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FXUS61 KOKX 252000
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
400 PM EDT Thu May 25 2017

.SYNOPSIS...
Low pressure tracks through the Tri-State Region tonight and and
then off the New England coast Friday into Friday night. Weak high
pressure over the area Saturday, gives way to high pressure
building down from southeastern Canada for the weekend. This
high then retreats to the northeast early next week as weak low
pressure tracks to the south. A cold front approaches from the
west on Tuesday, then crosses the area Tuesday night. This front
then stalls out nearby as high pressure builds in from the
southwest, producing potentially unsettled weather for the
middle of next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Middle level dry air continue moving over the region into this
evening as impressive upper level low begins tracking from the Ohio
Valley into the Middle Atlantic region. A vigorous vorticity max
will round the base of the upper trough and approach the northeast
as the trough goes negatively tilted tonight.

For this evening, lingering light rain or drizzle remain possible.
No significant rain is expected however as lift is weak and
saturation is confined to the lowest 5 kft. Some patchy fog is also
possible, but model soundings do show some drying near the surface
which may negate widespread fog development.

Moisture and lift increase after 03z from south to north as the
upper low and energy approach. Significant DPVA and steepening lapse
rates will support showers and scattered thunderstorms. The CAPE is
elevated as the low levels are inverted. The best instability
appears to lie along and East of the Hudson River. Due to the
anomalous nature of the upper low and strength of the energy,
feel thunder is possible anywhere across the area overnight.
High resolution mesoscale models, such as the HRRR, NAM-3km, and
NCAR and SPC SSEO ensemble all support this reasoning. The
normalized probability of greater than 40 dBZ on the SPC SSEO is
over 90 percent across Long Island and southeast Connecticut
06z-12z with slightly lower percentages further west. No severe
weather is forecast.

Surface low pressure will move along or near the Long Island coast
overnight so winds will not be as strong as earlier today.
The warm front may even briefly move across portions of eastern Long
Island before the low lifts to the north and east.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Upper low and surface low become vertically stacked as they move off
the New England coast on Friday. Wrap around showers and possible
thunder linger for a few hours around day break across eastern
Connecticut and the Forks of Long Island. Otherwise, clouds
will be slow to clear as moisture lingers below 10 kft. NW
downsloping flow should help to create some breaks in the
clouds, especially across the western half of the area. These
breaks will help boost temperatures into the 70s, with cooler
readings in the middle to upper 60s further east where clouds
linger longest.

Model soundings indicate some instability between about 5 and 10
kft, so clouds may fill back in with any breaks. There is also the
possibility of a few iso-sct showers. No thunder is forecast since
the instability does not look to get much above -5C with heights
building aloft behind the upper low.

Weak ridging passes Friday night as high pressure moves into the
region from the west. Lingering moisture will keep skies partly to
mostly cloudy with lows near normal values.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
The region is in between two shortwaves passing to the north and
south Saturday and Saturday night, so with most significant forcing
outside of the area, have at most slight chance pops in this time
frame, with temperatures near to slightly above normal.

Onshore flow will dominate from Sunday through Monday.

The result will be mainly gray sky conditions with spotty light rain
or drizzle mainly over higher elevations mainly to the N/W of NYC
from Sunday into Sunday night as a northern stream shortwave ridge
crosses the area. A 700-500 hPa shortwave approaches late Sunday
night and crosses the area on Monday, making for a more widespread
rain over the region then.

With the onshore flow/damming high, have undercut guidance by mixing
in NAM and ECMWF 2-meter temperatures. Highs will run 5-10 degrees
below normal Sunday and Monday and lows a few degrees above normal
Sunday night (due to reduced diurnal range).

A broad closed low slow tracks from Ontario into western Quebec from
Monday night through Thursday, with shortwaves rotating around the
base of the low from time to time. the timing of these shortwaves is
somewhat difficult this far out, but for now it appears that most
energy will be focused mainly to the N of the region. As a result,
there is a chance of isolated to scattered showers - mainly over
northern portions of the Tri-state. Also, cannot rule out an
isolated rumble of thunder Tuesday/Tuesday night with the passage of
a surface cold front.

Temperatures Tuesday-Thursday should run near to slightly above
normal.


&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
An area of low pressure will move northeast over the region
tonight...and just to the northeast of the region Friday.

IFR/LIFR cigs continue into tonight. LIFR/IFR visibilities late
afternoon/evening will be contingent on drizzle development. Showers
with a chance for thunderstorms between 02z and 09z. Heavy downpours
are the main threat.

Gradual improvement to MVFR/VFR cigs Friday morning...with
quicker improvement to VFR vsby. Chance for showers.

