000
FXUS61 KOKX 081741
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1241 PM EST Fri Dec 8 2023
.SYNOPSIS...
High pressure will slowly move offshore today through Saturday.
A strong cold front approaches on Sunday and passes through
Sunday night. High pressure then builds in on Monday and remains
in control through the middle of next week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
Temperatures continue to be a bit warmer than previous forecast.
adjusted highs up a bit more. Otherwise, forecast continues to
be on track. Highs should top out in the upper 40s to around 50
today.
High pressure will slowly move offshore today. The core of the high
pressure stays well north and south of the area. The pressure
gradient will remain weak, keeping surface winds quite light,
near or less than 5 kts.
The forecast models have not handled well with the cloud cover and
have underestimated the amount of cloud coverage.
Increased clouds coverage above most model forecasts as a result and
used the lower end of guidance for high temperatures forecast. In
this case, the max temperature forecast was taken from a blend of
MAV and MET guidance, which was relatively lower than NBM. Still
expect a relatively warmer day than the previous, with highs in
the low to mid 40s.-- End Changed Discussion --
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
High pressure will continue to slowly move out into the Atlantic
tonight. The pressure gradient remains weak and with more ridging
and even some negative vorticity advection present in the mid
levels, radiational cooling will be more but not totally effective.
Some clouds are expected to linger around tonight but winds are
forecast to decrease and become nearly calm along the coast and for
inland locations will be calm. So, used a blend of MAV and MET MOS
for the forecast low temperatures, which indicated lower
temperatures relative to NBM. Late tonight into early Saturday
morning, put in patchy fog in locations that will have pretty
much calm winds, across the interior. The fog will be possible
as well along the coast but wind speeds will be a little higher
compared to the interior. The fog could possibly get locally
dense across parts of the interior but confidence is low on
this occurring.
For Saturday, the mid level ridging trend ends during the day with a
negative height trend afternoon into early evening. At the surface,
a small drop in the pressure reading is expected as high pressure
continues to move out into the Atlantic. This will result in some
increase to the pressure gradient, driving a more southerly flow
into the area. This will in turn increase the low level warm air
advection. Would also expect clouds to increase as well especially
in the mid to upper levels well ahead of the trough to the west. For
the high temperature forecast, used the NBM 50th percentile. Because
of the recent model underestimation of cloud coverage and winds
still being light (at or less than 10 kts), wanted to select a lower
temperature solution and the NBM 50th percentile was actually
slightly cooler than the deterministic NBM.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
A 500mb trough digs in to our west on Sunday, then lifts during the
day Monday with its axis shifting through the forecast area Monday
evening. At the surface, a strong cold front approaches us on Sunday
and passes through during Sunday night. While it`s passing through,
an area of low pressure develops along the front in Tennessee or the
Middle Appalachians and passes to our north as is further develops
and strengthens.
Rain chances ramp up through the day with the entire forecast area
likely seeing rain by the end of the afternoon. The rain could be
heavy at times mainly during Sunday night as a strong low level jet
develops over us and combines with deep synoptic lift aloft and an
anomalously moist air mass. Some models continue to show some
elevated instability, so with deep lift, will keep in an isolated
thunderstorm in the forecast. Rain chances continue into Monday even
behind the front as the flow aloft remains cyclonic and we`ll be
within the right entrance region of an upper jet streak. Should
precipitation actually occur Monday morning over the higher
elevations well NW of the city, some snowflakes may mix in with
showers. 1.5-2.5" of rainfall is expected Sunday afternoon through
Monday morning. The heaviest rainfall is most likely to occur during
Sunday night. Minor urban/small stream flooding will be possible,
mainly Sunday night - confidence in this is moderate. Cannot
completely rule out flash flooding either, but this is a lower
confidence forecast as chances are low given flash flood guidance
and the progressive nature of the storm system.
