FXUS61 KOKX 150555

Area Forecast Discussion
National Weather Service New York NY
155 AM EDT Thu Apr 15 2021

Weak low pressure will move east off the Mid Atlantic coast
tonight, then intensify Thursday into Thursday night as an
upper level low approaches from the Great Lakes. Low pressure
will exit the area Friday through early Saturday. Weak high
pressure will then build in through early next week. A cold
front will approach toward the middle of next week.


Forecast has been updated to capture latest trends. Have slowed
down precip as showers continue to fall apart west of our area.
The rest of the forecast remains on track.

Showers to the west of NYC are falling apart as they encounter
dry low level air and should not amount to much through this
evening. As the upper level low approaches from the west tonight
and the sfc low moves off the Mid Atlantic coast, low level
convergence as an inverted trough starts to develop N of the sfc
low plus difluent flow aloft should result in increasing
changes for showers, with likely PoP across Long Island and most
of srn CT and chance elsewhere. Low temps tonight on the milder
side of MOS guidance, with lower 50s in NYC and NE NJ, and
mid/upper 40s to the north/east.


Mode guidance has trended wetter with the system impacting the
area during this time. An inverted trough extending N of the
intensifying sfc low, with low level WAA to its east, should
result in at least a moderate rainfall. Rain should become
heavy at times from late day Thu into Thu evening across S CT
and Long Island, during peak low level WAA/destabilization. Any
elevated CAPE should be shallow so do not expect thunder, but
with TT nearing 50 cannot totally rule it out either.

With most of the precip along and E of the inverted trough, NYC
and points west may not see much precip late Thu night, but CAA
on the back side of the intensifying low as it passes between
Montauk and the 40/70 benchmark should pull down enough cold air
to allow precip to mix with or change to wet snow across
interior S CT and the lower Hudson Valley, with a coating of
accumulation possible on grassy surfaces especially in the
higher elevations of northern Fairfield/New Haven.

Temps Thu and Thu night are a blend of MOS guidance and model 2m
temps, weighted more toward the NAM, with highs in the mid 50s
in NE NJ, and upper 40s/lower 50s elsewhere, then low temps
ranging from the lower 40s in NYC and immediate burbs, to the
mid 30s well inland.


Scattered light rain will stick around Friday as the low is
slow to exit our area. It is possible that southern areas dry
out for several hours and then see showers work their way back
into the area as the low retrogrades. Winds will continue to be
gusty and with a northwest flow expect highs well below
seasonable, in the 40s to lower 50s.

Very brief ridging builds in aloft to keep the first half of the
weekend dry. Slight chance PoP returns late Sunday as a piece
of shortwave energy breaks off of an upper low that is currently
over the northwest coast. This will suppress the ridging and
with little moisture may produce light showers. Winds will drop
off significantly Saturday evening with calm winds prevailing
through the start of the week.

The pattern remains unsettled through the middle of next week.
Another shortwave dips just south of our area bringing another
chance of light Showers Monday afternoon. Brief ridging aloft
then builds in to keep the first half of Tuesday dry. The next
feature to look at is a surface low over the Great Lakes that
will head northeast and drag a cold front over the area. There
is still much uncertainty with this feature and where it
develops a secondary low. Any precip with the passing front
looks to be late Tuesday through Wednesday.


A complex frontal system moves into the region overnight and
remains through Thursday. A coastal low moves off the Delmarva
toward morning and tracks east through Thursday, and north
Thursday night.

VFR becoming MVFR, with local IFR along the Connecticut coast.
Light rain is possible late overnight and around daybreak
Thursday. Becoming IFR Thursday morning with light rain.
Moderate to heavy rain Thursday afternoon into the evening.
Conditions begin to improve to MVFR at the NYC metro terminals
and northwest Thursday evening as steady rain ends.

Winds S to SW under 10 kt overnight, becoming S to SE Thursday
morning. With low pressure moving through the terminals
Thursday afternoon wind direction and timing of wind shifts
become uncertain. And as a coastal low becomes predominate winds
shift to N to NW Thursday evening, and increase to 10-15 kt.

 ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...

Amendments likely for changing flight categories and timing of
rain tonight. Low confidence forecast with uncertainty in
timing of rain and flight categories.

.Late Thursday night...NYC metro terminals and northwest, MVFR
becoming VFR toward daybreak. A chance of rain and snow at KSWF
late. NW winds gusting 15-20 kt after 08Z. East of the NYC
metro terminals IFR to possibly LIFR in moderate rain.
.Friday...NYC metro terminals and northwest VFR possibly MVFR
with a chance of rain. East of the NYC metro terminals MVFR with
a chance of rain.
.Saturday and Sunday...VFR.
.Monday...Mainly VFR. Slight chance of rain.

Detailed information, including hourly TAF wind component forecasts,
can be found at: http:/www.weather.gov/zny/n90


SCA conditions are likely for the eastern Sound/ocean waters Thu
afternoon via increasing E flow, then on all ocean waters Thu
night in NW-N on the back side of departing low pressure.
Expecting peak gusts 25-30 kt and max ocean seas 5-7 feet,
though there could be a few gusts as high as 35 kt on the ern
ocean waters late Thu night.

SCA conditions likely for all waters Friday through Friday
evening, with the ocean waters holding on to stronger wind gusts
a bit longer. Mainly below SCA conditions for the weekend
through early next week.


Basin avg QPF late tonight into Fri now over and inch north/east
of NYC, with ams over 2 inches for parts of srn CT. This could
cause nuisance flood impacts across southern CT and perhaps
parts of Long Island from late day Thu into Thu night.





NWS OKX Office Area Forecast Discussion