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Area Forecast Discussion
Issued by NWS Upton, NY
Issued by NWS Upton, NY
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362 FXUS61 KOKX 171959 AFDOKX Area Forecast Discussion National Weather Service New York NY 359 PM EDT Sat Aug 17 2024 .SYNOPSIS... A weak low tracks slowly eastward through the Great Lakes region tonight, and approaches Sunday. Meanwhile another low develops during Sunday over southeastern Pennsylvania and eastern Maryland. This low then deepens Sunday night into Monday and tracks northeast bringing a cold front across the area late Sunday night into Monday. A secondary frontal passage moves through Tuesday. High pressure builds in for the middle and end of the week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... With the potential for one round of moderate to heavy rainfall late tonight into early Sunday morning have issued a Flood Watch that begins at 06Z Sunday, for northeastern New Jersey into the Lower Hudson Valley west of the Hudson River. The watch continues through Sunday and into late Sunday night. Rainfall rates late tonight may be near 1 inch per hour. Isolated flash flooding is also possible a little farther to the east, into New York City and Putnam and Westchester counties, with poor drainage and urban flooding possible. With the upper ridge remaining into the western Atlantic, rainfall will be slow to move eastward tonight, and some eastern sections may remain dry until late tonight or toward Sunday morning. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/... A Flood Watch is in effect from late tonight, 06Z Sunday, through late Sunday night, 06Z Monday, for the potential for scattered flash flooding, urban and poor drainage flooding, and possibly fast responding streams of northeastern New Jersey. Rainfall rates could be near 1 inch per hour, and at times approach 2 inches per hour. Total rainfall in the watch area will be around 2 inches to 2.5 inches with locally as much as 3 inches possible. This will be with a slow moving frontal system and with training showers and isolated thunderstorms, as the flow nearly parallels the trough. Also, precipitable waters increase to just over two inches Sunday, and warm cloud process increase along with a 20-230kt low level jet during Sunday and into Sunday night. This system will be slow moving eastward as downstream riding remains across the western North Atlantic. An then during Sunday a frontal wave develops near the mid Atlantic coast, across southeastern Pennsylvania into the Delmarva. This low provides lift for heavy rainfall as this low tracks slowly northeast to east across northeastern New Jersey into New York City and then to the northeast of the area during Monday. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... The area remains under a large-scale 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. There is still some uncertainty as to how quickly the trough lifts with the upper-level energy rotating over New England, but consensus has been that the trough departs late Wednesday into Thursday and ridging begins to move over the area from the west. At the surface, a relatively strong high pressure system builds into the Mid- Atlantic and Northeast from Wednesday through the weekend. This will provide fairly calm and dry conditions through the rest of next week. This high pressure will be accompanied with primarily N/NW winds and a much cooler airmass. The airmass should be fairly anomalously cool for middle to late August. High temperatures on Tuesday and Wednesday may not rise out of the upper 60s to low 70s for much of the area. Even coastal areas, highs will only be in the low to maybe middle 70s. 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 /20Z SATURDAY THROUGH THURSDAY/... A frontal system approaches the terminals through the TAF period. Mainly MVFR conditions are expected through the TAF period. Intermittent showers expected across all terminals except for KGON. KGON expected to remain mostly dry during the TAF period. KGON could have some showers towards the end of the TAF period during the day Sunday. There could be an isolated embedded thunderstorm as well tonight into Sunday. Chances for thunderstorms increase Sunday afternoon. At this time, too much uncertainty for thunderstorm timing and locations to put in any TAFs. Regarding winds, overall expecting SE winds near 10 kt much of the TAF period. Some occasional gusts 15-20 kt will be possible this afternoon as well as Sunday afternoon, mainly for NYC terminals. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... There could very well be some fluctuation in category during the TAF period. Categories could fluctuate between MVFR and VFR this afternoon into this evening. IFR will be possible at times Sunday. OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY... Sunday afternoon-Sunday night: Showers moving in from the west. A chance of thunderstorms. MVFR to occasional IFR conditions. Monday: Showers with a chance of thunderstorms. MVFR or lower at times. Tuesday: 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 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, and was extended through Monday night. Elevated wave heights on the ocean zones will allow for SCA conditions to continue Monday night and possibly into the day on Tuesday with some marginal wind gusts near 20-25kt with the passage of a cold front. 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 mid-week. && .HYDROLOGY... A Flood Watch is in effect late tonight into late Sunday night for Northeastern New Jersey and into the Lower Hudson Valley west of the Hudson River. Locally heavy rainfall is possible late tonight, and again during Sunday into Sunday night, particularly west of the NYC metro and Hudson River. The threat of heavy rainfall expands to the east into Western Long Island and portions of southern, and with the slow movement of low pressure and lower rainfall amounts and rainfall rate was not confident enough to go farther to the east with the Flood Watch. Total rainfall amounts from tonight through Monday night range from around a half inch east to around 2 inches from NYC metro on north and west. Locally higher amounts, possibly up to 3 inches, are possible across northeastern New Jersey into the Lower Hudson Valley. 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. A more widespread threat for localized flash flooding, along with nuisance flooding of urban and poor drainage areas, sets up on Monday. No hydrologic concerns Tuesday through next weekend. && .TIDES/COASTAL FLOODING... A high rip current risk is in place through Monday. This is due to SE to S long period swells from Hurricane Ernesto. Ocean seas are forecast to be highest Sunday into Monday, with heights up to 6-7 ft. There is potential for high surf along the ocean beaches during this time frame as well as beach erosion. Minor coastal flooding is expected this evening along the back bays of Nassau, where a statement has been issued. Advisories will likely be needed for subsequent high tide cycles for the back bays of Nassau and Queens, the lower NY Harbor, and the SW CT coastline, where water levels may touch minor thresholds through much of this upcoming week per elevated astronomical high tides due to the full moon on the 19th and swell from Hurricane Ernesto. Please refer to NHC for official forecasts regarding Hurricane Ernesto. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...Flood Watch from 2 AM EDT Sunday through late Sunday night for NYZ067-069. High Risk for Rip Currents through Sunday evening for NYZ075-080- 081-178-179. NJ...Flood Watch from 2 AM EDT Sunday through late Sunday night for NJZ002-004-006-103>108. MARINE...Small Craft Advisory until 6 AM EDT Tuesday for ANZ350-353-355. && $$ SYNOPSIS...MET/MW NEAR TERM...MET SHORT TERM...MET LONG TERM...MW AVIATION...JM MARINE...MET/MW HYDROLOGY...MET/MW TIDES/COASTAL FLOODING...MW/BG