Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 250820 AFDOKX Area Forecast Discussion National Weather Service New York NY 420 AM EDT Mon Sep 25 2017 .SYNOPSIS... High pressure prevails through Tuesday then slowly retreats to the east Tuesday night and Wednesday as Hurricane Maria moves northeast off the Mid-Atlantic Coast. Refer to the latest National Hurricane Center advisories for the official forecast of Maria. A cold front crosses the Tri-State Wednesday night, followed by high pressure building in from the west through Thursday night. Another cold front approaches from the west Friday, then crosses the area Friday night, followed by Canadian High pressure building in for the upcoming weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... High pressure over the region will result in a sunny day with above normal temperatures. Some low stratus may however roll in late in the day right along the coast. 850 mb temperatures are forecast to be around 17C, so highs away from the sea breeze will be well into the 80s with perhaps a few spots reaching 90. Even the coolest spots should be able to reach at least into the upper 70s in spite of a sea breeze. Highs will likely fall short of records, however. See the climate section below for more details. There is a high rip current risk at the ocean beaches through this evening due to southerly swells from Hurricane Maria. Will also keep up the high surf advisory for the south shores of Suffolk County today into this evening, although it looks like widespread surf heights might not reach 7 feet across the area. Not enough confidence to drop the advisory altogether. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Looks like low stratus and fog will push in from the ocean as tonight progresses. Models suggest just enough turbulent mixing to preclude widespread dense fog, but there is a chance that a few spots end up with dense fog before the night is through. Clouds will help keep low temperatures above normal. The tricky part of the forecast for Tuesday comes from the uncertainty of the magnitude of stratus and fog that happens tonight. Models at least appear to be in agreement that there will be less lower level moisture during the afternoon hours. Inland areas will have a better chance of seeing lower clouds break up sooner in the day, but there could still be a pretty good deal of cirrus from Hurricane Maria. Temperatures aloft will still be quite warm under high pressure, so in spite of the cloud cover, expecting high temperatures to be above normal once again. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... The axis of a northern stream shortwave ridge passes to the north Tuesday night, with associated subsidence keeping things dry. Lows Tuesday night should be around 10-15 degrees above normal. A northern stream trough passing to the N Wednesday and Wednesday night, should help create a sufficient weakness in the ridge to the east of Hurricane Maria, to allow the storm to track well SE of Long Island. There could be some isolated to scattered showers due to a combination of some moisture from Maria and the passing shortwave. The associated cold fronts passage late Wednesday night could provide enough lift for a rumble of thunder or two as well. Highs Wednesday should be around 10 degrees above normal and lows Wednesday night around 15 degrees above normal. WSW-SW flow aloft settles over the area Thursday-Friday, helping to continue to push Maria well offshore. Do have slight chance pops Thursday and Thursday night (diminishing from W to E) as there is some question on exactly how fast the surface cold front exits to the east, and whether it could become anafrontal. Friday should be dry, with the cold front expected to be well to the east and no significant shortwave progged to move over the area. A positively tilted trough approaches Friday night, then crosses the area Saturday. This warrants slight chance pops, initially over W zones late Friday night, then over the entire area by Saturday afternoon. If confidence increases in the amount of low level moisture available for the system to work with, pops could end up needing to be raised to chance on Saturday. Deep layered northern stream ridging then builds in behind the departing trough. There is some question how fast it begins to build in (As soon as Saturday night or waiting until Sunday) for now went with a blended timing based on the ECMWF/GFS/CMC. It should be dry regardless of the timing of the ridge. Temperatures Thursday-Sunday start out above normal Thursday, should be near normal Friday, then below normal Saturday and Sunday. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... High pressure remains across the region through the TAF period. Expect similar conditions as last night, although fog may be a bit more widespread outside of NYC terminals. MVFR, to a few locally IFR vsbys develop through 10z or so. Stratus may also develop for a couple of hours at KGON late. VFR returns 12z to 14z and will remain for all terminals during the day Monday. Stratus and fog likely to return tonight into early Tue morning and is expected to be even more widespread, however timing is uncertain and could be several hours off from current forecast. Light and vrb winds into the morning then increase to 5-10 kt out of the E-SE during the aftn/early eve and then become light/vrb again tonight into early Tue morning. .OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY... .Monday night-Tuesday...MVFR or lower conditions possible with areas of fog and/or stratus outside city terminals. .Tuesday night-Wednesday...MVFR or lower conditions 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...Mainly VFR. && .MARINE... Long period swells will keep ocean seas at advisory levels for at least Friday. As per local policy limiting a SCA to a maximum of 4 periods in duration and collaboration with the surrounding offices, will extend the SCA on the ocean through Tuesday night for now. The advisory will likely need to be extended further in time. A light pressure gradient over the region will limit winds over the waters to around 10 kt or less through Thursday. The pressure gradient tightens Thursday night and remains so on Friday with winds up to around 15 to 20 kt. There is also a chance for gusts to 25-30 kt, mainly on the coastal ocean waters. The pressure gradient then relaxes later Friday, with winds probably returning to being at most around 10 kt by Friday evening. && .HYDROLOGY... Dry weather is expected through Tuesday. Any rainfall Tuesday night through Sunday should total less than 1/2 inch, so no significant hydrologic impacts are anticipated during this time frame. && .CLIMATE... The following are the record high temperatures for Monday September 25, 2017 along with the forecast high temperatures: Record High Temperature Forecast High Temperature ----------------------------- ------------------------- Central Park........90 (1970) 88 LaGuardia...........90 (2010) 87 Kennedy.............87 (2010) 81 Islip...............87 (2010) 82 Newark..............91 (1970) 88 Bridgeport..........85 (1970) 82 && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...High Rip Current Risk through this evening for NYZ075-080-081- 178-179. High Surf Advisory until 9 PM EDT this evening for NYZ080-081. NJ...None. MARINE...Small Craft Advisory for hazardous seas until 6 AM EDT Wednesday for ANZ350-353-355. && $$ SYNOPSIS...JC/Maloit NEAR TERM...JC SHORT TERM...JC LONG TERM...Maloit AVIATION...JE MARINE...JC/Maloit HYDROLOGY...JC/Maloit CLIMATE...JC

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