SYNOPSIS...
High pressure will remain offshore this week, bringing heat and
humidity into the area from Thursday into Saturday. A weak front
should produce a line of thunderstorms late Thursday afternoon
and evening, some of which may be severe. A cold frontal
passage is expected on Saturday, with Canadian high pressure
building in its wake for Sunday and remaining to the west into
early next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Updated for current conditions.
Quiet weather expected as high pressure remains offshore and
provides a light S/SW flow. Diurnal clouds will dissipate around
sunset but there is some question as to whether or not we see
low clouds form south of Long Island and drift northward late
tonight into much of Tri-State area. For now, not completely
convinced that will happen but at very least we should see
another round of patchy fog/low clouds inland across lower
Hudson Valley and possibly over parts of Fairfield County CT.
We should see cloudiness increase toward sunrise as clouds from
showers/storms across eastern Great Lakes head toward
Northeast. Models show most of these clouds passing well to our
north but we should see at least some mid/high clouds overnight.
Light S/SW flow will help keep lows in 70s tonight with some
upper 60s inland.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/...
-- Changed Discussion --
* Dangerous heat/humidity Thu and Fri
* Potential for severe thunderstorms late Thu
Heat:
We are issuing Excessive Heat Warnings for NYC and NE NJ and
maintaining Heat Advisories elsewhere for Thu into Fri.
Increasing SW flow on periphery of western Atlantic ridge and
approaching shortwave will help temperatures soar well into 90s
both days, if not near 100 degrees in NYC and urban areas of NE
NJ. Dewpoints will also surge back into low to mid 70s much of
the time which yields heat indices of 95-100 across much of Tri
State area and as high as 105 in NYC and NE NJ. Thu looks to be
hotter of two days but not by much. It does look a little more
marginal to reach 105 heat index Fri in NYC/NE NJ but we felt it
was best to continue the Excessive Heat Warning since it`s very
close.
We do think there will be at least some mid/high cloudiness
around to start the day but these should move off to east by
late morning, which will allow for plenty of sunshine before
storms arrive later in the day. Tightening gradient combined
with SW low level jet will result in breezy conditions during
afternoon with 20-30 mph gusts expected.
Severe Weather:
Approaching surface trough (weak front) and upper trough is
expected to bring potential for showers/storms later Thu
afternoon and evening. Environment should feature plenty of
instability and strong low level shear which is favorable for
severe thunderstorms. Mid level lapse rates are rather weak but
that can easily be overcome by having so much instability.
Expecting storms to develop in Hudson Valley early in afternoon
which may form into lines or small segments as activity heads
SE, reaching NYC in the 4-7 PM timeframe before heading offshore
Thu evening.
Main concern is potential for damaging winds and localized
flooding from briefly heavy rain. Hail is also possible but with
such a warm airmass in place, melting on the way down would
make it difficult to be much larger than penny size. It is
important to note that the environment is also one that is
favorable for short-lived tornadoes, but the one factor against
it is relatively high LCL heights (1200+m). Typically you need
to have LCL heights under 1000m and especially below 800m to be
more favorable. Certainly something that is possible, however,
but wind damage appears to be the greater threat.
As with heat potential, the presence of mid/high clouds in
morning could disrupt convective potential if the cloudiness is
able to last into afternoon. This does not appear likely at this
time but is something to consider as things begin to unfold
tomorrow morning.-- End Changed Discussion --
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
No significant changes made.
Conditions will continue to be warm overnight Friday, with lows
in the 70s once again region-wide and although Saturday will be
hot again, it will be a few degrees cooler thanks to increasing
clouds due to an approaching cold front. Highs will range from
the upper 80s to lower 90s. Heat advisories may need to be
extended into Saturday as heat index values across much of Long
Island, NYC, NE NJ, and southern Connecticut will be in the
95-100 range.
Models are in fairly good agreement with the timing of the cold
front passage Saturday into Saturday evening, pushing offshore
by early Saturday night. However, there will still be some
timing differences in where and when showers and thunderstorms
will develop.
Thereafter, Canadian high pressure builds in at the surface for
Sunday and remains west of the area through Tuesday night.
Aloft, a trough will be in place for the Northeast and into the
Mid- Atlantic while a ridge builds over the Plains and Rockies.
