733
FXUS61 KOKX 300830
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
430 AM EDT Tue Jul 30 2024
.SYNOPSIS...
A frontal system approaches the area from the west late today
and moves through the area into Wednesday. A series of weak
fronts then move through the area Thursday through Sunday.
&&
.NEAR TERM /THROUGH TONIGHT/...
The upper level low that has impacted the area over the last few
days departs to the north this morning. Ample low level moisture
will remain as weak flow keeps it in place. Patchy fog for
interior areas will gradually dissipate this morning as the
boundary layer mixes a bit after sunrise.
While the area will generally remain under a large-scale upper
trough, brief height rises aloft are expected today as we become
sandwiched between the departing low to the north and an
approaching shortwave to the west. This should allow for
generally dry conditions today with perhaps some clearing in the
skies. Highs today will be in the middle to upper 80s.
As the shortwave approaches, the surface frontal system will
begin to impact the area late this afternoon and into tonight.
Strengthening southerly flow will advect additional moisture to
allow PWAT values of 1.8-2" into tonight. The frontal system
will force more shower and thunderstorm activity late in the day
and overnight, however, it is uncertain as to the extent of
shower and thunderstorm activity that develops and if it will be
able to persist into the night as the atmosphere becomes more
stable.
&&
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
The frontal system remains in the vicinity of the area on
Wednesday with multiple rounds of unorganized shower and
thunderstorm activity likely. Coverage and timing of this
activity is fairly uncertain as the environment remains moist
and relatively unstable. Otherwise, overcast skies are expected
with highs in the low to middle 80s. The NYC metro may approach
90 depending on the extent of the shower and thunderstorm
activity.
The cold front is expected to push through the area sometime in
the afternoon or overnight Wednesday. While this should result
in diminished shower/storm activity into Wednesday night, there
won`t be much of a change in airmass as dew points are still expected
to be in the low 70s, though skies should clear a bit. Lows will
be in the low to middle 70s.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Key Points:
* Multiple rounds of showers and thunderstorms possible mid week
into the weekend.
* 95 to 100F heat indices possible Thu thru Sun, particularly for
northeastern New Jersey, the lower Hudson Valley, New York City,
and portions of northwestern Long Island and SW CT.
An active upper flow through the period, with area on northern
periphery of SW/SC US upper ridging and Bermuda upper ridging. More
distinct features are northern shortwave troughing approaching on
Wed and gradually sliding east on Thu. Brief shortwave upper ridging
on Friday, followed by the next northern shortwave/closed low
digging into the Great Lakes/Ohio valley Thu Night/Friday before
gradually shearing through the NE through the weekend.
Surface trough approaches Wed AM, with ongoing shower/embedded tsra
activity coincident with theta-e rich and marginally unstable
airmass advecting in on 35-40 kt llj. This activity likely slides
east through the morning as the initial trough moves east. This
trough will likely be replaced by a subsequent
approaching/developing trough with potential for additional
scattered shower/tstms activity in aft/eve, particularly across
areas from NYC and N&W.
Low/mid level environment gradually dries out Wed Night Into Thu in
wake of this trough. Upper troughing remains on Thursday, with
surface trough approach/development once again Thu aft. A drying
airmass on deep westerly flow should limit instability and moisture,
keeping shra/tsra activity limited. Heat should begin building on
Thu with deep mixing and downslope flow, with more in the way of
sunshine. Highs in the upper 80s to lower 90s, with heat indices in
the lower to mid 90s.
Shortwave ridging surface/aloft on Friday should allow for heat and
humidity to continue to build, before potential for late day/evening
shra/tsra activity with approaching convectively enhanced shortwave
energy ahead of deepening Great Lakes/Ohio Valley upper low.
Thursday and Friday could be the hottest air temps of the period
with westerly flow aloft and deep mixing, with widespread highs in
the upper 80s to lower 90s likely, and possibly running as high as
the lower to mid 90s away from south coasts. Heat indices in the
lower to mid 90s, with upper 90s for NYC/NJ metro and Lower Hud.
