Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 140002 AFDOKX Area Forecast Discussion National Weather Service New York NY 802 PM EDT Tue Apr 13 2021 .SYNOPSIS... High pressure over the area tonight will move offshore on Wednesday. Low pressure approaches from the west late Wednesday into Wednesday night. A coastal low will impact the area Thursday and Friday. Another low pressure system could impact our area early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Forecast has been updated to capture latest trends. A middle and upper level ridge over the area will support dry and relatively calm conditions tonight. The main forecast challenge tonight revolves around how much lingering stratocu there will be across southeast Connecticut this evening and how much would return there and over eastern Long Island late at night. The latest thinking is that stratocu should fill back in over these locations late tonight as a light NNE flow off the Atlantic continues, leading to a mostly cloudy sky. Farther west across western Long Island, NYC metro, NE NJ, and western CT, mostly clear skies are forecast. Low temperatures will be in the lower to middle 40s for most locations with the NYC metro only falling into the upper 40s to near 50 degrees. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... The middle and upper level ridge weakens on Wednesday, with surface high pressure shifting south and east of the region. The overall trend for the day will be increasing middle and high level clouds ahead of the approaching large upper level low that is currently over the northern Plains along the US/Canada border. A broad area of low pressure ahead of the upper low, which should be spinning over the Great Lakes on Wednesday, will also be nearing the region in the afternoon. Model guidance has been hinting at some light rain developing across eastern PA in the afternoon, which then pushes towards northeast NJ and the Lower Hudson Valley by evening. There is weak warm advection developing west of the NYC metro late in the day, but overall support for precipitation is low. Have capped PoPs at slight chance in the late afternoon. Low level flow will be light and should allow temperatures to warm quickly after sunrise, reaching the lower and middle 60s. Increasing onshore flow late in the day should put a lid on the temperature rise and lower readings near the coast into the 50s. The large upper level low will continue approaching the region Wednesday night. The probability for rain increases through the night, with the highest chances occurring after midnight. Upper level divergence increases along with stronger warm advection leading to the development of a more widespread rainfall around day break Thursday morning, especially across the western half of the region. A more consolidated low pressure area should be beginning to organize along the Middle Atlantic coast by day break Thursday. && .LONG TERM /THURSDAY THROUGH TUESDAY/... The most active period of the long term will be Thursday and Friday with a system that will bring periods of heavy rainfall and gusty winds to our area. A secondary low forms and strengthens off the Delmarva coast with the help of a jet streak to our south. The low tracks northeast just over southern portions of our area before it becomes vertically stacked and weakens as it slowly heads offshore. Widespread moderate, and periods of heavy rain can be expected most of the day on Thursday. Models are showing PW values of an inch which is nearing the 90% moving average of SPC`s sounding climatology. Winds shift and become more northerly early Friday morning allowing for CAA. With cold air aloft it is possible some northern areas and high elevations experience wet snow mixed in Friday morning. Critical thickness values show heights that would favor snow through much of the column, however surface temperatures and wetbulb look to remain above freezing. With much uncertainty no snow amounts are forecast at this time. Total rainfall amounts are expected to be between 1 and 2 inches, with locally higher amounts possible. Winds will peak Thursday afternoon and evening with gusts up to 30 mph. Lingering light rain is possible as the low heads northeast on Friday. Northerly flow will keep high temperatures well below seasonable, in the mid 40s to low 50s. Brief ridging aloft should keep the area mostly dry for the weekend before a shortwave brings a chance of some light rain on Monday. Some model disagreement remains with a system for early next week. There is potential for another coastal system to bring rain and gusty winds to our area. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... Weak high pressure remains in place through Wednesday afternoon. VFR through Wednesday afternoon. Winds with a southerly component under 10 kt tonight, with inland terminals becoming light and variable. WNW to WSW winds pick up Wednesday morning before backing S to SE with sea breezes and increasing to around 10 kt. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... No unscheduled amendments are expected. .OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY.... .Wednesday night...Rain becoming likely. MVFR evening, IFR overnight. .Thursday and Thursday night...Rain with IFR conds. .Friday...MVFR to IFR with a chance of rain. .Saturday and Sunday...VFR. Detailed information, including hourly TAF wind component forecasts, can be found at: http:/ && .MARINE... A weak pressure gradient over the waters through Wednesday will lead to sub-SCA conditions. Onshore flow will begin to increase Wednesday night as low pressure approaches the waters, but winds and seas should remain below SCA levels. SCA conditions look likely for all waters Thursday afternoon through Friday morning with the ocean waters holding on to those conditions a bit longer. Expecting 25 - 30 knot winds with seas 5 to 7 feet. && .HYDROLOGY... No hydrologic concerns exist through Wednesday. A coastal low will bring a long duration rainfall to our area with periods of heavy rain possibly. Some nuisance flooding may result. Rainfall totals between 1 to 2 inches, with locally higher amounts, are expected. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...DJ/DS/JT NEAR TERM...DS/JT SHORT TERM...DS LONG TERM...DJ/JT AVIATION...JC/BG MARINE...DJ/DS/JT HYDROLOGY...DJ/DS/JT is the U.S. government's official web portal to all federal, state and local government web resources and services.