FXUS61 KOKX 140225

Area Forecast Discussion
National Weather Service New York NY
1025 PM EDT Tue Apr 13 2021

High pressure over the area tonight will move offshore on
Wednesday. Low pressure approaches from the west late Wednesday
into Wednesday night. A coastal low will impact the area
Thursday and Friday. Another low pressure system could impact
our area early next week.


The forecast is mainly on track. Minor adjustments were made
mainly to cloud cover, temperatures and dewpoints for the next
few hours.

A middle and upper level ridge over the area will support dry
and relatively calm conditions tonight. The main forecast
challenge tonight revolves around how much stratocu returns for
the overnight hours, particularly over southeast Connecticut
and eastern Long Island late at night. The latest thinking is
that stratocu should fill back in over these locations late
tonight as a light NNE flow off the Atlantic continues, leading
to a mostly cloudy sky. Farther west across western Long Island,
NYC metro, NE NJ, and western CT, mostly clear skies are

Low temperatures will be in the lower to middle 40s for most
locations with the NYC metro only falling into the upper 40s
to near 50 degrees. Lows expected to drop into the mid-upper 30s
in the Pine Barrens region.


The middle and upper level ridge weakens on Wednesday, with
surface high pressure shifting south and east of the region.
The overall trend for the day will be increasing middle and
high level clouds ahead of the approaching large upper level
low that is currently over the northern Plains along the
US/Canada border. A broad area of low pressure ahead of the
upper low, which should be spinning over the Great Lakes on
Wednesday, will also be nearing the region in the afternoon.
Model guidance has been hinting at some light rain developing
across eastern PA in the afternoon, which then pushes towards
northeast NJ and the Lower Hudson Valley by evening. There is
weak warm advection developing west of the NYC metro late in the
day, but overall support for precipitation is low. Have capped
PoPs at slight chance in the late afternoon. Low level flow will
be light and should allow temperatures to warm quickly after
sunrise, reaching the lower and middle 60s. Increasing onshore
flow late in the day should put a lid on the temperature rise
and lower readings near the coast into the 50s.

The large upper level low will continue approaching the region
Wednesday night. The probability for rain increases through the
night, with the highest chances occurring after midnight. Upper
level divergence increases along with stronger warm advection
leading to the development of a more widespread rainfall around
day break Thursday morning, especially across the western half
of the region. A more consolidated low pressure area should be
beginning to organize along the Middle Atlantic coast by day
break Thursday.


The most active period of the long term will be Thursday and Friday
with a system that will bring periods of heavy rainfall and gusty
winds to our area. A secondary low forms and strengthens off the
Delmarva coast with the help of a jet streak to our south. The low
tracks northeast just over southern portions of our area before it
becomes vertically stacked and weakens as it slowly heads offshore.
Widespread moderate, and periods of heavy rain can be expected
most of the day on Thursday. Models are showing PW values of an
inch which is nearing the 90% moving average of SPC`s sounding
climatology. Winds shift and become more northerly early Friday
morning allowing for CAA. With cold air aloft it is possible
some northern areas and high elevations experience wet snow
mixed in Friday morning. Critical thickness values show heights
that would favor snow through much of the column, however
surface temperatures and wetbulb look to remain above freezing.
With much uncertainty no snow amounts are forecast at this time.
Total rainfall amounts are expected to be between 1 and 2
inches, with locally higher amounts possible. Winds will peak
Thursday afternoon and evening with gusts up to 30 mph.

Lingering light rain is possible as the low heads northeast on
Friday. Northerly flow will keep high temperatures well below
seasonable, in the mid 40s to low 50s.

Brief ridging aloft should keep the area mostly dry for the weekend
before a shortwave brings a chance of some light rain on Monday.

Some model disagreement remains with a system for early next week.
There is potential for another coastal system to bring rain and
gusty winds to our area.


Weak high pressure remains in place through Wednesday afternoon.

VFR through Wednesday afternoon. Winds with a southerly
component under 10 kt tonight, with inland terminals becoming
light and variable. WNW to WSW winds pick up Wednesday morning
before backing S to SE with sea breezes and increasing to around
10 kt.

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

No unscheduled amendments are expected.

.Wednesday night...Rain becoming likely. MVFR evening, IFR
.Thursday and Thursday night...Rain with IFR conds.
.Friday...MVFR to IFR with a chance of rain.
.Saturday and Sunday...VFR.

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


A weak pressure gradient over the waters through Wednesday will
lead to sub-SCA conditions. Onshore flow will begin to increase
Wednesday night as low pressure approaches the waters, but
winds and seas should remain below SCA levels. SCA conditions
look likely for all waters Thursday afternoon through Friday
morning with the ocean waters holding on to those conditions a
bit longer. Expecting 25 - 30 knot winds with seas 5 to 7 feet.


No hydrologic concerns exist through Wednesday. A coastal low
will bring a long duration rainfall to our area with periods of
heavy rain possibly. Some nuisance flooding may result. Rainfall
totals between 1 to 2 inches, with locally higher amounts, are





NWS OKX Office Area Forecast Discussion