000
FXUS61 KOKX 271422
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1022 AM EDT Thu Jul 27 2023
.SYNOPSIS...
High pressure will remain offshore this week. An upper level
disturbance will pass through this afternoon and evening. A cold
frontal passage is expected Saturday afternoon and evening. High
pressure will begin to build from Southern Canada on Sunday and
remain in control through the middle of next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
* Dangerous heat/humidity
* Potential for severe thunderstorms this afternoon/early
evening
The fcst is on track this mrng with only minor tweaks to the
grids. Maintained the excessive heat warning for NYC and urban
NE NJ as temps rise to the mid/upper 90s and dewpoints remain
mostly in the lower 70s, yielding max heat index values around
or just over 105. Farther east into coastal SW CT and along the
north shore of western Long Island, high temps will be lower
(lower 90s) but dewpoints higher (mid 70s) and this may yield
some isolated spots where the heat index may also reach 105.
Outside of this area, highs in the upper 80s/lower 90s plus high
dewpoints will yield heat index values from 95 to 104, so the
heat advisory continues for the rest of the CWA. Tightening
pressure gradient combined with SW LLJ will result in breezy
conditions during the afternoon with gusts 20-30 mph expected,
possibly up to 35 mph along the south shore of Long Island.
A line of storms developing this afternoon over ern PA and
central NY and moving SE into the area is still modeled. Expect
this line to move through from about 17Z-23Z, crossing the NYC
metro area between 19Z-21Z. Main threat from these storms will
be damaging winds via large MLCAPE up to 2000 J/kg per NAM,
momentum transfer of 40-kt mid level flow from aloft, also via
steep low level lapse rates and inverted-V soundings. There is
also a low- end tornado threat inland, more so across southern
CT where models show potential for enhanced lift beneath the
right entrance region of an upper jet streak to the north, while
hodographs show veering low level profiles supportive of
rotating storms during the afternoon, and where low level
vorticity could be locally enhanced via channeling of sfc wind
up river valleys and via possible sea breeze interaction closer
to the CT coastline.
Hail is also possible given large CAPE values aloft, but with
such a warm air mass in place and high WBZ heights, melting on
the way down would make it difficult to be much larger than
penny size.-- End Changed Discussion --
&&
.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Fri should be dry with temp and humidity levels close to those
of Thu, with highs in the 90s and dewpoints mostly in the 70s
yielding similar heat index values.
Guidance remains in fairly close agreement on the timing of a
cold front on Sat bringing one last round of showers/tstms in
the afternoon/evening, but not before temps again rise into the
90s along with high humidity. The heat advisory was extended
into Sat for areas outside of urban NE NJ and NYC, and it is
possible the excessive heat warning may need to be extended in
time for at least parts of NE NJ.
&&
.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
The heat and humidity from late this week and into the first
half of the weekend will end on Sunday. The upper level
pattern shifts back to one that has been more persistent for
much of the summer, with upper level troughing over the
northeastern US and upper level ridging over the western and
central US. This pattern looks to remain in place through at
least the middle of next week. There is a bit less confidence
heading late in the week as the troughing may weaken a bit
although there are signs of another shortwave which could
amplify the trough again. The core of the ridging should still
reside well to our west keeping any significant heat at bay for
our region.
The cold front that passes through on Saturday should continue
moving offshore on Sunday. Have left in a slight chance for a
shower in the afternoon as the upper trough axis settles
overhead. Otherwise, high pressure begins to build in from
southern Canada on Sunday. This high will remain in control
through the middle of the week before starting to slide towards
the Western Atlantic late in the week. A frontal system may
approach late in the week, which may bring the next chance of
showers/thunderstorms. However, probabilities are low at this
time due to it being about a week out and fairly large
differences with amplitude and timing of the associated
shortwave aloft.
Went pretty close to the NBM for temperatures given the larger
scale pattern. This yields readings slightly below normal
through the period. Dew points look to fall into the 50s Sunday
through at least Tuesday bringing a more comfortable feel to the
air.
&&
.AVIATION /14Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
High pressure will remain offshore with a weak front moving
through the terminals this afternoon and evening.
Any sub-VFR conditions this morning expected to end in the next
hour then mainly VFR conditions through the TAF period. Showers
and thunderstorms are forecast this afternoon and early
evening. Some of the storms could produce brief MVFR to IFR
along with strong wind gusts with a brief wind shift to the NW.
Outside of thunderstorms, S-SW winds increase to 10-15 kt with
gusts 20-25 kt. Winds and gusts may be a bit stronger closer to
the coast this afternoon. Winds will weaken and become SW-W and
possibly NW tonight.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Onset time of wind gusts may be off by 1-2 hours.
Timing of thunderstorms may be off by 1-3 hours. Any
thunderstorm could produce strong gusty winds and a brief wind
shift to the W-NW.
OUTLOOK FOR 15Z FRIDAY THROUGH MONDAY...
Friday: Mainly VFR.
Saturday: Mainly VFR. Chance of mainly afternoon and evening
showers and thunderstorms with MVFR.
Sunday: Mainly VFR. Slight chance of an afternoon shower.
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.
Persistent S-SW flow increases Thursday with gusts reaching SCA
levels (25-30kt) on the ocean waters, the bays of Long Island,
and eastern part of Long Island Sound. It`s possible that a few
gusts reach 35 kt on the ocean waters on the ocean, and if these
gusts are more frequent than expected a short fused gale
warning may be required for the ocean waters and possibly the
south shore bays from about 3-4 PM until 8-9 PM.
Winds subside later Thu night and Fri. However, seas may remain
elevated above 5 ft from late day Fri into Sat night as winds
increase ahead of an approaching cold front.
A weak pressure gradient Sunday into early next week will bring
below SCA conditions to the waters.
&&
.HYDROLOGY...
Locally heavy rain is possible this afternoon into the early
this evening, which may cause minor nuisance and poor drainage
flooding. Locally heavy rain may also be possible with the cold
frontal passage on Sat.
&&
.TIDES/COASTAL FLOODING...
Persistent S-SW winds will bring a high risk of rip currents to
the ocean beaches Thursday, especially during the afternoon and
evening.
A moderate risk of rip currents is forecast on Friday.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...Heat Advisory until 8 PM EDT Saturday for CTZ005>012.
NY...Heat Advisory until 8 PM EDT Saturday for NYZ067>071-078>081-
177-179.
Excessive Heat Warning until 9 PM EDT Friday for NYZ072>075-
176-178.
High Rip Current Risk until 9 PM EDT this evening for NYZ075-
080-081-178-179.
NJ...Heat Advisory until 8 PM EDT Saturday for NJZ002.
Excessive Heat Warning until 9 PM EDT Friday for NJZ004-006-
103>108.
MARINE...Small Craft Advisory from 3 PM this afternoon to 8 PM EDT this
evening for ANZ331.
Small Craft Advisory until midnight EDT tonight for ANZ332.
Small Craft Advisory until 8 PM EDT this evening for ANZ340-
345.
Small Craft Advisory until 9 AM EDT Friday for ANZ350.
Small Craft Advisory until 6 AM EDT Friday for ANZ353-355.-- End Changed Discussion --
&&
$$
SYNOPSIS...BG/DS
NEAR TERM...JMC/BG/DS
SHORT TERM...BG
LONG TERM...DS
AVIATION...DS/MW
MARINE...BG/DS
HYDROLOGY...BG/DS
TIDES/COASTAL FLOODING...