000
FXUS61 KOKX 041130
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
730 AM EDT Wed Oct 4 2023
.SYNOPSIS...
High pressure over the region through Thursday will slowly
weaken beginning Thursday night, and give way to an approaching
frontal system on Friday. The associated cold front will pass
through Saturday into Saturday night. Low pressure will then
linger to the north as high pressure slowly build from the south
and west.
&&
.NEAR TERM /THROUGH TONIGHT/...
The warmest day of the current spell expected as high pressure
at the sfc and aloft both strengthen. Used bias corrected blend
of GFS/ECMWF MOS temps which have been fairly close to actual
high temps during this warm spell, which yields highs in the
mid/upper 80s from NYC west, lower 80s most elsewhere, and upper
70s closer to south facing shorelines of NYC, Long Island, and
S CT. based on current fcst temps, record high temps may be
approached at LGA/EWR and set at ISP. Climate section below
provides details.
Another clear night expected tonight, with light onshore flow
and development of river valley fog as has been the case the
last few nights. Some guidance blankets the entire CWA in dense
fog overnight, think this is overdone since this will be the
first night of onshore flow, but with inland river/valley fog
already having been an issue the past several nights, can`t rule
out a hybrid radiative/advective combo becoming more widespread
especially out east. For now have added more fog to the grids
for late tonight where already occurring this morning, and also
to SE CT/Long Island per time-lagged GFS LAMP/HRRRX forecast.
Low temps should range from 60-65 invof NYC, to the 50s
elsewhere.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
One last mostly sunny/warm day expected, though not as warm as
Wed as the vertically stacked high begins to slide east out
into the Atlantic. High temps should still reach the lower 80s
in NE NJ, with mid/upper 70s elsewhere.
Second night of onshore flow may lead to more widespread fog
development Thu night. As the sfc ridge axis lifts to the north,
sct to numerous warm advection showers should start to develop
late Thu night offshore and spread to Long Island late Thu
night, then to the rest of the area daytime Fri. Low temps again
in the lower 60s in NYC and 50s elsewhere should warm up to the
lower/mid 70s in most places on Fri, perhaps to the upper 70s
in NE NJ.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
At the start of the long term period, the orientation of surface
high pressure well to our north and east will continue the
already prolonged period of SE-E onshore flow. This will advect
an increasingly humid air mass into the area. In the meantime,
an upper level trough approaches from the west as Tropical Storm
Phillipe approaches from the south and east. The upper level
trough will eventually become negatively tilted before closing
off. At the surface, an associated cold front will swing through
the area. There is much more interaction near our area with the
upper level trough/surface cold front and Phillipe than was
shown in the guidance 24+ hours ago. The original thinking was
that a wave of low pressure would form over or near the area
along the the cold front. It now looks like the negatively
tilted trough may bend Phillipe back to the north and west well
north of our area. The exact details will need to be fine tuned
over the next several days.
Regardless, a good 1-1.5 inches of rainfall is possible through
Saturday, with the potential for periods of moderate to heavy
rain. Both the NAM and GFS show PW increasing to 1.5-1.75 inches
ahead of the cold front early Saturday. This has lowered
slightly compared to 24 and 48 hours ago. NBM probabilities for
1 inch of rain over the 24 hr period ending 00Z Sunday have
increased slightly after holding steady for the past two days.
It now has a 35-45% chance over the northern half of the area
and 25-35% across the southern half. See the Hydrology section
below for more details on expected impacts.
Rain chances taper off early Sunday and a cool air mass is
advected in behind the cold front. The closed upper level low,
as well as the surface low, remain over the northeast through
the end of the forecast period. This will lead to a period of
well below normal temperatures. The coolest days will be Sunday
and Monday. Highs will be in the mid 50s to lower 60s, with lows
in the 40s.
Refer to the National Hurricane Center, https:/www.nhc.noaa.gov for
official forecasts on Philippe.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
High pressure moves offshore late today into tonight.
Mainly VFR thru the TAF period. Some patchy fog currently at
some of the outlying terminals. VFR conditions return for all by
14z. Fog returns tonight. NYC likely stays VFR.
Winds will be light and variable early this morning, then out of the
SE today mainly around 5 kt in the afternoon. The winds will remain
light into the evening push, mainly out of the S-SE at 5 kt or less.
Winds become light and variable again tonight.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Uncertainty in fog development tonight. Vsbys likely stay VFR,
but can not completely rule out lower conditions.
OUTLOOK FOR 12Z THURSDAY THROUGH SUNDAY...
Thursday: VFR.
Friday: MVFR or lower possible in chance of rain showers
afternoon.
Saturday: MVFR or lower in rain showers.
Sunday: VFR. W-NW winds 15-20kt with gusts up to 25 kt.
Detailed information, including hourly TAF wind component
forecasts, can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
After an extended quiet period with high pressure in control and
a 2-3 ft SE swell, ocean seas will be building Fri night, and
should reach 5 ft by Sat morning. A cold front will move through
late Saturday and could bring gusts 25-30 kt to all waters from
Sunday through early Mon.
Ocean seas will remain elevated into early next week as long
period swells from distant Tropical Storm Philippe move into
the waters. Refer to the National Hurricane Center,
https:/www.nhc.noaa.gov for official forecasts on Philippe.
&&
.HYDROLOGY...
A period of showers is likely late Friday through late Saturday,
with about 1-1.5 inches of rainfall expected at this time. The
WPC now has southern CT and portions of the Lower Hudson Valley
in a Day 4 marginal risk of excessive rainfall. The main threat
in the marginal area is minor nuisance flooding, with the
potential for isolated flash flooding.
&&
.EQUIPMENT...
Data from the Peconic River at Riverhead NY tidal gauge appear
to have improved. Will monitor the gauge over the next few days
to make sure it is in line with other nearby gauges.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...BG/JT
NEAR TERM...BG
SHORT TERM...BG
LONG TERM...JT
AVIATION...JT
MARINE...BG/JT
HYDROLOGY...BG/JT
EQUIPMENT...