Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 230541
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
141 AM EDT Sun Apr 23 2017

.SYNOPSIS...
High pressure will slowly build into the region from the west
overnight, across the area on Sunday, then move offshore on
Monday. A wave of low pressure over the Southeast states on
Monday, will track slowly up the eastern seaboard through
midweek. High pressure will build back in for the end of the
week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Shearing northern stream shortwave energy slides through the
region and to the south by morning...with high pressure
building in from the NW. Gradual drying and clearing is expected
from NW to SE overnight.

Minor adjustments to temps and dews to better reflect current
conditions and trends.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/...
Region will lie in a near zonal upper flow between a polar
upper low over interior Ontario/Quebec and a closed upper low
moving trough the deep south. At the surface...high pressure
builds into the region Sunday morning and then east Sun
afternoon into Sunday night.

Tranquil conditions Sunday night...with increasing mid-deck
late ahead of a slowly approaching low pressure system from the
south.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
NWP is in good agreement with the H5 pattern through much of the
upcoming week...with timing and amplitude differences at the end
of the week and into next weekend.

A split flow over the Eastern US starts the period with a cutoff
low pres system over the SE states with ridging to the N and E.
The ridge over the Atlantic will amplify as the week
progresses...creating a blocking pattern and forcing the low up
the eastern seaboard. While it is quite certain that the local
area will be impacted by this storm...the details remain
uncertain...the NAM/GEM in one camp keeping the system over land
and tracking it over or near NYC Tue night/Wed morning...and
the GFS/EC tracking it just S and E of Montauk. These
differences will hopefully be resolved in the next few model
runs as it will impact where the inverted sfc trough develops
with the axis of heaviest rain.

Due deep layered ridging ahead of the storm...have slowed up
timing of pops...and have kept Monday mostly dry with better
chances Monday night as subsidence weakens. Winds will also
increase and become gusty Mon night and Tue. 30-40 kt LLJ lifts
through Tue aftn/eve...but a low level inversion should keep
most of these winds aloft. These stronger winds will also depend
on where the low tracks. If the low tracks over NYC the higher
winds will remain to the east.

The forward progression of the system is also uncertain...and
current forecast may be too quick decreasing pops to chc Wed
morning. System departs Wed night with ridging aloft developing
over the east and a broad trough out west. This will lead to
warming temps through the remainder of the week. A cold front
moves towards the area on Thu...but most guidance has
showers/tstms mostly dissipating before it reaches the region.
This front is then forecast to stall near the area into next
weekend with potential waves of low pressure keeping it
unsettled.

As for temperatures, near seasonable levels through mid week,
if not a bit cooler during the daytime due to cloud cover and
rain. A significant warmup is possible for the end of the week
with rising heights aloft.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
VFR as high pressure builds from the west this morning and
passes east this afternoon.

NNW-N winds prevail early this morning,generally 10 kt or less.
Winds become light N-NE after day break and then turn to the
S-SE this afternoon under 10 kt.

.OUTLOOK FOR 06z MONDAY THROUGH THURSDAY...
.Sunday night ...VFR.
.Monday...VFR during the day. Chance MVFR in rain at night.
.Tuesday...IFR/LIFR in rain. NE gusts 20-25 KT near coast
possible during the day.
.Wednesday...MVFR possible early, becoming VFR.
.Thursday...VFR.

&&

.MARINE...
Forecast winds and seas on track with no changes made at this
time.

Seas below 5 feet with a continuing east to southeast long
period swell. Swell heights have subsided however, periodic 5
foot seas will still be possible overnight across the far
southeastern ocean waters.

Winds and seas should run below SCA levels Sunday into Monday
as high pressure builds from the north tonight into Sunday
night. The high weakens Monday as low pressure moves off the
southeastern coast begins to track slowly to the north.

The low pressure system over the SE states Monday will track
slowly N-NE through midweek. A prolonged and increasing
easterly flow will set up from Monday night into Wednesday.
Winds and seas are expected to build to SCA levels Mon eve with
the potential for gale force winds Mon night into Tue. Winds
diminish Tue night...but seas on the ocean will be slow to
subside and possibly linger into Thu.

&&

.HYDROLOGY...
Between 1/2 and 1 1/2 inches of rainfall is possible late
Monday into Wednesday depending on the track of low pres.

No hydrologic impacts are anticipated at this time.

&&

.TIDES/COASTAL FLOODING...
Potential for minor coastal flooding for vulnerable coastal
communities with the Tue high tide cycles due to a potential
coastal storm working up the coast. The evening cycle may have
the higher threat as only 1/2 to 1 ft of surge is needed to
reach minor flood thresholds.

&&

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

&&

$$
SYNOPSIS...24/NV
NEAR TERM...MET/NV/PW
SHORT TERM...NV
LONG TERM...24
AVIATION...DS
MARINE...24/MET/NV/PW
HYDROLOGY...24/NV
TIDES/COASTAL FLOODING...



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