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Area Forecast Discussion
Issued by NWS Upton, NY
Issued by NWS Upton, NY
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533 FXUS61 KOKX 181053 AFDOKX Area Forecast Discussion National Weather Service New York NY 653 AM EDT Sun Aug 18 2024 .SYNOPSIS... Low pressure tracks slowly eastward through the Great Lakes today as a secondary low develops over the Mid Atlantic. This low moves north and east into the local area tonight, sending a cold front through the area Monday. A secondary frontal passage moves through Tuesday. High pressure then builds in for the middle and end of the week. && .NEAR TERM /THROUGH TONIGHT/... Slow moving frontal system tracks into the region today, bringing a couple rounds of heavy rainfall with it. Ribbons of showers, some moderate to heavy, have moved into the region overnight and early this morning. This activity could produce locally heavy downpours that result in flooding. In addition, with recent thunderstorms over SE PA and NJ, have included the mention of possible thunder in a corridor extending northward thru NJ into NYC and the Lower Hudson Valley. A quick inch of rainfall is possible with this activity, and could lead to urban and poor drainage flooding depending on placement and duration. This entire system will be slow moving eastward as downstream ridging remains across the western North Atlantic. A frontal wave develops along the Mid Atlantic coast into this evening, before pushing north into the local area. This low provides lift for additional heavy rainfall later today and tonight. 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 that lead to flooding. PWATs already over 1.5 inches in the OKX 00Z sounding increases toward 2 inches today, and efficient warm cloud processes could allow for elevated rainfall rates with this activity. 00Z HREF signals the potential for rainfall rates perhaps as high as 2 inches in an hour, especially over New Jersey and Lower Hudson Valley zones. While total QPF looks to average a general 1 to 2 inches for locations along and west of the Hudson River, including the NYC metro, localized amount could approach 3 or 4 inches depending on placement and training of cells. All this said, the Flood Watch remains in effect through late tonight for zones west of the Hudson River for the potential of scattered flash flooding, urban and poor drainage flooding, and possibly flooding of faster responding streams in NE NJ. Areas to the east look to miss out on the axis of heaviest rainfall based on latest hi-res guidance, so opted not to expand the watch any further east with this update. Certainly, if the axis shifts a bit east, or if training convection develops, flooding could be an issue here as well, including in NYC and urban centers. WPC has kept the slight risk for excessive rainfall in place for similar areas, expanding just a bit to the east to include the entire NYC metro and SE CT. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... An unsettled start to the work week as the upper trough and frontal system continue to impact the region. Cold front and weak coastal wave of low pressure approach on Monday as the trough axis begins to shift into the Northeast. Another round of showers and possible thunderstorms likely Monday into Monday night. This will mainly be associated with the cold front, but the nearby low could enhanced rainfall. Still some uncertainty on severity and placement, but there will remain a threat for locally heavy rainfall, nuisance flooding, and an isolated flash flooding occurrence. The area remains under a broad trough with vorticity maxima moving through Monday night and into Tuesday. As the trough tries to lift during the day on Tuesday, additional energy descends from the north to allow for another round of forcing. At the surface, this should translate into the form of a secondary frontal passage that brings another round of showers with possible embedded thunderstorms, especially Monday night into Tuesday morning. Any residual showers should diminish into the afternoon on Tuesday with the passage of the surface cold front. This will set the stage for drier and cooler conditions to take hold into midweek. Behind the fropa, highs on Tuesday could be the coolest since late May for some, generally in the upper 60s and lower 70s. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... No significant changes in the long term. A drier, cooler pattern develops midweek behind the frontal system as dry air advects south with surface high pressure building in. Lingering trough over the Northeast may persist into late week, reinforced by a closed upper low dropping south out of Canada. This high pressure will be accompanied with primarily N/NW winds and a much cooler regime, perhaps the coolest since late spring. High temperatures Wednesday may not rise out of the low 70s for much of the area. Lows Wednesday night and Thursday night will likely be fairly chilly, with some locations for the interior and outlying areas possibly dropping into the low 50s or upper 40s, depending on the strength of any radiational cooling. Temperatures will gradually moderate into late week and the weekend with highs by Friday and Saturday rising back into the upper 70s to low 80s. