180
FXUS61 KOKX 271111
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
711 AM EDT Tue Aug 27 2024
.SYNOPSIS...
Weakening low pressure moves farther south away from the region
through tonight. Weak high pressure builds in from the north and
west today through tonight. The next frontal system approaches
Wednesday. The associated cold front moves across Wednesday
night. High pressure returns and builds in from the north
Thursday into Thursday night. High pressure remains in place
Friday. A low pressure system then impacts the area for the
weekend and into the beginning of next week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Forecast mainly on track. Just some adjustments regarding clouds
and fog.
Fog has developed into daybreak with light winds, temperatures
cooling to near the dewpoint and moisture laden grounds. Much of
the fog is expected to be patchy but with some larger areas of
fog particularly for those locations that received more rain
earlier in the day and along river valleys. Have forecast areas
of fog for parts of Orange County NY, interior NE NJ, Western
Suffolk County NY as well as New London County CT. Some of the
fog could become dense, reducing visibilities to less than 1
mile the first half of this morning, before 900 AM. A special
weather statement is out for parts of the region to address this.
The fog is expected to dissipate with diurnal heating by around
8 to 9am or shortly thereafter.
Otherwise for today, expecting height rises in the mid levels.
Negative vorticity advection in the mid levels. Ridging and
suppression will keep clouds minimal allowing for mostly sunny
sky and continued dry conditions. Weakening low pressure moves
farther south and east from the region into the open Atlantic.
Weak high pressure building in at the surface from the north and
west will allow for sea breeze circulations to develop.
Going with the NBM 75th percentile for highs today. The NBM
used the previous day ended up being 1-2 degrees less with its
high temperature forecast compared to observations. High
temperatures today are expected to reach well into the 80s with
upper 80s in and around the NYC Metro. Max heat indices in the
lower 90s for parts of NE NJ.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
Very mild temperatures expected for tonight, with forecast lows
ranging from the 60s to lower 70s for the majority of the area.
Conditions are expected to remain dry but clouds will be
increasing into early Wednesday.
Ridging in mid levels lessens with ridge flattening out. An
embedded weak shortwave passes well north of the region by late
tonight into early Wednesday. This will bring an increase in
clouds. Lows tonight used a combination of NBM and NBM 75th
percentile.
Nearly steady height tendency Wednesday in mid levels. At surface, a
cold front approaches from the north and west. There will be
increased SW flow ahead of the cold front, allowing for more warm
air advection. Models indicating 850mb temperatures a few degrees C
warmer than the previous day by late afternoon into early evening,
so likewise this will translate to much warmer surface temperatures
compared to the previous day. Using similar to previous day, NBM
75th percentile but adjusting down with NBM dewpoints (used more
weight towards consensus of MOS with dewpoints compared to NBM), the
resulting heat indices reach mid 90s to near 100 for western half of
the region.
Had high enough confidence based on latest NBM data and past
verification plus seeing how limited the convective output was for
Wednesday afternoon, to go forward with issuing the heat advisory
for much of NE NJ, NYC Metro, as well as Rockland, Westchester and
Northern Nassau counties in NY. This is based on reaching the one
day heat index criteria of 100 degrees. These zones have near or
more than half of the zone forecast to meet this threshold. There
are some localized spots where there are forecast heat index values
of 99 to 100 outside the advisory area, but did not have enough
confidence for heat advisory issuance for these zones.
Models do not depict any MCS like structure for thunderstorms and
exhibit variance in precipitation locations. Some CAMs show lots of
pop-up convection within the area Wednesday afternoon while other
CAMs hardly depict much of any convection within the region. Left
POPs as chance but did add enhanced wording for heavy rain, gusty
winds and small hail in the timeframe of 2pm until 8pm Wednesday.
With the increased CAPE (up to around 1000 J/kg) and shear (0-6
km AGL near 30-40 kt), some strong to severe thunderstorms are
possible. SPC has highlighted much of the area in a slight risk
for severe thunderstorms Wednesday afternoon into Wednesday
evening.
Now, after the cold front passage late Wednesday night, more of a
significant airmass change is expected. The northerly flow
increases and eventually becomes more easterly on Thursday,
ushering in a cooler and drier airmass.
Mainly dry weather conditions are forecast late Wednesday night
through Thursday night. However, there are slight chances for
showers for parts of the region with some model uncertainty on
the timing and placement of the front after it passes through
the region.
