090
FXUS61 KOKX 111914
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
214 PM EST Wed Dec 11 2024
.SYNOPSIS...
A strong frontal system impacts the region into tonight.
A secondary cold front moves through Thursday, followed by
strong high pressure building over the region into the weekend.
A weakening disturbance approaches late in the weekend, before
another frontal system potentially impacts the area early next
week.
&&
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Winds have been slow to get to previously forecasted levels.
However, over the past hour a few reports starting to come
regarding downed branches, and this is supported by
observations. Mesonet coastal obs along south shore of LI and
now even along coastal CT picking up. In the meantime a squall
line is doing its best to organize in far Western NJ. The
development of this line and how well it can hold together will
ultimately determine if high wind warning criteria can verify
across much of where warnings are in place, or if there will
just be a couple of localized reports out east.
All headlines and additional discussion are encapsulated below
from previous discussion.
Active weather day across the Tri-State as a strong frontal system
impacts the area.
*Key Messages*
*A Flood Watch is in effect for southern CT from 1 pm this
afternoon through 1 am Thursday.
*A High Wind Warning remains in effect for Long Island, and
southeastern CT. A Wind Advisory remains in effect for the NYC
metro, Southern Westchester, and southwestern CT 1 pm this
afternoon through 10 pm this evening.
*Peak southerly winds 25 to 35 mph with gusts of 60 mph for Long
Island and southeastern CT. Peak southerly winds 20 to 30 mph
with gusts 45 to 50 mph in the Wind Advisory area. These winds
likely occur in a 1 to 3 hour period this afternoon/early
evening. Trees and power lines could blow down with possible
power outages.
*Widespread moderate to locally heavy rain into early this
evening. A few thunderstorms possible, especially
afternoon/evening when a line of low topped convection
organizes and sweeps across from around the NYC metro on east.
*Rainfall totals range from 2 to 3 inches. Locally higher
amounts possible, especially across southern Connecticut and
Long Island where 4 to 5 inches possible. Mainly minor urban
and poor drainage flooding the main threat, but localized flash
flooding possible. Some quickly responding rivers and streams
could reach flood stage in southern Connecticut.
Anomalous, deep upper trough has dug down to the Gulf Coast
and becomes negatively tilted this afternoon while pivoting
towards the Middle Atlantic and northeast this evening. At the
surface, a warm front will lift to the north this morning. A
strong cold front will then approach into the afternoon with
deepening low pressure passing from the Middle Atlantic into New
England by this evening. The cold front should quickly race
offshore tonight with the low moving into southeastern Canada.
Some embedded bands of heavy rain occur as deep subtropical
moisture is fed northward ahead of the trough and approaching
frontal system. Moderate to locally heavy rain continues this
afternoon, but there may be a brief min in coverage out east.
There will also be a low topped convective line developing just
ahead of the cold front this afternoon. The high-res CAMs have
been consistent on this developing as far west as the interior
of NE NJ and Lower Hudson Valley. The line will then quickly
move east into the evening, but may become a bit more organized
as it passes east of the NYC metro into S CT and Long Island
due to the intense low level jet (75-85 kt). Once the convective
line moves east, trailing stratiform rain will continue, but
only for an hour or two before the rain completely ends. Dry
conditions are expected to prevail late this evening into the
overnight from west to east.
There is a Flood Watch for southern CT in collaboration with
WFO BOX. 00z HREF probability matched mean (PMM) QPF in CT
ranges from 2 to 4 inches with some local areas 4 to 5 inches.
Where these highest amounts occur is still uncertain. Ensemble
river forecasts also indicate low potential for a few quicker
responding rivers to rise to near flood stage. Headwater
guidance indicating that 3 inches/6hr or 4 inches/12hr would be
sufficient for sufficient for some quicker responding
river/streams to reach minor flooding across Southern CT. The
dynamic storm system, organized low topped convection,
anomalously high PWATs, and intense low level jet/forcing also
support the Flood Watch. While there is potential for locally 4
to 5 inches in some spots on Long Island, mainly minor urban and
poor drainage flooding would be the more likely result.