Regarding winds for this event, 925mb winds continue to be progged
to reach 60-80kt over roughly the eastern half of the forecast area
Sunday night. Even if a relatively stronger low level inversion were
to be in place during the time that the LLJ moves through, about
half of that speed could potentially reach the surface. The hourly
NBM probabilities for wind gusts greater than 54 mph are at about a
50-80% chance of occurring for the immediate coastlines on Long
Island and southeast Connecticut. These chances are less than 20%
for Manhattan, NE NJ, the lower Hudson Valley and SW CT. Parts of
Queens and Brooklyn are around 20-30% chance of this occurring. Peak
wind gusts may reach wind advisory criteria for some areas along the
coast east of Manhattan given the setup and potential help from heavy
downpours. The current forecast has gusts 40-45mph for coastal areas
and 30-40mph for most inland areas during Sunday night. I used the
NBM 10th percentile for winds in this forecast. The NBM
deterministic seemed too high, but given the last few runs of most
available guidance, they all show gusts at or above this current
forecast (with the exception of the GDPS and RDPS). When this event
falls into the timeframe of some CAMs this will really help in
determining how much of the LLJ will mix down to the surface.
High pressure then builds in through the rest of Monday and remains
in control through Thursday with an extended period of dry weather
and highs generally in the 40s.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
High pressure will slowly move offshore through Saturday.
Mainly VFR conditions are forecast. The only exception is the
potential for MVFR to IFR fog late tonight into early Saturday
morning, mainly for KSWF and KHPN.
Light flow is forecast through the TAF period with wind speeds below
10 kt. The wind direction will continue becoming S-SE this afternoon
and then mainly variable tonight. Wind gradually become SE again
late Saturday morning into the afternoon.
...NY Metro(KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Wind direction may be variable at times this afternoon.
MVFR visibilities possible early Saturday morning.
OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY...
Saturday Afternoon-Night: VFR.
Sunday: MVFR or lower in developing showers from west to east
through the day. S winds 15-20 kt with gusts 25-30 kt in the
afternoon.
Sunday Night: IFR in showers. Isolated thunderstorms possible. S
winds 15-25 kt with gusts 30-40 kt. A few gusts to 45-50 kt
possible. The strongest winds are most likely near the coast. LLWS.
Monday: MVFR or lower early in showers, then VFR. S-SW wind gusts 30-
40 kt eastern Long Island and Southeast Connecticut early.
Otherwise, W-WNW 15-20 kt with gusts 25-30 kt.
Tuesday: VFR. SW gusts 15-20 kt in the afternoon.
Wednesday: VFR. W gusts 15-20 kt in the afternoon.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
Below SCA today through Saturday.
Winds and seas should ramp up quickly during Sunday with small craft
conditions quickly going to gales in all likelihood by late in the
day/early evening. Solid gales are expected across all waters Sunday
night, with gales likely lingering into Monday morning for most of
the waters. Gales may continue well in the afternoon on the ocean.
Storm Watch conditions are possible on the eastern ocean waters
based on the new forecast, but confidence in this remains low at
this time. Ocean seas are likely build to 10-15 feet during this
time with waves over 5 ft possible across portions of eastern Long
Island Sound. SCA conds on the ocean for Tuesday as seas remain
elevated.
&&
.HYDROLOGY...
There are no hydrologic concerns through Saturday night.
1.50 to 2.50 inches of rain are expected from Sunday afternoon
through Monday morning. The heaviest rainfall is most likely to
occur during Sunday night. Minor urban/small stream flooding
will be possible, mainly Sunday night - confidence in this is
moderate. Cannot completely rule out flash flooding either, but
this is a lower confidence forecast as chances are low given
flash flood guidance and the progressive nature of the storm
system.
&&
.TIDES/COASTAL FLOODING...
-- Changed Discussion --
A strong cold front will bring increasing southerly flow late
Sunday into Sunday night. The system brings potential for minor
coastal flooding with the Monday morning high tide cycle.
However, the strongest southerly flow is most likely to occur
between high tide cycles. Winds will quickly shift to the west
early Monday morning, which will help keep water levels down
during times of high tide.
There remains a large amount of spread in the surge guidance.
The highest chance for minor coastal flooding at this time
appears to be for the south shore back bays and over the western
Long Island Sound along the Westchester and Fairfield coasts.
If the higher end of the surge guidance and stronger onshore
winds linger closer to high tide, then minor coastal flooding
would be more widespread, and a localized moderate coastal
flooding threat would exist.-- End Changed Discussion --
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...JM/BR
NEAR TERM...JM/JP/BR
SHORT TERM...JM
LONG TERM...BR
AVIATION...DS
MARINE...JM/BR
HYDROLOGY...JM/BR
TIDES/COASTAL FLOODING...DS