FXUS61 KOKX 112148 CCA

Area Forecast Discussion...CORRECTED
National Weather Service New York NY
548 PM EDT Sat Jul 11 2020

A cold front will move across late tonight into early Sunday and
will weaken. Another cold front approaches Monday and moves
across Monday night. Shortwave over New England exits to the
east Tuesday as a weak cold front pushes south. Surface high
pressure builds behind Wednesday then shifts over the Atlantic
Thursday. Trough and surface boundary approach southern New
York Friday then stalls over the weekend.


Convection has developed along a pre-frontal trough this
afternoon. The southerly low level flow veers to more
southwesterly flow several kilometers above the surface. Bulk
shear 0-6km around 25-30 kt with forecast surface CAPE around
2000-2500 J/kg. Max values of both expected between 18 and 00Z,
so likely around 21Z. Layer precipitable waters of around 2
inches with greatest low level Theta-E advection late this
afternoon. Greatest downdraft CAPE conveyed by models to arrive
late this afternoon into early this evening, highest areas
across western parts of the forecast region.

The main focus area is more towards the Lower Hudson Valley as
clouds have kept temperatures relatively cooler and therefore
more stable towards NYC and to the east.

Gusty winds, heavy rain, and small hail will be possible with
thunderstorms. There will be small chances of severe thunderstorms,
mainly due to damaging winds, as well as flash flooding for a few
particular thunderstorms.

High surf of 4 to 6 ft and dangerous rip currents are expected


Main feature going into early this evening will be the MCV
approaching from the west. This feature will lift to the northeast
through central and northern New England tonight. The MCV is tied to
a mid level vort max that will take a similar track. This will help
bring a cold front across at the surface late tonight. Winds will
switch from more southerly to more westerly flow behind the

Showers and thunderstorms are expected to diminish rather
quickly this evening with both the loss of diurnal instability
and upper level forcing. Mesoscale models agree with this
general evolution of convection.

A gradual decrease in clouds is forecast tonight. The more
westerly flow will provide a decrease in dewpoints late tonight
into early Sunday, making for less humid conditions.

For Sunday, the region will be in between shortwaves aloft. The
cold front at the surface will move farther east of the region.
Another cold front begins to approach the area late from the
west. Westerly flow will make for both a warmer day as there
will be more sun but also a relatively less humid day as
dewpoints lower. This will be a function of the adiabatic mixing
within the boundary layer as drier air mixes down to the surface.
The max temperatures are in the mid 80s to lower 90s with heat
indices in the upper 80s to lower 90s.

A high risk of rip currents continues for Atlantic Ocean
beaches on Sunday, with continued 5-6 ft swell at 8-9 sec


For Sunday night, the cold front will continue to approach from
the west. Clouds increase late with a return of a chance of
showers and thunderstorms late at night. There will be a trough
approaching from the west. Flow becomes more southerly Sunday
night into Monday. The cold front moves in Monday with higher
chances of showers and thunderstorms with the increase in
temperatures and therefore increase in instability during the
day. Highs are forecast in the low to upper 80s and dewpoints
are forecast in the upper 60s to lower 70s.

Heavy rain possible with some thunderstorms as precipitable
waters increase to around 1.75 inches with more southerly flow
in the atmospheric column. Training of cells possible also with
parallel flow from low to upper levels.

Convection coverage lowers Monday night as the cold front moves
east of the region and weak high pressure starts to build in
from the west. Forecast lows Monday night are mainly in the
lower 60s to upper 60s.

Upper level shortwave over New England pivots through New York
Tuesday as this happens a weak cold front pushes south. Model
guidance indicates isolated to scattered showers could be
possible along the boundary in the late morning/afternoon hours
mainly for the Lower Hudson Valley and southern Connecticut.
Afternoon highs should hold in the upper 80s with partly cloudy

By the evening the surface boundary dries out southern New York
dropping precipitable water values below 0.75 inches. This coupled
with subsidence caused by the exiting trough should lead to
rain/cloud free conditions through the late evening. Temperatures
could drop off into the low 70s/ upper 60s overnight due to the
clear skies.

Wednesday and Thursday are dominated by a ridge building into the
Northeast. The ridge flattens somewhat Friday into Saturday but
there are some more model differences here with varying
amplifications of 500mb height. At the surface, more of a
Bermuda high begins to set up. This will mark a return of warm
and humid conditions. Forecast max heat indices increase
slightly during the period from mid to upper 80s to more in the
low to mid 90s. Dry weather forecast on Wednesday and Wednesday
night but chances of showers and thunderstorms will return

For the Atlantic Ocean beaches, a moderate rip current risk will
be likely into early next week with possible high rip current risk
for Monday.


A weak cold front approaches from the west this afternoon.

MVFR/IFR ceilings and visibilities continue at KISP and KGON
due to a persistent low cloud bank. Otherwise, generally VFR
conditions expected this afternoon outside of any showers and
thunderstorms. These could allow for a brief return of MVFR or
lower conditions for all terminals. TSRA activity continues
north and west of NYC terminals, and is expected to increase in
coverage through the afternoon and early evening, 21-00Z, into
NYC terminals. Areas east of NYC terminals are uncertain with
respect to thunderstorm development given the persistent low
clouds, but not enough confidence to leave out of TAFs at this

Southerly flow through the afternoon and evening, with gusts to
15-20 kt during the afternoon. Any gusts should diminish this
evening, with winds shifting to the WSW overnight.

.Sunday and Monday...Continued chance mainly afternoon SHRA/TSRA,
with MVFR or lower conditions possible.
.Tuesday and Wednesday...VFR.
.Thursday...VFR with chance of afternoon SHRA/TSRA with MVFR or
lower conditions possible.


SCA on the ocean remains through Sunday night with seas of 5-6
ft. This will be mainly due to seas as wind gusts are marginal
with gusts near 25 kt going into this evening with otherwise
gusts near 20 kt. The 5 ft ocean seas could linger Monday into
Monday Night before subsiding below 5 ft Tuesday. Sub-SCA
conditions are forecast for all waters thereafter through
Thursday night. Non-ocean waters remain below SCA through the
entire forecast period.


Localized urban and poor drainage flooding threat persists into
early this evening and this is mainly in the Northeast NJ to
Lower Hudson Valley area. There is a low risk of flash flooding
as well considering some of these areas received significant
rainfall yesterday.

Otherwise, no significant widespread rain expected through next


Potential for beach flooding and beach erosion during the times
of high tide.


NYC NOAA Weather Radio Station KWO35 (162.55 MHz) is undergoing
its final stages of testing, and is operating at full power.


NY...High Rip Current Risk through Sunday evening for NYZ075-080-
     High Surf Advisory until 9 PM EDT this evening for NYZ075-080-
MARINE...Small Craft Advisory until 8 AM EDT Monday for ANZ350-353-355.




NWS OKX Office Area Forecast Discussion