NYC Office Forecast Discussion
251
FXUS61 KOKX 010234
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1034 PM EDT Mon Aug 31 2026
.WHAT HAS CHANGED...
Thunderstorm chances lower Wednesday. Main thunderstorm chances
Tuesday and Thursday. Mostly marginal flood and severe risk.
&&
.KEY MESSAGES...
1) Shower and thunderstorm forecast through Tuesday night. Marginal
flood risk and marginal to slight severe weather risk.
2) Fog potential overnight into early Tuesday.
3) After a lull in shower and thunderstorm activity Wednesday, more
showers and thunderstorms forecast Wednesday night through Thursday
night. Also, marginal severe and flood risk.
4) Drier conditions expected for the holiday weekend.
&&
.DISCUSSION...
.KEY MESSAGE 1...
A warm front moves in overnight. A mid level shortwave and its
PVA also move in. The warm front front is slow to move with its
NE movement within our region overnight into Tuesday. This
front then slowly pushes southwest Tuesday afternoon through
Tuesday night, becoming essentially a back door cold front.
A more unstable low level environment takes shape overnight
into Tuesday across the area. Multiple rounds of showers and
thunderstorms are conveyed within the reflectivity fields of
CAMs. Limited instability overnight, mainly an isolated
thunderstorm possibility.
The highest instability will be across the western half of the
region for Tuesday afternoon into Tuesday evening. This area will
have highest chance of thunderstorms and the slight risk of severe
thunderstorms. Also with the higher risk of severe thunderstorms
will come a relatively higher probability for flooding with those
same thunderstorms. To the east, more of a marginal severe
thunderstorm risk. Overall, flash flooding is a marginal risk for
most locations.
Looking at the HREF, the mean surface CAPE increases to near 1000-
1500 J/kg Tuesday across the local region for afternoon, then
decreases from east to west towards the evening. Looking at the
LREF 250mb heights, one jet streak passes to the north late
Tuesday into Tuesday night, with orientation from NW to SE. Our
area is away from the favorable quad of lift, that being the
left front of that jet streak. However, the higher winds aloft
will present divergence.
Precipitable waters still shown to climb to near 2 inches for
Tuesday, providing a moisture rich airmass for heavy downpours
to be realized.
0-6 km AGL bulk shear shown in models forecast to reach near
40-50 kt, and with the shear, this in combination with the CAPE
will make for an increased threat of severe thunderstorms
Tuesday into Tuesday evening. The HRRR shows some small
discrete areas of higher 2-5km max updraft helicity so a brief
tornado will be possible.
.KEY MESSAGE 2...
With moisture laden grounds overnight into Tuesday morning, and
surface winds being light as well as moist air advection, there
will be potential for fog. Patchy fog is forecast across the
entire region. This might get more expansive than forecast for
some locations.
.KEY MESSAGE 3...
The forecast has trended more stable for Wednesday. The frontal
boundary is expected to stay south and west of the region Wednesday
before starting to move back in Wednesday night into Thursday.
Not much of any chance of thunderstorms for Wednesday with
increasing chances Wednesday night and especially Thursday.
Looking at the NBM, the mean CAPE shows less than 1000 J/kg for
Wednesday into Wednesday night across the local area before
getting back to that value towards Thursday morning. Thursday
afternoon, NBM mean surface CAPE climbs back to 1000-1500 J/kg,
highest for western portions of the region.
Looking at the LREF, next jet streak moves in Thursday afternoon
into Thursday night, but this time while the streak magnitude with
250mb winds is weaker, our area is closer to left front quad.
Also, the heights lower a bit more with stronger troughing late
Thursday into Thursday night. Therefore, more forcing vertically
for convection. Divergence aloft a factor again for Thursday into
Thursday night. Models indicate similar 0-6 km AGL bulk shear
as Tuesday, near 40-45 kt Thursday into Thursday night.
Overall, a marginal flood and severe risk for much of the area with
thunderstorms Thursday into Thursday night. There is still quite
a bit of uncertainty with the frontal placement and its timing
as well as the thunderstorms for Thursday.
.KEY MESSAGE 4...
A drier pattern setting up Friday into the holiday weekend. High
pressure begins to build in from the north. Mainly dry conditions
are expected. Temperatures are not expected to deviate too much from
normal. Less humid conditions are also forecast.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
A warm front approaches from the south overnight and stalls over
the region during Tuesday. The front will then likely move just
south of the area Tuesday night.
MVFR conditions are developing. Ceilings likely dropping to IFR by
03-06z at most terminals with periods of -RA/BR, then during Tuesday
MVFR and some IFR prevail for eastern terminals. IFR becomes more
likely once again towards the tail end of TAF period (Tue evening)
for the 30 hr terminals.
Light winds overnight and variable at times through Tuesday. During
the day Tuesday the sfc front may get into southern portions of the
area, resulting in more of a S/SW flow for most terminals.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Variability in wind direction can be expected thru the TAF period,
especially on Tue with a front in the vicinity.
There is the potential for IFR for portions of the day Tuesday.
.OUTLOOK FOR 00Z WEDNESDAY THROUGH SATURDAY...
Tuesday night-Wednesday: A chance of thunderstorms Tuesday evening.
MVFR or lower possible with periods of rain.
Thursday: MVFR or lower at times with chances for showers and tstms.
Friday: Mainly VFR. A period of MVFR or lower possible in SHRA.
Saturday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
The pressure gradient across the waters this week is not
expected to be that steep. Mainly below SCA conditions are
forecast. Marginal SCA conditions for eastern parts of the ocean
forecast late Tuesday night into Wednesday and late Thursday.
Rip Currents:
There is a low risk for rip current development on Tuesday with
light winds and low swells under 2 ft. The risk increases to
moderate on Wednesday with 3 to 4 ft E swells at a 7 sec period, and
NE winds 10 to 15 kt developing by late afternoon.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
DISCUSSION...JM
AVIATION...JE
MARINE...JM