Area Forecast Discussion
Issued by NWS Upton, NY

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561 FXUS61 KOKX 250530 AFDOKX Area Forecast Discussion National Weather Service New York NY 130 AM EDT Thu May 25 2017 .SYNOPSIS... Low pressure will move slowly east across the area Thursday night, then move east of the area Friday. Weak high pressure returns for Saturday. Another frontal system will then impact the area for the latter half of the holiday weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Clouds, mainly high and mid level, were advancing northward as seen on satellite, with lower clouds expected after 05Z as warm frontal boundary approaches. Increased cloud cover into Thursday morning. Isentropic lift increases ahead of an approaching warm front resulting in rain developing from SW to NE aft 06Z. Rainfall prior to 12Z should be mostly light. Decided to go with higher categorical POPs between 06Z and 12Z. For forecasts of Coastal Flood Advisories and Statements with this evening`s high tides, read the Tides and Coastal Flooding Section. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/... As an upper low over SE MO mvs very slowly NE, an upper lvl short wave rotating arnd its base will become negatively tilted. Moisture from the Gulf of Mexico and SW Atlantic Ocean will converge and be tapped from a secondary low developing near VA. Widespread moderate rain of up to 0.50 inch with isolated higher amounts, more than fcst by the models, is fcst between 12Z and 18Z Thu, leading to possible minor urban flooding of low lying and poor drainage areas. Coastal flood advisories have been issued for Thursday evening`s high tide cycle. And, a coastal flood watch has been issued for parts of the coastal areas for the Thursday evening`s high tide cycle. See the tides and coastal flooding section. As the low lifts further north closer to the area, the widespread moderate rain is forecast to become lighter Thursday afternoon. Additional rain is forecast Thursday night as the stacked low passes directly over the local area. Storm total rainfall is forecast to range from 1.0 to 1.5 inches with isolated higher amounts through the day Friday. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... A cutoff low lifts NE through the Gulf of Maine Friday, bringing scattered to numerous showers (SE CT). Highs Friday should be within a few degrees of either side of normal. Northern stream ridging builds in Friday night-Saturday night, with associated subsidence keeping things dry, except for maybe some lingering showers early Friday evening as the upper low continues to depart. However, a shortwave passing over the top of the ridge could bring some mid clouds mainly on Saturday. Lows Friday night should be near to slightly above normal, highs on Saturday near normal and lows Saturday night a few degrees above normal. The northern stream ridge axis slides to the east Sunday, allowing for shortwaves rotating around the base of a broad closed low over S Central Canada to move across the area from time to time early next week (unfortunately the timing of specific shortwaves this far out is problematic at best), at the same time a combination of weak coastal lows passing to the S and high pressure building down from SE Canada should produce onshore E-SE flow. So could see some rain/drizzle with any shortwave given the increase in low level moisture Sunday-Monday morning, then possibly some showers/thunderstorms late Monday with the strongest shortwave passing. Weak ridging builds in from Monday night into Tuesday, followed by more shortwaves rotating around the S Canada closed low, which has slid a bit farther E into Hudson bay/NW Ontario), Tuesday night and Wednesday - with maybe some more isolated- scattered showers. Temperatures should be within a few degrees of either side of normal Sunday-Monday night, then run above normal Tuesday- Wednesday. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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An area of low pressure will move across the region through the TAF period. MVFR cigs starting to develop across the southern terminals. Low clouds will continue to lower and thicken overnight, becoming IFR or less everywhere by 12z. Rain overspreads the region for the morning push, and remains through about 18-21Z. Thereafter, precipitation should become more showery in nature, with some areas of drizzle in between the showers. There is a chance that visbilites fall below a mile in fog after 18z. Generally looking at an easterly wind through the period 10-15kt with gusts 20-25kt. winds lighten late. .OUTLOOK FOR 06Z FRIDAY THROUGH MONDAY... .Thursday night...LIFR/IFR in rain. .Friday...MVFR/IFR possible. Chance of showers. .Saturday...VFR. .Sunday-Monday...MVFR/IFR possible in showers.
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&& .MARINE... Seas on the outer ocean waters east of Moriches Inlet were up to 6 feet, a few hours ahead of forecast, so increased seas in the southeast flow ahead of an approaching warm front. A Small Craft Advisory/SCA remains in effect for Atlantic Ocean coastal waters through the day Thursday and might need to be extended for seas through Thursday night. An SCA was issued for all remaining local coastal waters from 6 am through 6 pm Thursday for E winds of 15 to 25 kt. As low pressure moves very slowly east across the area through Thursday night, periods of rain along with isolated thunderstorms are forecast after 2 am tonight through the day Thursday. As the low moves east of the area, winds will shift from the W at 10-15 kt with gusts to 20 kt on Friday with additional scattered showers possible. Small craft level seas should continue on the coastal ocean waters Friday and Friday night. Otherwise, with a light to moderate pressure gradient limiting sustained winds to 15 kt or less Friday- Monday, sub-small craft conditions are forecast for the waters around Long Island for the Memorial Day Weekend. && .HYDROLOGY... 1.00" to 1.50" of rain is forecast from 06Z Thursday until 00Z Friday. Higher amounts are possible in any thunderstorms that develop on Thursday. Minor urban and small stream flooding is possible Thursday. Another round of rain is possible 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... The Wednesday evening high tide cycle has passed along the south shore. Water levels have receded below the minor coastal flooding benchmarks and additional coastal flooding is no longer expected. The coastal flood advisories and coastal flood statements for the south shore and into coastal; New Jersey for this evening have been discontinued. Local and brief minor coastal flooding is possible with tonight`s high tide along southwestern Connecticut and coastal Westchester county. A coastal flood statement remains. Astronomical tides are lower for the Thursday morning, however, a strengthening easterly flow late tonight into Thursday morning will bring the potential for localized brief and minor flooding with Thursday mornings high tide. The primary threat for widespread minor and potentially moderate coastal flooding still exists for the Thursday night high tide cycle. How quickly easterly winds begin to weaken Thursday night will be key to the potential for seeing widespread versus localized moderate coastal flooding along the southern bays of NYC and Western LI. Along Western LI Sound, NY/NJ Harbor including Manhattan, and the southern bays of Suffolk County, widespread minor coastal flooding is likely with less than 1/2 ft of surge needed in many places to reach minor flood thresholds. Minor flood thresholds could briefly be touched along the eastern bays of LI and SE CT. The potential for dune erosion looks to be low and localized during Thursday Night high tide. && .OKX WATCHES/WARNINGS/ADVISORIES...
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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. 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 Watch this evening for NYZ075-178-179. Coastal Flood Advisory from 7 PM this evening to 1 AM EDT Friday for NYZ072. NJ...Coastal Flood Advisory from 7 PM to 10 PM EDT this evening for NJZ006-106-108. MARINE...Small Craft Advisory from 6 AM this morning to 6 PM EDT this evening for ANZ330-335-338-340-345. Small Craft Advisory until 6 PM EDT this evening for ANZ350- 353-355.
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&& $$ SYNOPSIS...GC NEAR TERM...GC/MET SHORT TERM...GC LONG TERM...Maloit AVIATION...BC MARINE...GC/MET/NV HYDROLOGY...GC/Maloit TIDES/COASTAL FLOODING...

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