987
FXUS61 KOKX 111041
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
541 AM 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 --
Active weather day across the Tri-State as a strong frontal system
impacts the area.
*Key Messages*
*A Flood Watch is now 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 will dig down to the Gulf Coast
this morning, become 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.
Rain will continue to overspread the area with the intensity
picking up through the morning. Some embedded bands of heavy
rain are possible 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 should 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 a few hours longer
before the rain ends. Dry conditions are expected to prevail
late this evening into the overnight.
Have gone ahead with 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.
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 /12Z WEDNESDAY THROUGH SUNDAY/...
A warm front draped across NYC and Long Island Sound up into
coastal SE CT will lift slowly north this morning. A strong
cold front will then approach this afternoon and evening.
IFR/LIFR cond should prevail this morning with intermittent light
to moderate rain. A narrow band of heavy rain (with some
isolated thunder) should move across during the afternoon and
early evening, with timing about 17Z-18Z KSWF, 19Z-20Z NYC
metros, 20Z-23Z KISP/KBDR, and 00Z-01Z KGON.
E-NE winds expected inland overnight until warm fropa, otherwise
SE-S winds expected overnight along the coast. Gusts develop
around daybreak, with LLWS for the NYC metro and lower Hudson
Valley terminals.
By 12Z-15Z LLWS should prevail at most terminals. Sfc gusts
meanwhile should increase to 30 kt by 15Z, and approach 35-45
kt for the city and eastern terminals toward 18Z. Sfc winds
start to peak closer to 21Z, with gusts as high as 50 kt.
Gradual improvement expected after fropa, from west to east
between 03Z-07Z.
...NY Metro (KEWR/KLGA/KJFK/KTEB)TAF Uncertainty...
AMD possible for changing conditions.
OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY...
Late tonight: Becoming VFR. W winds G30kt.
Thursday: VFR. W winds 15-20G30kt.
Friday and Saturday: VFR.
Sunday: MVFR or lower cond possible with light rain and low
clouds, especially late.
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 this morning, becoming 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...
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 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.
&&
.TIDES/COASTAL FLOODING...
Water levels should remain below minor benchmarks with this
mornings high tide. 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...
CT...Wind Advisory from noon today to 10 PM EST this evening for
CTZ005-006-009.
Flood Watch from 1 PM EST this afternoon through late tonight
for CTZ005>012.
High Wind Warning from noon today to 10 PM EST this evening
for CTZ007-008-010>012.
NY...Wind Advisory from noon today to 10 PM EST this evening for
NYZ071>075-176-178.
High Wind Warning from noon today to 10 PM EST this evening
for NYZ078>081-177-179.
NJ...Wind Advisory from noon today to 10 PM EST this evening for
NJZ006-104-106-108.
MARINE...Storm Warning from noon today to 10 PM EST this evening for
ANZ331-332-335-340-345-350-353-355.
Gale Warning until 6 AM EST Thursday for ANZ338.
&&
$$
SYNOPSIS...DR/DS
NEAR TERM...DS
SHORT TERM...DS
LONG TERM...DR/DS
AVIATION...BG
MARINE...DR/DS
HYDROLOGY...DR/DS
TIDES/COASTAL FLOODING...