000
FXUS61 KOKX 201050
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
650 AM 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/...
A band of rain was just south of Long Island at 1030Z, so
probabilities are reasonable. Otherwise, made only minor changes
to the temperatures and dew points for current conditions.
Weak low pressure was along the North Carolina coast at 08Z,
with an inverted trough extending up to the Delmarva. The
inverted trough moves into the area early this morning. With
weak forcing and precipitable water starting out at 1 to 1 1/2
inches any rain that falls will be light. Then from late morning
into this evening, until 02Z to 03Z, 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. The CAMs have shifted the axis of the
heaviest rain to the west, and rainfall totals have also
increased. 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.
&&
.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 /12Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
Low pressure along Cape Hatteras works slowly north along the
eastern seaboard. The low and its associated coastal front will move
across the area today, followed by a cold frontal passage Sat night.
Ceilings settle in to MVFR/IFR during the morning hours. There is
even a chance for pockets of LIFR. Rain moves in mainly after 12Z
and will continue through the day. There is 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 at this time to mention thunder in the TAFs for any of
the terminals.
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 will be 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 ceilings and 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 Saturday afternoon/early evening.
OUTLOOK FOR 06Z SUNDAY THROUGH WEDNESDAY...
Saturday night: Low chance for a thunderstorm in the early evening.
IFR/LIFR in drizzle, improving to MVFR and then quickly to VFR west
to east towards and after 05-07Z.
Sunday through Wednesday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.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...
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. Although flash flooding is not completely
out of the question, confidence is low in any occurrence of
this, mainly due to antecedent dry conditions, and while there
is increased confidence in the axis of heavier rain, there
remains some uncertainty. 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.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 11 AM this morning to 6 PM EDT
Sunday for ANZ350-353-355.
&&
$$
SYNOPSIS...JE/MET
NEAR TERM...MET
SHORT TERM...MET
LONG TERM...JE
AVIATION...JE
MARINE...JE/MET
HYDROLOGY...JE/MET