Easterly winds 10-20 kt with gusts to 25 kt this
afternoon...weakening this evening. Light and variable winds
tonight...becoming northwest and gusty Friday morning.

NY Metro Enhanced Aviation Weather Support...

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

KJFK TAF Comments: High confidence in IFR/LIFR cigs for evening
push...while IFR/LIFR vsby will be conditional with drizzle. TSRA
possible between 02z and 09z.

KLGA TAF Comments: High confidence in IFR/LIFR cigs for evening
push...while IFR/LIFR vsby will be conditional with drizzle. TSRA
possible between 02z and 09z.

KEWR TAF Comments: High confidence in IFR/LIFR cigs for evening
push...while IFR/LIFR vsby will be conditional with drizzle. TSRA
possible between 02z and 08z.

KTEB TAF Comments: High confidence in IFR/LIFR cigs for evening
push...while IFR/LIFR vsby will be conditional with drizzle. TSRA
possible between 02z and 08z.

KHPN TAF Comments: High confidence in LIFR conds for evening
push...VLIFR possible. TSRA possible between 02z and 09z.

KISP TAF Comments: High confidence in IFR/LIFR cigs for evening
push...while IFR/LIFR vsby will be conditional with drizzle. TSRA
possible between 02z and 09z.

.OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY...
.Friday...W/WNW wind gusts 20 to 25 kt developing late
morning and continuing into afternoon. Winds generally left of
310 magnetic. Conditions gradually improve to MVFR/VFR in the
late morning to afternoon. SHRA possible.
.Saturday...VFR.
.Saturday Night-Monday...MVFR/IFR possible in showers. E/SE
winds.
.Tuesday...Improving to VFR. S/SE winds.

&&

.MARINE...
Easterly winds will gradually weaken into this evening as the
pressure gradient relaxes. Will let the SCA continue through 6
pm as winds on LI Sound are still 25-30 KT and winds further
south are still running near marginal SCA levels. Winds on the
ocean will continue to fall below SCA levels into this evening.
Ocean seas will remain elevated above 5 ft through Friday. These
seas will gradually subside Friday night with sub-SCA conditions
elsewhere.

A light pressure gradient over the region Saturday-Tuesday should
limit winds to 10 kt or less. Given the absence of any significant
swell, in addition, conditions should be below small craft advisory
conditions over the waters around Long Island Saturday-Tuesday.

&&

.HYDROLOGY...
An additional 0.50 to 1.0 inches of rain is forecast through
Friday morning. The highest amounts will likely occur across
eastern Connecticut and eastern Long Island. Locally higher
amounts are possible where thunderstorms occur overnight. Minor
urban and poor drainage flooding is possible.

It should then be mainly dry Friday night-Sunday.

Another round of rain is possible from Sunday night into late
Monday. At this time, it is to soon to specify, what, if any,
hydrologic impact will be experienced from this system.

&&

.TIDES/COASTAL FLOODING...
A Coastal Flood Warning continues for moderate flooding
potential for the south shore back bay locations of Nassau
County for tonight, and advisories are in place for minor
flooding potential for areas adjacent to western Long Island
Sound, NY Harbor, and the south shore back bays of the western
Long Island. Minor flood thresholds could briefly be touched
along the eastern bays of LI and SE CT.

How quickly easterly winds begin to weaken this
evening will be key to the potential for seeing widespread
versus localized moderate coastal flooding along the southern
bays of Western LI. Less than 1/2 ft of surge is needed in many
places to reach minor flood thresholds.

The threat for minor coastal flooding is likely to continue during
the nighttime high tides for the southern bays of Western LI/NYC
through the Memorial Day Weekend. While along western Long Island
Sound, lower NY Harbor, and eastern Great South Bay...minor coastal
flooding is possible at those times.

Beach erosion is expected with the prolonged easterly
sweep...but the potential for dune erosion looks to be low and
localized.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Coastal Flood Advisory from 10 PM this evening to 1 AM EDT
Friday for CTZ009-010.
NY...Coastal Flood Advisory from 7 PM to 10 PM EDT this evening for
NYZ074-075-178.
Coastal Flood Advisory from 10 PM this evening to 1 AM EDT
Friday for NYZ071-073-078-176-177.
Coastal Flood Advisory from 8 PM this evening to midnight EDT
tonight for NYZ080.
Coastal Flood Advisory from 7 PM this evening to 1 AM EDT
Friday for NYZ072.
Coastal Flood Warning from 7 PM to 11 PM EDT this evening for
NYZ179.
NJ...Coastal Flood Advisory from 7 PM to 10 PM EDT this evening for
NJZ006-106-108.
MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ330-
335-338-340-345.
Small Craft Advisory until 6 PM EDT Friday for ANZ350-353-355.

&&

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