Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 260905 AFDOKX Area Forecast Discussion National Weather Service New York NY 505 AM EDT Tue Sep 26 2017 .SYNOPSIS... High pressure slowly retreats to the east through Wednesday as Hurricane Maria tracks northeast off the Mid Atlantic Coast. Refer to statements form the National Hurricane Center for the latest on Maria. A cold front moves through the region Wednesday night, followed by brief high pressure building in from the west through late week. Another cold front passes through Friday night, followed by high pressure settling in through the weekend. This high then slides offshore on Monday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... The main story today is that long period swells from Hurricane Maria will produce high, dangerous surf and strong rip currents at Atlantic Beaches. With swells at 44025 progged to 7-8 ft at 15 seconds at 44025 and 9-10 ft at 15 seconds at 44017, expect to sea breaking waves up to 6 to 9 ft at western beaches and 7 to 10 ft at eastern beaches (and this might be a tad conservative, depending on the exact angle of incidence with the beach). As a result have extended the high surf advisory west to encompass NYC and Nassau County Atlantic Beaches (was just for Suffolk County Atlantic Beaches) and have continued with the high risk of rip currents for all Atlantic Beaches. Otherwise...the axis of a northern stream ridge builds over the region today, as the northwest extension of the sub-tropical ridge retreats to the east. The result should be sufficient subsidence to keep the region dry. This subsidence also will help keep moisture trapped beneath an inversion with a base from 975-925 hPa over the area. As a result expect low level stratus/fog to be slow to erode from W to E with some possibility that the twin forks of Long Island and maybe even coastal New London County never have the deck fully erode. The evolution of this stratus/fog deck will go a large way in determining highs for today. For now leaned towards cooler MET guidance over eastern areas and went more with a blend farther W, and leaned towards warmer MAV/ECS guidance over W portions of the lower Hudson Valley. Highs should range from 5-10 degrees above normal, but could end up quite a bit cooler,e specially over far E zones if the stratus deck does indeed maintain itself all day. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... Swells from Maria will continue to produce high, dangerous surf through Wednesday and quite likely dangerous rip currents as well, with swells progged to around 10 ft/14 seconds at 44025 and 10-11ft/14 seconds at 44017. As a result have extended the high surf advisory for all Atlantic Beaches through 22z Wednesday and have continued with the high rip current risk for tonight. Otherwise, the northern stream ridge axis exits to the northeast and WSW flow sets up aloft for Wednesday. There could be a weak 700 hPa shortwave passing Wednesday afternoon, so have a slight chance of showers then, otherwise it should be dry. The fog/stratus deck should return tonight, and likely will be more extensive than it was last night/early this morning. The main thing that is unknown is how dense the fog will be/will the area be more mainly just stratus. So for now playing things as patchy fog, but definitely cannot rule out areas of dense fog, especially over eastern areas. Lows tonight should be around 10-15 degrees above normal. This deck should be slower to erode on Wednesday than today. As a result, even with low level temperatures forecast to be a degree or so warmer than today, did not change high temperatures much from today. Once again, continue to have a bust potential on the low side (by 5-10 degrees) if the stratus deck does not erode at all. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... A cold front moves through the region Wednesday night. Meanwhile, moisture associated with Maria tries to sneak in mainly over the eastern zones. Will go with low chances of showers for most areas, but focused more to the east of the city. Aside from a lingering shower possible early in the morning in the vicinity of the twin forks, Thursday should be dry as high pressure builds in. Leaned towards the warmer side of guidance for high temperatures based on forecast 850-900mb temps during the afternoon. It will begin to feel less muggy as well with dewpoints falling to around 50 by the end of the day. A return to seasonable temperatures then follows for Friday as high pressure remains over the region. Global models differ in the timing of the next cold front, but best guess right now is that it moves through at some point during Friday night with a slight chance of showers. An upper trough/cold pool aloft follows for Saturday so some instability showers are possible. Kept PoPs at slight chance for this. Highs for Saturday mostly 65-70. High pressure continues to build in for Sunday and Monday with dry weather and high temperatures generally around 70. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... Weakening high pressure remains across the region through the TAF period. Flight categories primarily in the IFR/LIFR range with oscillating visibilities with KEWR, KTEB, AND KLGA right on the edge of this sharp contrast in visibilities . The low visibilities and ceilings will continue through 11-12z and then start to mix out from W to E due to heating and daytime mixing. KISP and KGON take a bit longer. The flow becomes onshore again and then decreases again into the evening. After light/vrb winds early this morning, NE/E winds 5-10 KT develop this morning and shift to the SE again mainly during the late morning/early afternoon. ...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: Timing of improving conditions may be off by up to 2 hours. The afternoon KJFK haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KLGA TAF Comments: Timing of improving conditions may be off by up to 2 hours. The afternoon KLGA haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KEWR TAF Comments: Timing of improving conditions may be off by up to 2 hours. The afternoon KEWR haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KTEB TAF Comments: Low confidence in how long visibilities remain down early this morning. Amendments possible/likely. KHPN TAF Comments: Low confidence in how long visibilities remain down early this morning. Amendments possible/likely. KISP TAF Comments: Timing of improving conditions may be off by up to 2 hours. .OUTLOOK FOR 00Z WEDNESDAY THROUGH SATURDAY... .Tuesday night-Wednesday...MVFR to IFR possible with patchy fog and/or stratus and a low chance of showers. .Wednesday night-Thursday...MVFR or lower possible with isolated to scattered shower activity. .Thursday night-Friday...VFR. .Friday night-Saturday...Mainly VFR, except MVFR possible in any showers. && .MARINE... A marine dense fog advisory continues through 14z today. This will be re-evaluated sing beach cams after the sunrises and based on the rate of erosion as well. There is some chance this may need to be extended, especially over E zones. Swells from Hurricane Maria will keep seas on the coastal ocean waters at well above Small Craft Advisory (SCA) levels through at least Wednesday night, so have extended the SCA for Hazardous seas through then. As far as winds go through Wednesday night, a light pressure gradient over the region will limit winds to around 10 kt or less through then. Lingering swell from Maria will likely allow seas to remain at SCA levels through late week before gradually subsiding this weekend as high pressure builds from the north. Gusts Thursday will be up to around 25 kt behind a cold front, but mainly on the ocean waters. Still a chance that a SCA could be needed on some of the other waters. Winds otherwise subside back below advisory criteria from Thursday night on. && .HYDROLOGY... No significant hydrologic impacts are expected over the next 7 days. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...High Rip Current Risk through late tonight for NYZ075-080-081- 178-179. High Surf Advisory until 6 PM EDT Wednesday for NYZ075-080-081- 178-179. NJ...None. MARINE...Dense Fog Advisory until 10 AM EDT this morning for ANZ330-335- 338-340-345-350-353-355. Small Craft Advisory for hazardous seas until 6 AM EDT Thursday for ANZ350-353-355. && $$ SYNOPSIS...JC/Maloit NEAR TERM...Maloit SHORT TERM...Maloit LONG TERM...JC AVIATION...JE MARINE...JC/Maloit HYDROLOGY...JC/Maloit

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