Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 130824 AFDOKX Area Forecast Discussion National Weather Service New York NY 424 AM EDT Fri Oct 13 2017 .SYNOPSIS... High pressure remains centered over the Canadian Maritimes today before moving over the North Atlantic tonight. A weak surface trough will develop along the Middle Atlantic coast tonight into Saturday and may persist nearby into Sunday morning. A cold front will then approach from the west late Sunday, and move across Sunday night. High pressure will then gradually build in and be in control through mid week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... High pressure centered over the Canadian Maritimes today will bring a low level E to ESE flow across the area. Aloft, anomalous ridging continues to build as 500 mb heights reach near 588 dam which is 1.5 to 2 standard deviations above normal for this time of year. Clouds will be on the increase first across the southwestern portion of the area this morning and then spreading eastward through the day. The high promotes surface ridging and dry conditions today with no discernible sources for lift. High temperatures will be near seasonable levels in the lower 60s inland and middle 60s elsewhere. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Surface ridging will remain in place tonight with the core of the high moving further east over the North Atlantic tonight. Upper level ridge axis is also progged to remain over the region. As the high moves further east, an inverted surface trough will sharpen along the Middle Atlantic coast tonight. The first half of the night will likely be dry, but as the surface trough begins to shift northward towards day break, there could be some light rain. Have capped PoPs off at slight chance since moisture looks relatively shallow and lift is weak. Lows will range from the lower 50s inland to the upper 50s near the coast. There still is disagreement among the models and ensembles with the placement of the inverted trough feature on Saturday. It appears there is enough hints that the feature will persist nearby through the day. Lift continues to be meager although there could be subtle shortwaves in the southwest flow aloft as the ridge axis pushes offshore. Will show low chance PoPs for light rain for the western half of the area into the early afternoon with slight chance further east closest to the stronger ridging. Overall moisture is relatively shallow from around 10 kft and lower, so not expecting any widespread precipitation at this time. The better chance for breaks in the clouds looks to occur in the afternoon which should help boost temperatures close to 10 degrees above normal. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Models in fairly good agreement with strong southern upper ridging, becoming suppressed this weekend, as a longwave trough develops and traverses the CONUS; moving through the eastern US early next week. At the surface...general agreement exists on a weak frontal trough/wave developing off the mid-Atlantic coast...gradually lifting north into the region Saturday Night into Sunday morning as surface high pressure moves offshore. There appears to be little in the way of mid-level support, but with a tap of sub-tropical moisture advecting in on a 30 kt llj, scattered shower development is possible. This feature appears to move NE Sunday afternoon, with the region lying in an unseasonably warm and humid airmass ahead of an approaching frontal system front the west. Highs Sunday are expected to run well above seasonable...into the 70s across much of the region, with lower 80s across NYC/NJ metro. Vigorous shortwave energy entering the NW US this morning will eventually move into the Central US, and then lift through the Great Lakes into Quebec Sunday into Sunday Night. This will have an intensifying low pressure system taking a similar track, with its trailing cold front approaching the region late Sunday, before crossing Sunday Night. Appears most of the precip with this system is post-frontal as shortwave energy remains well NW and right rear jet dynamics lag behind and the strongest to the NW as well. Best chance of showers appears to be Sunday Night and for NW portions of the region. With the longwave trough axis still to the west and right rear jet forcing still moving into the region...cant rule out some showers lingering into Monday morning across eastern zones. As noted in previous forecast, cloud cover could be slow to decrease on Monday in this setup. A gusty caa NW flow and cloud cover should make for a chilly Monday...with high struggling into the upper 50s and lower 60s. Coolest shot of air so far for the fall season likely for Mon Night into Tuesday as longwave trough crosses and cold pool settles into the region. If winds can decouple across the interior...patchy frost development is possible as temps fall into the lower to mid 30s. Otherwise...highs on Tuesday likely struggle into the upper 50s to lower 60s once again. Thereafter...tranquil conditions and a moderating trend back to above normal temps looks likely for Wed/Thu as heights rise aloft and surface high pressure builds in from the SW. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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High pressure over New England builds south across the area overnight, and remains through Friday. VFR cigs will fluctuate with MVFR through 12z. There are likely to be some timing issues and the onset could be a few hours off from forecast. During the afternoon ceilings may briefly improve to VFR, around 3500 feet. NE winds through the TAF period, around 10 kts. Coastal terminals may see winds a few kts higher during the 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: Onset of MVFR cigs could be a few hours off from forecast. The afternoon KJFK haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KLGA TAF Comments: Onset of MVFR cigs could be a few hours off from forecast. The afternoon KLGA haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KEWR TAF Comments: Onset of MVFR cigs could be a few hours off from forecast. The afternoon KEWR haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KTEB TAF Comments: Onset of MVFR cigs could be a few hours off from forecast. KHPN TAF Comments: Onset of MVFR cigs could be a few hours off from forecast. .OUTLOOK FOR 06Z SATURDAY THROUGH TUESDAY... .Friday night-Saturday...MVFR conditions possible. Chance light rain and drizzle into Saturday. .Sunday...VFR, then chance of late day/evening showers with MVFR conditions mainly NW of the NYC metros. SW winds G25KT. .Monday...Chc early AM showers with MVFR, otherwise VFR. NW winds G20KT. .Tuesday...VFR.
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&& .MARINE... Gusts on the ocean continue around 25 kt early this morning, but will gradually weaken and should see gusts under 20 kt by this afternoon. Otherwise, winds on the waters will remain below SCA levels through Saturday night. Ocean seas should also subside through the day today, but should be at or just above 5 ft through tonight. Have therefore extended the SCA advisory through 10z Saturday. Wave Watch and NWPS still indicate ocean seas around 5 ft during the day Saturday, but have elected to hold off on extending the advisory that far out as its possible seas end up a foot lower. Marginal SCA seas are possible to continue on the ocean Sat Night into Sun with a 30 kt llj moving through the waters and se swells continuing to work in. Higher likelihood of SCA gusts and seas on the ocean looks to be in SW flow ahead of an approaching cold front Sunday afternoon, and then with NW flow in its wake Sun Night into Mon morning. A brief period of SCA gusts are possible on all waters...pre and post frontal as well. Another chance for SCA conds is possible Mon eve/night via a brief northerly reinforcing push of cooler air. && .HYDROLOGY... No hydrologic issues expected. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ350-353- 355. && $$ SYNOPSIS...DS/NV NEAR TERM...DS SHORT TERM...DS LONG TERM...NV AVIATION...CB MARINE...DS/NV HYDROLOGY...DS/NV

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