773
FXUS61 KOKX 011609
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1209 PM EDT Thu Aug 1 2024
.SYNOPSIS...
Weak surface high pressure eventually transitions to an
increasingly active pattern towards this weekend. A frontal
system will be approaching and eventually moving in. The
associated cold front likely pushes through late in the
weekend. Weak high pressure returns for Monday. Another frontal
system approaches for the middle of next week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Only minor adjustments were made to dewpoints and temperatures
with this update. Otherwise, the forecast remains on track.
The surface pressure field will be weakening today into this
evening. Behind the trough, more of a westerly flow will allow
for a mainly dry day with slightly less humidity especially away
from the coast.
Brief mid level ridging today into this evening will promote
subsidence and keep conditions mainly dry. At the surface, a trough
weakens during the day. With this boundary and where the most
instability will be generated with daytime heating, generally more
towards the southwest parts of the forecast region. There is a
slight chance of showers and thunderstorms for parts of the region
this afternoon into early this evening.
Went with higher temperatures guidance considering the westerly
flow. In combination with the dewpoints and the humidity, much
of the region is set to achieve heat index values in the mid to
upper 90s. Only exceptions will be Eastern Suffolk NY and
Southern Suffolk NY as well as Orange and Putnam within the
Lower Hudson Valley, where heat index values will be more in the
lower 90s. The Lower Hudson Valley expected to have the lower
dewpoints in the region, in the low to mid 60s for this
afternoon.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
Mid level heights will become nearly steady in tendency tonight
into Friday, followed by a decline in heights for the first
half of the weekend. This will be as a mid level trough
approaches from the west. Models focusing on two time periods
for when positive vorticity increases with embedded shortwaves
traversing the local region, late Friday night into early
Saturday and late Saturday night into early Sunday. Models for
the late Saturday into early Sunday time period also indicate an
increase in 0-6 km bulk shear to around 30 kt, allowing for
possible strong to severe thunderstorms.
Not much change in the pressure field Friday into Friday night.
However, aloft more of a troughing pattern develops. A trough
will gradually be approaching from the west. At the surface, low
pressure develops and approaches from the west Friday night with
a warm front moving north of the region. A cold front will
eventually move into the region towards early Sunday.
For Friday, low level winds expected to be more SE allowing for
cooler and more humid conditions. The combination of heat and
humidity will still be high enough for mid to upper 90s heat
indices for much of the region except for coastal Middlesex CT,
coastal New London CT, and Southern and Eastern Suffolk NY with
cooler onshore marine influence, thereby making for lower heat
indices, mostly lower 90s. For Lower Hudson Valley especially
Orange and Putnam, cooler temperatures will make for lower heat
indices as well, again lower 90s.
Heat advisory updated with expansion in area and extension in
time. Much of NE NJ, NYC and Nassau NY were already in the heat
advisory and this has been extended until 8pm Friday. The areal
expansion of the heat advisory goes to Western Passaic NJ,
Westchester NY, Rockland NY, NW Suffolk NY, Fairfield CT, New
Haven CT, Northern Middlesex CT, as well as Northern New London
CT. For these zones, the heat advisory goes from 1pm this
afternoon until 8pm Friday.
With more unsettled pattern and more synoptic forcing moving
into place, POPs increase for showers and thunderstorms. These
will have a threat for heavy rain. See hydrology section for
more details.
Forecast has cooler temperatures for Saturday but the airmass
will still be very humid, allowing for heat indices of mid to
upper 90s to remain in the forecast. Not enough confidence to
extend heat advisory out this far yet as more showers and
thunderstorms will limit the temperature growth.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
An upper level trough and associated surface cold front approach on
Sunday and moves across the area Sunday night. A decent S-SW flow
ahead of this system will keep an abundant amounts of moisture over
the region, with PWATs exceeding 2 inches during the daytime Sunday.
With the upper trough and cold front nearby, showers and
thunderstorms becoming likely during the afternoon. Some of the rain
may be locally heavy. Dew points will remain rather high, in the
lower and middle 70s, however with more clouds to deal with
temperatures should be about 2-5 degrees cooler than Saturday, so at
this time, not expecting any heat headlines.
The front moves through sometime Sunday night into early Monday
morning, with drier conditions expected to start the new week.
Another slow moving frontal boundary will impact the region during
the middle of next week, with chances for showers and thunderstorms
once again. Will cap POPS at chance for now, but it looks like the
best chances for any precip will be on Wednesday.
Temperatures on Monday will climb into the middle and upper 80s to
near 90, however Tuesday through Thursday, temperatures will remain
in the lower and middle 80s.
&&
.AVIATION /16Z THURSDAY THROUGH MONDAY/...
VFR through the TAF period with weak high pressure remaining
over the area.
Light W-WNW flow to start this morning with CT coast terminals
becoming S-SSW. Winds will continue to become S and increase
this afternoon, especially at coastal terminals. It will take a
few longer for the S flow to reach terminals further north, and
it may remain W at KHPN and KSWF through the afternoon.
Winds will diminish again tonight, becoming light and variable.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Timing of S wind shift may be off by 1-2 hours.
A few occasional gusts into the upper teens to lower 20 kt
possible this afternoon, mainly for KEWR.
An isolated shower cannot be completely ruled out late this
afternoon or evening.
OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY...
Friday-Sunday: Chance of MVFR or lower in afternoon/evening
showers/tstms.
Monday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
SCA for higher ocean seas until 9am this morning east of
Moriches Inlet. Otherwise, expecting sub-SCA conditions with a
weak pressure gradient in place today through Saturday night.
Increasing/persistent S-SW flow will likely result in SCA
conditions on Sunday with seas close to or slightly above 5 ft.
In addition, with the approach of a cold front, can not rule out
some marginal small craft wind gusts at times. Conditions are
expected to fall below small craft criteria during Monday.
&&
.HYDROLOGY...
Multiple rounds of showers and thunderstorms are possible
through this weekend. The higher likelihood appears to be late
Friday into the first half of the weekend, with activity
lingering into Sunday. While widespread flood impacts are not
expected, localized urban and poor drainage flood impacts are a
possibility with high humidity and PWATs exceeding 2 inches in
place. WPC has a marginal risk of excessive rainfall for much of
the area Saturday into Sunday.
Rainfall forecast Friday afternoon through Saturday night ranges
from near a quarter of an inch out east to 1 to 2 inches to the
north and west of NYC. Locally higher amounts will be possible.
&&
.TIDES/COASTAL FLOODING...
Winds diminish and turn more SW-W today, but still expect at
least a moderate risk of rip currents at ocean beaches, today
into Friday, due to residual 3-ft swell.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 8 PM EDT Friday for CTZ005>010.
NY...Heat Advisory until 8 PM EDT Friday for NYZ069>071-078.
Heat Advisory until 8 PM EDT Friday for NYZ072>075-176>179.
NJ...Heat Advisory until 8 PM EDT Friday for NJZ002.
Heat Advisory until 8 PM EDT Friday for NJZ004-006-103>108.
Air Quality Alert until 11 PM EDT this evening for NJZ004-006-
103>108.
MARINE...None.
&&
$$
SYNOPSIS...BC/JM
NEAR TERM...JM/BR
SHORT TERM...JM
LONG TERM...BC
AVIATION...DS
MARINE...BC/JM
HYDROLOGY...BC/JM
TIDES/COASTAL FLOODING...