NYC Office Forecast Discussion

FXUS61 KOKX 220531

Area Forecast Discussion
National Weather Service New York NY
131 AM EDT Wed May 22 2019

High pressure builds in through Wednesday, then offshore
Wednesday night. A warm front will approach on Thursday and
move across the area Thursday night. High pressure returns to
the region on Friday. The first in a series of fronts will move
into region during Saturday night, with subsequent fronts moving
across the region during the remainder of the Holiday weekend.


Forecast on track with minor adjustments made to temperatures
and dew points to reflect latest observations.

Otherwise, clear skies will prevail into the night as high
pressure builds into the region. Gusty winds have begun to
subside. The pressure gradient however should remain
sufficiently tight to hinder any favorable radiational cooling
conditions overnight. As such, mixing will aid in low
temperatures closer to seasonable values, in the 40s across
outlying areas and in the 50s elsewhere.


Deep layer ridging builds overhead into Wednesday, with flow
lightening sufficiently enough to allow for sea breeze
development in the afternoon. Skies will initially be clear, but
some cirrus could overspread the area in the afternoon as
subtle short waves move along the periphery of the upper ridge.
Otherwise, expect seasonable highs.

The ridge axis then becomes shunted southward overnight with the
approach of a strong short wave. Between the attendant surface
low to the west and high pressure moving offshore, flow will
become more southerly, allowing a return to warm advection, and
leading to a subsequent increase in clouds. Although a few
showers will be possible, subsidence aloft will gradually
decrease the coverage of showers overnight, with the greatest
chance of rain persisting across the lower Hudson Valley into
portions of New Jersey. The return to southerly flow and
increase in cloud cover will maintain low temperatures close to
or a few degrees above climatological normals.


The overall pattern to begin the period will feature an
intermountain west US trough and a southeastern US ridge. Later in
the period the western trough will deamplify and progress east in
the Central CONUS and Midwest along with a de-amplification and
displacement south of the southeastern ridge.

To begin the period the region will undergo warm advection as a warm
front off to the west will begin to approach the region. Thicknesses
and 850 mb temperatures will rise throughout the day on Thursday. As
the high moves offshore a southerly flow is expected to get
established, especially across the eastern half of the area. This
should serve to stabilize locations across the eastern half of the
CWA throughout the day with a good CAP in place, at least initially.
However, further west and southwest more destabilization is expected
to occur. There is some timing differences with the shortwave that
moves just north of the region, with the timing consensus from the
numerical guidance focusing on Thursday evening and the first half
of Thursday night. If this shortwave feature and any subsequent
height falls can make its effects felt into the western half of the
CWA by late in the day and during the early evening then the chances
of convection, and possibly some severe convection will be enhanced.
SPC has the area under a marginal to slight risk of severe weather
on Thursday into Thursday evening, with the higher risk across
locations west of New York City. The convective threat does appear
to be highly conditional, meaning that if the ingredients come
together any convection could become severe. However, not seeing
consistency with the features amongst the models to feel confident
in seeing severe weather at this time. Instability overall is not
overly impressive, however there may be enough instability to work
on as winds to pick up aloft and some signs of airmass stacking are
evident across western parts of the region later on Thursday. Effect
Bulk Shear will increase and should work on any convection that does
develop. There will be slightly backed surface winds, so it looks
like a good set up for good 0-1 km directional shear. Therefore any
storms that do develop could have some rotation with them, with the
main threat with any storms likely being wind. The mid level
shortwave will move along quickly so any showers and convection
should move out of the region by 6-9z Friday with clearing skies
into Friday morning.

By 12z on Friday a deep northwest flow with CAA gets established as
clearing skies should set up quickly in the wake of the departing
shortwave. Deep layer ridging is progged to take place during Friday
resulting in a good deal of sunshine. A northwest wind be may be a
bit gusty at times, but otherwise it will be a pleasant and dry day.

Upper level ridging is expected to hold through most of Saturday,
with some height suppression then taking place late Saturday into
Saturday night. This will lead to the approach of a warm front late
Saturday into Saturday night. The forecast then looks to be a bit
more difficult beginning around then with lower confidence going into
the remainder of the holiday weekend. The region should get into the
warm sector on Sunday with the modeling differing on some of the
details. As the trailing cold front gets closer to the region late
Sunday and Sunday night the chance for showers and possibly
thunderstorms will increase. The big question then becomes have
quickly does the cold front progress south and east on Monday. With
the upper level pattern that is forecast there is a chance that the
boundary will stall and get hung up over the region. This would
result in unsettled weather for the holiday on Monday. The shortwave
will then eject east which would set up dry and cool advection in
its wake leading to pleasant conditions into Tuesday.

Temperatures are expected to average near normal to slightly above
normal through Saturday night. Temperatures will then get slightly
warmer Sunday into Monday, before settling to near normal levels
again by Tuesday.


High pressure builds into the region overnight and Wednesday.

VFR through the TAF period. Light nw winds mainly aob 10 kt
overnight. North winds increase slightly 10-15 kt after 12Z.
Winds eventually shift to the south, due to high pressure
passing southeast and seabreezes developing.

.Late tonight...VFR, with a slight chance of showers.
.Thursday-Thursday night...Mostly VFR. Chc MVFR with shra AM.
Chc MVFR/IFR with shra/tstm late day and night. Chc S gusts
.Friday-Friday night...VFR. NW gusts 20-25kt during the day.
.Saturday...Mostly VFR, except MVFR or lower in a possible
shower/thunderstorm late day and evening.
.Sunday...Mostly VFR. CHC shra/MVFR.


Although an occasional gust to 25 kt may be possible initially,
winds continue to subside overnight as high pressure builds
across the waters. Sub-SCA conditions then prevail into Thursday
as the pressure gradient becomes weak.

A cold front will move through during Thursday night and early
Friday resulting in a wind shift from the south to the
northwest. Winds and seas are expected to come up for a time
during Thursday night into Friday with marginal SCA conditions
out on the ocean, with the best chance of SCA conditions out on
the eastern ocean. A moderate NE flow could then keep seas up on
the eastern ocean waters at marginal SCA levels Fri night,
followed by a relaxing pressure gradient into Saturday with
lower seas and light winds. Winds and seas will then increase
somewhat again Sat night in a moderate S to SW flow potentially
resulting in marginal SCA conditions.


There is the chance for a period of showers and possibly a few
thunderstorms during late Thursday and Thursday night.
Significant hydrologic impacts are not expected at this time,
although there may be some minor urban flooding in association
with any heavier rain associated with any thunderstorms.


NYC NOAA Weather Radio Station KWO35 (162.55 MHz) remains off
the air.





NWS OKX Office Area Forecast Discussion