Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 200237 AFDOKX Area Forecast Discussion National Weather Service New York NY 1037 PM EDT Fri Oct 19 2018 .SYNOPSIS... High pressure along the mid Atlantic and southeastern coast will drift into the western Atlantic tonight as low pressure moves through eastern Canada and a cold front approaches from the northwest. The cold front will move across the region late Saturday into Saturday evening. Strong high pressure builds west of the region for the second half of the weekend, building into the local area Sunday night into Monday. This high will shift off the Mid Atlantic coast on Monday followed by a weak clipper like system tracking through New England on Tuesday. High pressure then returns for mid week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Forecast is on track with only minor changes made for this update to reflect current conditions. Light returns on the radar continue to move into western portions of the CWA, though returns are slightly stronger than seen in previous update. Temperature/dewpoint spread has decreased somewhat as the lower layers moisten. Despite this, there will continue to be more in the way of virga as there is a large dry layer at and above about 1 km as seen on the 00Z sounding. Western sections will have seen some of this eroded somewhat, but returns are dissipating as they move into the CWA; evidence that the dry layer still exists in those areas. The forecast remains consistent with the previous forecast and current model guidance. As such, precipitation is expected to develop later this evening as the upper ridge moves into the western Atlantic and one shortwave rotates through the eastern longwave trough. Increased probabilities to likely for the overnight with increased confidence and model consistency. This will be associated with a second shortwave rotating through the upper longwave trough and associated cold frontal boundary. With the front isentropic lift will be increasing. A mild airmass remains in place ahead of the cold front and temperatures are expected to remain mild and not drop off too quickly. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... The amplifying eastern trough and strong western ridge will keep the progression of the front slow, and the chances of precipitation will remain through Saturday and into Saturday evening. The low level forcing and isentropic lift with the cold front will be decreasing Saturday and lowered probabilities to low chance and slight chance. However, the upper shortwave remain rather strong and with the amplifying upper trough these chances may need to be increased. For now, the precipitation looks to be over around or just after 06Z Sunday, with the surface cold front east to the forecast area. Strong cold advection Saturday night will send temperatures to below seasonal levels once again. && .LONG TERM /SUNDAY THROUGH FRIDAY/... High pressure builds into the region on Sunday with dry and breezy conditions as the pressure gradient over the area remains fairly tight. Although downsloping winds should offset some of the cold air advection, high temperatures are still forecast to fall short of normal highs by about 10 degrees. Winds subside Sunday night as the ridge axis of high pressure shifts in. This will allow temperatures to fall below freezing for many inland locations and Pine Barrens Region, with mid and upper 30s for coastal sections. The high moves offshore on Monday with a slightly moderating airmass over the region. High temperatures will still be below normals however. A warm front approaches Monday night, followed by a cold front during Tuesday. These are associated with a low pressure system moving through New England. Models haven`t really trended wetter for this time period, so will continue with a dry forecast for now. The warm advection prior to the cold front will at least allow for highs to reach near-normal levels on Tuesday. High pressure builds in behind this system, with dry weather for Wednesday and Thursday. A return to below-normal temperatures both days with Wednesday possibly being on the breezy side. Models show high pressure holding on long enough to go with a dry forecast for Friday as well. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... Strong low pressure will move across southeast Canada through Saturday with its attending cold front approaching from the west. This front is forecast to move across area terminals Saturday afternoon, followed by a reinforcing cold front Saturday evening. Gusts in SW flow continue to be occasional/isolated this eve, and am now thinking that frequent gusts may hold off at most locations until the 07-10z time frame. Once they do develop, expect gusts 15-25kt, highest at along the CT coast and on LI, and persisting through the daylight hours Sat. Winds shift to the W 14-18z and then NW aft 00z Sun from NW to SE. Moisture streaming in well ahead of the front should lead to a period of light showers and MVFR conditions from about 11Z-14Z at the NYC metros. It is possible the onset could be an hour or two sooner than that. .OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY... .Saturday night...VFR. A few showers are possible. NW winds 10-15G20KT. .Sunday...VFR. NW winds 15-20G20-30KT. .Sunday night...VFR. NW winds 10-15G20KT in the evening. .Monday...VFR. .Tuesday...VFR. WSW winds G15-20KT. .Wednesday...VFR. NW winds G15-20KT. && .MARINE... Low level winds were slow to increase, and mix to the water. However, SCA conditions will be developing by early this evening, with gale conditions on the ocean waters as mixing in the southwest flow and low level winds do increase. Gale conditions are still expected into Saturday morning when winds will begin to diminish, and then SCA level winds will remain through Saturday, and into Saturday night. The gale warning on the ocean, and the SCA on the remainder of the waters remains in effect. On the non ocean waters SCA wind gusts may linger into Saturday night. SCA conditions expected on Sunday with a gusty NW flow, and there will be chance of a few gale force gusts over the ocean waters. Winds and seas then subside Sunday night with all waters likely below advisory criteria by daybreak on Monday. A high pressure ridge will then bring a period of relatively tranquil conditions over the waters for Monday and Monday night. Low pressure then moves through New England on Tuesday with a tightening pressure gradient over here. This brings a good chance of SCA conds over the ocean as well as the eastern Sound and bays. && .HYDROLOGY... No hydrologic issues are expected through the middle of next week. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO35 (162.55 MHz) remains off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 PM EDT Saturday for ANZ330-335- 338-340-345. Gale Warning until 11 AM EDT Saturday for ANZ350-353-355. && $$

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