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Area Forecast Discussion
Issued by NWS Upton, NY
Issued by NWS Upton, NY
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643 FXUS61 KOKX 171126 AFDOKX Area Forecast Discussion National Weather Service New York NY 726 AM EDT Sat Aug 17 2024 .SYNOPSIS... High pressure remains centered offshore today as a weak low tracks through the Great Lakes. The low approaches on Sunday, with an associated warm front lifting through into Sunday night. A cold front then follows Monday, with a secondary frontal passage into Tuesday. High pressure then builds through the end of the week. && .NEAR TERM /THROUGH TONIGHT/... Increased PoPs across western half of the area this morning with some light rain showers pushing east thru NJ and the Lower Hudson Valley. This activity will remain light and brief where it occurs, and likely dissipates into mid morning as it runs into ridging. Otherwise, forecast on track and previous discussion follows. Upper ridging in place locally shifts to the east as surface high pressure remains centered offshore today. Digging trough over the Great Lakes begins to approach, and a frontal system on the leading edge will begin to approach. While much of the day appears dry across the bulk of the forecast area, increasing moisture and lift should stir a few showers on the far western edge of the region, mainly across the Lower Hudson Valley and further from the influence of the offshore ridging. Otherwise, increasing cloud cover and warm, with temperatures this afternoon topping out near 80 for most. Given the flow, the elevated smoke plume that has been in place the last few days shifts east and offshore. The shower activity expands in coverage this evening and tonight with passing shortwave energy, but still appears mostly confined to the western half of the region. Some varying solutions from the 00Z CAMs, with the NAM 3km much less enthused with rainfall tonight, and the HRRR much more bullish and farther east with the placement. For now, opted for lower likely PoPs (60%) given the disagreement, with this mainly extending over NE NJ and the Lower Hudson Valley and decreasing to the east. Not entirely out of question a few embedded thunderstorms develop tonight as well, though this remain rather limited. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... Unsettled start to the week as the upper trough and frontal system track through the Northeast and bring several periods of rainfall. Scattered showers around Sunday morning should lessen in coverage by lunchtime, and much of the afternoon could remain dry, especially east. Into the evening, rain chances increase once again as a frontal boundary begins to approach. Limited shear and instability should keep activity mainly sub-severe and disorganized, but can`t rule out thunderstorms. Of greater concern is the potential for training convection and heavy downpours given a persistent moisture feed from the south increasing PWATs to near 1.75" during this time, raising the risk of heavy downpours that could lead to flooding. This threat appears highest from NYC on north and west, and lines up with where WPC currently has a slight risk for excessive rainfall on Sunday. Though still some uncertainty with the placement of the axis of heaviest rainfall, which will be critical in fleshing out the nature and location of the threat. A cold front follows Monday into Monday night with the potential of a weak wave forming along the boundary as it moves through the region, instigating another round of showers and thunderstorms. There remains the potential for locally heavy rainfall, as well as an isolated flash flood threat with this activity. Rain chances finally start to lower Monday night into early Tuesday as the complex progresses east and a much drier regime begins to take hold. Total QPF through this period averages around a half inch across eastern areas, to between 1 and 2 inches from NYC and points north and west. && .LONG TERM /TUESDAY THROUGH FRIDAY/... It appears that a cold front will be over us or just shifted through during Tuesday morning. High pressure will have a tough time building behind its passage during the rest of Tuesday as an upper trough axis remains over us. Chance of showers at any point of the day, but overall it should be dry most of the time. Can`t completely rule out a thunderstorm in the afternoon due to the cold pool aloft, but will leave it out of the forecast for now. The trough axis shifts east during Wednesday, and with limited moisture, it should be a dry day. The flow aloft flattens for Thursday and Friday with a continuation of dry weather as surface high pressure builds in. Highs only in the 70s for Tuesday through Thursday, then around 80 on Friday. && .AVIATION /11Z SATURDAY THROUGH WEDNESDAY/... Weak high pressure remains in control today, then a warm front approaches from the west tonight. Mostly MVFR early on, then improving to VFR everywhere by late morning. Can`t rule out a passing shower or two during the daytime for all but KBDR/KISP/KGON, but will leave it out of the TAFs. MVFR returns tonight with a chance of showers, but showers are more likely towards Sunday morning. SE winds around 10kt today, remaining SE tonight at 5-10kt. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... Timing for improvement to VFR could be off by an hour or two. KJFK possibly prevails at IFR thru 13z. Chance of tempo -shra/MVFR vsbys 15-18z. OUTLOOK FOR 12Z SUNDAY THROUGH WEDNESDAY... Sunday and Monday: MVFR or lower in SHRA. Chance of TSRA. Tuesday: Mainly VFR. MVFR or lower possible in any SHRA...mainly eastern terminals. Wednesday: VFR. Detailed information, including hourly TAF wind component forecasts, can be found at: https:/www.weather.gov/zny/n90 && .MARINE... Rough ocean seas and long period swells will persist this weekend and into early next week as distant TC Ernesto passes well offshore in the open Atlantic. This will also lead to rough conditions around inlets. Please refer to the National Hurricane Center for official forecasts regarding Hurricane Ernesto. A Small Craft Advisory is in effect for the ocean zones through Sunday night for elevated swells increasing toward 7 ft. This will likely need an extension through at least Monday with lingering seas. Swells and seas should diminish Tuesday into Wednesday with seas below 5 ft sometime on Tuesday. Otherwise, below SCA conditions are expected Sunday through the middle of the week. && .HYDROLOGY... Locally heavy rainfall is possible Sunday into Sunday night, particularly west of the NYC metro and Hudson River. This threat expands to much of the area Monday into Monday night. Total rainfall amounts range from around a half inch east to 1 to 2 inches from NYC metro on north and west. Locally higher amounts are possible. Isolated to scattered instances of flash flooding is possible across the more flood prone areas of NE NJ and adjacent areas of the Lower Hudson Valley, and perhaps as far east as NYC. A more widespread threat for localized flash flooding, along with nuisance flooding of urban and poor drainage areas, sets up on Monday. No additional hydrological concerns follow Tuesday through late next week. && .TIDES/COASTAL FLOODING... A high rip current risk is in place through Sunday. This is due to SE to S long period swells from Hurricane Ernesto. The high risk will likely need to be extended into Monday. Please refer to NHC for official forecasts regarding Hurricane Ernesto. Ocean seas are forecast to be highest Sunday into Monday, with heights up to 7 ft. There is potential for high surf along the ocean beaches during this timeframe as well as beach erosion. Minor coastal flooding is possible for the back bays of Long Island and across the CT coast of Western Sound 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...High Risk for Rip Currents through Sunday evening for NYZ075-080- 081-178-179. NJ...None. MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ350-353-355. && $$ SYNOPSIS...JC/DR NEAR TERM...DR SHORT TERM...DR LONG TERM...JC AVIATION...JC MARINE...JC/DR HYDROLOGY...JC/DR TIDES/COASTAL FLOODING...