NBM used for temperatures. Forecast lows Wednesday night all in
the 60s. Forecast highs Thursday only in the 70s. Then for
Thursday night, forecast lows range from the mid 50s to mid 60s.
Dewpoints drop to the 50s to near 60 Wednesday night and remain
mainly in the mid to upper 50s for Thursday and Thursday night.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
High pressure remains positioned over much of the Northeast on
Friday with the center of the high over SE Canada and the Canadian
Maritimes. This will allow for relatively dry and calm conditions
for Friday, though a primarily east flow will keep temperatures a
bit cooler than normal with highs only in the middle 70s.
Global models then come to a consensus that a frontal system will
begin to impact the area sometime on Saturday with the surface high
departing to the east. Upper level flow becomes fairly zonal during
the weekend with an eventual trough digging into the area from the
west into Sunday. At the surface, a weakening cold front moves into
the area on Saturday from the west. This may result in some shower
or thunderstorm activity as it moves through. Models differ on
timing of the progression of the front so Saturday may end up being
mostly dry until the evening or overnight.
Models then differ in how the digging trough aloft impacts the
surface frontal system. Some models push the initial cold front
offshore bringing a secondary dry cold front through on Sunday and
into Monday. The GFS and CMC however stall the initial cold front
along the coast and have a low pressure system develop over the Mid
Atlantic, pushing through Sunday and into Monday which brings
several rounds of additional showers and storms. For now, kept a
slight chance of rain SUnday through Monday to reflect this
uncertainty.
Otherwise, temperatures will generally be at or slightly below
average through the long term. High temperatures on Friday and
Saturday are expected to be in the middle to upper 70s. Highs Sunday
and Monday increase slightly to the low 80s. Another cool down is
possible behind the frontal system going into the beginning to
middle of next week.
&&
.AVIATION /11Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
Weak high pressure moves overhead today.
Mainly VFR through the TAF period. Localized MVFR/IFR cigs or
visibility is possible through 14Z, mainly at KSWF, KISP, and
KGON.
Light and variable wind this morning becomes mainly S at less
than 10 kt. Winds gradually increase this evening and tonight
becoming more SW at around 10-12kt into the Wednesday morning
push.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
No unscheduled amendments expected.
OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY...
Wednesday: Mainly VFR. Chance of MVFR or lower in PM showers or
thunderstorms.
Thursday-Friday: Mainly VFR. Slight chance of afternoon/evening
showers/thunderstorms north and west of the NYC terminals.
Saturday: Chance of showers, possible thunderstorms and MVFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
With a weak pressure gradient across the coastal waters, conditions
are expected to remain below SCA criteria through Wednesday
morning. Before and after cold front Wednesday afternoon through
Thursday night, there could be SCA level conditions on the
ocean. For non-ocean waters, seas will be well below SCA
thresholds the whole short term through Thursday night but wind
gusts get close to SCA thresholds Wednesday and Thursday with
gusts up to near 20 kt.
A weak pressure gradient will keep all waters below SCA criteria
Friday through this weekend.
&&
.HYDROLOGY...
No hydrologic problems are expected through tonight.
Models are indicating a very warm and humid airmass developing
across the region, especially along the coastal sections for
Wednesday into Wednesday evening. Layer precipitable waters
reaching near 1.75 to 2 inches for much of the region Wednesday
into Wednesday evening. A more substantial lowering of
precipitable waters is forecast for late Wednesday night through
Thursday to less than 1 inch by early Thursday and then to near
to less than a half inch by early Thursday evening.
Steering flow approximated from 700-500 mb flow of mostly around 30-
35 kt should preclude most flooding issues, as this flow will allow
for faster translational movement of showers and thunderstorms.
However, minor flooding will still be possible with any multiple
rounds of larger areas of showers and thunderstorms that move
across as heavy downpours could easily occur. This would be more
probable for those locations that are low lying and poor
drainage.
&&
.TIDES/COASTAL FLOODING...
There is a low risk of rip current development along Atlantic
facing beaches today, increasing to moderate on Wednesday with
stronger southerly flow and southerly waves.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Heat Advisory from 11 AM to 8 PM EDT Wednesday for NYZ069>075-
176>178.
NJ...Heat Advisory from 11 AM to 8 PM EDT Wednesday for NJZ004-006-
103>108.
MARINE...None.
&&
$$
SYNOPSIS...JM/MW
NEAR TERM...JM
SHORT TERM...JM
LONG TERM...MW
AVIATION...MW
MARINE...JM/MW
HYDROLOGY...JM/MW
TIDES/COASTAL FLOODING...