Weakening mean upper troughing Saturday into Sunday as Great
Lakes/Ohio Valley trough shears NE. Lead shortwave and trough axis,
along with surface troughs moving across the area will continue
potential for aft/eve shra/tsra activity. Air temps may not be as
high for the weekend with approaching troughing, but a deepening
southerly flow will likely allow for a moistening profile and TDs
increasing. So net result would likely be continued widespread heat
indices in the lower to mid 90s, with upper 90s for NYC/NJ metro and
Lower Hud, and surroundings.
Heat advisories may be needed Thu into Sun with the possibility of
multiple days reaching heat indices of at least 95 degrees across at
least northeastern New Jersey, the lower Hudson Valley, New York
City, and portions of northwestern Long Island and SW CT. There will
be little relief at night as temperatures are expected to be several
degrees above normal, in the lower and mid 70s.
&&
.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
An upper level low will linger over New England today. A weak
surface trough approaches tonight.
Southerly flow 10 kt or less expected early this morning, with
MVFR cigs possibly between 08-14z, especially for terminals
outside of NYC. Some of these terminals may even fall to
IFR/LIFR.
Cigs increase back to VFR around 14-16z, and the southerly flow
will increase with speeds 10-20G20-30kt. The strongest gusts
will be at KJFK/KLGA.
Confidence not high for thunder at the terminals this afternoon,
in fact all the CAMs have backed off on any precipitation so
will go with a dry forecast. Precipitation chances do increase
after 00z Wednesday, so will include PROB30s to cover this
threat. There does remain some uncertainty to whether or not
there will be any thunder after 00z. This will need to be
monitored.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
AMD possible for winds deviating from fcst. Start and end time
of gusts may be off by an hour or two.
Removed mention of tsra in the forecast for Tuesday afternoon
with confidence low of occurrence. Better chances for TSRA
remain west of the terminals.
OUTLOOK FOR 06Z WEDNESDAY THROUGH SATURDAY...
tonight and Wednesday: showers possible after 00z Wednesday,
along with MVFR/IFR cigs in low stratus into Wednesday morning.
Chance low cigs continue into Wednesday afternoon.
Wednesday night and Thursday: VFR.
Friday and Saturday: Chance of MVFR or lower in
afternoon/evening showers/tstms.
Detailed information, including hourly TAF wind component
forecasts, can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
A Small Craft Advisory remains in effect through 6AM Wednesday
morning. Winds and seas continue to increase today, with 20 to
25 kt gusts and 5 ft seas. Conditions may briefly lower to sub-
SCA early this morning, before building once again this
afternoon. Highest gusts are likely for the western ocean zone,
with 25 to 30 kt possible. This is due to stronger low level
through and tighter pressure gradient. Seas build back to 5 ft
tonight. SCA gusts expected for the south shore bays during
this time as well.
Marginal SCA ocean seas likely to continue into Wednesday in
persistent S flow with potential for occasional SCA gusts. Sub
SCA conditions likely return Thu into Fri with weak pressure
gradient.
An increasing and persistent south to southwest flow may allow for
ocean seas to build to SCA levels later Saturday into Sunday.
&&
.HYDROLOGY...
Multiple rounds of showers and thunderstorms are possible
late today into Wednesday and again this weekend. Low
predictability on specific hydrologic impacts this far out.
While widespread flood impacts are not expected, localized urban
and poor drainage flood impacts are possible.
&&
.TIDES/COASTAL FLOODING...
High risk of rip currents Tonight through Wednesday with 15 to 20 kt
southerly flow and 4-6ft@7 sec periods swells.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Risk for Rip Currents through Wednesday evening for NYZ075-080-
081-178-179.
NJ...None.
MARINE...Small Craft Advisory from 11 AM this morning to 2 AM EDT
Wednesday for ANZ345.
Small Craft Advisory until 6 AM EDT Wednesday for ANZ350-353-
355.
&&
$$
SYNOPSIS...NV/MW
NEAR TERM...MW
SHORT TERM...MW
LONG TERM...NV
AVIATION...BC
MARINE...NV/MW
HYDROLOGY...NV/MW
TIDES/COASTAL FLOODING...