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FXUS61 KOKX 252000

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

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. 


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.


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. 


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 


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:/

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.

.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 Night-Monday...MVFR/IFR possible in showers. E/SE
.Tuesday...Improving to VFR. S/SE winds.


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

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.


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.


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 


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 
     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 
NJ...Coastal Flood Advisory from 7 PM to 10 PM EDT this evening for 
MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ330-
     Small Craft Advisory until 6 PM EDT Friday for ANZ350-353-355.


LONG TERM...Maloit

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