795
FXUS61 KOKX 091126
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
726 AM EDT Tue Jul 9 2024
.SYNOPSIS...
A frontal boundary will remain nearly stationary going into the
middle part of this week. The front starts to gain more northward
movement as a warm front going into Thursday as a low pressure
system with remnants of Beryl eventually move into the Eastern Great
Lakes. An associated cold front approaches for Friday. The
frontal boundary becomes nearly stationary within or near the
region going into Saturday before dissipating Sunday. Another
frontal system approaches Monday into Tuesday.
&&
.NEAR TERM /THROUGH TONIGHT/...
SPS in effect until 830 am for patchy dense fog for much of the
coast and some interior parts of Southeast CT. Otherwise,
forecast on track.
A surface frontal boundary remains located north and west of NYC
today through tonight. Models exhibit good agreement with area being
on northwest periphery of 500mb ridge with 500mb heights staying
between 588 and 591 dm. More negative vorticity advection seen in
the 500mb analysis through today.
POPs no higher than 30 percent, overall more subsidence aloft
suppressing the vertical motions. May perhaps have some isolated
to widely scattered showers and thunderstorms as indicated by
several CAMs and their reflectivity fields. This will be more
dependent on sea breeze collisions with the lingering frontal
boundary and therefore higher chances for showers and
thunderstorms, closer to 30 percent are north and west of NYC
where the front is.
Surface fog burns off late morning with diurnal heating. Southerly
flow continues. More SW flow across interior and lighter. Relatively
higher and more southerly flow Long Island and Southern CT.
Model consensus of 850mb temperatures, around 21 degrees C for
the peak by late day. More SW flow at 850mb during the day, more
southerly flow at 850mb tonight. Used MAVs in combination with
NBM for high temperature forecast but preferred the MAV and MET
combination for dewpoints. The NBM seemed too high with dewpoint
values. Highs are forecast to reach upper 80s to mid 90s for
much of the region. Heat advisory remains in effect for much of
the same region as previously forecast but did add in Southern
Nassau County with at least half of that particular zone
reaching near 100 degree heat index this afternoon. Some 100 to
104 degree heat indices are forecast for parts of NYC and the
interior with a few spots potentially seeing some isolated 105
degree heat index readings as well.
Tonight used the same combination of MAV and NBM which will keep
warmer min temperatures only within the 70s across the forecast
region. It will be quite humid. However, with lack of surface
instability decreased the POPs for showers and thunderstorms.
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
At 500mb, vort max with shortwave moves into Great Lakes. 500mb
heights over local region stay around the same values. Spoke of
vorticity maximum comes near the region but stays NW of the region
by early Wednesday evening. This spoke of vort maximum goes
into northern New England through Wednesday night as vort max
to the west makes its way farther northeast just getting
northeast of the Great Lakes.
The model consensus of 850 mb temperatures decreases relative to
the previous day, closer to 19 to 20 degrees C for the peak
value for Wednesday.
Surface winds more southerly for all locations within region, even
more SE for some places. Overall, along with some extra cirrus
well ahead of next low pressure system, these factors are
expected to lead to a relatively slightly less warm day for
Wednesday.
POPs return north and west of NYC late day Wednesday and for
Wednesday night, may occur farther east within a larger potion of
the forecast region. Felt NBM was too high with these POPs so
used another blend of model guidance and manually lowered.
A cold front will be approaching from the west associated with a
parent low with remnants of Beryl that will be moving through
Eastern Great Lakes.
The cold front looks to slow down as it approaches the region.
However, it will act as a focus of convergence and higher POPs as a
result. Shifted the higher POPs within likely range to encompass
more of the region Thursday into Friday. Also added in mention
of heavy rain. See hydrology section for more details.
Concerning the heat, more SE flow along the coast will keep
immediate coastline cooler such that Long Island and SE
Connecticut coastlines have max heat indices only in the lower
90s. Elsewhere, max heat indices forecast are in the mid 90s to
near 100. Thus the heat advisory was extended in time for Lower
Hudson Valley and the Southern CT zones to match up with NE NJ
and NYC, now all going until 8pm Wednesday with the heat
advisory. Less heat for Thursday, although NE NJ will be close
with all areas well below heat advisory criterion for Friday.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
A stationary front will remained stalled along the east coast Friday
night into Saturday, providing the continued chance for showers and
convection. At the same time, a large high pressure system will be
positioned directly to our east over the Atlantic Ocean.
