000
FXUS61 KOKX 231742
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1242 PM EST Sat Dec 23 2023
.SYNOPSIS...
-- Changed Discussion --
High pressure centered east of New England will continue moving
east and out to sea this afternoon. A weakening warm front will
approach tonight and dissipate over the region on Sunday. High
pressure will reestablish itself on Christmas Day, then move
offshore on Tuesday. The next frontal system and associated low
pressure system will affect the region on Wednesday before
slowly shifting away from Thursday into Friday.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
Earlier band of graupel/rain dissipated over/near NYC between
10-11 AM. Overcast skies meanwhile have spread to all but the
forks of Long Island and SE CT, and even there bkn stratocu have
moved in from offshore, so the overall trend is for a cloudy
afternoon.
High temps adjusted somewhat based on latest bias-adjusted GFS
LAMP numbers, which range from the upper 30s inland NW of NYC,
to the mid 40s across parts of NYC, Long Island, and SE CT.-- End Changed Discussion --
&&
.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
Weak shortwave approaches from the northwest tonight and then
slowly cuts off and sinks SE through the region Sunday and to
the southeast Monday. At the surface, high pressure slides
farther offshore with a weak warm frontal/surface wave
approaching from the west tonight, and gradually dissipating
over the region on Sunday.
Models have been in general agreement with sufficient
moisture/theta-e advection ahead of the surface wave and lift
by approaching shortwave/jet streak to overspread light precip
over western portions of the region after midnight tonight and
then likely the entire region on Sunday as the closed low sinks
southeast.
Thermal profiles look marginally cold enough for a period of
light snow/sleet or mix with rain for areas well NW of NYC
(Orange/W Passaic/Putnam/N Fairfield) late tonight into Sunday
morning. Based on forecast sounding analysis, there appears to
be enough saturation in snow growth area for snow development
aloft, but as typical the magnitude of low-level warm nose and
precip intensity (diabatic cooling processes) will determine
mixing with or changeover to sleet or ra. Reality is likely
between NAM with aggressive warm nose, and weaker warm nose GFS.
NBM POWT for wintry precip are quite low for this area tonight
into Sunday, with less than 20% prob of snow for W Orange and
less than 10% for rest of NW interior, and 0% prob for sleet or
fzra. Rain probs are 70%+, basically indicating mainly rain,
perhaps mixed with some sleet/snow, and a localized fzra threat
where air/ground temps are at freezing. SPC HREF p-type
likewise indicating rain as primary p-type, with DESI HREF sounding
analysis indicating a noticeable warm nose. Overall, low prob
for a light coating of snow across Western Orange County (west
of the Hudson Highlands) late tonight into early Sunday morning.
If rain is the predominant p-type, surface/ground temps would
be primary determinant for fzra potential. Air and ground temps
are expected to rise above freezing during the day, and with
thickening cloud cover tonight, most areas should have air and
ground temps remain just above freezing. There is a low threat
that western portions of Orange county (west of the Hudson
Highlands) could be cold enough air/ground temps for spotty
icing.
So overall low confidence and coverage in wintry precip
(particularly fzra), so no winter headlines at this time, but if
traveling late tonight into Sunday morning across NW interior
(particularly W Orange County), monitor for a potential short fuse
SPS or winter wx advisory for fzra if precip is heavier than
forecast and/or surface temps do cool more than expected.
Temps should safely warm above freezing for NW interior by mid
morning for plain rain showers areawide. For the coastal plain,
thermal profiles will only be conducive for rain, spreading SE
into NYC/NJ metro late tonight into early Sunday morning and
possibly into ern Long Island and SE CT by early afternoon.
Lingering stratus likely, with isolated light rain showers and
patchy drizzle possible Sunday Night into early Monday morning
with weak onshore flow and shortwave sliding overhead. Continued
weak waa will keep thermal profiles warm enough for just plain
rain Sunday Night/Mon AM. Gradual drying likely Monday
afternoon, but stratus will likely be stubborn.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
There has been little change to the forecast thinking for the middle
to late next week time frame. The NBM was largely used for this
update.
