000
FXUS61 KOKX 110047
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
747 PM EST Sun Dec 10 2023
.SYNOPSIS...
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A strengthening frontal system pushes through tonight into
Monday morning. The deepening low pressure along it will move
away quickly into Canada by Monday evening. High pressure will
then build from the southwest on Monday night into Tuesday. A
cold front approaches Tuesday night and pass through late
Tuesday night or Wednesday morning. Another strong high will
then build from the west for later in the week, then shift off
the New England coast Saturday night.-- End Changed Discussion --
&&
.NEAR TERM /THROUGH MONDAY/...
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***Flooding rain and strong to damaging winds for portions of
the region tonight***
Forecast on track, with a very dynamic system will impact our
area into tonight, continuing to advance downstream from
Appalachians and into the the eastern coastal plain. The complex
frontal system along with the cold front is forecast to be
progressive across the southern U.S. as the base of the upper
trough becomes negatively tilted as it swings from the Lower
Mississippi Valley to the East Coast through tonight, with a
deepening surface low forecast to track from the Mid Atlantic
into the Northeast late tonight into Monday AM.
A train of heavy rain with embedded thunderstorms aligned from
north to south from E PA down through VA ahead of cold front
will begin to overspread the region over the next few hours.
A large area of rainfall rates of 1/4 to 1/2"/hr being observed
upstream, with locally up to 1"/hr.
This is all due to a conveyor belt of moisture with anomalous
high for this time of the year PWATs and Integrated Water Vapor
Transport. All the ingredients are in place for a widespread
heavy rain event, with a thick warm cloud layer up to 9 to 10
kft, PWATs up to 1.5 inches, and mean RH up around 95 percent. A
very strong LLJ of 60-65 kt providing a classic warm tongue at
850 and 925 mb, along with a trough going negatively tilted is
suggestive of an active night. This saturated deep layer column
shown by all guidance and upstream soundings only increases
confidence for a significant event. To the east of the boundary
is lots of high theta E or low latitude air origin, thus the
warm rain processes will be in place to drive some higher
rainfall rates. WPC has put the area in a rare slight risk of
excessive rainfall, with a moderate risk across portions of
Central and Eastern CT. See the hydrology section for further
details.
Winds expected to ramp up along the coast, particularly LI and
SE CT through 10pm. The period of strongest winds along the
east side of the frontal boundary will be going forward until
about 1-2 AM for the eastern half of the city and Nassau, and
until 3 AM for Central LI, and until 6-7 am for far eastern
portions of LI and New London, CT. Gusts up to 55-60 mph seem
like they can happen. The forecast model soundings do not have
the strongest of inversions, and have more of an isothermal look
to them, thus a 2-3 hour window for the strong to damaging wind
gusts is in place. Also, the a wet soil from tonight`s heavy
rain could result in some uprooted trees. Thus the High Wind
Warning continues, with the addition now of Southern New London,
CT. Northern New London, CT is now in a wind advisory until
late Mon morning. The front should begin to pivot through
eastern areas towards 8-10z. The winds will decrease a bit
momentarily into the start of the morning commute for a couple
of hours as the winds switch around to the NW quickly.
Across NW zones, particularly Orange County look for the precip
to end as a brief period of snow. With surface temps likely
still being above freezing any snow will have difficulty
sticking, with perhaps a coating or so on the grassy surfaces.
Reasonable worst case would be a slushy 1-2 inches for
elevations above 750-1000ft, and maybe a slushy inch on grassy
surface down to valley level. he column dries out quickly so
any steady snow would end quickly, with snow showers lingering
into the mid morning hours, especially in the higher elevations.
During Monday morning lingering showers will move away to the
northeast, thus toward mid to late morning day skies will be
clearing from SW to NE. The winds will pick up again, but not get to
the highest levels seen during the night. Gusts of 35 to 40 mph
appear to be a good bet for the mid to late morning as cold
advection is maximized as the upper trough axis pivots through. Late
in the day and into the evening the pressure gradient begins to
decrease somewhat. It will be a good 10 to 15 degrees cooler with
40s across the area into the afternoon.-- End Changed Discussion --
&&
.SHORT TERM /MONDAY NIGHT/...
As high pressure builds from the southwest look for the winds to
gradually decrease with gusts still around 20 to 25 mph at times
during the evening. After midnight under clear skies any gusts
should end with temperatures falling to seasonably cold levels.
Temperatures should get below freezing in most places with lows in
the middle and upper 20s in the more rural area, to mainly lower 30s
across the city and urban locations.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
No changes to the long term. Followed the NBM closely.
Quasi-zonal flow aloft in the wake of one departing trough on Tue
will give way to another northern stream trough on Wednesday, which
should drive a cold front through either late Tuesday night or
Wednesday morning. Confluent mid level flow after this trough
passage, followed by ridging aloft Fri, will then maintain strong
sfc high pressure over the area, with perhaps a weak intervening
cold frontal passage Friday night. Guidance has been trending
towards hanging on to high pressure over the area through the
weekend. As high pressure shifts east is where model spread starts
to really increase. There is potential for another low pressure
system to impact the area late Sunday, but large differences remain
in timing, strength and location.
Forecast follows the NBM for the most part given close enough NWP
model guidance agreement during this time frame, with only minor
adjustments. Fair wx should prevail through the period, with only
slight chance to chance PoP for next Sunday. Near normal temps Tue-
Wed, and a little below normal Wed night-Thu after the cold frontal
passage, should moderate to a few degrees above normal Fri-Sat via
ridging sfc and aloft.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
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** HIGH AVIATION IMPACTS EXPECTED THROUGH MOST OF THE TAF PERIOD **
A strong frontal system approaches and moves through tonight.
