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Area Forecast Discussion
Issued by NWS Upton, NY
Issued by NWS Upton, NY
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119 FXUS61 KOKX 151141 AFDOKX Area Forecast Discussion National Weather Service New York NY 741 AM EDT Thu Aug 15 2024 .SYNOPSIS... A weak disturbance moves through today with high pressure otherwise in place through Friday night. A warm front then approaches from the west Saturday into Saturday night. The associated frontal system continues to approach Sunday, with an attendant cold front moving through late Monday or early Tuesday. High pressure then returns into mid next week. && .NEAR TERM /THROUGH TONIGHT/... The forecast is mainly on track. Only hourly temperatures and dewpoints for the next few hours were adjusted with this update to better fit the latest trends. 500mb low remains spinning over the Canadian Maritimes today. This will promote a cyclonic flow aloft over the forecast area and help steepen mid-level lapse rates. Shortwave lift pivots through the region as well - stronger over the eastern zones. Expecting scattered showers and thunderstorm with this setup. Similar to yesterday, additional convection could spring up along outflow boundaries, and strong gusts may occur with a dry sub-cloud layer. Csn`t even rule out at least small hail over the CT zones given stronger shear plus the amount of CAPE in the hail growth zone with favorable wet-bulb zero heights. The day otherwise starts with sunshine filtered through some cirrus clouds before cumulus/convective debris increase during the afternoon. Highs in the middle and upper 80s for most spots. Any lingering convection diminishes this evening with the loss of daytime heating, followed by dry conditions overnight. NBM looked good for low temperatures. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Upper low over the Canadian Maritimes drifts east, allowing for deep- layered ridging over us and dry weather. Highs generally 85-90, and getting a little more muggy. A warm front associated with low pressure moving through the Great Lakes then slowly approaches Friday night through Saturday night. Overrunning moisture ahead of the front brings us a chance of showers starting on Saturday. Showers then become more likely Saturday night as the front nears. Western zones will have higher chances being closer to the lift associated with the warm front. Higher elevated instability will reside there too, so kept in a slight chance of thunderstorms as well. NBM was used for temperatures. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... An upper trough sits over the Eastern US to start the period, with a frontal system attempting to work through the region. Meanwhile, Hurricane Ernesto will be making it`s closest approach to the region on Sunday, though still passing hundreds of miles offshore as it treks into the North Atlantic. Local impacts will be limited to elevated surf and dangerous rip currents along area beaches early next week, and additional information on this threat can be found in the tides and coastal flooding section farther down. Please refer to the NHC for official forecast information on Ernesto. A couple rounds of shower and thunderstorm activity moves through with the frontal system, the first late Sunday into Sunday evening, and another ahead of a trailing cold front late Monday into early Tuesday. Parameters don`t appear too threatening in terms of widespread severe weather, relatively low instability and shear, though locally heavy downpours are possible and could lead to nuisance flooding. The system looks to finally exit offshore Tuesday, and drier conditions advect down into mid next week as heights rise and weak surface high pressure builds in from the Midwest. Capped PoPs at 60% with the frontal system, but largely followed the national blend for this update. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... Weak high pressure generally remains in control through the TAF period. VFR forecast. Mainly a light N/NW flow this morning, and a similar flow persists today, though sea breezes turn coastal terminals southerly or southwesterly by late afternoon, before becoming light and vrb tonight with high pressure settling overhead. Flow becomes southerly Friday afternoon as the high shifts offshore. Speeds remain at or under 10 kt. A few scattered showers or thunderstorms are possible this afternoon and early evening, generally between 18Z and 00Z, with the best chance of seeing this at inland and CT terminals, KSWF, KHPN, KBDR, and KGON. Brief category declines possible with any heavier shower or a thunderstorm. Though this is also possible at NYC and LI terminals, coverage is expected to be more isolated closer to the coast and have left out of TAF at this time. Any activity dissipates in the early evening, and skies clear overnight into Friday morning. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... AMD possible late this morning and afternoon for timing of sea breeze. Low potential for showers and thunderstorms this afternoon. OUTLOOK FOR 12Z Friday THROUGH MONDAY... Friday: VFR. Saturday and Sunday: Showers likely with chance of tstms, especially in the afternoon/early evening, and especially from the NYC metros north and west. MVFR or lower conditions possible. Monday: Mainly VFR. MVFR or lower possible in any SHRA/TSRA in the afternoon. Detailed information, including hourly TAF wind component forecasts, can be found at: https:/www.weather.gov/zny/n90 && .MARINE... High pressure provides a weak pressure gradient and a light wind regime overall through Friday with sub-SCA levels. However, the combination of southerly winds with an approaching frontal system and increasing long period S to SE swells from Hurricane Ernesto during Friday night into Saturday will build ocean seas to 5 to 6 feet Saturday, and 6 to 7 feet Sunday. Seas peak Sunday and subside Monday into Monday night. A small craft advisory will likely be needed on the ocean waters for Friday night through Monday night. Please refer to the NHC for official forecasts of Hurricane Ernesto. && .HYDROLOGY... No impacts expected with today`s isolated to scattered shower/thunderstorm activity. The next chance of rain will then be on Saturday, with better chances Saturday night. Anticipated rainfall during this period is only up to around a quarter inch, thus no impacts are expected for now, but there`s still a chance for models to trend with higher rain amounts and introduce the possibility of minor nuisance/poor drainage flooding. Showers and thunderstorms Sunday and Monday could produce locally heavy downpours that lead to nuisance flooding of urban and poor drainage areas. At this time, the risk for flash flooding is low. && .TIDES/COASTAL FLOODING... The rip current risk starts out as low this morning, but will be increasing to moderate this afternoon, then continue to increase into Friday, reaching a high risk Friday afternoon and likely remaining that way through the upcoming weekend. The increasing rip current risk is due to increasing incoming SE to S long period swells from Hurricane Ernesto. Please refer to NHC for official forecasts regarding Hurricane Ernesto. Minor coastal flooding may be possible early next week during high tide cycles Sunday through Tuesday as swells build and astronomical tides increase due to the full moon on Monday. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JC/DR NEAR TERM...JC SHORT TERM...JC LONG TERM...DR AVIATION...DR MARINE...JC/DR HYDROLOGY...JC/DR TIDES/COASTAL FLOODING...