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Forecast Discussion for New York City/Upton, NY
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099
FXUS61 KOKX 180701
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
301 AM EDT Sat Jul 18 2026
.WHAT HAS CHANGED...
SPC has expanded the enhanced risk for severe thunderstorms
north and east to include much of the Lower Hudson Valley, NE
NJ, and NYC metro.
&&
.KEY MESSAGES...
1) Scattered severe thunderstorms and flash flooding possible this
afternoon into this evening. A Flood Watch remains in effect 10 AM
this morning until 2 AM Sunday for NE NJ, NYC metro and Southern
Westchester.
2) Areas of smoke expected this morning into the afternoon with
reduced air quality and visibilities possible. Air quality alerts
remain in effect from State DEPs until midnight.
2) Dangerous rip currents are expected at ocean beaches through
this evening, potentially lingering at Suffolk beaches on Sunday.
3) Another round of showers and thunderstorms possible late Tuesday
into a portion of Wednesday.
&&
.DISCUSSION...
.KEY MESSAGE 1...
An upper level trough digs down into the Great Lakes Saturday and
swings across eastern Canada and the northeast US Saturday night.
Ahead of this feature, shortwave energy will pass across the area
this afternoon as a warm front lifts north of the area into the
afternoon. A pre-frontal trough will follow late in the afternoon
with the main cold front moving across the area this evening with
the potential of another line of showers/storms. Severe
thunderstorms and potential flash flooding are the main concerns
this afternoon and evening.
It is important to note the exact location of the severe and
flooding hazards may not become clear until a few hours before
the onset due to the aforementioned uncertainties.
PWATs are progged to reach between 2 and 2.25 inches, which is well
above the observed 90th percentile per OKX RAOB climo.
Freezing levels look to range from 13-15 kft with deep warm cloud
layers, supporting efficient warm rain processes. These ingredients
support the potential for heavy downpours in any convection this
afternoon and evening. There is still some uncertainty with the
amount destabilization today, especially with lingering smoke this
morning and potentially apart of the afternoon (see key message 2
for more details on the smoke). The passage of the shortwave should
allow the smoke to move away from the area in the afternoon. The
greatest instability may set up just to our southwest, especially as
the shortwave moves across the area. There should still be at least
1000-1500 J/kg of MUCAPE, but surface based CAPE could be limited
this afternoon, unless greater destabilization occurs further
north. The mid level flow is also fast enough to keep the
convection moving across the area, which may limit the flooding
potential. The latest HREF has a small area of 30 percent chance
of greater than 3 inches in 3 hours just south of of our NE NJ
and NYC metro zones. This is close to our flood watch and most
susceptible areas for flash flooding, so no changes were made to
the flood watch. Peak hourly rainfall rates of 1.5-2"/hour are
possible. Isolated instances of flash flooding in some urban
areas across the I-95 in S CT and potentially western LI are
possible, but not enough confidence for an expansion of the
watch at this time. WPC has maintained the slight risk for
excessive rainfall.
SPC has expanded the enhanced risk into much of the Lower Hudson
Valley, NE NJ, and NYC metro with a slight risk remaining
elsewhere. As noted above, there is uncertainty with the amount
of destabilization due to smoke and potential of a round of
convection as early as late morning and early-mid afternoon. The
00z HREF is indicated a mean SBCAPE of around 1000 J/kg across
NE NJ into the NYC metro, but an ensemble maximum of upwards of
2000-3000 J/kg this afternoon for these areas. Elsewhere, the
mean is around 500 J/kg with an ensemble max of 1500-2000 J/kg.
The max surface CAPE values are possible if the smoke clears
sooner and if the first round of convection is weak or moves
out quicker. Bulk shear around 40 kt continues to be progged
and there is low level directional shear/curvature in the wind
profiles. The main threat from any severe storms will be
damaging wind gusts. There is also a risk of a tornado,
especially if the warm front lingers nearby, which would enhance
low level helicity and shear. If we are able to get clearing
and the first wave does not leave behind subsidence, then the
potential line of storms with the cold front/pre-frontal trough
could also contain a few severe thunderstorms.
