discussion on 2023-05-21

000
FXUS61 KOKX 201602
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1202 PM EDT Sat May 20 2023

.SYNOPSIS...
Low pressure approaches along the coast and passes through the
region today into this evening. Meanwhile, a cold front
approaches to the west and moves through tonight. High pressure
builds to the west Sunday. A pair of cold fronts swings through
from the northwest on Monday and late Wednesday into early
Thursday, otherwise high pressure will be in control through the
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --With the latest radar trends and the 12Z models coming in with
an axis of moderate to heavy rainfall through the NYC metro
area through midnight have issued a Flood Watch for these
region.

A band of moderate to heavy rain moving through southern
Connecticut at 1545Z with another band moving through northeast
New Jersey and NYC with rainfall totals so far are about one
and a half inches. Generally looking at a widespread 1 to 2
inches through midnight outside of the watch area with 2 to 3
inches, possibly near 4 inches at a few locations along the
heaviest rain axis.

Weak low pressure was along the North Carolina coast. From late
morning into this evening, until 02Z to 04Z, a low level jet of
40 to 50 kt along with forcing along a coastal front will
provide lift, and precipitable water values will be increasing
to 1 1/2 to near 2 inches, moderate rainfall becomes likely with
periods of heavy rainfall. Periods of moderate to heavy
rainfall will also be likely across the eastern areas later into
the afternoon and evening as the low and low level jet move
north and east. Rainfall rates are expected to be 1/2 to 3/4
inches per hour, however, there may be brief periods when rates
could be near 1 inch per hour. Have removed the mention of
thunder as lapse rates are not favorable, will there is some
elevated CAPE of 100 to 200 J/kg.

Meanwhile a northern stream low will be moving through the
eastern Great Lakes today with a cold front approaching the
western areas bu 00Z Sunday. The front and weak coastal low will
slowly shift east this evening into tonight. As the low level
jet moves east and precipitable water values begin to decrease
the moderate to heavy rain will come to an end from west to
east. By 12Z Sunday the precipitation should be east of the
area as the cold front passes to the east.-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
A large scale upper trough will remain over the northeast and
eastern Canada Sunday and Sunday night as surface high pressure
builds to the west, with the center of high pressure to the
north. Clearing is expected as weak subsidence increases.
High temperatures Sunday will be near seasonal levels, in the
lower 70s.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
A cold front should be getting offshore on Monday, with high
pressure in control for much of the upcoming week. A second cold
front is progged to come down from the northwest towards Wed night.
At this time it appears there will be no sensible wx with this
feature as well with shower activity likely staying north of the
area. High pressure will follow once again for the late week period.

Went with a consensus approach with regard to temps throughout. A
pair of dry cP air masses with fairly low dew points should lead to
a strong diurnal curve throughout. Night time temps are expected to
be around normal, with day time temps anticipated to be near to
slightly above normal. Inland locations will experience warmer
temperatures overall compared to coastal locations, in line with the
time of year. The question is whether temps may actually be cooler
than currently progged for Thursday and Thursday night behind a cold
front. Current thinking has the air mass modifying quite a bit as it
presses south, therefore stayed close to the NBM with the NBM
deterministic being on the lower end of the member spread.

&&

.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
Low pressure along the Mid Atlantic coast works slowly north along
the eastern seaboard today. The low and its associated coastal front
will move across the area, followed by a cold frontal passage
tonight.

Ceilings have settled in at IFR or lower. There are pockets of
LIFR at some terminals. Rain will continue through the day.
There remains some uncertainty where the axis of heaviest rain
will set up. An isolated thunderstorm is possible during the
afternoon/early evening hours. There is too low of a chance to
mention thunder in the TAFs for any of the terminals. Conditions
improve to VFR tonight towards 06z from west to east after a
period of LIFR conditions during the evening (especially at the
coastal terminals). Coastal terminal visibilities get down as
low as a half mile before conditions improve late.

Winds veer to the S/SE late this morning and afternoon as a coastal
front pushes north across the area. The strongest winds will be
around 10 to 12 kt at the coastal terminals. LLWS at KGON for late
this afternoon and evening.

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

There will likely be timing issues with subtle wind shifts today due
to some uncertainty with the position of a coastal front. An
extended period of LIFR ceilings is possible at all the city
terminals and may be reflected in subsequent TAF issuances.

Low chance of a thunderstorm this afternoon and early this evening.

OUTLOOK FOR 12Z SUNDAY THROUGH WEDNESDAY...

Sunday through Wednesday: VFR.

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

&&

.MARINE...
No changes to the winds and seas at this time.

Marginal SCA gusts will be developing on the ocean waters this
morning into this afternoon as weak low pressure along the coast
approaches and moves through the area. With a stronger pressure
gradient to the east gusts near 25 kt will be more likely east
of Moriches Inlet. However, with the southerly flow ocean seas
will be building to 5 to 6 feet. Once seas build to SCA levels
they will be slow to subside and do not fall below 5 feet until
Sunday evening. For now have extended the SCA through Sunday.
The non ocean waters will remain below advisory levels today
through Sunday night.

Sub small craft conditions are anticipated with ocean seas running
at 3 to 4 ft much of the time through mid week. High pressure to the
north is expected to result in a relatively weak pressure gradient
for the first half of next week with only a residual east to
northeast wind much of the time.

&&

.HYDROLOGY...
-- Changed Discussion --Storm total rainfall has increased, especially across
southwestern Connecticut into New York City, and Nassau county,
with rainfall of 2 1/4 to 2 3/4 inches possible, with locally
higher amounts likely, possibly nearing 4 inches at a few
locations. Outside of the axis of heavies rain totals will about
1 to 1 3/4 inches. A flash flooding has been issued. However,
any flooding that does occur will more likely be of the
minor/nuisance type.

No hydrologic impacts are anticipated in the extended timeframe
with another period of dry weather taking place.-- End Changed Discussion --

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...Flood Watch through this evening for CTZ009.
NY...Flood Watch through this evening for NYZ069>075-176>179.
NJ...Flood Watch through this evening for NJZ006-104-106-108.
MARINE...Small Craft Advisory from midnight tonight to 6 PM EDT Sunday
     for ANZ350-353-355.-- End Changed Discussion --

&&

$$