Mostly IFR through the night with rain, heavy at times, and iso
TSTM. Precipitation likely mix with or change over to wet snow
for morning push at KSWF. Little to no accumulations expected,
with a reasonable worst case of a slushy inch on grassy
surfaces). Conditions gradually rise through MVFR from w toe Mon
AM, to VFR Mon PM.
Strengthening southerly flow this evening, more so from approx
KJFK/KLGA eastward. Peak gusts 35 to 45 kt likely for JFK, KISP
and KGON until FROPA. LLWS for all but KSWF until the cold
front passage. 2kft winds 60kt+ at KISP and KGON, and 45-55kt
for the other terminals.
FROPA timing is 1-4Z for western and NYC terminals and 6-10Z for
eastern coastal terminals as the cold front slows down. Behind the
FROPA, winds shift to the NW-WNW with gusts 25-35kt lasting well
into the day Monday.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Isolated TSRA possible through around 05z. Peak wind gusts may
be more occasional until FROPA. Frequent NW winds gusts around
30 kt, MVFR/IFR conds and shra likely for Mon AM push. VFR with
winds and gusts gradually subsiding for Mon aft/eve push.
OUTLOOK FOR 00Z MONDAY THROUGH FRIDAY...
Monday Night: WNW winds 10 to 15 kt in eve gradually
diminishing to less than 10kt by daybreak.
Tuesday: VFR. SW gusts 15-20 kt in the afternoon.
Wednesday: VFR. W to NW gusts 15-20 kt in the afternoon.
Thursday and Friday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
Continuing with Gale and Storm warnings on the area waters as a
strong cold front pushes across the waters tonight. Storm warnings
are in effect for the central and eastern ocean zones as well as the
south shore bays, Peconic and Garners Bays and the eastern part of
Long Island Sound. These locations have the best chances to see wind
gusts reach 50 kt, especially from about midnight tonight through
early Monday morning. The Storm warnings are up until 11am, however
its possible they will be able to be dropped down to a Gale warning
earlier. Gales are then expected on all waters through much, if not
all of the day Monday, with small craft conditions likely into at
least the first of Monday night.
Sub small craft conditions may prevail for a good portion of Tuesday
across the waters in all likelihood, with small craft conditions
returning through the remainder of the period. Meanwhile W flow
gusting up to 25 kt on all waters Tue night, should shift NW by Wed
morning after a cold frontal passage. Gusts could peak at 30 kt on
the ocean Wed night. Lingering 25 kt gusts are possible, especially
on the eastern ocean and the open Sound waters into daytime
Thursday.
&&
.HYDROLOGY...
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A flood watch remains in effect through Monday morning for the
entire area. Across portions Central and Eastern Southern
Connecticut, 3 to 5 inches of rainfall is likely, with locally
6+ amounts possible. For Long Island 2 to 4 inches is likely,
with locally 4+ inch amounts possible. Most of this rain will
fall in a 12 hour period.
As a result, widespread minor urban and riverine flooding is
likely areawide, with an isolated to scattered flash flood
threat areawide. More widespread flash flood conditions are
likely for S CT where, with locally more severe flooding
possible, including moderate flooding of several quick
responding rivers and streams. There is an elevated threat to
life in this area.
WPC has much of the forecast area in a Slight Risk in
their excessive rainfall outlook for today and tonight, with a
rare Moderate Risk for Central and Eastern portions of Southern
CT. Based on the current rainfall forecast main stem rivers
across CT are forecast to reach minor and moderate flood stage.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
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A strong cold front will bring a gale to storm force southerly
flow into tonight. The system brings potential for localized
minor coastal flooding with the Monday morning high tide cycle
for the south shore bays of Queens and Nassau, coastal CT and
the twin Forks of LI. Winds quickly shift to the W-NW late
tonight/early Monday morning before the time of high tide
(although will be close along E LI Sound and Twin forks of LI),
which will limit magnitude of surge and additive wave impacts
during the times of high tide Mon AM.
Surge should build quickly overnight during low tide, but then
drop post frontal passage. Storm surge guidance appears to be
underdoing the magnitude of surge during low tide, and there is
typically erratic surge behavior (double peak) with strong S/SE
flow events followed by a strong windshift. Stevens surge
guidance has increased by 1/2 ft in many places over the last 12
hrs, (particularly with the 95th percentile), indicative of the
predictions challenge.
For that reason, forecast has been heavily leaned to Stevens
NYHOPS 95th percentile numbers, and adjusted upward for wave
runup on south facing coastlines. This should capture the
potential for minor flooding along the south shore bays of
Queens and Nassau, coastal CT and the twin Forks of LI.
High coastal water levels, freshwater runoff, and river level
rises will likely exacerbate residual flood conditions Monday
morning.-- End Changed Discussion --
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch through Monday afternoon for CTZ005>012.
Wind Advisory until 11 AM EST Monday for CTZ008-010-011.
High Wind Warning until 11 AM EST Monday for CTZ012.
NY...Flood Watch through Monday afternoon for NYZ067>075-078>081-
176>179.
High Wind Warning until 11 AM EST Monday for NYZ078>081.
Wind Advisory until 6 AM EST Monday for NYZ075-176>179.
NJ...Flood Watch through Monday afternoon for NJZ002-004-006-
103>108.
MARINE...Gale Warning until 6 PM EST Monday for ANZ331-335-338-355.
Storm Warning until 11 AM EST Monday for ANZ332-340-345-350-
353.
&&
$$
SYNOPSIS...JE/JT
NEAR TERM...JE
SHORT TERM...JE
LONG TERM...JT
AVIATION...NV
MARINE...JE/JT
HYDROLOGY...JE
TIDES/COASTAL FLOODING...