Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 170545
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
145 AM EDT Thu Aug 17 2017

.SYNOPSIS...
An area of high pressure will build into the region through
tonight, then slowly shift offshore Thursday. A warm front will
approach Thursday night. A cold front slowly approaches from
the west on Friday, moving across the region on Saturday. High
pressure returns on Sunday into Monday before the next cold
front approaches from the west on Tuesday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Minor updates to reflect current temperature and dew point
trends.

Dry conditions tonight and into tomorrow as high pressure
continues to move eastward then offshore by Thursday.
Temperatures tonight will be in the lower to mid 60s along the
coast and mid 50s inland. Patchy fog possible late tonight and
through early Thursday morning.

Swells from the departing Hurricane Gert will gradually
decrease, with a moderate risk of rip currents continuing at
area beaches tonight.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/...
Mostly sunny conditions expected on Thursday as high pressure
begins to shift offshore Thursday allowing for the return of
a southerly flow. As a low pressure system lifts through the
Great Lakes, a warm front will lift northward towards the area
late Thursday afternoon. Showers and possible thunderstorms
will start to develop north and along the warm front late
Thursday afternoon then spread across the region Thursday night.

Temperatures on Thursday will be in the upper 70s to lower 80s
with nighttime temperatures in the upper 60s to lower 70s.

There will be a moderate risk of rip currents at ocean beaches
for Thursday.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Main concern in the long term period surrounds a frontal system
progged to affect the area Friday into the first portion of
Saturday. The parent low pressure system will be spinning across the
northern Great Lakes Friday morning, with its warm front draped near
the region. Low level warm advection near the warm front is the main
source for lift with the expectation that showers will grow in
coverage through the morning. The warm front should lift to the
north in the afternoon, but abundant cloud cover should preclude any
significant instability. Will continue to mention chance of thunder,
with showers becoming likely through the morning and afternoon. The
new 12z suite of models and ensembles are in good agreement that the
main cold front will still be off to the west across upstate NY and
PA Friday evening. With the main upper trough still located well to
the west, do not think there will be any severe weather, with the
latest Day 3 SPC outlook confining a marginal risk closer to the
cold front. The front will gradually move to the east Friday night
into Saturday morning, but will not completely move offshore until
Saturday night. Showers with possible thunder will continue Friday
night before tapering off Saturday morning out east.

Locally heavy rain is possible anywhere Friday into early Saturday,
but difficult to pinpoint since convection will throw off QPF on
models, especially at this time range. Three quarters to one inch of
rainfall is possible on average Friday through Friday night.

The main moisture feed and lifting mechanism will then be offshore
Saturday afternoon, with just a slight chance for a shower or storm
as the cold front moves through. The upper trough is still expected
to lag behind the front Saturday night, but have elected to remove
PoPs due to cold advection behind the front and much drier air
moving in.

The upper trough should be offshore Sunday morning, with rising
heights aloft expected through early next week as ridging takes
shape across the southeastern US. This should bring a brief warming
trend, with higher humidity levels and temperatures warmer than
normal for this time of year in the middle and upper 80s. However,
we still lie near the main belt of the westerlies to our north and m
models signal a longwave trough developing over the eastern states
late Tuesday into Wednesday along with the next cold front.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
High pressure builds into the area overnight before sliding
offshore Thursday. A warm front will approach from the SW
Thursday night.

VFR through the TAF period outside any overnight patchy fog.
Dewpoints are forecast to drop overnight, so fog development
is expected to be less widespread compared to last night.

Northerly winds 5kt or less prevail tonight. As the high shifts
offshore on Thu winds will veer to the SE-S with seabreeze
enhancement possible in the afternoon.

.OUTLOOK FOR 00Z FRIDAY THROUGH MONDAY...
.Thursday night through Saturday night...MVFR or lower flight
cat possible in showers/tstms.
.Sunday And Monday...VFR.

&&

.MARINE...
Long period southerly swells from Hurricane Gert should slowly
subside tonight into Thursday as the hurricane moves farther
out to sea. Thursday night winds and seas will remain below
advisory levels as a cold front approaches from the west.

Increasing southerly flow on Friday ahead of a cold front will bring
the chance for some gusts close to SCA levels on the ocean waters
west of Fire Island inlet, with gusts closer to 20 kt elsewhere on
the ocean. Ocean seas could build near 5 ft as well late Friday into
Friday night. The front should cross the waters through the day on
Saturday with subsiding seas and winds remaining below SCA levels.
Sub-SCA conditions are forecast Sunday and Monday.

&&

.HYDROLOGY...
Locally heavy rainfall is possible Friday into early Saturday.
An average of 3/4 to 1 inch of rainfall is forecast. However, it is
difficult to pinpoint where heavier showers/storms will develop at
this time. No significant hydrologic impacts are expected, but some
minor urban flooding is possible.

&&

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

&&

$$
SYNOPSIS...Fig/DS
NEAR TERM...MD/Fig
SHORT TERM...Fig
LONG TERM...DS
AVIATION...CB
MARINE...Fig/DS
HYDROLOGY...Fig/DS


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