648
FXUS61 KOKX 052012
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
412 PM EDT Mon Aug 5 2024
.SYNOPSIS...
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A slow moving cold front sags southeast into the area late tonight.
The front stalls nearby through Tuesday night and possibly into a
portion of Wednesday. A series of weak fronts then move through from
Thursday through Monday.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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Convective activity across Central NY and into the Southern Tier
will have to be monitored for the late evening and into a portion of
the overnight. Based on NWP CAM guidance the best chance at seeing
some showers and t-storms would be for northern most zones. However,
with the humid environment in place one cannot be to certain that
NWP CAM guidance has a good handle on things. Especially if the
activity congeals some into more of a MCS. Do not have the
confidence to stray too far away from guidance, but do have chance
PoPs for northern NE NJ, the Lower Hudson Valley, and So. CT, with
slight chance PoPs slightly further south of there. However with
high dew points east of the Appalachians and to the coast this is
the type of situation where the activity can survive further to the
southeast. With the forcing to the north with the jet stream will
stay the course. A cold front will gradually draw closer from the
northwest through tonight.
Dew point reading will be in the upper 60s to lower 70s region wide,
so it will be another humid and warm night. Night time minimum
temperatures will range primarily in the 70s, with a few upper 70s
in the NYC / NE NJ metro. There are likely to be less cloud cover
further SE across the area for a good portion of the night,
especially if any convective debris stays north.-- End Changed Discussion --
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/...
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There is not the greatest agreement with respect to shower activity
across northern and northeastern zones through Tuesday morning as a
shortwave scrapes northeastern portions of the area. A cold front
which pushes in from the northwest will slow and likely stall to at
least some degree during the day Tuesday. The mid-level 700 mb
analysis shows various ripples of weak shortwave activity. Thus with
shortwave energy around at various times into the afternoon and
evening, and the front getting over the area, any convergence zone
should lead to shower and thunderstorm development with such a humid
environment and PWATs of 2 inches and up. Thus a Flood Watch has
been issued with this package. There remains uncertainty in terms of
coverage, but with the boundary setting up it appears to be a
situation where training / repeating cells over the same area
leading to flooding potential. The instantaneous rainfall rates are
a concern. 1 to 2 inch per hour rainfall rates at times appear to be
a lock for locations that get under any stronger convection /
reflectivity. With low level lapse rates lacking, the expectation is
that any t-storms would stay sub severe, with perhaps some stronger
gusts in any stronger convective activity. It will still be quite
warm and muggy, but with the enhanced cloud cover over the region
heat headlines are not an issue, with daytime maxes ranging from the
upper 70s to middle 80s and remaining quite humid.
During Tuesday evening into Tuesday night the guidance is suggestive
of scattered pockets of heavy showers with embedded t-storm
activity. The HREF PMM is suggestive of more coverage across NE NJ
which would be a problem, especially with lower FFG values here with
convective activity from the past few days. In any event, the high
instantaneous rainfall rates would be make a lot of locations prone
to potential flood issues regardless of antecedent conditions,
especially along the most reactive rivers and smaller flashier
streams and the more urban environments. It will remain warm and
muggy Tuesday night with the frontal boundary remaining in place and
not clearing the area, thus there will be no real air mass change.
There appears to be a consensus that the heavier rain and embedded t-
storm activity gets further to the south and southeast at some point
on Wednesday. The question is whether the frontal boundary remains
in place throughout Wednesday morning, thus the Flood Watch carries
through until noon on Wednesday. The front is expected to gradually
get further southeast late Wednesday afternoon, thus the expectation
is that the coverage of heavier rainfall would decrease into
Wednesday afternoon. The question for Wednesday afternoon mainly
concerns far southern and eastern areas, and whether the heavier
rain activity can get completely to the east and south. There
remains a good degree of uncertainty with respect to this.
Rainfall amounts are going to average 1 to 2 inches spatially
across the area, however one should not focus on average
rainfall totals, and should focus more on rainfall rates. See
the hydrology section for more details.-- End Changed Discussion --
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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Key Points:
* Highly complex forecast with great uncertainly but also potential
medium to high impact due to the potential interaction of a warm
front Thu night-Fri with tropical moisture well in advance of
Debby, then from Fri night-Sat if the circulation of Debby passes
close by.
* The future track of Debby, and larger scale weather systems
influencing the storm`s track, will play a big part in how this
portion of the forecast unfolds. Refer to the latest official
forecasts from the National Hurricane Center.