This will introduce a cooler and drier airmass into the region
for Sunday onward. Highs are expected to be a couple of degrees
below normal while dew points drop into the 50s (possibly even
into the upper 40s if enough mixing and drier air move into NW
portions of the forecast area). Dew points may rise into the
lower to middle 60s by Tuesday afternoon.
Next system approaches Wed which will bring our next chance of
showers.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
Offshore high pressure remains with a weak surface front moving
in Thursday. Possible low clouds and patchy fog for some
terminals late tonight into early Thursday. Showers and
thunderstorms forecast for late Thursday afternoon into early
Thursday evening.
Mainly VFR conditions expected during the TAF period. There could be
some exceptions at times. Some low clouds are possible as well as
patchy fog late tonight into early Thursday morning. Have tempo
groups for lower conditions at KSWF and KHPN late tonight into early
Thursday morning where there are relatively higher chances for these
lower conditions. Otherwise, brief MVFR to IFR will be possible with
showers and thunderstorms late Thursday afternoon into Thursday
evening with heavy downpours. These thunderstorms could bring
strong wind gusts and hail.
Winds will be mainly S-SW through the TAF period. Wind speeds near 5-
10 kt mainly tonight into early Thursday morning and then winds
increase to near 15 kt late Thursday morning through the early
Thursday evening with gusts near 20-25 kt.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Timing of thunderstorms could vary 1-2 hours from TAF.
Low chance of MVFR to IFR overnight into early Thursday morning.
OUTLOOK FOR 00Z FRIDAY THROUGH MONDAY...
Friday: Possible showers and thunderstorms at times afternoon
into evening with brief MVFR to IFR possible, but coverage of
storms should be lower than Thu. Otherwise, VFR.
Saturday: Chance of showers and thunderstorms with MVFR to IFR
possible at times. Otherwise, VFR.
Sunday and Monday: VFR.
Detailed information. including hourly TAF wind component
forecasts, can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
A Marine Weather Statement continues for Long Island Sound. The
US Coast Guard still indicates a large debris field caused by
recent flooding across New England.
Light S/SW winds on waters through tonight.
Persistent S/SW flow increases Thursday with gusts reaching SCA
levels (25-30kt) on the ocean waters, the bays of Long Island,
and the far eastern part of Long Island Sound. It`s possible
that a few gusts reach 35kt on the ocean waters to the south of
Montauk Point but confidence isn`t high enough to upshift to
Gale Warnings there.
Winds subside later Thu night and Fri. However, a brief period
of 25 kt gusts is again possible on Sat with passage of a cold
front, and ocean seas up to 5 ft expected as southerly flow
increases ahead of the approaching front.
Ocean seas then subside by late Sat night and remain below SCA
levels through Mon as winds become more NW.
&&
.HYDROLOGY...
Locally heavy rain is possible from late afternoon into early
evening Thu, which may cause minor nuisance and poor drainage
flooding.
&&
.TIDES/COASTAL FLOODING...
There is a low risk of rip currents at the ocean beaches through
this evening.
Persistent S/SW winds will bring a higher risk of rip currents
to the ocean beaches Thursday, especially during the afternoon
and evening.
For Friday a moderate risk of rip current development is
expected.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory from 11 AM Thursday to 9 PM EDT Friday for
CTZ005>012.
NY...Heat Advisory from 11 AM Thursday to 9 PM EDT Friday for
NYZ067>071-078>081-177-179.
Excessive Heat Warning from 11 AM Thursday to 9 PM EDT Friday
for NYZ072>075-176-178.
High Rip Current Risk from Thursday afternoon through Thursday
evening for NYZ075-080-081-178-179.
NJ...Heat Advisory from 11 AM Thursday to 9 PM EDT Friday for
NJZ002.
Excessive Heat Warning from 11 AM Thursday to 9 PM EDT Friday
for NJZ004-006-103>108.
MARINE...Small Craft Advisory from noon Thursday to midnight EDT
Thursday night for ANZ332-340-345.
Small Craft Advisory from 8 AM Thursday to 6 AM EDT Friday for
ANZ350-353-355.
&&
$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...JM
MARINE...
HYDROLOGY...
TIDES/COASTAL FLOODING...