000
FXUS61 KOKX 251451
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1051 AM EDT Fri Aug 25 2023
.SYNOPSIS...
A slow moving frontal system moves approaches today, and then
crosses the area tonight into Saturday morning. A cold front will
cross the region Saturday evening. Canadian high pressure builds
in for Sunday, and then centers north of the area on Monday. A
frontal boundary approaches from the south and southwest Monday
night into Tuesday. A cold front slowly pushes through on
Wednesday, with high pressure following for the latter portion of
next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
A broad, ragged band of rain showers continues to slowly
advance east this morning, now through NYC, NE NJ, and the lower
Hudson Valley as of 14z. Rainfall rates have lowered as well,
and showers should remain light to moderate, helping to
preclude hydro concerns for the moment. A developing LLJ ahead
of the weak surface wave advancing east aids further development
into the afternoon, particularly for eastern areas. Farther
west, drier air working in aloft may help to destabilize
conditions enough to break a weak cap and allow for a few
thunderstorms to develop in the warm sector. These could produce
locally heavy downpours that lead to nuisance flooding of urban
and poor drainage areas this evening. Forecast remains on track
and previous discussion follows.
Convectively enhanced shortwave energy moving through active
northwest upper flow approaches from the eastern great Lakes
this morning and slide east by early afternoon. A subsequent
stronger shortwave slides into the Great lakes today and
approaches tonight.
At the surface, a broad slow moving low pressure system moves
into W PA/NY this morning, with its associated warm front
approaching the region. This warm front likely lifts north of
the area during the day as S/SW llj strengthens, with broad
surface wave and pre-frontal trough approaching this evening and
crossing the area tonight.
Locally heavy downpours and isolated embedded tstms (decreasing
trend for tsra thru the morning) moving across NYC/NJ metro and
Lower Hud in an increasingly sub- tropical environment (deep
moisture, 12-13kft warm layer, 2 1/2 PWATS, and weak
instability) lifted by approaching shortwave and developing llj
converging in vicinity of eastward moving warm front. Main
threat is for minor urban and poor drainage flooding with up to
1"/hour rainfall rates being realized in training downpours.
The threat for localized flash flooding is very low and
localized based on these rates, perhaps across southern
portions of NYC and LI where nose of LLJ may enhance
instability/lift and rainfall rates through the morning. Some
hints of this with latest HRRR, but will have to be monitored.
Shortwave should slide east by early afternoon, with the region
likely getting warm sectored. Mid-level drying evident in wake
of this, with some partial clearing possible for western areas
in the afternoon. This should allow for marginal instability
development in a marginally sheared environment from NYC and
points N&W, but with a weak 800-900mb cap. With a lack of
trigger/focus in the afternoon, expectation is for only isolated
shra/tsra activity this afternoon. Activity likely increases
across western portions of the area late today/this evening as
surface wave/trough approaches. This may present a conditional
small window threat for isolated strong to severe wet microburst
late this afternoon into evening from NYC and points N&W if
weak cap is broken.
Shower/heavy downpour activity should increase in coverage
ahead of eastward sliding trough/surface wave aided by LLJ
across LI/CT tonight. Although instability weakens and is
elevated, the increased shower coverage in a sub tropical
environment will present an urban and poor drainage flood threat
from any training convection/downpours. The heaviest activity
should finally slide east by daybreak Saturday as surface trough
and llj slides east, with trailing cold front entering western
portions of the region with lighter shower activity.-- End Changed Discussion --
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Models in general agreement with mean NE troughing through the
period.
A shortwave trough slides through the Great Lakes into NE US
Sat, with surface wave pushing offshore and trailing cold front
passing through the region Sat morning. Mainly an isolated
shower threat with cold frontal passage in the AM with
lift/moisture/instability axis already to the east. Drying
conditions in its wake Sat AM.
Cyclonic flow Saturday afternoon, and lingering weak surface
troughing, will likely result in sct to bkn diurnal afternoon
instability cu development. Temps should run near seasonable
upper 70s to lower 80s with offshore flow. Then a Canadian cold
front approaches late Sat, crossing Sat eve. An isolated
instability shra/tsra possible with cold frontal passage late
Sat/Sat eve. A pronounced 750-850mb cap should limit any
strong/severe tstm threat.
NW winds in the wake of the passage with an early autumn- like
airmass advecting into the region for Sun/Mon as Canadian high
pressure builds to the north and then NE. With backside
shortwave sliding through on Sunday potential for an isolated
shra/tsra developing across highest terrain of interior in a
marginally unstable environment. Temps will be running a few
degrees below seasonable (mid to upper 70s) for late August with
low humidity levels.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
High pressure will be in place to begin Monday. The high will
however move northeast with a shortwave showing up in the guidance
and likely approaching Mon night. A stationary boundary down to the
south will start to move north as a warm front later Mon night into
Tuesday. Around the same time frame Tropical Cyclone Franklin is
expected to lift north in the Western Atlantic. The system is
progged to stay offshore with no direct impacts. However, some
indirect impacts will be dangerous rip currents due to an increasing
swell and high surf. Some of the guidance has hinted at perhaps some
tropical connection with theta e ridging and perhaps some enhanced
convection for Mon night and early Tue. Not completely buying this
at this time, but bears watching in subsequent packages. For now
have slight chance of showers introduced for Mon. evening, with
chance showers for later Mon night into Tue. The cold front
associated with the upper trough begins to pivot through late Tue
night into Wed. This will maintain shower chances and a slight
chance of thunder for portions of the area into Wed.
