000
FXUS61 KOKX 071656
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1156 AM EST Thu Dec 7 2023
.SYNOPSIS...
A weakening low pressure area along a front approaches the region
today into early this evening. High pressure then moves across the
area later tonight and then moves offshore Friday. High
pressure will be in control Friday and Saturday. A strong cold
front approaches on Sunday and passes through during 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 --
Much of the western half of the area reported light snow over
the past couple of hours, with nothing more than a quick dusting
observed. Based on latest radar imagery, this activity has
shifted slightly farther east and has weakened. The light
snow/flurries will continue through the early afternoon, but not
make it into the eastern half of the area is it encounters drier
air. The current forecast is on track and little adjustments
were made.
Aloft, in the mid levels, a shortwave approaches with its positive
vorticity advection into this afternoon.
At the surface, a weakening low pressure area has brought a few
light snow showers into mainly western parts of the region. The
precipitation forecast was created after evaluating the
reflectivity forecasts of mesoscale models such as the HRRR, HRW
NSSL, HRW ARW, HRW FV3 and the NAM Nest which all depict
discrete areas of light precipitation across parts of the region
late this morning into this afternoon.
A weakening pressure gradient will allow for a less breezy day
then the previous day but extra clouds will mitigate daytime
high temperatures. These are forecast to range from the upper
30s to lower 40s for most locations. A blend of NBM and NBM
50th percentile was used for the max temperature forecast.-- End Changed Discussion --
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
The large scale feature across the local region will be high
pressure building in more later at night, which will have its
cores remain well to the north and south of the region. This
will keep the pressure gradient more relaxed. Also, the local
area will be in the weaker part of this high pressure.
In the mid levels, that shortwave that was mentioned in the
near term section will still be nearby. For the easternmost
parts of the region, there will be some positive vorticity
advection this evening. The mesoscale models depict pop up
shower activity in the vicinity of the Twin Forks for the
evening hours into the start of the overnight. Coverage is
isolated to scattered at most. With well established westerly
flow and limited moisture, keeping the POPs only slight chance
for Eastern Long Island for snow showers and flurries or
sprinkles in nearby sections along the coast as well as into SE
Connecticut.
Dry conditions expected outside of the eastern parts of the region
this evening and by overnight for the entire forecast region.
These dry conditions continue through Friday.
Winds overall will be relatively light due to the weak pressure
gradient. Gusts diminish this evening with no gusts expected on
Friday.
Low temperatures for tonight will range from the mid 20s to mid
30s. A blend of NBM, MAV, MET guidance was used.
Temperatures will warm up Friday compared to the previous day with
more return SW flow developing which will allow for low level warm
air advection. Again used a blend of NBM, MAV and MET guidance with
forecast highs ranging from the low to upper 40s.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Ridging aloft occurs on Friday night and Saturday with surface high
pressure in control, keeping us dry. Associated subsidence will
compress the boundary layer further increasing temperatures
aloft and raising the pressure. This in turn will lead to a
lower lapse rate, so any mixing of these temperatures down to
the surface will not be a warm if it weren`t for the subsidence
inversion. Highs on Saturday will be slightly above normal in
the mid-50s for southern coastal areas. Northern interior areas
will be in the low-50s. SOuth winds will also help with warming
and keeping overnight lows from cooling too much.
Global 00Z guidance is mostly in agreement with the evolution of a
frontal system late Sunday into Monday with only minor timing
differences. A longwave trough will develop in Colorado and New
Mexico moving into the Great Plains allowing a Colorado Low to
develop in north Texas/Oklahoma Saturday morning. A shortwave
develops within the longwave trough in the Upper Midwest that
accelerates the low northeast into the Great Lakes and subsequently
into Canada Saturday night. The longwave then becomes much more
amplified as it moves into the Mississippi and Ohio River Valleys.
It develops another low in the Tennessee Valley on Sunday morning
along a strong cold front extending from the first low that has now
moved into Quebec. Unlike previous guidance, as the trough moves
towards us and passes Sunday into Monday, it is no longer expected
to become negatively tilted. The only 00Z guidance with this
solution is the UKMET. This means this system may not be as potent
as previously forecasted, but it still will be and may pass by a
little quicker once it has arrived. Sunday night into early Monday
morning the cold front is expected to pass with the low overhead,
which will then further develop as it moves into New England on
Monday.
