000
FXUS61 KOKX 052159
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
559 PM EDT Thu Oct 5 2023
.SYNOPSIS...
High pressure slides east tonight into Friday. The high will give
way to an approaching frontal system that will drag a cold front
through the area Saturday into Saturday night. Meanwhile, tropical
storm Philippe is forecast to track north, about 250 to 300 nm
east of Montauk Point on Saturday. The post tropical low
pressure tracks into Eastern Canada early next week allowing
weak disturbances to move through the area during the week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
-- Changed Discussion --
Forecast is on track with only minor changes needed to reflect
current conditions. Continue to monitor an area of low stratus
and fog just east of Block Island moving westward. Some
observations upstream over Cape Cod and Nantucket Island are
reporting dense fog. Previous discussion follows.
Strong shortwave energy digs into the Upper
Mississippi Valley, around a southern Ontario closed low and
deep eastern Central US trough, while a broad upper low off the
SE US coast gradually lifts north, influencing TS Philippe to
accelerate north towards Bermuda.
At the surface, regionally, a frontal system associated with the
Ontario Low pushes into the eastern great Lakes, with a strengthening
S/SE low-level flow increasing theta-e advection and low-level lift
into the area. This moistening under a strong subsidence inversion
will likely have stratus developing, and perhaps some patchy drizzle
across southern and western areas with weak lift as heights
fall.
Before the stratus develops, patchy radiational fog development
is possible across the interior, which could be locally dense.-- End Changed Discussion --
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
An upper level trough continues to dig through the Great
Lakes/Ohio Valley on Friday, with southern closed low lifting up
the coast. The anomalously deep trough (2-3 std below normal)
negatively tilts towards the area Friday Night into Saturday,
with southern shortwave lifting north through the area. The
negatively tilting trough closes off Sat Night to the NW of the
area.
At the surface, a strong cold front moves into the western PA/NY by
Fri evening, then into far western portions of the area Sat, and
across the region by Sat eve/night. Meanwhile, TS Philippe is
forecast to move north Friday Night thru Saturday, tracking
250-325 miles e of MTP Sat afternoon as it is transitioning to
extra tropical. Based on this forecast track, the developing
frontogenetic/deformation banding on the west side of Phillipe
is likely to stay east of the area. Shower activity will
gradually increase Friday into Friday Night with approach of
lead and southern shortwave energy aiding lift of an gradually
increasing Atlantic and sub-tropical moisture feed. The rain
shower activity will likely be most prevalent and heaviest N&W
of NYC with orographics and in vicinity of weak warm front/pre-
frontal trough. There will likely be a focus for a 6 hr period
of moderate to heavy rainfall late Friday Night into Saturday in
response to strong lift and weak instability ahead of
negatively tilting shortwave and right rear quad of ULJ (or even
possible couple jet) lifting an initially moist airmass with
both gulf and sub-tropical connection (+1-2 std PWATS)
convergence in a zone between the approaching cold front and
warm front/pre- frontal trough.
With above forcing, convergence zone and tropical moisture this
situation bears monitoring for potential PRE characteristics.
Interestingly, based on sounding analysis, the best mid-upper lift
on Sat appears to be offset from the deepest moisture and warm cloud
rainfall efficiency Friday Night into early Sat, perhaps as
Phillipe showing its extra-tropical influence. There is some
weak diurnal instability evident on Saturday as the shearing
southern shortwave lifts through and ahead of the negatively
tilting primary shortwave, which could help support a narrow
axis of deeper convection.
NBM probabilities for 1 inch of rain over the 6 hr period from Sat
12z to 00z Sun continue to be quite low at 5-10%. NBM probs of 1" in
24 hrs are around 30 to 40% for Lower Hudson valley and 10-20% for
the coast. The 12z HREF though is indicating 10% ensemble potential
of 3"/3hr btwn Sat 09z-12z as the sub-tropical moisture stream and
frontal system moisture stream begin to converge, with 12z HRRR
indicating potential for localized 1-2"/hr rainfall rates. Current
indication is that this enhanced convergence/lift area initially
develops/focuses across NYC, NE NJ and Lower Hud late Fri
Night/Sat AM, and then translate east across southern CT on
Saturday. Expect refinement of the location, movement, rainfall
amounts and rates over the next 12 to 24 hrs as this event gets
more completely resolved by high-res models, but potential is
there for a 3-6 hr period of locally enhanced rainfall rate
threat, particularly for areas N&W of NYC where better forcing
is pivoting through combined with orographic enhancement.
Rain tapers off Sat Eve/Night as closed low closes to the NW of the
area and cold front wraps into transitioning post-tropical storm
Phillipe heading into northern New England. W/NW winds of 15-
25G30mph ushering in a cooler and drier airmass.