The 75-85 kt llj overspreading the coast in the afternoon and
early evening, combined with only a weak low-level inversion,
will present potential for damaging wind gusts across LI and SE
CT, with wind advisory winds gusts for the remainder of the
coastal plain, including NYC. BUFKIT analysis and HRRR wind gust
potential continue supporting the ongoing high wind warning for
LI, coastal New Haven, and Middlesex and New London counties
for 55 to 60 mph gusts Gusts 45 to 50 mph look probable for the
next tier of counties inland. Winds will shift to the W with
cold frontal passage in the evening, and continue gusty with
cold advection (25-35 mph) much of the night. SPC has also
placed Long Island and SE CT in a slight risk for severe
thunderstorms with the aforementioned convective line. However,
similar potential is is covered within the high wind warning.
Temperatures will reach unseasonably warm levels in the lower
60s, potentially middle 60s in NE NJ, this afternoon. This will
be about 3 to 4 degrees below record highs for today`s date.
Temperatures drop significantly behind the front tonight with
lower to middle 30s likely by day break Thursday. Gusty winds
and drying low levels overnight should allow any standing water
to evaporate, limiting black ice potential where temps do drop
below freezing inland.-- End Changed Discussion --
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Strong cold advection follows the cold frontal passage on
Thursday, with a secondary front moving through late in the
day. The parent low pressure deepens as it tracks into Quebec,
and surface high pressure begins to build in from the west. This
tightened pressure gradient will keep a strengthened flow in
place. The cold air aloft should allow mixing toward 850 mb,
keeping conditions blustery through the day with westerly gusts
25 to 35 mph. With 850 mb temps progged around -11C to -13C,
afternoon temperatures should only achieve the mid 30s inland to
the lower 40s near the coast. The gusty conditions will make it
feel like it is in the 20s. Conditions will remain dry under
mostly sunny skies.
Winds will begin to drop off Thursday night as the pressure
gradient relaxes and high pressure moves towards the east
coast. Lows will generally be in the low to mid 20s with some
upper teens inland.
The high pressure will strengthen as it settles over the
northeast on Friday. Most of the models have the high pressure
peaking around 1046-1048 mb over New England Friday night/Early
Saturday morning. Dry and cold conditions will continue during
this time with highs on Friday only in the 30s and nighttime
temperatures in the upper teens inland and lower to middle 20s
elsewhere.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
No changes were made to the forecast Saturday through next
Tuesday.
The strong 1046-1048 mb surface high passes just north
of the local Tri- State into Saturday, and the flow veers
around and becomes onshore by Sunday as the center slips into
the Canadian Maritimes. This will help nudge temperature up from
the 30s and 40s Saturday to the 40s and low 50s Sunday.
Increasing low level moisture with the flow should lead to a
good amount of lower clouds on Sunday as a weak mid level wave
and warm front approach, though it remains unclear if the
associated precip dissipates before reaching the area. Another
frontal system may move through early next week, but guidance
disagrees with timing and intensity. Kept PoPs capped at chance
(50%) for now until the picture becomes clearer, but at this
time the first few days of next week appear unsettled. Left
precip at rain and/or snow at this stage, but more likely would
be either all rain or perhaps a wintry mix well inland based on
soundings and warmer air moving in aloft.
&&
.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
HIGH IMPACT EVENT FROM LATE MORNING INTO EARLY EVENING WITH
STRONG SFC WINDS AND LLWS...
A warm front has lifted north of the area. A strong cold front
will approach and move through this afternoon and evening.
Mainly IFR/LIFR cond attm, with bands of moderate to heavy
showers except through the afternoon. S winds continue to increase
this afternoon and early evening, with gusts up to 45 kt for
KEWR/KTEB/KHPN, 40 kt for KJFK/KBDR, and 45 kt for KISP/KGON.
Southerly LLWS also expected to continue at FL020 50-70 kt into
early evening.
Gradual improvement expected tonight after fropa, with winds
shifting W but still gusting 25-30 kt. Winds remains gusty
tomorrow under VFR conditions.