A strong low-level jet is expected to develop ahead of the front,
leading to strong warm air advection at the surface. Highs will
reach the low-60s on Sunday, preceding the cold front. The low-level
jet will reach its peak over the eastern half of the CWA where winds
are expected to be the strongest around midnight at about 60-70 kts
(model guidance varies between 50 and 80 kts), with south winds
first beginning to increase across the area Sunday afternoon. Wind
gusts are currently projected to peak 40-45 mph for the southern
half of the CWA with northern interior areas reaching peak
gusts around 35-40 mph. After the frontal passage late Sunday
night into early MOnday morning, breezy WNW winds will take over
sustained at 15-20 mph on Monday before weakening Monday night
as the pressure gradient weakens from the departing low.
Rain is expected to start in the late afternoon to evening on
Sunday then clear after the frontal passage before or just after
daybreak on Monday. Mostly rain is expected, but light brief
snow or flurries are possible in Western Passaic or Orange
county before the rain ends as the air rapidly cools and dries.
PWATs will be around 1.3 to 1.6" which is right around or just
above the max moving average. Its reasonable to assume that
periods of moderate or heavy rain will be possible. With the
quick moving front, however, it may not last long enough for any
significant flooding concerns, with only minor nuisance
flooding being the more likely outcome. 1-2 inches are expected
in total. NBM probabilities show around 60-80% chance of greater
than 1" in 24 hours with that lowering to 40-60% chance of
greater than 2" of rainfall in 24 hours. The higher chances
would likely be concentrated in the western half of the CWA.
High pressure then builds in through the rest of Monday and remains
in control through Wednesday with an extended period of dry weather
and near normal temperatures.
&&
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
A weakening low pressure area along a front approaches the region
today into early this evening. High pressure then moves across the
area later tonight and then moves offshore Friday.
Mainly VFR conditions expected through the TAF period. Ceilings
lower ahead of an approaching weak low today. There is a chance
of MVFR conditions in the afternoon, mainly due to ceilings,
but north and west of NYC terminals, MVFR visibilities will be
possible as well due some light snow showers or light
snow/light rain mix. However, these showers will be brief. Some
snow flurries are possible near KGON for this evening also. Not
expecting any snowfall accumulation.
Winds will become more westerly with wind speeds of 5-10 kt this
morning then increase to 10-15 kt with gusts up to 20 kt this
afternoon. Gusts subside this evening with winds lowering back
to near 10 kt and further lowering overnight into Friday. The
wind direction becomes more variable on Friday.
...NY Metro(KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Timing of MVFR may vary a few hours from TAF. Gusts up to 20 kt
may be more occasional this afternoon.
OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY...
Friday-Saturday: VFR.
Sunday: MVFR or lower in developing rain from west to east
during the day. Slight chance of thunderstorms at night. S
winds increasing with gusts 30 to 40 kt, mainly late day into
night. Highest winds will be at the coastal terminals. LLWS
likely.
Monday: Chance of rain showers earl with MVFR possible.
Otherwise, becoming VFR. W-WSW wind gusts 30-40 kt early,
becoming more WNW with wind gusts 20-30 kt late.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
Mainly below SCA conditions are expected across the forecast
waters today through Friday with a relatively weak pressure
gradient in place. Gusts up to 20 kt are expected on most of the
waters with some occasional gusts up to 25 kt for the ocean this
afternoon. Conditions are forecast to remain below SCA thresholds
Friday night through Saturday night.
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. Ocean seas are likely build to 10-15 feet during this
time with waves over 5 ft across portions of eastern Long Island
Sound.
&&
.HYDROLOGY...
No hydrologic issues expected through Saturday night.
1 to 2 inches of rain are possible from late Sunday afternoon
through Monday morning. It appears that the heaviest rainfall is
most likely to occur during Sunday night. Minor 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.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...JM/BR
NEAR TERM...JM/BR/JT
SHORT TERM...JM
LONG TERM...BR
AVIATION...JM/JP
MARINE...JM/BR
HYDROLOGY...JM/BR