A continued S/SW flow will allow for a very moist and humid
environment with PWATs Friday night and into Saturday in the 1.8"-
2.2" range. This sets the stage for any showers or thunderstorms to
produce heavy rainfall. Guidance varies on timing and exact location
of the rain, but will continue to see the chances of rounds of
showers and storms until the front/surface trough dissipates on
Sunday under a weak ridging pattern aloft.
Sunday should be free of chances for rain, due to a lack of boundary
to initiate any activity. Mostly sunny skies will also be a
welcomed sight given its the second day of the weekend and all
prior days were wet.
Monday and Tuesday will see weak shortwave ridges and troughs
passing aloft while at the surface another frontal boundary
approaches, bringing rain chances back into the forecast. The start
of next week will also be very warm and humid, with more heat
indices expected to be above 95.
&&
.AVIATION /11Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
A weak frontal boundary or surface trough will remain in close
proximity to the area through the TAF period.
Widespread IFR/LIFR conditions this morning for KJFK, KISP,
KHPN, KBDR, and KGON in fog/low stratus. VFR by 13 or 14Z and
remaining so for the rest of the day. Due to stronger winds at
the surface and aloft, IFR conditions may be less widespread
tonight, with the best chances still for eastern terminals. VFR
through early afternoon tomorrow.
Chance for isolated showers/thunderstorms north of NYC. PROB30
only added to KSWF, at this time. Amendment to add in KHPN is
possible.
S winds 5-7 kt or less early this morning. Winds then increase
out of the S late morning at 5-10 kt, increasing to 10-15 kt
this afternoon. Occasional gusts of 20 kt are possible, but not
expected to be frequent enough to add into the TAFs. Winds then
weaken 5-10 kt tonight. Tomorrow winds increase out of the
south 10-15 kt, with gusts above 20 kt by 16Z.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Terminals experiencing IFR/LIFR at 12Z will likely clear to VFR
by 13-14Z. Amendments when clearing is expected.
OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY...
Wednesday Afternoon through Saturday: MVFR or lower possible at
times with periods of showers/thunderstorms.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
Weak pressure gradient will keep conditions below SCA for all
waters through tonight. Ocean and possibly the South Shore Bays
will have SCA potential Wednesday through Thursday night.
Otherwise, sub-SCA conditions are forecast to continue although
for the ocean SCA level seas will probably continue Friday into
the start of the weekend.
SCA conditions are possible on ocean waters with waves 5-6 feet
through Friday night, dropping below SCA criteria by Saturday
afternoon. Winds will likely be below SCA criteria during this time.
Sub-SCA criteria is expected over the weekend.
&&
.HYDROLOGY...
With high PWAT airmass across the region, above the 2 inch
mark according to consensus of models towards mid to late week,
any thunderstorm will be capable of producing heavy rain this
week. This may cause minor flooding with localized flash
flooding a possibility as well but for now will be a very low
percentage chance.
Much of the rain is forecast in the Wednesday through Friday
timeframe. Range is mainly from near a quarter of an inch to
around 1 inch. The forecast rain used WPC, NBM, RFC, and the
previous forecast.
While rounds of rain may continue on Saturday and again Monday into
Tuesday, there are no significant hydrologic concerns during this
time frame.
&&
.TIDES/COASTAL FLOODING...
There is a moderate rip current risk today as southerly winds
increase to near 10-15 kt and seas may build an additional foot
compared to Monday. Seas continue to build into Wednesday with
slightly stronger onshore flow to allow for a high risk of rip
currents.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory from 8 PM this evening to 8 PM EDT Wednesday for
CTZ005>010.
NY...Heat Advisory until 8 PM EDT Wednesday for NYZ067>075-176-178.
Heat Advisory until 8 PM EDT this evening for NYZ078-177-179.
NJ...Heat Advisory until 8 PM EDT Wednesday for NJZ002-004-006-
103>108.
MARINE...Dense Fog Advisory until 10 AM EDT this morning for ANZ331-332-
338-340-345-350-353-355.
&&
$$
SYNOPSIS...JM/BR
NEAR TERM...JM
SHORT TERM...JM
LONG TERM...BR
AVIATION...BR
MARINE...JM/BR
HYDROLOGY...JM/BR
TIDES/COASTAL FLOODING...