000
FXUS61 KOKX 162036
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
336 PM EST Fri Feb 16 2024
.SYNOPSIS...
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Low pressure moves across the Middle Atlantic tonight and then
passes south and east of Long Island Saturday morning. High
pressure builds into the area late Saturday into Saturday
night. Another area of low pressure passes well to the north
Sunday and Sunday night, sending a cold front through early
Monday. High pressure builds into the region thereafter,
tracking off the New England coast on Wednesday. Low pressure
then approaches from the west, potentially impacting the region
late week.-- End Changed Discussion --
&&
.NEAR TERM /THROUGH SATURDAY/...
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Winter Weather Advisory has been expanded to include all of NE
NJ, NYC metro, Southern Westchester and Long Island from
midnight to 10 am.
High pressure briefly moves over the area this evening. Low
pressure will then move across the Middle Atlantic tonight and
and then track ENE off the coast south and east of Long Island
Saturday morning. The latest 12z models have all trended further
north compared to recent runs. It appears that the 18z HRRR and
18z 12kmNAM and 3kmNAM have continued this trend. The main
change has been a notable trend to increase QPF and lift,
especially across the southern tier of the region. A dprog/dt on
the entire precip axis of the GFS has shown a notable shift
northward with each cycle. This northward trend is noted on most
other guidance as well.
The main features with this system will be lift from an intense
jet streak that passes across the Middle Atlantic. While it is
oriented west to east, there should be some lift within the left
exit region to support the precip shield blossoming well north
of the low. An area of strong 700 mb frontogenesis is also noted
on the modeling with the max located just south of NYC metro
and Long Island late tonight into early Saturday morning. In
fact the latest NAM has the corridor of the strongest 700 mb
frontogenesis awfully close to the NYC metro and Long Island.
Models may be restricting the amount of precip on the north
side, which has occasionally happened within a zone of a tight
thermal gradient. While the two systems are vastly different,
snow was much heavier on the northern fringe of the last event
on Tuesday due to strong 700 frontogenesis coupling with upper
level jet support. Think there is some room here for some higher
qpf and resulting moderate snow to be nudged a bit further
north than the latest consensus of the current guidance.
Liquid equivalent amounts have been raised with amounts now
ranging from around a tenth far north interior to one quarter
to around three tenths on average for NYC metro and western
Long Island. Some of of the modeling has hinted at a bit higher
amounts reaching the southern part of the area which would not
be surprising given the close proximity of the area of 700 mb
frontogenesis coupling with the upper jet dynamics. These key
features are weaker further north, so have only raised liquid
amounts slightly from previous forecast.
The air mass in place is dry with dew points in the teens. There
is no strong high or surface ridging in place so it should not
take too long for snow to reach the ground where lift and snow
growth are efficient tonight. Snow should be entering the area
from the west around midnight and quickly spread east into the
early morning hours. The aforementioned strong lift just south
of Long Island supports a corridor of moderate snow with rates
around one half to three quarters of an inch from around 3am to
6am. Some localized areas near the coast could briefly see one
inch per hour rates. The snow should begin to lessen in
intensity shortly after daybreak, but some light snow or
flurries may linger into the middle of the morning, especially
east of the city. The Advisory runs until 15z, but may need to
be extended if accumulating snow lingers longer than expected
out east.
The snow will not be as wet as the last event with the
expectation of a more fluffier snow character. However, have
gone a bit more conservative with snow ratios as varying levels
of snow growth are likely going to be present due to the nature
of the snow bands and lift across the area. Thinking initially
snow ratios will be around 10:1 near the coast and 11:1 inland
as the snow is light with weaker lift and snow growth. The
ratios should increase a bit, but have tempered them down from
NBM output and are generally around 11-12:1 at the coast and
13:1-14:1 inland. It should be noted if snow growth remains poor
away from the snow banding, then ratios could end up averaging
closer to 10:1. If the 700 mb frontogenesis banding is a bit
further north then modeled, higher ratio snow is possible which
would in turn raise snowfall totals.
Total snowfall ranges from around 2 to 4 inches in the Advisory
area, highest across southern portions of the NYC metro and
urban NE NJ corridor and western Long Island. Amounts on Long
Island are a bit lower, but close enough to three inches that an
Advisory was expanded there. The forks of Long Island may be
less, but much of the eastern zones were closer to Advisory
levels. Amounts drop off to 1-2 inches well NW of the city and
southern CT and around an inch interior CT. A reasonable worst
case scenario of 5 to 6 inches exists in NYC metro, NE NJ,
western Long Island, and 3 to 4 inches most elsewhere except
eastern CT where it is 2 to 3 inches.
