Area Forecast Discussion
Issued by NWS Upton, NY

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265 FXUS61 KOKX 121959 AFDOKX Area Forecast Discussion National Weather Service New York NY 359 PM EDT Wed Jun 12 2024 .SYNOPSIS...
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Weak high pressure over the area tonight will shift offshore Thursday into Thursday night. A cold front approaches from the west on Friday, moving through Friday night. High pressure then builds in from the Great Lakes this weekend, before sliding offshore early next week.
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&& .NEAR TERM /UNTIL 7 AM THURSDAY MORNING/...
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Weak high pressure resides over the region through tonight. Sea breeze circulation will weaken this evening. Winds overall will become lighter tonight. Not much in terms of cloud coverage is expected. This will set up more efficient radiational cooling within the valley and rural sections. Made these locations slightly cooler than previously forecast. Lows forecast range from the low to mid 50s in these valleys and outlying areas to more in the upper 50s to mid 60s range for most locations elsewhere. Some patchy fog particularly within valleys and some rural locations can be expected due to radiational cooling late tonight towards early Thursday morning.
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&& .SHORT TERM /7 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
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The high pressure moves out into the Atlantic Thursday. The synoptic pattern will favor the development of the Ambrose Jet with southerly winds for SW Long Island increasing to around 15 kt with otherwise a southerly wind near 10 kt elsewhere within the forecast region during the afternoon. It is expected to be a mostly sunny day with high temperatures getting well into the 80s for a majority of the region. Winds weaken with a weakening pressure gradient Thursday night. Again not much in the way of cloud coverage is expected. Lows will only be within the 60s with a warmer airmass moving into the area. Not as much low level saturation is expected so did not mention any fog in the forecast.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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**Key Points** * Showers and thunderstorms are expected to move through the region Friday afternoon and evening, with some potentially strong to severe and capable of producing damaging winds and large hail. * Heat builds early to mid next week and heat indices could exceed 100F at times, especially north and west of NYC. An active start to the period with lowering heights as a trough digs south out of Canada, and a shortwave swings east into the local area on Friday. An associated cold front will advance toward the region with it, passing through and offshore Friday night. Ahead of the front, showers and thunderstorms are expected to develop in a warm, moist air mass. Surface temperatures into the 80s during the afternoon and dew pts in the mid to upper 60s should aid the convective development, and BUFKIT soundings indicate CAPE increasing across the interior to over 1000 J/kg by early afternoon. SPC has areas north and west of NYC outlined in a slight risk, indicative of the potential for scattered severe thunderstorms. CSU`s machine learning output is in agreement with this assessment. Timing of this threat looks to span from afternoon into the early evening hours, earliest across the Lower Hudson Valley, and latest along SE CT and eastern LI as the line advances south and east. In addition to a threat for damaging winds and large hail with these storms, increasing moisture will bring the risk of heavy downpours with any storms. PWATs ahead of the front climb to as high as 2 inches, and with a warm cloud layer well above 10 kft, efficient rain processes could aid in torrential downpour development. While total QPF averages around a half an inch across the region with this forecast, localized amounts could exceed an inch or two in a relatively quick period of time, so rates will be key to any flood threat. Fortunately, the speed of the system should preclude more widespread hydro concerns, with the most likely solution being more typical nuisance urban and poor drainage flooding. Isolated instances of flash flooding can not be ruled out though, but areal extent of this appears low at this time. The front advances offshore into early Saturday and high pressure builds in from the NW during the weekend with dry conditions and more comfortable dewpoints. High temperatures will be pretty close or just above normal on Saturday and Sunday. Ridging develops across the East late this weekend and early next week, likely bringing the most prolonged heat spell of the year thus far. Global ensemble means peg H85 temperatures around 20C mid next week. Coupled with dew points well into the 60s, heat indices could approach or exceed 100F at times mid next week, especially north and west of NYC. This could eventually necessitate the first heat headlines of the season and the threat will need to be monitored. Generally stayed close to the national blend with only subtle adjustments for this update.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
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High pressure in control through Thursday with a weak surface trough lingering this evening. VFR. Generally light flow which may be variable into the evening. Coastal sea breeze is moving slowly inland through this evening. Winds will become more SW/S with its passage. Light and variable to light SW flow overnight once again strengthening out of the SW Thursday morning 10-15kt. Some gusts Thursday afternoon may be 20-25 kt, especially along the coast. NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... Timing of sea breeze passage may vary by a couple of hours. OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY... Thursday afternoon: VFR. SW gusts 20-25 kt. Friday: Mainly VFR. MVFR or lower possible in TSRA in the afternoon and evening. Saturday-Monday: VFR. Detailed information, including hourly TAF wind component forecasts, can be found at: https:/www.weather.gov/zny/n90
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&& .MARINE...
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Conditions are expected to remain below SCA thresholds on the forecast waters through Thursday night with a relatively weak pressure gradient in place. Latest Wavewatch guidance appeared to be running slightly higher compared to current ocean buoy obs so wave forecast used a blend of latest Wavewatch and the previous forecast. Southerly winds may occasionally gust toward 25 kt on the ocean Friday and seas could approach 5 ft. These conditions improve by Saturday, and sub SCA conditions are then expected on all waters thru early next week.
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&& .HYDROLOGY...
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Showers and thunderstorms Friday afternoon and early evening could produce heavy downpours that lead to brief minor flooding. A general half inch of rainfall is expected across the region, but localized amounts could exceed 1 to 2 inches in areas that see longer duration thunderstorms. Impacts will most likely be limited to minor urban and poor drainage flooding due to the quick movement of this system, but isolated flash flood instances can not be ruled out.
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&& .TIDES/COASTAL FLOODING... There remains a low risk of rip currents at the ocean beaches today, with a moderate risk by Thursday afternoon for all ocean beaches. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JM/DR NEAR TERM...JM SHORT TERM...JM LONG TERM...DR AVIATION...MW MARINE...JM/DR HYDROLOGY...JM/DR TIDES/COASTAL FLOODING...