Refer to the National Hurricane Center, https:/www.nhc.noaa.gov for
official forecasts on Philippe.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
High amplitude trough in association with strong low pressure over
northern New England Sunday will track into southeastern Canada and
retrograde into southern Ontario, north of the Great Lakes by Monday
night. This upper trough will remain over the Northeast and
upper Mid-West through much of next week, with some
weakening/deamplification as the low becomes vertically stacked
and weakens over Ontario. During this time frame, weak
disturbances in association with the cyclonic flow aloft will
move through the region. Where and when is still somewhat
uncertain at this point, but best timing right now look to be
Monday night through Tuesday night. However, it will not be
raining the entire time, with at most about a 30% chance of
showers during this time frame.
As far as temperature is concerned, a cooler air mass will be
advected into the region for much of the week. Temperatures on
Sunday and Monday will only be in the upper 50s to lower 60s. Some
moderation is expected by Tuesday onward as temperature are forecast
to rise into the lower to upper 60s.
&&
.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
High pressure centered well east of the New England coast will
gradually retreat farther offshore through Friday, while a frontal
system approaches from the west.
VFR through early this evening, then widespread IFR/LIFR conditions
overspread the area, mainly after 00Z. Occasional VLIFR with vsbys
1/4 mile or less. A few showers and/or areas of drizzle remain
possible late tonight into Friday.
S-SE winds 5-10kt will become E-SE this evening at 5 kt or less.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Timing of lowering cigs/vsbys this evening could vary by 1-3 hours.
OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY...
Friday: LIFR/IFR to start, improving to MVFR. Chance of VFR for a
period at KEWR/KTEB/KLGA/KSWF. Chance of rain showers and/or
drizzle.
.Friday Night...LIFR/IFR conditions return. Showers becoming
likely, especially across the NYC and Lower Hudson Valley terminals.
Saturday: MVFR or lower in rain showers. Improving late with a cold
frontal passage and NW winds 10-15kt G20-25kt.
Sunday: VFR. W winds 15-20kt G25-30kt.
Monday: Mainly VFR. Chance of showers late. SW G15-20kt
Tuesday...Manly VFR. Chance of showers. S-SW G15-20kt.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
Dense fog potential is there this evening into Fri morning as
offshore stratus gradually advects towards the coast.
Sub SCA winds are expected through Saturday morning, but ocean seas
build to 5 ft Friday night as swells increase from TC Phillipe. By
Saturday night, ocean seas are expected to be 9-10 ft. SCA winds
likely behind a strong cold frontal passage late Saturday,
continuing into Sunday. SCA criteria gusts are likely on all
waters Saturday night through Sunday night, with occasional
gales possible on the ocean waters.
SCA conditions look to continue for Sunday and into the first
part of Sunday night on all waters, though winds and waves will
be diminishing starting late Sunday afternoon. Waves peak on
the ocean to 6 to 10 ft, while 4 to 6 ft are expected on the
central and eastern sound waters by Sunday afternoon. A strong
WSW to W flow is expected, with sustained winds of 20 to 30 kt
on all waters, and gusts 30 to 35 kt. Gales are possible on the
ocean for Sunday, so will continue to monitor for this
possibility.
By late Sunday night, only the ocean waters are expected to remain
in SCA as wave heights above 5 ft. From Monday through Tuesday, sub
SCA conditions are expected on all waters.
Refer to the National Hurricane Center, https:/www.nhc.noaa.gov for
official forecasts on Philippe.
&&
.HYDROLOGY...
A basin wide average of 1 to 1 1/2" is likely from NYC and
points N&W, tapering to 1/4 to 1/2" along the coast from Friday
thru Sat evening. 12z HREF is indicating a 10% probability of
3"/3hr at the end of the forecast period early Saturday morning
in vicinity of NYC/NJ metro, which does pose some concerns for
isolated flash flooding across NYC/NJ metro and the quick
reacting river basins across NE NJ, Lower Hud and SW CT due to
saturated soils and streamflows at 75th percentile or greater.
HRRR also indicating potential for some very localized swaths of
1-2"/hr rainfall rates in this area, which supports a localized
flash flood threat from any training downpours/embedded tstms.
Higher probability appears to be for minor urban and poor
drainage and small river/stream flooding.
Still too early and low confidence for a Flood Watch, but if
high res guidance becomes more bullish on coverage/duration of
these enhanced rainfall rates aver the next 24 hrs, a watch may
be needed.
&&
.TIDES/COASTAL FLOODING...
Long period SE swells from Phillipe will build to 6 to 8 ft Fri
NIght into Sat Night, presenting likelihood of additional beach
erosion/escarpment from an east to west sweep of 5 to 9 ft
breaking surf. Because water levels are not astronomically
high, the dune erosion threat during times of high tide is
isolated.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 6 PM Friday to 8 PM EDT Sunday for
ANZ350-353-355.
&&
$$
SYNOPSIS...JP/NV
NEAR TERM...JP/NV
SHORT TERM...NV
LONG TERM...JP
AVIATION...DW
MARINE...JP/NV
HYDROLOGY...JP/NV
TIDES/COASTAL FLOODING...