The system pulls away from the area later Saturday morning into
the afternoon. A trailing shortwave pivots across the northeast
in the afternoon. A few snow flurries or snow showers are
possible in the afternoon.
Temperatures start out in the upper 20s to around 30 in the
early morning before warming into the middle and upper 30s in
the afternoon.-- End Changed Discussion --
&&
.SHORT TERM /SATURDAY NIGHT/...
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Heights will begin rising aloft Saturday night with high
pressure building towards the region from the southwest. Any
lingering clouds should quickly clear in the evening. Winds are
likely to increase in the evening as the pressure gradient
steepens ahead of the approaching high pressure. Gusts 20-25 mph
are possible at the coast. These winds should weaken by early
Sunday morning allowing lows to reach the teens inland and the
lower to middle 20s near the coast.-- End Changed Discussion --
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
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Upper trough lifts out Sunday into Monday, with zonal flow
setting up into midweek. As the trough exits, a weak wave of
low pressure passes well to the north, dragging a dry cold front
across the region early Monday. Flow veers NW behind it as
surface high pressure builds into the Northeast, and conditions
appear to remain dry for several days. The high tracks offshore
midweek and onshore flow sets up for the remainder of the
period. Global guidance continues to keep a developing coastal
low well to the south on Wednesday, as the region remains
protected by the nearby offshore high.
Meanwhile, temperatures nudge upwards through the week, with
forecast highs in the mid to upper 30s on Sunday, rising to the
mid 40s by Thursday. Next chance for widespread precipitation
appears to come late Thursday into Friday as low pressure
approaches from the west. Plenty of time until then to monitor,
capped PoPs at chance (50%) for now given the inherent
uncertainty, otherwise, largely stayed close to the national
blend.-- End Changed Discussion --
&&
.AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
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A wave of low pressure passes to the south and east late
tonight into Saturday morning.
VFR through this evening. Light snow brings MVFR conditions in
from the west around 06-07Z. Conditions lower to IFR a few
hours later, mainly for the NYC and Long Island terminals. There
is more uncertainty with cigs for terminals farther north. LIFR
vsbys are possible mainly between 08-11z and currently in a
TEMPO group. Steady snow ends around 12-13Z, with MVFR cigs
lingering through the morning. There is also a chance for snow
showers through the morning, that could bring vsbys down to
MVFR. VFR expected by the afternoon.
Total snowfall forecast amounts by late Saturday morning will
be around 3 to 4 inches for NYC and Long Island terminals, 2 to
3 for KHPN and 1 to 2 for KSWF, KBDR and KGON.
NW winds and gusts slowly weaken this afternoon, with gusts ending
around 00Z Saturday. Winds diminish to less than 10 kt tonight,
becoming light N/NE at the coast, possibly light and variable, and
light and variable elsewhere. Winds then become W/NW again late
tomorrow morning, with 20 to 25 kt in the afternoon.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Gusts will continue to lower through the afternoon and could end a
few hours before or after what is shown in the TAF.
Amendments likely tonight with changing categories from moving in.
OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY...
Saturday Afternoon. VFR, with potential for lingering MVFR early
afternoon. W/NW wind gusts 20-25 kt.
Sunday: VFR. WSW wind gusts 25-30 kt.
Monday-Wednesday. VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
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Gales have ended on the waters and have converted them over to
Small Craft Advisories. Non-ocean waters and ocean west of Fire
Island Inlet run through 23z and waters east of Fire Island
Inlet through 03z as elevated seas linger a bit longer.
Conditions should fall below SCA levels overnight into Saturday
morning. Winds start to increase Saturday afternoon, but SCA
conditions are likely to return Saturday evening and continue
into Saturday night.
Increasing SW flow ahead of a cold front likely brings SCA
conditions to all waters Sunday and Sunday night. Gusts up to 30
kt on most waters likely, with ocean seas building 5 to 8 ft. A
brief period of gales is possible on the ocean as well.
Conditions improve into early Monday, and sub SCA conditions are
then expected on all waters through midweek.-- End Changed Discussion --
&&
.HYDROLOGY...
No issues expected through the upcoming week.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None.
NY...Winter Weather Advisory from midnight tonight to 10 AM EST
Saturday for NYZ071>075-078>081-176>179.
NJ...Winter Weather Advisory from midnight tonight to 10 AM EST
Saturday for NJZ002-004-006-103>108.
MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ331-
332-335-338-340-345-355.
Small Craft Advisory until 10 PM EST this evening for ANZ350-
353.-- End Changed Discussion --
&&
$$
SYNOPSIS...DR/DS
NEAR TERM...DS
SHORT TERM...DS
LONG TERM...DR
AVIATION...JT
MARINE...DR/DS
HYDROLOGY...DR/DS