606
FXUS61 KOKX 271732
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
132 PM 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/...
-- Changed Discussion --
Have lowered today`s max temps by 1 to 2 degrees in most spots
for this afternoon as NBM has continued its trend being a bit
too warm much of the time for most place with daytime temps.
Sea breeze boundary pushes north across eastern sections this
afternoon also aids in temps being slightly cooler east. Fair
weather cumulus is struggling to form, with the bulk of any
cumulus shallow and and focus mainly across the sea breeze
boundary for eastern sections over the next few hours.
High temperatures this afternoon reach well into the lower and
middle 80s with upper 80s in the NE NJ Metro. Max heat indices
to around 90 for parts of NE NJ.-- End Changed Discussion --
&&
.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 /18Z TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --
VFR with high pressure in control through this evening. A cold
front begins approaches tonight and moves across the area on
Wednesday.
S-SE sea breezes will continue moving inland through the
afternoon. Some interior sites may remain VRB or light SW-W
into the evening. Winds briefly diminish this evening before
gradually increasing and becoming SW towards day break
Wednesday. SW winds around 10 kt are expected in the morning,
but will veer to the W and then NW into the afternoon. NW winds
10-15 kt with gusts up to 20 kt expected in the afternoon.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Timing of wind shift to the S-SE may be off by 1-2 hours at
KLGA, KEWR, and KTEB this afternoon.
A shower is possible Wednesday morning. There is also a low
probability of a shower/thunderstorm Wednesday evening, but
confidence is too low to include in TAF at this time.
OUTLOOK FOR 18Z WEDNESDAY THROUGH SUNDAY...
Wednesday PM: VFR. NW wind gusts 15-20 kt. Low probability of a
shower/thunderstorm.
Thursday: Mainly VFR. Slight chance of an afternoon/evening
showers/thunderstorm north and west of the NYC terminals.
Friday: VFR.
Saturday: Chance of showers, possible thunderstorms and MVFR.
Sunday: Mainly VFR. Slight chance of showers.
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...JE/JM
SHORT TERM...JM
LONG TERM...MW
AVIATION...DS
MARINE...JM/MW
HYDROLOGY...JM/MW
TIDES/COASTAL FLOODING...