A closed low digging into the northern Plains and upper Great Lakes
late this week, as well as Western Atlantic ridging, will both play
a huge role in the future track of Debby. As far as the 05/12Z
global model guidance is concerned, am favoring the ECMWF and in
part the Canadian over the GFS. GFS appears to linger the
circulation for too long over the Southeast and then shear it out
when finally moving NE-ward this weekend, while the ECMWF/Canadian
are closer on the idea of the circulation moving west of the area
Sat morning even if the latter still appears to be shearing it out
too much. Today`s 05/12Z ECMWF shows a more intact circulation and
stronger Atlantic ridging, leading to an inland track with the
center passing across northern NJ early Sat morning, while the
05/12Z ensemble mean suggests a track slightly farther east and
directly over the CWA. These have both trended north with respect to
the 05/00Z and 04/12Z cycles.
Even before the actual circulation of Debby (no matter what its
classification) approaches, we may have to deal with a tropical
predecessor heavy rainfall event on Friday as a leading warm front
approaches from the south, with good southerly moisture transport
and possibly enhanced lift via weakly coupled jet streaks, one
departing over New England and and another riding up the coast. Then
as the actual circulation approaches late Fri night and passes on
Sat, would expect another round of heavy rain along and west of the
track, and deterministic/ensemble QPF`s bear this out, showing
fairly high probabilities of 4+ inches of total rainfall through the
weekend still centered over the CWA or in areas just north.
If the circulation center passes through or just to the west, there
could be some wind issues mainly along the coast, via strong onshore
flow.
All the above are still highly uncertain and subject to changes in
the future track and status of Debby as the circulation eventually
comes northward.
Daytime highs should run below normal through Sat, then rebound
closer to normal for Sunday and Monday as rain chances decrease.-- End Changed Discussion --
&&
.AVIATION /20Z MONDAY THROUGH SATURDAY/...
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Weak high pressure gives way to a slowly approaching cold front.
The front passes through the area late tonight into Tuesday
morning, but stalls close to the area.
Mainly a VFR forecast. MVFR will be possible for most terminals
starting towards noontime Tuesday as showers become more likely.
Can`t completely rule out thunder, but will leave the mention
out of the TAFs for now.
SE to SW sea breezes at around 10kt for most terminals. Winds
bcmg lighter and veering W overnight. Wind shift NE then E to SE
during Tuesday, increasing back to around 10kt.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Winds might vary SW to SE at KTEB this afternoon.
OUTLOOK FOR 18Z TUESDAY THROUGH SATURDAY...
Tuesday PM...Mainly VFR. SHRA with iso TSTM possible.
Tuesday Night-Wednesday: MVFR to IFR in SHRA.
Thursday: Chance of MVFR or lower in SHRA.
Friday: MVFR/IFR in SHRA. SE gust 20-25kt possible.
Saturday: MVFR/IFR in RA/SHRA. E to NE gusts around 25kt
possible.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
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Marginal small craft conditions for the central and eastern ocean
waters for tonight. Otherwise, sub small craft conditions are
anticipated through Tuesday night. Another period of marginal small
craft conditions may take place on Wednesday for the ocean waters as
ocean seas hover around 4 ft and wind gusts to 20 kt or thereabouts.
There is quite a bit of uncertainty for the end of the week due to
the future track of Debby. Long period southerly swells may start
arriving Thursday into Friday, but at this time seas are kept right
around 4 ft. Seas should increase above 5 ft Fri night, and if the
circulation center of Debby passes to the west, gale force wind
gusts may be possible late Fri night into Sat. The forecast could
significantly change, so please refer to latest forecast information
from the NHC as a starting point.-- End Changed Discussion --
&&
.HYDROLOGY...
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A Flood Watch is in effect for Tuesday afternoon through
Wednesday morning. WPC continues with a slight risk of
excessive rainfall for Tuesday into Tuesday night. While
uncertainty remains with coverage and duration of heavy to
potentially torrential rainfall, a heightened potential of
localized flash flooding with 1 to 2 inch per hour rain rates
exists, especially for the more urban locales. There remains a
chance that locally heavy rainfall continues into a portion of
Wednesday morning.
Heavy rainfall is possible late this week into the weekend, first
from Thu night into Fri as a warm front lifting northward into the
area interacts with tropical moisture well in advance of Debby, then
from Fri night into Sat if the circulation of Debby passes close
by.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
A high risk of rip currents is expected to continue through at least
Tuesday evening, likely into Tuesday. This is due to southerly
swells of around 4-5 feet.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...Flood Watch from Tuesday afternoon through Wednesday morning
for CTZ005>012.
NY...Flood Watch from Tuesday afternoon through Wednesday morning
for NYZ067>075-078>081-176>179.
High Risk for Rip Currents through Tuesday evening for NYZ075-080-
081-178-179.
NJ...Flood Watch from Tuesday afternoon through Wednesday morning
for NJZ002-004-006-103>108.
MARINE...None.-- End Changed Discussion --
&&
$$
SYNOPSIS...JE/BG
NEAR TERM...JE
SHORT TERM...JE
LONG TERM...BG
AVIATION...JC
MARINE...JE/BG
HYDROLOGY...JE/BG
TIDES/COASTAL FLOODING...