077
FXUS61 KOKX 251105 CCA
AFDOKX
Area Forecast Discussion...CORRECTED
National Weather Service New York NY
705 AM EDT Sun Aug 25 2024
.SYNOPSIS...
High pressure will remain based in the Western Atlantic and
will continue to weaken across the local region for the
remainder of this weekend and through Monday. A surface trough
of low pressure develops tonight into Monday near and within the
region, eventually dissipating by Tuesday. A warm front lifts
north early Wednesday, with a weak low and cold front moving
through Wednesday night. High pressure returns Thursday and
Friday. A frontal boundary approaches next weekend.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Clouds have increased into daybreak with generally mostly cloudy
conditions early to the middle of this morning. Reduced the
amount of patchy fog this morning as temperatures have been
relatively warmer with therefore more of a dewpoint depression.
Otherwise, forecast mainly on track.
Not much change in mid level heights today with more of a negative
trend late this afternoon into early this evening. On the large
scale, a trough across the Northeast and New England will have an
approaching cutoff low moving southward within Quebec.
The more negative height trend will also be accompanied by an
approaching area of higher vorticity. This positive vorticity
advection will allow for vertical forcing to increase.
At the surface, high pressure will continue to slowly weaken. High
pressure center will remain based in the Western Atlantic. Models
are indicating potential for surface trough development within the
forecast region this afternoon.
CAMs indicate shower and thunderstorm possibilities this afternoon
into tonight, mainly across portions of the interior. POPs of slight
chance to chance for showers and thunderstorms are in the forecast,
with the relatively highest chances for showers and thunderstorms
confined to locations north and west of NYC early this evening.
Forecast highs are well within the 80s today using a blend of
MOS consensus and NBM. Dewpoints are more in the upper 50s to
lower 60s. Both parameters are a few degrees higher than those
of the previous day.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
-- Changed Discussion --
The cutoff low within the mid level trough continues to move south
tonight into early Monday, getting into Northern New England. This
will translate to further height falls in the mid levels.
At the surface, with diurnal heating waning, the instability will be
lowering, allowing for shower and thunderstorm activity to decrease
from early to late evening. Mainly dry conditions are expected
overnight into Monday morning.
The numerical weather prediction models however do retain a
trough like signature in the surface pressure fields in the
local region tonight into Monday. This will act as a focus for
more showers and thunderstorm to develop Monday into Monday
night. In the mid levels, the cutoff low opens back up to a
trough and passes farther south and eventually east of the local
region.
The models are showing in the upper levels at the 250 mb level, a
northerly jet streak moving in Monday afternoon into Monday night.
The left front quad of this jet will be within the forecast region,
setting up for enhanced synoptic lift.
The models have trended higher with 0-6 km bulk shear compared to
the previous night model initializations. The 0-6 km bulk shear
is shown to be more in the range of 30-40 kt.
The models are indicating more instability across eastern
sections of the region, with values of near 1000 to 2000 J/kg.
Model BUFKIT sounding convey CAPE within the hail region of -10
to -30 degree C in the atmosphere as well as steepening lapse
rates between 925mb and 700mb for Monday afternoon into Monday
evening.
The 06Z run of the HRRR shows potential for large hail across
eastern sections of the region for late Monday afternoon through
Monday evening as well as higher wind gusts up to near 50 kt with
some thunderstorms.
The increased low level shear and vertical forcing as well as
the daytime instability will allow for more organization to
thunderstorms, with some of them potentially getting strong to
severe. Main threat would be damaging wind gusts and large hail.
Storm Prediction Center severe outlook shows probabilities for
severe wind gusts are still marginal and at 5 percent for Monday
into Monday night.
Drier conditions return by late Monday evening and prevail through
Tuesday. The mid level trough will be moving farther east of the
region, allowing for mid level heights to eventually rise. At the
surface, the trough of low pressure will be moving farther southeast
of the region, allowing for return of high pressure.
Forecast high temperatures once again are well into the 80s for
Monday and Tuesday. However, it will feel more humid as forecast
dewpoints get more into the mid 60s.-- End Changed Discussion --
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
NE troughing slides east Tuesday Night, with flattening upper flow
(possible very brief shortwave ridging) on Wed. Models are
converging an a weak northern stream shortwave/s dropping into
northern new England Wed NIght/Thu, and east Thu Night. Then general
model agreement on southern ridging briefly building back towards
the region for Friday, before a broad and strong Central Canadian
trough slide east through the Great Lakes for the weekend, with lead
shortwave pivoting through the area Sat/Sun. There is typical Day 5-
7 model spread on on amplitude of troughing/timing of embedded
shortwaves for the weekend.