Behind the frontal boundary look for a cP air mass with cooler
temperatures and comfortable conditions into the later portion of
next week by Thursday. Temperatures overall through the period will
average approximately 3 to 5 degrees below average, with noticeably
lower humidity Wed night into Thursday.
Monitor https:/www.weather.gov/okx/tropical for the latest NHC
forecasts on this tropical system and others.
&&
.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
A warm front remains north of the terminals today with cold
front approaching and passing through late tonight into Saturday
morning.
Mainly MVFR for the rest of the day. Tempo VFR is possible. Also
some showers possible before late afternoon, but probably not
lasting long enough or widespread enough to include in TAFs.
Somewhat better chance of a shower late afternoon into early
evening - tempo group for this has been maintained for now. Even
a slight chance of thunder late this afternoon/evening but not
enough probability to include in TAFs. MVFR/IFR for the
overnight with more showers possible.
Winds will be southerly, generally under 10kt inland and
10-15kt at the coastal terminals through early this afternoon.
Some wind gusts take place at some of the coastal terminals this
morning and early this afternoon. The winds remain S tonight
and lighter, before becoming SW late tonight, then NW towards
12z Sat.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Occasional gusts 20-25kt possible at KJFK. Tempo VFR possible
through this afternoon. Brief IFR still possible at any point
today. Prevailing IFR possible late tonight.
The afternoon KJFK haze potential forecast is YELLOW...which implies
slant range visibility 4-6SM outside of cloud.
The afternoon KLGA haze potential forecast is YELLOW...which implies
slant range visibility 4-6SM outside of cloud.
The afternoon KEWR haze potential forecast is GREEN...which implies
slant range visibility 7SM or greater outside of cloud.
OUTLOOK FOR 12Z SATURDAY THROUGH TUESDAY...
Saturday: VFR, early AM isolated shower/tstm possible across eastern
terminals. Isolated shower in PM.
Sunday and Monday: VFR.
Tuesday: MVFR or lower in SHRA/TSRA especially in the afternoon and
evening.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
SCA wind gusts expected on the ocean waters, southern and eastern
bays and LI Sound today as llj strengthens overhead, then relegated
to ocean waters and eastern nearshore waters this evening as llj
shifts east. Winds fall below SCA late tonight on all waters as
llj slides east. In response, waves on the ocean waters build
to 5 to 7 ft today into this evening, slowly falling below SCA
as winds subside on Saturday.
Brief marginal SCA conds may be possible on the ocean waters Sat
Night with gusty NW flow in wake of cold frontal passage, although
these winds have trended weaker.
Thereafter, sub SCA conditions favored for Sun into Mon on all
waters (although ocean seas may run 3-4 ft in mixed E and SE swell),
with high pressure building in.
By Monday night into Tuesday look for SE swells to become more
energetic with swells likely building further as tropical
cyclone Franklin lifts north in the Western Atlantic late Monday
into Tuesday. Small craft conditions develop by Tuesday with
ocean seas expected to climb to 5 to 6 ft, and perhaps to 7 ft
further east Tuesday afternoon and Tuesday night.
&&
.HYDROLOGY...
-- Changed Discussion --
Flood threat appears to be more of a minor urban and poor
drainage flooding late today into tonight across LI and CT as
shower/tstm coverage/intensity should be less than this morning,
with a very low and localized flash flood potential based on
the subtropical environment. Total basin average rainfall of 1
to 2 inches areawide through tonight, with localized 3" amounts
possible.
No hydrological concerns at this time from Saturday through the
Thursday. There remains low predictability on any heavy rain
threat associated with a slow moving frontal system Monday night
through Tuesday night next week.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
There is a high risk for rip current development Today into
Saturday with 5 ft+ southerly wind waves.
Swells from tropical cyclone Franklin will likely build late Monday
into Tuesday, continuing into midweek, increasing likelihood for
high surf and dangerous rip currents. In addition, a full moon on
Wed Night will have astro tides increasing through the mid to late
week period. Combined with the high surf, the potential for
areas of ocean beach erosion/flooding and scattered areas of
dune erosion increases during the times of high tide Tue/Wed.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Risk for Rip Currents through Saturday evening for NYZ075-080-
081-178-179.
NJ...None.
MARINE...Small Craft Advisory until 2 AM EDT Saturday for ANZ331-332-
340-345.
Small Craft Advisory until 8 PM EDT this evening for ANZ335.
Small Craft Advisory until 2 PM EDT Saturday for ANZ350-353-
355.
&&
$$
SYNOPSIS...JE/NV
NEAR TERM...DR/NV
SHORT TERM...NV
LONG TERM...JE
AVIATION...JC
MARINE...JE/NV
HYDROLOGY...JE/NV
TIDES/COASTAL FLOODING...