Area Forecast Discussion
Issued by NWS Upton, NY

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153 FXUS61 KOKX 220551 AFDOKX Area Forecast Discussion National Weather Service New York NY 151 AM EDT Wed May 22 2024 .SYNOPSIS... High pressure off the coast will be in control through Wednesday night. A cold front will approach on Thursday and weaken as it moves into the area Thursday night into early Friday. The front will eventually dissipate south of Long Island on Friday as weak high pressure returns from the north. Another low pressure system will approach from the west for Saturday. Its associated cold front will move across Saturday night. Weak high pressure will return for Sunday before more frontal systems potentially impact the area early next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... No meaningful adjustments or changes with this update as the forecast remains on track. Skies should remain partly cloudy to mostly clear into the overnight, except perhaps over parts of coastal CT and the forks of Long Island which could see some fog development late tonight. Confidence in this not very high as winds veer SW tonight. Just some cirrus from time to time attempting to streak across from the west. Low temps will range widely from east to west, from the lower 50s across the forks of Long Island and SE CT, to the mid/upper 50s most elsewhere, and lower/mid 60s for NYC and NE NJ. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/... The high will remain in place daytime Wed, with more widespread warmth as low level flow will be SW rather than S. Most areas north/west of NYC should see high temps in the mid/upper 80s, with 80-85 for most of NYC and interior CT, and 70s across Long Island and coastal CT. Most of the south shore of Long Island however may not make it any higher than the upper 60s. A pre-frontal trough and associated mid level shortwave trough approach late Wed night and may bring a few showers/tstms mainly to areas from the NYC metro area north/west. Lows Wed night will once again vary from east to west, with 55-60 for Long Island and S CT, lower 60s most elsewhere, and mid 60s for NE NJ. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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Key Points: * Very warm day Thursday upper 70s to near 90 for high temperatures. Lower 90s heat indices for parts of NYC, NE NJ, Lower Hudson Valley into SW CT. * Marginal strong to severe thunderstorm threat for Thursday into Thursday night. * Potential for some rounds of showers for the holiday weekend. Upper levels feature a SW to NE jet streak of which its right rear quad will be more in the central to northern New England Thursday into Thursday night. Relatively weak jet level winds are forecast over the area Friday into the weekend but another jet streak moving north of the area Sunday night. Then SW flow in jet levels early next week with a longer wavelength trough approaching the Eastern Seaboard towards the middle of next week. At the surface, a parent low fills in while moving farther northeast within Ontario Thursday. Its associated cold front will weaken as it approaches the local region. Before the arrival of the cold front, there will likely be a pre-frontal trough making for early day showers and thunderstorms north and west of NYC. Regarding the thunderstorms, some of them have the possibility of being strong to severe with hail and strong wind gusts for the entire forecast area. However, higher severe chances near NYC and locations to the north and west, including Western Long Island, NE NJ, Lower Hudson Valley and SW CT. From NCAR Ensemble Forecasts 00Z 5/20/24 initialization, highest CAPE Thursday across most interior places, towards Passaic NJ, Orange NY, Putnam NY, Rockland NY, Northern Westchester NY, Northern Fairfield CT (around 1500 J/kg). Convective inhibition is shown to the east. 0-6 km AGL bulk shear as shown by different forecast models getting to range of 30-40 kt, allowing for some organization of convection with strong downburst potential. Farther west locations are forecast to have more CAPE, driving the downburst potential with thunderstorms as well as greater vertical development for hail growth. Lots of uncertainty on timing and placement of showers and thunderstorms. Not much rainfall total, approximately 0.25 inch or less. CAPE is highest in the 2 to 8PM timeframe so would think this would be the window for much of the strong to severe thunderstorm potential. General timeframe between 2PM and 8PM from NW to SE for the thunderstorms to develop, grow and move southeast. The convective mode will probably be a broken squall line or a combination of convective clusters as well as a broken squall line. Parent low filling in Thursday within Ontario, decreasing pressure over time, resulting weakening of cold front moving through the area. Some models are indicating the front slows down and stalls out as well as dissipate within the region. The front is therefore becoming less well defined with time. May very well be a situation where Eastern Long Island and Southeast Connecticut do not receive any rainfall Thursday into Thursday night as the more maritime environment stabilizes the low levels enough for approaching showers and thunderstorms to breakup and weaken as they approach. Weak high pressure follows for Friday into Friday night. Some shower chances remain early for coastal sections, especially Long Island but drying conditions are expected going into the afternoon. Dry conditions continue until late Friday night. This is when another low pressure system will be approaching from the west. More rain showers are in the forecast and these are forecast as well for Saturday with possibly a few thunderstorms with daytime heating. Chances for showers continue Saturday night with an associated cold front moving across. Weak high pressure returns for Sunday into Sunday night with mainly dry conditions much of the time. Showers return to the forecast late Sunday night into early next week with another frontal system approaching. Temperatures gradually on a cooling trend over the course of the long term, staying above normal Thursday through Sunday but near to below normal for early next week.
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&& .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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Weak surface high pressure remains in control and just offshore through Wednesday. The high drifts offshore Wednesday evening as a surface trough approaches into late Wednesday night. VFR through Wednesday evening, with KGON possibly becoming IFR toward 06Z Thursday. Scattered showers are possible ahead of the trough late Wednesday evening into the overnight, for the NYC terminals and west. A rumble of thunder is possible, especially at KSWF. Light southerly flow continues overnight. South to southwest winds increase Wednesday morning into the afternoon with sea breezes likely mid to late afternoon. NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... No unscheduled amendments expected. Southerly winds will be enhanced by a developing sea breeze mid to late afternoon. The sea breeze is expected to reach KEWR and KTEB by late afternoon. OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY... Late Wednesday Night: VFR with IFR conditions developing mainly east of the NYC terminals. The chance of a few showers, with a thunderstorm possible, for western most terminals later at night. Thursday: VFR in the morning, then becoming MVFR with showers and thunderstorms likely during the afternoon. Friday: VFR. Saturday and Sunday: Generally VFR. A chance of showers with brief MVFR possible. Detailed information, including hourly TAF wind component forecasts, can be found at: https:/www.weather.gov/zny/n90
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&& .MARINE... Fog is possible overnight on the central/ern Sound, Peconic/Gardiners Bays, and the ocean waters E of Moriches Inlet. Ocean seas likely get close to 5 ft at times W of Fire Island Inlet on increasing S flow 15-20 kt toward the late day/early evening Wednesday in S-SW flow. Otherwise, sub SCA cond expected through the weekend. && .HYDROLOGY... No hydrologic impacts expected. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...BG/JM NEAR TERM...JE/BG SHORT TERM...BG LONG TERM...JM AVIATION...MET MARINE...BG/JM HYDROLOGY...BG/JM