...NY Metro (KEWR/KLGA/KJFK/KTEB)TAF Uncertainty...
AMD likely for changing conditions.
OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY...
Thursday: VFR. W winds 15-20G30kt.
Friday and Saturday: VFR.
Sunday: MVFR or lower cond possible with light rain and low
clouds, especially late.
Monday: MVFR possible in showers.
Detailed information, including hourly TAF wind component
forecasts, can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
No changes made to the marine headlines.
Low pressure and its associated cold front will impact the
waters into this evening. Southerly winds and ocean seas will
quickly increase and become Gales by midday. A strong low level
jet moves across this afternoon and early evening brining a
period of storm force winds on all waters except the NY Harbor.
Rough seas are expected with this system, up to 4-7 ft on the
Sound and 12-18 ft on the ocean late afternoon into tonight.
Westerly gales are expected tonight in the wake of the system,
mainly on the ocean and eastern Sound.
Gales are likely to continue through Thursday afternoon, mainly
on the ocean. Winds lower below 25 kt on all waters Thursday
night and ocean seas gradually lower from over 10 ft Thursday
morning, to under 5 ft by late Friday morning. Sub SCA
conditions then persist on all waters Friday into the weekend.
&&
.HYDROLOGY...
-- Changed Discussion --
A widespread 2 to 3 inches of rainfall likely into this evening.
Locally 4 to 5" amounts are possible across southern Connecticut
and potentially up to 4 inches locally across portions of Long
Island. Rainfall rates should mainly be one quarter to one half
inch per hour, but heavier pockets of rain could reach around 1
inch per hour. 1 inch+ per hour rates appear more likely to
occur in a narrow line of showers and embedded thunder this
afternoon and early evening, especially across southern
Connecticut and Long Island. The line will be quick moving which
will limit the duration of the heavier rainfall and flood
potential. However, headwater guidance indicating that around 3
inches/6hr or 4 inches/12hr would be sufficient for some quicker
responding river/streams to reach minor flood stage. A Flood
Watch is in effect this afternoon and evening across southern
CT. Otherwise, the primary threat from this rainfall will be
minor urban and poor drainage flooding. A localized occurrence
of flash flooding cannot be ruled out.
No other hydrologic impacts are expected Thursday through early
next week.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
While peak surge is expected to occur this afternoon and early
evening, water levels for most locations should once again
remain below minor flooding benchmarks. But with a gradual
windshift from southerly storm force to SW SCA just before or
during the time of evening high tide, potential for areas along
the southern bays of LI, south facing shoreline of twin forks,
and coastal CT to see minor coastal impacts from combo of
elevated water and splashover from wave action. This includes
the eastern Great South Bay as water levels may remain elevated
and could touch minor benchmarks as a strong southerly flow
switches to the southwest, preventing water from escaping the
bay quickly.
The combination of 10-15 ft breakers during the evening high
tide will cause widespread beach flooding and erosion.
Scattered area of dune base erosion, and localized washovers
possible for LI beaches where dunes protection is compromised.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...Wind Advisory until 10 PM EST this evening for CTZ005-006-009.
Flood Watch until 1 AM EST Thursday for CTZ005>012.
High Wind Warning until 10 PM EST this evening for CTZ007-008-
010>012.
NY...Wind Advisory until 10 PM EST this evening for NYZ071>075-176-
178.
High Wind Warning until 10 PM EST this evening for NYZ078>081-
177-179.
NJ...Wind Advisory until 10 PM EST this evening for NJZ006-104-106-
108.
MARINE...Storm Warning until 10 PM EST this evening for ANZ331-332-335-
340-345-350-353-355.
Gale Warning until 6 AM EST Thursday for ANZ338.-- End Changed Discussion --
&&
$$
SYNOPSIS...DR/DS
NEAR TERM...JE/DS
SHORT TERM...DS
LONG TERM...DR/DS
AVIATION...BR
MARINE...DR/DS
HYDROLOGY...DR/DS
TIDES/COASTAL FLOODING...