Discussion on 2023-04-18

000
FXUS61 KOKX 181135
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
735 AM EDT Tue Apr 18 2023

.SYNOPSIS...
High pressure continues to build into the area today and
Wednesday, and moves offshore Wednesday night. A warm
front approaches Wednesday night and moves through the region
Thursday as low pressure tracks through the Great Lakes. Another
low develops on the cold front Friday night and impacts the
region through the weekend, moving east Monday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Forecast on track this morning with just a few minor adjustments
to reflect current conditions. Otherwise, a 500mb closed low
over Canada and upper level troughing will result in cyclonic
flow aloft today. Meanwhile, surface high pressure well to the
west of the region will be slow to build into the area. The
cyclonic flow aloft should result in a partly to mostly cloudy
skies today. Some of the guidance is hinting at the possibility
of some isolated showers today, however with a fairly dry sub-
cloud layer, not sure much reaches the ground. Will continue to
run with a dry forecast today. The decent cyclonic flow over the
area will also result in a rather breezy day, with gusts 25-30
mph. The flow will be W-SW. High temperatures today will be in
the 50s, with a few spots possibly reaching 60 in the NYC/NJ
metro area.

The upper trough starts to lift out of the area tonight. This should
result in winds diminishing and becoming less gusty. Not sure if
winds decouple and go calm for inland areas, but forecast lows well
NW of city are in the mid 30s. Will need to monitory trends to
possibly introduce frost into the forecast for areas where the
growing season is underway. Closer to the coast, while the winds
will diminish, some gusts into at least the first half of the night
will remain possible. Lows tonight are generally in 30s and
lower 40s.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
High pressure builds over there region Wednesday and offshore
Wednesday night. Conditions remain dry with temperatures in the
upper 50s and lower 60s. The high moves further offshore on
Thursday, with a more amplified upper ridge building over the area.
Also, a warm front associated with an area of low pressure over the
Great Lakes moves into the area on Thursday. There is some
uncertainty with just how far north the warm moves during this
period, which may have an impact on temperatures on Thursday.
Stuck fairly close to the NBM in this period. Thinking that
the warm air advection with low level return flow around the
offshore high should allow temperatures to once again return
to well above normals as highs climb into the upper 60s and 70s
across the interior. Closer to the coast, the flow off the cooler
waters will keep temperatures in the upper 50s to middle 60s.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
A highly amplified ridge develops and moves slowly into the western
Atlantic through the upcoming weekend, and keeps the surface low
well to the west, with this surface cold front moving into the
region Sunday. The ECMWF is showing some light precipitation mainly
for the Lower Hudson Valley and northeast New Jersey late in the day
Saturday, however the GFS and Canadian are dry through this time
frame. Therefore, much, if not the entire forecast area, may be dry
through Saturday. However, kept the NBM POPs for this time frame
given uncertainty.

Yet another wave may develop on the front over the northeast late
Sunday night into Monday keeping chances of precipitation in the
region. Added isolated thunderstorms for late Sunday morning into
Sunday evening as both the ECMWF and the GFS show some surface based
CAPE, mainly for New York City and points north and west. Used the
NBM probabilities as the timing and percentages look reasonable with
the expectations of the warm front, initial cold front, and the
waves of low pressure.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --Dry and breezy conditions continue in the wake of a cold frontal
passage and high pressure building. Another weak trough passes
through late today.

VFR through the TAF period.

W to WSW winds 10-20 kt with gusts 20-25kt through daybreak.
Winds may be more SW for the first couple of hours of the TAF
period with gusts being more occasional, especially outside the
metro terminals. More persistent and stronger gusts of 25-30 kt
are expected this morning and afternoon for most terminals. A
few gusts may approach 35 kt (mainly for KJFK). Gusts end this
evening, with KJFK ending the latest (after 06Z Wednesday,
though there is a chance that gusts never really stop, becoming
more occasional after 06Z).

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

Gusts may be more occasional through 13z-14Z today.

 OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY...

Wed: VFR. Westerly flow, gusts 20-25 kt in afternoon.

Thursday: VFR with southerly flow.

Friday: VFR. Light S/SE flow.

Saturday: MVFR or lower possible with chance of showers.

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

&&

.MARINE...
Nearshore winds gusts have come up to SCA levels on the western
waters. These winds are expected to spread eastward through the
night. As a result, have started the SCA for all waters now
which will continue through the day Tuesday. The SCA on the
ocean waters will continue through 03z Weds as seas and possibly
gusts as well are still within advisory thresholds.

Small craft advisories are in effect for all waters as nearshore
wind gust to 25kt. The SCA for the non-ocean waters are up until
00z, and for the ocean waters, til 03z. Seas on the ocean may reach
5 ft today. Once winds and seas fall below SCA levels tonight,
expect sub-SCA conditions through at least Thursday night as high
pressure builds near the waters.

Southerly winds will increase Saturday night into Sunday as a cold
front approaches to the west. Wind gusts on the ocean waters may
approach SCA levels Saturday night, with 25 to 30 kt expected across
all waters by late Sunday morning into early Sunday afternoon.
Though just how much mixing, and thus how strong the gusts will be,
is still uncertain thanks to warmer air moving across the cooler
ocean waters. However, with a long duration, and increasing
southerly flow, ocean seas are expected to build to around 5 to
8 ft by the end of the day Sunday.

&&

.FIRE WEATHER...
RH values are expected to drop to around 30% during the daytime
today and again on Wednesday. Wind gusts will be stronger today
however given mainly dry conditions over the past week, will need to
monitor for enhanced potential of fire spread both days.

&&

.HYDROLOGY...
No hydrologic impacts are expected through the weekend.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ331-
     332-335-338-340-345.
     Small Craft Advisory until 11 PM EDT this evening for ANZ350-
     353-355.

&&

$$
SYNOPSIS...BC/JP
NEAR TERM...BC
SHORT TERM...BC
LONG TERM...JP
AVIATION...JP
MARINE...BC/JP
FIRE WEATHER...
HYDROLOGY...BC/JP