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Area Forecast Discussion
Issued by NWS Upton, NY
Issued by NWS Upton, NY
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753 FXUS61 KOKX 060439 AFDOKX Area Forecast Discussion National Weather Service New York NY 1239 AM EDT Sat Jul 6 2024 .SYNOPSIS... A trough of low pressure remains west of the area tonight. A cold front then approaches on Saturday, slowly moving through the area Saturday night. A cold front southeast of the region eventually dissipates and allows for high pressure to briefly build in for Sunday through Sunday night. Another frontal system approaches early next week with its associated cold front moving in towards midweek. This frontal boundary could very well linger nearby from mid to late week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Weakening showers and thunderstorms are beginning to exit to the east and will completely exit over the next hour or two. A prefrontal trough will remain stalled over the area this morning which most 00Z CAMs have picked up on. They attempt look to redevelop scattered showers with isolated chances for thunder across portions of the CWA, around daybreak. The best coverage will be areas north and west of the city, but have increased POPs across the CWA for early-to-mid morning with this update and lowered POPs for the afternoon/evening which appears like it may be a more isolated event. Anomalously high 2"+ PWATs this morning could lead to some moderate to heavy downpours, but any flash flood concerns should remain isolated. Patchy fog chances will continue through early/mid-morning. More discussion to follow in the 4AM update. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/... The trough over the Great Lakes continues to lift northeast into Ontario/Quebec Saturday into Saturday Night, with shortwave axis pivoting across W PA/NY Saturday Night. Heat advisory continues for NE NJ through Saturday for second day of heat indices of 95 to 100 F. Have expanded the Heat Advisory to include Western Passaic as well as Orange and Rockland in NY. There is slightly greater coverage of 95 F heat indices likely across the region on Saturday, but not enough confidence to expand heat advisory into NYC and the remainder of the the Lower Hudson Valley. Can not rule out parts of these areas reaching the criteria, however one concern will be the potential for additional cloud cover/shower activity which may limit temperatures a bit. Either way, expect a rather muggy day with dew points in the lower to middle 70s. The pre-frontal trough remains stalled over the area Saturday, with the potential for a few rounds of heavy downpours and thunderstorms ahead of and along it. Sat afternoon and evening appears to be the best chance for a few strong to severe thunderstorms, once again, mainly across NYC and points N&W. The main threat with any storms on Saturday and saturday night will be the potential for heavy rainfall. PWATS remain above 2"+ inches. Again one of the forecast challenges remains the differences between the NWP and CAMs which are varied in timing, location, intensity of convection. So at this point an isolated severe/flash flood threat exists on Saturday, mainly for NYC and points N&W. Any thunderstorm activity should weaken in intensity as it slowly moves eastward towards the coast Saturday evening and Saturday night However, there is still the potential for locally heavy downpours and embedded thunderstorms near the coast. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... After analysis of some large scale numerical weather prediction models with their MSLP, surface winds, and precipitation forecasts the following features are noted. The models analyzed were the NAM, GFS, ECMWF, and the Canadian, although for forecasts of Monday night onward, just the GFS, ECMWF and Canadian were compared. The models exhibit better agreement with high pressure over the area with mainly dry conditions Sunday through Sunday night. They have agreement with southerly flow across the region for early next week and more convective potential for Tuesday through Tuesday night. The models show cold front lingering nearby for Wednesday but vary more with rain from mid to late week. ECMWF particularly seems to be most aggressive with convection showing a continual cycle of shower and thunderstorm development along the front for mid to late week. Some relatively drier dewpoints Sunday behind a cold front will have some lower heat indices forecast within the region. Forecast highs mostly in upper 80s to lower 90s with max heat indices in the lower 90s with some mid 90s for parts of the region, mostly in NE NJ. More areas in mid 90s with max heat indices forecast for Monday with relatively higher dewpoints compared to previous day. Forecast highs are mostly in the 80s for Tuesday and the rest of the days of the forecast. Showers with mostly chance POPs return to the forecast Tuesday afternoon through the rest of the forecast. Forecast has chances of thunderstorms Tuesday afternoon through Wednesday night. Otherwise, thunderstorms have slight chance. Highest coverage and thunderstorm potential appear to be Tuesday afternoon into early Wednesday surrounding the cold front moving and how fast it makes its way through. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... A slow moving frontal system impacts the terminals through Saturday night. Most of the showers and storms have passed east of the Hudson River, mainly across southern CT. Additional showers are possible early Saturday morning, with potential of thunder. Have gone with VCSH for now due to lower confidence in timing and coverage. Showers/storms are also possible Saturday afternoon and evening. MVFR-IFR will continue to develop and overspread the terminals tonight. Ceilings may also lower to LIFR, especially across Lower Hudson Valley, southeast CT, and Long Island terminals. Some improvement is expected after 12z with VFR likely NYC terminals on NW, but conditions may remain IFR into early afternoon across Long Island and southeast CT. S-SE winds under 10 kt tonight and then increasing to 10-15 kt by Saturday afternoon. Winds begin to shift to the SW Saturday evening. NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... Additional showers possible late tonight into Saturday morning and a thunderstorm cannot be ruled out. Timing for flight category changes tonight through Saturday morning may be off by 1-2 hours. Timing of TSRA Saturday afternoon will likely be refined in subsequent forecasts. OUTLOOK FOR 00Z SATURDAY THROUGH WEDNESDAY... Saturday Night: MVFR or lower possible, especially Long Island and Southern CT. Continued chance of showers/tstms east of NYC metro. Sunday and Monday: VFR. Tuesday: Chance of MVFR in showers and thunderstorms in the afternoon, mainly west of NYC. Wednesday: Chance of MVFR in showers and thunderstorms. Detailed information, including hourly TAF wind component forecasts, can be found at: https:/www.weather.gov/zny/n90 && .MARINE... Small craft advisories remain in effect for the ocean tonight through Saturday night as a strengthening S flow increases to 15-20kt and seas build to 4 to 6 ft. Potential for occasional Great South Bay gusts to 25 kt as well. With a relatively weak pressure gradient in place, conditions on the waters are expected to remain below small craft advisory thresholds Sunday through the middle of next week. && .HYDROLOGY... Scattered showers and thunderstorms may produce locally heavy downpours and a continues threat for minor/poor drainage flooding this evening. Approaching shortwave and slow moving frontal boundary crossing tonight into Saturday night will bring potential for localized 1- 2"/hr rainfall rates with isolated to scattered thunderstorms. Localized flash flood threat exists for the area from any training convection during this timeframe, with the threat maximized across NYC/NJ metro and points N&W during peak heating Sat aft/eve. Model precipitable waters show an increase up to near 2.2 to 2.4 inches Tuesday into Tuesday night. With cold front moving in, there will be a marginal risk for excessive rainfall. There will be a chance for flooding with widespread minor flooding potential as well as a low percentage probability for localized flash flooding. Otherwise, no other widespread hydrologic issues are expected. && .TIDES/COASTAL FLOODING... High risk of rip currents until 9pm Saturday evening for all ocean beaches. Building onshore swell observed at ocean buoys around 4 ft with wave period of 6 to 10 seconds going into this evening. Ocean seas are expected to continue to build Saturday to near 5 ft and then slightly subside Sunday to near 4 ft. Onshore winds will be relatively higher Saturday along the ocean beaches with wind speeds of around 10 to 15 mph. The winds become more variable in direction and decrease in speed for Sunday. These factors will result in the high risk of rip currents remaining at all ocean beaches of NYC and Long Island through Saturday and into the first half of Saturday evening. There is a moderate risk of rip currents forecast for the ocean beaches on Sunday. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...Heat Advisory from noon today to 8 PM EDT this evening for NYZ067-069. High Risk for Rip Currents through this evening for NYZ075-080-081- 178-179. NJ...Heat Advisory from noon today to 8 PM EDT this evening for NJZ002. Heat Advisory until 8 PM EDT this evening for NJZ004-006- 103>108. MARINE...Small Craft Advisory until 2 PM EDT Sunday for ANZ350-353-355. && $$ SYNOPSIS...BC/JM NEAR TERM...BC/DBR/BR SHORT TERM...BC LONG TERM...JM AVIATION...DS MARINE...BC/JM HYDROLOGY...BC/JM TIDES/COASTAL FLOODING...