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Forecast Discussion for New York City/Upton, NY
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263 FXUS61 KOKX 312048 CCA AFDOKX Area Forecast Discussion...CORRECTED National Weather Service New York NY 448 PM EDT Fri Jul 31 2026 .WHAT HAS CHANGED... No significant changes. && .KEY MESSAGES... 1) Pop-up shower and thunderstorm potential through early evening. Mainly dry tonight but relatively warmer than previous night. 2) Airmass becomes warmer and more humid Saturday with low temperatures at night trending higher Saturday night compared to the previous night. Mainly dry conditions expected. 3) More rain potential next week with a heavy rain threat early in the week. && .DISCUSSION... .KEY MESSAGE 1... With a deep cold pool within an exiting trough, there is enough forcing combined with some low level instability to generate a few showers and thunderstorms. This is in accordance with the reflectivity forecasts for CAMs for the local area through early this evening. The surface high pressure across the area is weak in magnitude and without sufficient subsidence, we are seeing some convective activity as a result. Thereafter with diurnal cooling for tonight, instability will diminish and with even less vertical forcing, any remaining showers or thunderstorms will quickly dissipate. The wind flow will remain light and onshore near the coast. Min temperatures trend a little warmer than the previous night. Also, there will once again be some potential for patchy fog mainly outside of NYC, especially in the valleys and rural areas which will cool off more. .KEY MESSAGE 2... Weak high pressure shifts offshore into the Western Atlantic the first half of this weekend, eventually giving way to an approaching low pressure system. Aloft, a deepening trough will approach from the west along with the developing low pressure system at the surface. More southerly flow Saturday will lead to a warmer and more humid airmass. Whole area in the 80s for highs, with upper 80s for parts of NYC and northeast NJ as well as parts of Lower Hudson Valley. Temperatures will trend warmer for lows Saturday night compared to the previous night, mostly mid 60s to lower 70s. Mainly dry conditions are expected but there could be an isolated shower or thunderstorm Saturday into early Saturday evening with daytime instability and relatively colder air aloft moving in from the west with an approaching trough. The possible shower or thunderstorm would be mainly to the north and west of NYC. .KEY MESSAGE 3... The approaching low pressure system at the surface and deepening trough approaching in the upper levels will make for a more tropical airmass with the increase in depth of southerly flow Sunday through Monday night. The chances of rain start to increase more substantially late Sunday night into Monday. The heaviest of the rain from the forecast model guidance looks to occur Monday into Monday night. PWATs indicated in the forecast models reach up to near 2.2 to 2.4 inches. There is also a possibility of thunderstorms as well, which would easily result in torrential downpours. The parallel flow from lower to upper levels increases the training of convection, where multiple rounds of heavy rain move across the same area. The total amount of rain Sunday night through Monday night ranges from near a half inch to amounts between 1 and 2 inches. Some locally higher rainfall amounts will be possible exceeding 2 inches. There is still quite a bit of uncertainty with this but refined forecasts are expected to narrow down with possible shifts of this rainfall range in subsequent forecasts. In addition, while instability will be limited with all the clouds, there is forecast some bulk shear 30-40 kt 0-6 km AGL, so there is a marginal risk for severe thunderstorms as well for Monday into Monday evening. Main threat would be wet microbursts with damaging wind gusts. Rain will not be as widespread Tuesday into midweek but more models are indicating still the chance for showers and thunderstorms. A wetter trend to the forecast compared to yesterday. In addition, there is some model indication of tropical moisture possibly extending later into the week along with chances of showers and thunderstorms with higher PWATs. However, the long range ensemble forecast mean does indicate a decrease in the PWATs for midweek compared to early week. Aloft, the deep trough splits with northern trough shifting farther northeast of the area into midweek while a cutoff low remains to the west of the area. && .AVIATION /21Z FRIDAY THROUGH WEDNESDAY/... High pressure remains near the terminals through the TAF period. Mainly VFR. Can`t rule out a possible isolated shower this afternoon. The best chances will be at KGON and KSWF. In addition, some patchy fog will be possible tonight. Will include a TEMPO for some lower VSBYs at KGON, but confidence not high enough to include at the other terminals. Winds will remain rather light through the TAF period. Sea breezes have already developed and are moving across Long Island and southern CT. Expect the seabreeze to reach KLGA around 20z or 21z. Winds fall back below 5kt tonight and increase again on Saturday 5- 10kt from the south. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... Amendments may be needed for timing of any afternoon showers. .OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY... Saturday: Mainly VFR. Sunday: Mainly VFR, chance of a late day shower or tstm. Monday: Sub-VFR in showers and thunderstorms. Tuesday: Sub-VFR in showers and thunderstorms. Wednesday: Sub-VFR in showers and thunderstorms. Detailed information, including hourly TAF wind component forecasts, can be found at: https:/www.weather.gov/zny/n90 && .MARINE... Conditions on the waters remain mainly below SCA thresholds through Saturday night but there could be some areas on the waters between Sandy Hook NJ and Fire Island Inlet NY where wind gusts reach 25 kts Saturday afternoon into early Saturday evening. Marginal SCA potential for wind gusts on Sunday with higher chances of SCA conditions on the ocean early next week and possibly for some non-ocean marine zones also. Rip Currents: There remains a moderate risk for rip currents at local ocean beaches through this weekend. Winds will become more onshore with more southerly flow, around 10 mph to 15 mph mostly with onshore swells of around 3 ft of near 7 to 8 second period. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...Air Quality Alert from 11 AM to 11 PM EDT Saturday for CTZ009. NY...None. NJ...None. MARINE...None. && $$ DISCUSSION...JM AVIATION...BC MARINE...JM |
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NWS New York City/Upton, NY (OKX) Office Forecast Discussions.
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