Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 251139 AFDOKX Area Forecast Discussion National Weather Service New York NY 739 AM EDT Sun Oct 25 2020 .SYNOPSIS... High pressure over New England starts the period. A surface low pressure system passes well to the south Sunday night, and then east of the area on Monday followed by another cold front approaching on Tuesday. A Mid Atlantic ridge settles in to the south through mid week while a weak shortwave trough passes east into Quebec to the north. A frontal system arrives into the Northeast late in the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... The forecast is on track this morning with only minor adjustments made to account for current observational trends. Temperatures have stayed up at many locations with winds slow to diminish, while dewpoints have dropped in the low to mid 30s across the board. The day starts out dry, as the cold front that passed through the area Saturday has stalled well to the southeast. Northwest winds are beginning to diminish as the pressure gradient has relaxed and a 1028mb surface high settles in across New England. Ridging is building to the south along its eastern periphery, and extending into the area, allowing for some mid level dry air to remain in place over the CWA. At the same time, GOES-16 6.19um water vapor channel depicts shortwave energy currently moving across GA/SC, with high level moisture streaming to the northeast. High clouds are already filtering into the area in advance of this system from the southwest. A surface low is also developing near the SC/NC border in association with the shortwave. Deep southwest flow aloft will continue to advect moisture north through the day on Sunday as the shortwave and surface low head northeast along the stalled front. Model soundings/time heights indicate that cloud cover will increase and lower into Sunday evening. Light precipitation should begin later Sunday afternoon as the southerly moisture advection erodes the mid level dry air. The question is how long does that take. Current thinking is precipitation onset across the southwestern sections of the CWA near 18Z-21Z, which is broadly supported by the most recent global models. Hi-res models are trending a few hours earlier into northeast NJ. Precipitation with this event should remain light overall, as best synoptic forcing remains well to the north and there is some mid level dry air locally to overcome at the onset. 00Z models are in better agreement tonight on the evolution of this event with respect to track of the surface low and associated precp shield impacting the area. Have trended PoPs up just a bit, particularly for 23Z-00Z period to likely across most of the CWA, but still below NBM PoPs, which are a hair higher. High temperatures will be cool on Sunday, in the low to mid 50s, with a combination of the cool airmass in place to start, then tempered by increased cloud cover later in the day. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/... Precipitation continues into Sunday evening and spreads north and east across the area, as the surface low passes well south of LI and heads northeast by Monday morning. Any lingering precipitation ends on Monday morning as the low pulls away. Precipitation totals of around 0.1-0.25 inches are expected areawide, with the highest amounts in northeastern NJ. The steadiest period for precipitation to occur is the period between about 06Z and 12Z Monday morning, but again, expecting it to be on the light side. Cloud cover will remain in place through much of the rest of Monday into Monday evening however, as another cold front approaches from the west. Easterly flow at the surface for much of the day Monday will keep cloud cover and drizzle potential in place into the afternoon, and have that reflected in the latest NDFD grids. Temperatures will be be a few degrees warmer than on Sunday, in the upper 50s to lower 60s, but still cool given the plentiful cloud cover and precipitation. && .LONG TERM /TUESDAY THROUGH SATURDAY/... The synoptic scale trough aloft with southwest flow overhead continues to bring moisture in from the southern states through midweek. Short wave impulses along this trough combined with the elevated precipitable water values around 1.10 to 1.30 inches make for light rain chances on both Tuesday and Wednesday. The weather pattern become quite active late Wednesday into Thursday. A jet enhanced frontal system over the Great Lakes enters northern New York Thursday. At the same time tropical moisture from TS Zeta is advected into southern New York as noted by the 1.75-2.00 inch PWATs. As these two systems meet expect widespread moderate to heavy rainfall throughout the East Coast lingering into Friday. The upper level trough then shifts east and offshore as we head into the weekend. Models show a 1030mb high pressure system building in behind with dew points in the 30s meaning an environmental regime change is possible next weekend. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... High pressure builds over the area from the northwest through this morning. A surface trough and warm front along the mid Atlantic coast approaches from the south late this afternoon. VFR through the rest of tonight and this morning. MVFR ceilings may develop between 00-03Z Monday at all terminals. NE winds today, shifting more toward the E this afternoon and evening. Wind speeds will be 10-15 kt for coastal terminals, 10 kt or less for terminals away from the coast. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... No unscheduled amendments expected. Amendments are possible toward 00Z Monday as ceilings begin to lower. .OUTLOOK FOR 12Z MONDAY THROUGH THURSDAY... .Monday...MVFR or lower conditions and -RA. .Tuesday...MVFR possible with a chance of showers. .Wednesday-Thursday...MVFR or lower possible in chance of -RA. Detailed information, including hourly TAF wind component forecasts, can be found at: http:/ && .MARINE... Seas on the ocean waters will diminish somewhat today, and may briefly fall below 5 ft late this afternoon into early evening as swells from departing Epsilon no longer affect the waters. Waves build again tonight in response to strengthening easterly flow ahead of the an approaching low pressure system that is forecast to pass south of the waters. Waves increase to 5 to 7 ft tonight into Monday morning, slowly diminishing through the afternoon. With 5+ ft waves expected through the day Monday, the SCA was extended in time to 6 pm Monday. Winds will remain below 25 kt Sunday with high pressure over the waters retreating into southern Canada. Winds increase tonight and may touch 25 kt at times on the ocean waters late tonight into early Monday morning. Elsewhere, winds should remain below 25 kt. Waves then range mainly from 3-4 feet over the ocean with light east to northeast winds through Wednesday. Late Wednesday southwest winds develop as the remnants of Depression 28 enter the marine zones. SCA criteria is possible Friday as waves of 6-7 feet with wind gusts of 25 kts over the ocean waters owing to the system making its closest approach. Please refer to National Hurricane Center products for further details on Epsilon. && .HYDROLOGY... No hydrologic concerns through Wednesday. Heavy rain is possible Thursday with the arrival of tropical moisture. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 PM EDT Monday for ANZ350-353-355. && $$ SYNOPSIS...DJ/DBR NEAR TERM...DBR SHORT TERM...DBR LONG TERM...DJ/DBR AVIATION...JP MARINE...DJ/JP HYDROLOGY...DJ/DBR is the U.S. government's official web portal to all federal, state and local government web resources and services.