Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 051140 AFDOKX Area Forecast Discussion National Weather Service New York NY 640 AM EST Mon Dec 5 2016 .SYNOPSIS... An upper level disturbance will pass through the Tri-State Region today. High pressure will build in on Tuesday. Low pressure developing off the Mid Atlantic coast Tuesday evening passes to the south of the region through Wednesday. A series of cold fronts will then move across the area Thursday into Friday. High pressure builds in for the first half of the weekend followed by a warm front passing to the north on Sunday. && .NEAR TERM /UNTIL NOON TODAY/... As of 5 am, in Connecticut, snow covered roads have been observed in Waterbury, and a spotter in New Canaan reported a half inch of snow which has changed over to rain. In New Jersey, a light coating on grassy surfaces was reported by a spotter in Ridgewood. The forecast was updated to keep the precipitation on Long Island all rain, and to speed up the end timing across all areas. Otherwise, the forecast was on track. A weakening 300 millibar jet stream will pass through the region this morning. At 00Z, the jet was at 160 kt over Illinois, however it is progged to only be in the 130s range when it reaches the forecast area. The radar composite indicates that precipitation will continue to overspread the region through sunrise. Snow across the north, trending towards rain as you move southward through the forecast area. It appears the heaviest precipitation will remain south of Long Island per the infrared satellite and radar depictions. This should keep snowfall accumulations at a minimum, as snowfall rates will make accumulations difficult under marginal thermal conditions. Special weather statements have been continued for this event. The back edge of the precipitation was moving along at about 42 kt per the radar, so if this momentum holds, the band of snow and rain will be gone by 10-13Z from west to east across the forecast area. A second round of more showery weather, such as what is happening over central Pennsylvania, is possible thereafter as the upper level trough moves through and lapse rates steepen above 600 millibars. Dry air pouring in a 700 millibars and downslope flow will be limiting factors for this activity. && .SHORT TERM /NOON TODAY THROUGH 6 PM TUESDAY/... High pressure builds in from the west this afternoon, and over the region late tonight into Tuesday morning. This will provide dry weather and clearing skies. By Tuesday afternoon, low pressure will be deepening near Cape Hatteras. It is possible that the northern fringe of the precipitation shield reaches the forecast area by dark. Low chances have been maintained in the forecast, although the timing has been slowed from the previous forecast based on the model consensus. A blend of the guidance, which was in good agreement, was used for temperatures through the period. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... A progressive upper flow across the Lower 48 will feature a southern branch short wave trough ejecting out ahead of an amplifying upper low over the upper Midwest and south central Canada at the onset of the period. This will allow for surface low pressure to pass off the Mid Atlantic coast Tuesday night into Wednesday, with a mainly rain event for the forecast area. The 00z GFS continues to be warmer aloft versus the ECMWF and NAM. A compromise of the two solutions results in some snow across far northern sections of the Lower Hudson Valley and interior SW Connecticut, with the potential for 1-2 inches. This will depend on how quickly the cold air erodes Tuesday night with high pressure retreating to the NE. Elsewhere, it will be a rain event with the up to half an inch possible. A building upper ridge along the west coast of North America Wednesday into Thursday will allow the upper trough/low to dig SE across the Great Lakes and into the Northeast states Thursday into Friday. This will result in a series of cold fronts passing through the area and an unseasonably cold airmass moving in for Friday and the weekend. This will also be accompanied by strong NW winds Friday into early Saturday. Outside of some snow flurries or sprinkles it will be primarily dry with scattered clouds, mainly north and west of NYC. Warm advection on Sunday ahead of low pressure moving into the Great Lakes may result in scatted rain/snow showers. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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A frontal system moves through during the morning, and is followed by high pressure late in the day. Conditions have lowered to MVFR across most of the terminals with some light light precipitation falling. Expect primarily rain except at KSWF where some light snow is falling. The snow at KSWF may mix with or change over to rain before ending. There is also a chance of IFR conditions between 12-14z. VFR returns during the afternoon and through the evening as skies clear. Winds will become Southwest everywhere by late morning and afternoon at around 10 kt as the system approaches and crosses the area. W/NW winds then prevail late in the day. A gust or two to 15 to 20 kt is possible briefly with the wind shift to the W. NW winds lighten during the evening. 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: Chance conditions could fall to IFR this morning, best chances between 12z-14z. An occasional higher gust is possible this afternoon. KLGA TAF Comments: Chance conditions could fall to IFR this morning, best chances between 12z-14z. An occasional higher gust is possible this afternoon. KEWR TAF Comments: Chance conditions could fall to IFR this morning, best chances between 12z-14z. An occasional higher gust is possible this afternoon. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: IFR conditions improve to MVFR around 13-15Z, then improve to VFR by 16z-18z. An occasional higher gust is possible this afternoon. KHPN TAF Comments: There remains a chance conditions remain MVFR this morning. An occasional higher gust is possible this afternoon. KISP TAF Comments: Chance conditions could fall to IFR this morning, best chances between 12z-15z. An occasional higher gust is possible this afternoon. .OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY... .Tuesday...VFR early, then MVFR possible with a chance of light rain or drizzle. .Tuesday night-Wednesday...IFR in drizzle and light rain. .Thursday...MVFR possible with a chance of rain. .Friday...VFR.
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&& .MARINE... Northwest flow will pick up this afternoon and evening behind a passing trough. A small craft advisory has been issued for the ocean and eastern Sound as a result. Elsewhere, winds are too marginal to issue an advisory at this time. Conditions improve lat tonight and Tuesday as high pressure builds over the waters. Low pressure passes to the south of the waters Tuesday night into Friday. Marginal SCA conditions are possible across the waters with east winds on the ocean waters approaching 20 kt with seas around 5 ft. Thursday into Thursday night another frontal system will move through the forecast waters with a strong cold passing through Thursday night. Strong and gusty northwest winds will develop behind the front with the potential for gale conditions Friday into saturday morning across all the forecast waters. && .HYDROLOGY... About a tenth of an inch of liquid is possible today. No hydrologic impacts are anticipated the next 7 days. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 4 PM this afternoon to 6 AM EST Tuesday for ANZ330-350-353-355. && $$ SYNOPSIS...JMC/DW NEAR TERM...JMC SHORT TERM...JMC LONG TERM...DW AVIATION...BC MARINE...JMC/DW HYDROLOGY...JMC/DW

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