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... A frontal system slowly approaches the terminals through the TAF period. Becoming mostly MVFR with some local IFR farther east. Showers possible at any time, and for the city terminals as points west, brief heavy downpours through 11-12z, and possibly again in the 12z to 15z time frame. MVFR conditions are likely to continue through this evening although there could be some brief improvement to VFR at times in the afternoon. Showers remain possible into this evening, especially along and west of the Hudson River corridor. Farther east, a brief shower is possible, but the most widespread shower activity likely holds off until after 00z Monday. There could be an isolated thunderstorm this morning, mainly NYC metro terminals on north and west. After a potential relatively lull late morning to early afternoon, chances of thunderstorms and heavy downpours increase a bit late this afternoon/evening for the same terminals. Have therefore included a PROB30 for this time period. Winds will mainly be SE around 10 kt or less through the TAF period. Coastal terminals could see winds a few kt higher at times, especially this afternoon. There is also a chance for a few gusts 15- 20 kt this afternoon. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... Timing of return to MVFR may be off by 1-3 hours. Amendments for changing flight categories and shower timing likely through the TAF period. Isolated thunderstorms possible 10-16z Sunday. Timing of PROB30 TSRA this afternoon and evening may be off by several hours with adjustments likely. OUTLOOK FOR 06Z MONDAY THROUGH THURSDAY... Late Tonight: Showers with MVFR, except IFR north and east of the city terminals. Monday: Showers with possible thunderstorms, especially afternoon and evening. MVFR or lower at times. Tuesday: Mainly VFR. A chance of showers with MVFR possible. NW wind gusts 15-20 kt. Wednesday-Thursday: 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, 12 to 15 second, will persist through Monday as distant TC Ernesto passes well offshore in the open Atlantic. This is also leading to rough conditions around inlets. Please refer to the National Hurricane Center for official forecasts regarding Ernesto. A Small Craft Advisory remains in effect for the ocean zones thru Monday night. Seas on the eastern LI Sound could also approach 5 ft at times today, though thinking this may be more occasional. Thereafter, elevated wave heights on the ocean zones will allow for SCA conditions to continue Monday night and possibly into the day on Tuesday. By Late Tuesday, wind diminish and wave heights should fall below 5 feet. Sub-SCA conditions are then expected with high pressure moving into the area by midweek. && .HYDROLOGY... A Flood Watch remains in effect thru late tonight for NE New Jersey and into the Lower Hudson Valley west of the Hudson River. Isolated to scattered instances of flash flooding are 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. Locally heavy rainfall is possible, mainly this morning, and again this late today into tonight, with rainfall rates up to an inch or two per hour. Farther east, the risk for flash flooding is lower, but cannot be entirely ruled out. Ponding and poor drainage flooding is the most likely solution here with any heavier activity. Additional rainfall expected on Monday and Monday night will lead to a more widespread threat for localized flash flooding, along with nuisance flooding of urban and poor drainage areas. Total rainfall through Monday night ranges from around a half inch east to between 1 and 2 inches from NYC metro on north and west. Locally higher amounts, possibly up to 3 or 4 inches, are possible across northeastern New Jersey into the Lower Hudson Valley. No hydrologic concerns Tuesday through next weekend. && .TIDES/COASTAL FLOODING... A high rip current risk is in place through Monday due to elevated, long period swells from passing TC Ernesto. Ocean seas are forecast to be highest today and Monday, and with surf heights up to 6 ft, local beach erosion is possible. A full moon on Monday as well as swell from distant TC Ernesto will elevated tide levels today into early this week. Minor coastal flooding is expected with high tide this evening across the back bays of Nassau and Western Sound along the southwest CT and S Westchester coast. Have issued a Coastal Flood Advisory for these locations. Localized minor coastal flooding is possible across southern Queens, Southern Brooklyn and lower NY Harbor. Locations may just touch minor benchmarks and a statement has been issued. Additional minor flooding is possible for high tide Monday evening and statements/Advisories will likely be needed for similar locations as with high tide this evening. Please refer to NHC for official forecasts regarding Hurricane Ernesto. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...Coastal Flood Advisory from 10 PM this evening to 1 AM EDT Monday for CTZ009. NY...Coastal Flood Advisory from 10 PM this evening to 1 AM EDT Monday for NYZ071. Flood Watch through late tonight for NYZ067-069. High Risk for Rip Currents through Monday evening for NYZ075-080- 081-178-179. Coastal Flood Advisory from 7 PM to 10 PM EDT this evening for NYZ179. NJ...Flood Watch through late tonight for NJZ002-004-006-103>108. MARINE...Small Craft Advisory until 6 AM EDT Tuesday for ANZ350-353-355. && $$ SYNOPSIS...DR NEAR TERM...DR SHORT TERM...DR LONG TERM...MW AVIATION...JC MARINE...DR HYDROLOGY...DR TIDES/COASTAL FLOODING...