At the surface, general agreement with high pressure sliding
offshore Tuesday Night, with a warm front passing north Tue
Night/Wed Am ahead of a weak surface low dropping southeast through
the eastern Great Lakes. This surface low and associated cold front
sink south towards the region Wed aft/eve and southeast Wed Night.
Ahead of it, a quick hit of late summer heat/humidity likely on
Wednesday. Increasing potential for one day of heat indices into the
mid to upper 90s for LoHud, NYC, NE NJ and surroundings. Potential
for late Wednesday aft/eve shra/tsra activity, although still some
timing/amplitude spread in the shortwave energy trigger. Potential
for some strong to severe thunderstorms late aft/eve (possibly
developing to the N&W of the region in region of better
forcing/shear, sinking southeast). Will also have to see how surface
wave gets resolved in CAMs as we approach 48 hr window, as this
could act as a mechanism for more focused tstm activity and
introduce a low flash flood threat.
A return to seasonable temps (or even slightly below) on Thu/Fri in
wake of cold front as Canadian high pressure builds a maritime
Canadian airmass into the region. Persistent onshore flow under waa
inversion aloft may result in stubborn stratus during this period,
and chance of diurnal showers with frictional convergence and
orographic lift.
Another round of unsettled weather possible for the weekend as
frontal system associated with board Canadian troughing, but low
timing predictability based on model spread.
&&
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
High pressure remains in control through tonight, with a weak
trough developing this afternoon/evening and moving through
tonight. A stronger trough approaches Monday aft/eve.
SCT cu likely this aft/eve, possibly bkn. Isolated SHRA/TSRA
possible, mainly for KSWF in the evening.
Light S-SW to variable winds early this morning veering to
light W for Sunday AM push. Light W-SW winds become S/SW with
afternoon sea breezes once again before becoming light S to
variable this evening. Light W/SW winds for Mon Am push.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Timing of the seabreeze may be off by an hour or so. Slight chance
of a shra/tsra for eve push.
OUTLOOK FOR 12Z MONDAY THROUGH THURSDAY...
Monday: VFR. Scattered aft/eve shra/tsra threat with MVFR or
lower possible. W/SW flow, aft coastal seabreeze.
Tuesday: VFR.
Wednesday and Thursday: VFR. Chance of MVFR or lower in aft/eve
shra/tsra.
Detailed information, including hourly TAF wind component
forecasts, can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
The pressure gradient remains weak across the region through
Tuesday, keeping seas and winds well below SCA thresholds.
With a weak pressure gradient over the area, sub-SCA conditions are
expected through the middle of next week.
Threat for marginal SCA ocean seas developing Thu into Fri with
potential for persistent 15G20kt NE flow in wake of cold front. NWPS
tends to be too low with wave heights in the flow regimes during
warm season, with forecast leaned towards WNA guidance
accordingly.
&&
.HYDROLOGY...
The upper level disturbance and surface low making for the
showers and thunderstorms this afternoon into this evening as
well as Monday into Monday night will be deprived of a
substantial moisture source. Layer precipitable water values
stay below 1.5 inches. The coverage will be limited for
convection and enough of a steering flow is expected to mitigate
flooding issues.
No widespread significant hydrologic impacts are anticipated through
the period.
A minor urban/poor drainage flooding threat exists Wednesday aft/eve
with potential for progressive scattered tstm activity along/ahead
of cold front. The threat for flash flooding is low and localized at
this point.
&&
.TIDES/COASTAL FLOODING...
There will be a moderate rip current risk today for all ocean
beaches except for SE Suffolk, but a moderate rip current risk
on Monday for all of the ocean beaches. This will be due to
increasing S-SW flow along all the ocean beaches Tuesday.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...JM/NV
NEAR TERM...JM
SHORT TERM...JM
LONG TERM...NV
AVIATION...NV
MARINE...JM/NV
HYDROLOGY...JM/NV
TIDES/COASTAL FLOODING...JM