Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 182228 AFDOKX Area Forecast Discussion National Weather Service New York NY 628 PM EDT Fri Aug 18 2017 .SYNOPSIS... A cold front will move slowly east across the area late tonight, then stall just east of Long Island on Saturday. High pressure will follow Saturday night through Tuesday. A cold front will pass across the area Wednesday night followed by high pressure. && .NEAR TERM /THROUGH SATURDAY/...
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...SEVERE THUNDERSTORM WATCH IN EFFECT FOR PORTIONS OF NORTHEAST NJ...SOUTHEAST NY...NYC...WESTERN LONG ISLAND AND WESTERN CT THROUGH 9 PM... Damaging wind gusts are possible with any thunderstorm that develops through 9 pm as they approach from the west. In addition to the severe weather threat, the threat of flash flooding remains high due to a combination of earlier rainfall of up to 4 inches in some areas, anomalously high dew points and precipitable water values up to 2.2 inches. Rates of an inch to two inches an hour are being reported with the storms moving through this evening. A Flash Flood Watch remains in effect for NE NJ, the Metro NJ/NYC area, including Rockland, Westchester, and Nassau Counties in NY and Southern Fairfield County in CT until 11 pm this evening with the expectation that showers and thunderstorms will increase ahead of the cold front. Satellite imagery shows a SW/NE dry slot advecting NE across NE NJ. This will increase sfc based and low lvl instability resulting in the development of organized convection mainly aft 20z this afternoon from SW to NE. There is a moderate risk of rip currents at ocean beaches, potentially becoming high this evening.
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&& .SHORT TERM /SATURDAY NIGHT/... Leftover showers and TSTMs will end with the passage of the cold front between 06z and 12z overnight. With light winds forecast during this time, areas of fog will develop, possibly dense across Long Island and Southern CT. With a digging upstream trough approaching Saturday, the cold front may not make it too far off the Long Island coast. In fact, it`s possible that it might retrograde a bit until the passage of this trough Saturday night. Dryer air will advect east across the area Saturday night as high pressure advects east toward the area. && .LONG TERM /SUNDAY THROUGH FRIDAY/... A broad area of high pres will build in Sun and Mon. This will produce seasonable temps and mostly clear skies. A thermal ridge will build into the region Tue into Wed, producing a mini heat wave. Some spots, particularly across nern NJ, may hit the 2 day heat advy criteria. As subtropical moisture becomes entrained in the flow, an increase in high clouds can be expected by Wed. The cold frontal timing has slowed slightly from the previous 12Z model suite, so right now the timing is for the late aftn and eve. Although the best chance for tstms will be with the fropa Wed, there will be chances prior, albeit lower, due to the unstable airmass and onset of lowering heights. Because of the progged position of the front and tendency of the guidance to smooth out the temp gradient, highs were manually raised on Wed. A significant cool down then looks to follow for the end of the week. The models have been very consistent with this signal, although the exact magnitude of the cold airmass remains in question. It would not be totally surprising to see some lows in the furthest outlying areas touch the upr 40s next weekend. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... A cold front slowly approaches the region this evening but lags nearby until early Saturday. Showers and thunderstorms cross all the NYC terminals between 21z and 01z. What is left of the line will be east of KISP and KGON by 04-05z. Any storm may contain gusty winds and torrential rain. MVFR/IFR/lIFR ceilings are likely with the convection. Little or no improvement is expected overnight since overall conditions will remain saturated and fog and stratus are likely to continue or redevelop. VFR returns Saturday morning as drier air works into the region. Southerly winds this afternoon, mainly between 10 to 15 kts. Gusts to 25 kt possible along the coast. Higher gusts possible with any thunderstorm. Winds become west and eventually northwest early Saturday but remain light. 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: High confidence of showers and thunderstorms between 21-01z. Amendments likely for changing ceilings and visibilities. KLGA TAF Comments: High confidence of showers and thunderstorms between 21-01z. Amendments likely for changing ceilings and visibilities. KEWR TAF Comments: High confidence of showers and thunderstorms between 21-01z. Amendments likely for changing ceilings and visibilities. KTEB TAF Comments:High confidence of showers and thunderstorms between 21-01z. Amendments likely for changing ceilings and visibilities. KHPN TAF Comments: High confidence of showers and thunderstorms between 21-01z. Amendments likely for changing ceilings and visibilities. .OUTLOOK FOR 00Z SATURDAY THROUGH WEDNESDAY... .Saturday-Monday...VFR. light NW wind becoming SW by Late Sunday and Monday. .Tuesday...Isolated showers and thunderstorms possible with MVFR or lower conditions...otherwise VFR. Light southwest wind. .Wednesday...Scattered showers and thunderstorms with MVFR possible. Gusty southwest wind to 20 kt. && .MARINE... A Small Craft Advisory/SCA remains in effect across the Atlantic Ocean coastal waters through tonight as a cold front approaches. Heavy showers and TSTMs are likely. Areas of dense fog are possible until sunrise. Weather conditions improve with the passage of a cold front Saturday morning as winds and seas fall below SCA levels. Winds and seas will increase ahead of a cold frontal passage late Tuesday and Wednesday. Seas on the ocean may linger aoa 5 ft Wed ngt behind the front. Winds and seas thereafter are progged to remain blw sca lvls. && .HYDROLOGY... Another round of heavy showers and thunderstorms is likely with up to 2 to 4 inches of rain possible. A Flash Flood Watch was issued for NE NJ, the Metro NJ/NYC area, including Rockland, Westchester, and Nassau Counties in NY and Southern Fairfield County in CT until 11 pm. Impacts from potential showers and thunderstorms Tuesday into Wednesday are uncertain at this point. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...Flash Flood Watch until 11 PM EDT this evening for CTZ009. NY...Flash Flood Watch until 11 PM EDT this evening for NYZ069>075- 176>179. NJ...Flash Flood Watch until 11 PM EDT this evening for NJZ002-004- 006-103>108. MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ350-353- 355. && $$ SYNOPSIS...JMC/GC NEAR TERM...GC/MD SHORT TERM...GC LONG TERM...JMC AVIATION...IRD/24 MARINE...JMC/GC HYDROLOGY...JMC/GC

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