Area Forecast Discussion
Issued by NWS Upton, NY

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793 FXUS61 KOKX 242037 AFDOKX Area Forecast Discussion National Weather Service New York NY 437 PM EDT Mon Jul 24 2017 .SYNOPSIS... High pressure builds north of the area this evening, while another frontal wave passes just south of Long Island late tonight into Tuesday. High pressure then builds into the area Tuesday night into Wednesday before moving offshore Wednesday night ahead of a cold front to the west. The cold front will slowly approach the area through late week before passing to the east on Friday. Brief high pressure builds across the area again before a surface low passes to the south early next week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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Conditions have dried out across the area as low pressure passes to the south and east of southern New England early this evening. In its wake, high pressure builds across New England with Northerly winds. In fact, the north winds have drawn anomalously cool air into the region with most locations in the upper 50s to lower 60s, the exception being the western third of the area where some thinning of the overcast has allowed temperatures to rise to around 70. The airmass across the region remains stable with the N/NE flow. Convection firing up across eastern PA this afternoon is unlikely to make it this far east, but nevertheless is something that needs be watched if the cloud cover across western section erodes and allow airmass to destabilize further. An approaching upper trough over the Great Lakes tonight aids the development of a frontal wave near the Delmarva that passes just south of LI. Based on latest guidance, it appears the low will pass far enough south to spare the region anything more than showers, with the best chance for measurable rain across LI. Overnight lows will range from the mid 50s inland, to the lower 60s at the coast. This about 5 to 10 degrees below normal. There remains a high risk of rip currents at ocean beaches through Tuesday.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
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Low pressure passes to the south and east in the morning with lingering showers possible into the afternoon as the upper trough moves across the area. A continued N/NE flow will result in mostly cloudy conditions with temperatures in the 60s to lower 70s. This is well below normal by about 10-15 degrees. There could be some late day clearing with subsidence on the backside of the upper trough and high pressure building in from the west. High temperatures could be warmer than forecast across wester sections if this clearing happens earlier in the day. Another unseasonably cool night is on tap for Tuesday night with continued clearing. There remains a high risk of rip currents at ocean beaches through Tuesday.
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/... Initially zonal flow will give way to a blocking pattern as high pressure builds across the western US and the western Atlantic, placing the Northeast in an unsettled pattern dominated by multiple low pressure systems. Wednesday will be one of the quieter days in the extended as high pressure builds across the area, eventually moving offshore overnight. Given the prolonged period of northeasterly flow, there is a low chance of some morning clouds and drizzle, although lower dew points suggest anything ongoing will likely dissipate quickly. Temperatures will be a few degrees below normal. By Thursday, the area returns to a more southerly flow ahead of a slow moving cold front, with a chance of afternoon showers and thunderstorms, especially to the north and west of the NYC metro. High temperatures will still be a few degrees cooler than climatological normals, though there will be a marked increase in humidity amidst moist advection which in turn will lead to low temperatures closer to normal. By Thursday night into Friday, the front will slowly move through the area bringing the greatest possibility of showers and thunderstorms to the area before drying out as high pressure builds eastward on Saturday into early next week. There is a little bit more uncertainty towards the weekend depending on the placement of a coastal low, which is currently forecast to pass well to the south but subsequent forecasts will need to be monitored. && .AVIATION /21Z MONDAY THROUGH SATURDAY/... A frontal boundary will remain south of the area through Tuesday. The rain is mostly over. There however will be another chance of showers this evening into late at night, but should mostly pass south of the terminals. Otherwise mainly MVFR conditions are expected. MVFR this evening will prevail before lowering to IFR heading into daybreak Tuesday after which conditions are expected to return to MVFR by late morning. NE winds near 10-15 kt gusting 20-25 kt are backing to a more northerly flow but will return to a NE flow tonight and closer to 10 kt for sustained winds. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component fcsts, can be found at http:/www.weather.gov/zny/n90 KJFK TAF Comments: Amendments possible in 00-08Z timeframe to include SHRA in TAFs. Possible brief reductions in vsby to MVFR/IFR during that timeframe. KLGA TAF Comments: Amendments possible in 00-08Z timeframe to include SHRA in TAFs. Possible brief reductions in vsby to MVFR/IFR during that timeframe. KEWR TAF Comments: Amendments possible in 00-08Z timeframe to include SHRA in TAFs. Possible brief reductions in vsby to MVFR/IFR during that timeframe. KTEB TAF Comments: Amendments possible in 00-08Z timeframe to include SHRA in TAFs. Possible brief reductions in vsby to MVFR/IFR during that timeframe. KHPN TAF Comments: Amendments possible in 00-08Z timeframe to include SHRA in TAFs. Possible brief reductions in vsby to MVFR/IFR during that timeframe. KISP TAF Comments: Amendments possible in 00-08Z timeframe to include SHRA in TAFs. Possible brief reductions in vsby to MVFR/IFR during that timeframe. .OUTLOOK FOR 18Z TUESDAY THROUGH SATURDAY... .Tuesday...VFR. NE winds 10-15 kt. .Tuesday night...Patchy fog with MVFR vsby possible late at KSWF, KHPN, otherwise VFR. .Wednesday and Wednesday night...VFR. .Thursday...Chance of showers and possibly a tstm with MVFR or lower conds NW of the NYC metros in the afternoon, otherwise VFR. .Thursday night-Friday night...MVFR or lower conditions possible, with chance of showers/tstms. .Saturday...Mainly VFR. && .MARINE... E/NE winds will gradually ramp down over the next few hours as low pressure passes to the south and east. Another wave of low pressure then passes off the Delmarva late tonight into Tuesday. This will keep a NE flow over the waters with seas slow to come down. SCA conditions are likely to linger on the ocean through at least Tuesday, primarily for seas. Easterly flow continues into Wednesday before gradually diminishing as high pressure builds across the area. Southerly flow will briefly allow seas to build ahead of a cold front that will pass through the area Thursday night into Friday, though seas should remain below SCA levels. High pressure builds again through early next week which will keep winds and seas low. && .HYDROLOGY... Light rainfall overnight, mainly along the coast, is not forecast to pose any hydrologic issues. Additional rainfall is possible Thursday through Friday night. Hydrologic impacts are not expected at this time. && .TIDES/COASTAL FLOODING... With the new moon that occurred early yesterday morning and the current easterly flow, tides are running astronomically high. Tidal departures of 1/2 to 1 ft departures are needed tonight. A coastal flood advisory has been issued for the south shore back bays of Nassau and Queens for tonight with statements across the NY Harbor and Western LI Sound for more localized flooding. Thereafter, any minor coastal flooding is forecast to be localized into Tuesday. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...High Rip Current Risk through Tuesday evening for NYZ075-080- 081-178-179. Coastal Flood Advisory from 9 PM to 11 PM EDT this evening for NYZ178-179. NJ...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ330- 335-340. Small Craft Advisory until 6 PM EDT Tuesday for ANZ350-353-355.
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&& $$ SYNOPSIS...MD/DW NEAR TERM...DW SHORT TERM...DW LONG TERM...MD AVIATION...JM MARINE...MD/DW HYDROLOGY...MD/DW TIDES/COASTAL FLOODING...

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