The cold front moves through the area around midnight, bringing an
end to the threat of showers and thunderstorms.
.KEY MESSAGE 2...
Smoke is beginning to filter back into the area from the south
early this morning as high pressure has moved offshore. HRRR,
RAP, and RRFS smoke fields all show areas of smoke lingering
across the area this morning and potentially into a portion of
the afternoon. The smoke should begin to clear out and move to
the east as a shortwave and showers/storms move across the area.
There will be reduced air quality and visibilities into at least
the early afternoon. NYDEP, NJDEP, and CTDEEP all have air
quality alerts in effect until midnight.
.KEY MESSAGE 3...
Dangerous rip currents are expected at ocean beaches through
this evening. A high rip current risk is in effect due to
a strengthening southerly flow at 15 to 20 kt and SE swells.
On Sunday, the high risk likely only continues for Suffolk
County and during the morning hours. Guidance is showing a
lingering 5 to 6 ft swell at 7s.
.KEY MESSAGE 4...
Guidance continues to be in good agreement on an amplified
shortwave trough moving across the northeast Tuesday into
Wednesday. The trough may then linger over the region through
the end of the week. The next cold front will approach on
Tuesday with increasing probabilities for another round of
showers and thunderstorms late Tuesday into Tuesday night. CSU
MLP is indicating a marginal risk for a severe thunderstorm and
WPC has placed the area in a marginal risk for excessive
rainfall. It is a bit too early for any specific severe or
flooding impacts, but will continue monitoring trends over the
next few days. Lingering showers may continue into a portion of
Wednesday. High pressure should build into the northeast with
mainly dry weather to end the week.
&&
.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
High pressure will give way to an approaching frontal system on
today. Expect a warm front to moves across the terminals late
this morning/early afternoon, followed by a cold frontal
passage tonight.
Then several rounds of showers and thunderstorms are expected to move
through the area today with MVFR or lower conditions. The
greatest uncertainty will be the increasing concentration of
smoke in the low levels returning this morning. The latest HRRR
shows the greatest concentration between 12Z and 18Z. MVFR vsby
restrictions possible in the smoke. MVFR or lower cigs more
likely for eastern terminals this afternoon into the evening.
Coastal terminals should expected a light S wind with more
outlying terminals becoming light and variable through about
sunrise. After sunrise, SW/S winds increase to 10-15 kt with
G20-25kt, with the highest across the eastern terminals. Low
chance for SW LLWS below 2kft.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Chance of MVFR developing in smoke tonight and persisting
through Saturday morning. Low confidence of IFR or lower in the
smoke.
.OUTLOOK FOR 06Z SUNDAY THROUGH WEDNESDAY...
Saturday night: MVFR or lower gradually improving to VFR.
Sunday and Monday: Mainly VFR.
Tuesday and Wednesday: MVFR or lower with showers/tstms.
&&
.MARINE...
An SCA remains in effect into tonight for all waters except the
NY Harbor and western LI Sound. Wind gusts should reach around
25 kt with seas building to around 5 ft on the ocean. 5 ft seas
may linger on the ocean tonight into early Sunday, so the
Advisory continues until noon on Sunday.
Conditions are then quiet until the next cold frontal passage
during the middle of next week. SCA conditions are possible
Tuesday through Wednesday night, with the potential of 7 to 10
ft seas.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Air Quality Alert until midnight EDT tonight for CTZ005>012.
NY...Air Quality Alert until midnight EDT tonight for NYZ067>075-
078>081-176>179.
Flood Watch from 10 AM EDT this morning through late tonight
for NYZ071>075-176-178.
High Risk for Rip Currents from 6 AM EDT this morning through this
evening for NYZ075-080-081-178-179.
NJ...Air Quality Alert until midnight EDT tonight for NJZ002-004-
006-103>108.
Flood Watch from 10 AM EDT this morning through late tonight
for NJZ002-004-006-103>108.
MARINE...Small Craft Advisory from noon today to midnight EDT tonight
for ANZ331-332-340-345.
Small Craft Advisory from noon today to noon EDT Sunday for
ANZ350-353-355.
&&
$$
DISCUSSION...DS
AVIATION...BC
MARINE...DS
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