*Key Points*
* Low pressure and its associated frontal system impact the region
Tuesday night through Wednesday night. The system slowly pulls
away from the area Thursday into Friday. Despite there being a
large amount of uncertainty on the evolution of the system, the
probability of a significant event is very low.
* Rain is likely at some point late Tuesday night through Wednesday
night, but timing, duration, and amounts remain uncertain.
* Temperatures start out above normal, but should trend closer to
normal by the end of the week.
Complex weather pattern is expected to evolve Tuesday through the
end of next week. Ridging will gradually shift over the western
Atlantic on Tuesday ahead of closed upper low over the central
states. The upper low slowly moves towards the Great lakes on
Wednesday. The models are struggling with a complex interaction of
several pieces of energy diving southward out of central Canada. The
closed low should overall slowly track eastward through the end of
next week. The model spread remains high with the details with the
intensity of the closed low.
At the surface, primary low pressure over the central states Tuesday
will track towards the Great Lakes on Wednesday. The associated
frontal system will approach the area Tuesday night and move across
the region Wednesday into Wednesday night. The guidance continues to
waiver on whether or not a secondary low will form along the front
over the Middle Atlantic/northeast. There are some subtle trends
over the last 24 hours for a more progressive front and weaker
secondary formation. The parent low may end up being dominant and
actually slowly deepen as it moves towards New England Thursday and
then southeast Canada on Friday.
Confidence is highest that any precipitation will be in the form of
rain due to the mild air mass ahead of the system. NBM probabilities
of 1 inch of rain in a 12 hour period have actually decreased
somewhat over the last 24 hours, generally below 10 percent. NBM
probabilities of 0.50 inches of rain in a 12 hour period generally
range from 20-30 percent. These probabilities hint that rainfall may
not be significant and this could be tied to the general consensus
of a progressive weaker surface system. These details could change
in the coming days as models begin to resolve some of the complex
upper level features. It bears watching due to the recent rainfall
events, higher streamflows and soil moisture.
NBM keeps a chance PoP through the end of the week. This is due to
differing evolutions within the ensembles with the upper low as it
moves over the northeast. It should remain mostly cloudy, but
precipitation chances hinge on any enhanced lift under the upper low
which is difficult to resolve at this time range.
&&
.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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High pres gradually drifts E over the Atlc thru Sun.
Mainly VFR thru the TAF period. A few pockets of light rain
possible late tngt, but most of the activity is expected to
remain N of the region. Mix with snow possible at SWF if the
pcpn occurs. Chance of occurrence is about 30 percent, so
continued the prob30. There could also be some marine stratus
and br from the ocean tngt. Again the probability is low and
this potential has been rolled into the prob30.
In the absence of any marine stratus on Sun, VFR can be
expected.
Winds light and vrb thru the TAF period.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Potential for the area to remain VFR thru the TAF period. If
marine stratus develops overnight, MVFR may linger thru 18Z Sun.
OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY...
Sun: Mainly VFR. Chance of MVFR if marine layer develops.
Christmas Day: VFR.
Tue: Becoming MVFR aft 00Z Wed. Chance of rain aft 06Z.
Wed-Thu: MVFR or lower with rain.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
Sub-SCA through Tuesday night with a weak pressure gradient in
place.
The next chance for SCA conditions occurs Wednesday into Wednesday
night with a frontal system. The highest chance for SCA winds exists
on the ocean.
&&
.HYDROLOGY...
River flood warnings are still in effect along the CT River
(handled by WFO BOX) and parts of the Passaic River basin
(handled by WFO PHI). Otherwise, no hydrologic impacts are
expected through Tuesday.
Rain is likely Tue night and Wed. Predictability remains low on
amounts and any hydrologic impacts.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...BG/DS/NV
NEAR TERM...BG/NV
SHORT TERM...NV
LONG TERM...DS
AVIATION...JMC
MARINE...BG/DS/NV
HYDROLOGY...DS/NV