Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 060941
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
541 AM EDT Thu Aug 6 2020

.SYNOPSIS...
A weak cold front stalls just south of the area today as high
pressure builds across the northeast. A series of frontal waves
will then track along the boundary tonight through early
Saturday. High pressure builds into the area for Sunday and
Monday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Forecast on track early this morning.

The region will lie between a Western Atlantic Ridge and a
shortwave trough from the Great Lakes down through the southeast
states. There is some hints at shortwave energy within
southwesterly flow, which will advect mid and upper level
moisture northward. At the surface, a frontal boundary stalls
just to the south of the area as high pressure builds across the
northeast. While there could be some returns on radar today,
much of this will be from middle level moisture. A sprinkle
cannot be ruled out, but have left the forecast dry through the
afternoon. The subcloud layer continues to be dry and there is
no instability.

High resolution models depict a convective complex passing to
the south of Long Island late this morning or early afternoon.
The subsidence and dry air from the high will keep any
precipitation with this well to south, but high clouds are
likely to stream northward within the SW flow.

Partly cloudy skies to start will become mostly cloudy this
afternoon. Temperatures will be held down due to increasing
clouds with highs generally in the low 80s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
The approach of more robust middle level energy occurs tonight
into Friday, which helps set up a series of frontal waves along
the stalled front to the south. Confidence in the northward
extent of showers/possible storms is still relatively low. The
GFS continues to be the most bullish with the highest QPF, with
the ECMWF and HREF mean less and more suppressed with the swath
of QPF. Have continued to take a middle of the road approach,
which keeps the highest probability of precipitation across the
NYC metro, Long Island, and coastal Connecticut. The timing of
the frontal waves is also a bit uncertain, but a model consensus
has the highest PoPs coming in after midnight and continuing
through Friday morning. The first frontal wave lifts to the NE
in the afternoon and there could be a bit of a lull before
another wave develops Friday evening on the stalled front.

Instability is limited due to NE to E flow and cloud cover, but
have mentioned isolated thunder beginning early Friday morning
as there is some elevated instability noted in forecast
soundings. Showers remain possible Friday night as the upper
trough axis moves across PA and upstate NY and the next wave
develops on the stalled front.

One aspect to note is that the precipitation and frontal wave
development is likely associated with convection. The evolution
of this convection to the south leads to a lower than normal
confidence level at this time range. Further adjustments to the
timing and coverage of precipitation are likely as the event
draws near.

Rainfall amounts a quarter inch or less inland and up to around
a half inch possible near the coast are forecast. Locally
higher amounts are possible if any heavier downpours develop.

High temperatures on Friday will be in the upper 70s to near 80.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
The middle and upper level short wave will be moving into the
region by 12Z Saturday. A chance of showers continues in the
morning. This wave will move out the stalled frontal boundary
by Saturday afternoon as the trough axis passes east. Consensus
models are also indicating a slight chance of showers and
thunderstorms in the afternoon as there may be enough lingering
moisture, instability and convergence with developing sea
breezes.

Upper ridging builds behind the shortwave Saturday night into
the beginning of next week, 12Z Monday. A weak and low amplitude
shortwave moves through Monday and may trigger showers and
thunderstorms. Surface instability and CAPE will be increasing
during the day with daytime heating. Lapse rates will also be
steep enough for convection. Heat and humidity will be building
Tuesday into Wednesday as return flow remains. However,
increasing clouds and the chance of precipitation may limit the
heat Wednesday. With a large closed low over southeastern Canada
Tuesday into Wednesday a surface cold front will be approaching
and may stall in the area Wednesday.

&&

.AVIATION /10Z THURSDAY THROUGH MONDAY/...
A frontal boundary will stall south of Long Island today and
remain over ocean into Fri.

VFR thru at least 6Z Fri. Low chance for shwrs aft 6Z Fri. The
prob was too low to include in the TAFS except for JFK, with
most of the activity expected to remain south of the area attm.
Cigs may lower to MVFR, especially NYC and Long Island, by 12Z
Fri.

Light winds thru the TAF period with a general veering flow
becoming nely. Sea breeze component flow this aftn, then nely or
vrb flow tngt.

AMD NOT SKED included for the KBDR TAF due to the ASOS outage.


     NY Metro Enhanced Aviation Weather Support...

Detailed information, including hourly TAF wind component fcsts,
can be found at: http:/weather.gov/zny/n90

KJFK TAF Comments: No unscheduled amendments expected.

The afternoon KJFK haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KLGA TAF Comments: No unscheduled amendments expected.

The afternoon KLGA haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KEWR TAF Comments: No unscheduled amendments expected.

The afternoon KEWR haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KTEB TAF Comments: No unscheduled amendments expected.

KHPN TAF Comments: No unscheduled amendments.

KISP TAF Comments: No unscheduled amendments expected.


.OUTLOOK FOR 06Z FRIDAY THROUGH MONDAY...
.Tonight...Low chance of showers. Chance of MVFR.
.Friday...Chance of rain showers. Isolated thunderstorms. Chance
of MVFR.
.Saturday-Monday...Mainly VFR.

&&

.MARINE...
Winds and seas will stay blw SCA levels thru Mon. There is a
chance that sw flow reaches SCA criteria on the ocean Mon ngt
and Tue.

&&

.HYDROLOGY...
No significant hydrologic impacts are currently anticipated with
any shower and isolated thunderstorms Thursday night through
Friday night.

No hydrologic impacts are expected this weekend into early next
week

&&

.EQUIPMENT...
KBDR ASOS is not reporting at this time due to a power outage.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$
SYNOPSIS...DS/MET
NEAR TERM...DS
SHORT TERM...DS
LONG TERM...DS/MET
AVIATION...JMC
MARINE...JMC
HYDROLOGY...DS
EQUIPMENT...



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